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Panel 9
See reader questions & answers on this topic! - Help others by sharing your knowledge Index: a. Backcountry Drinking [Comparison of filters, boiling and iodine] Alan Dove, Bill Tuthill 1996 Filters: First Need, Katadyn, MSR, PUR Boiling, Iodine: PolarPure, Potable-Aqua b. GIARDIASIS Memo from Center from Disease Control, 1990 memo by Dennis D. Juranek replaced with URL link to the CDC c. Other research articles on giardiasis and cryptosporidiosis d. FDA Web pointer e. REI Water Filter Chart Comparison of specs: cost, pore size, field cleaning, weight, pump force, output speed, etc. 1996 f. review of Katadyn Minifilter Alan Malkiel g. Misc. ========== TABLE OF CONTENTS of this chain: 9/ Water Filter wisdom <* THIS PANEL *> 10/ Volunteer Work 11/ Snake bite 12/ Netiquette 13/ Questions on conditions and travel 14/ Dedication to Aldo Leopold 15/ Leopold's lot. 16/ Morbid backcountry/memorial 17/ Information about bears 18/ Poison ivy, frequently ask, under question 19/ Lyme disease, frequently ask, under question 20/ "Telling questions" backcountry Turing test 21/ AMS 22/ Babies and Kids 23/ A bit of song (like camp songs) 24/ What is natural? 25/ A romantic notion of high-tech employment 26/ Other news groups of related interest, networking 27/ Films/cinema references 28/ References (written) 1/ DISCLAIMER 2/ Ethics 3/ Learning I 4/ learning II (lists, "Ten Essentials," Chouinard comments) 5/ Summary of past topics 6/ Non-wisdom: fire-arms topic circular discussion 7/ Phone / address lists 8/ Fletcher's Law of Inverse Appreciation / Rachel Carson / Foreman and Hayduke # --enm: At this time, there is a report of a giardia "vaccine" in test, # but no word on methods. No vaccine reported by CDC to July 2009. At this time (bordering on technically being War), there is no clarity that any of the methods cited on this panel are 100% foolproof for removing or destroying biological agents or any kind (lethal or incapacitating) from a drinking water source. This panel should not be cited (excepting the CDC report). Instead contact your local Public Health Service officials. Bring sources of contaminated water to their attention. From: "Jerry M. Wright" <wrightjm@erols.com> To: "Eugene Miya" <eugene@cse.ucsc.edu> Subject: Giardia panel Date: Wed, 7 Mar 2001 21:10:51 -0500 Message-ID: <MABBJMACAOJKIGGDMLIDKEDGCAAA.wrightjm@erols.com> Importance: Normal Here's an interesting recent publication. Don't know if it's in the panel but should be. Risk of giardiasis from consumption of wilderness water in North America: a systematic review of epidemiologic data. AUTHORS: Welch TP AUTHOR AFFILIATION: Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA 70112, USA. twelch2@mailhost.tcs.tulane.edu SOURCE: Int J Infect Dis 2000;4(2):100-3 ... Published reports of confirmed giardiasis among outdoor recreationalists clearly demonstrate a high incidence among this population. However, the evidence for an association between drinking backcountry water and acquiring giardiasis is minimal. Education efforts aimed at outdoor recreationalists should place more emphasis on handwashing than on water purification ... Backcountry Water Drinking --Why Not Just Drink the Water? In the Great Outdoors, there are potentially four dangers of drinking water straight from a source (assuming it's freshwater, # -- enm: it's actually more than 4, but this list is fine): chemical pollutants, protozoa and larger parasites, bacteria, and viruses. In this panel, we will first discuss a few of the methods used in the backcountry to avoid these dangers, then give a brief description of the toxins and pathogens found in water, and which method is best suited to neutralizing each. --Methods of Purification The oldest (and cheapest) method of purifying water is to boil it. Boiling for five minutes will kill any biological hazards you could expect to find. Most pathogens are actually long dead by the time the water boils, but the five minute boil will g et them all (remember to add 1 minute to this time for each 1,000 feet above 10,000 feet). Boiling will NOT neutralize chemical pollutants. Chemical purification involves the use of iodine or chlorine to kill the nasties in the water. This method is lightweight and relatively inexpensive, but will not neutralize chemical toxins. In addition, you must make sure that water at 25 deg. C (7 5deg. F) sits for 20-30 minutes with iodine in it for purification to take place. If the water is colder (as it usually is), you will need to let it sit longer - possibly overnight for cold stream water. Warm the water against your body or even on y our stove if you want it to be purified faster. Once the appropriate time has elapsed, the "band-aid" taste of iodine can be neutralized with a small amount of ascorbic acid (vitamin C). Used properly, iodine will kill most protozoa and all bacteria and viruses in water. After prolonged use, some people develop thyroid problems, so be aware of this potential side effect. The latest rage in water purification is the use of filters, and a large number of them are available (see the review later in this panel). There are a couple of things to bear in mind when shopping for filters. First, only a system which includes a n iodine matrix will kill viruses (see below). Second, a filter with pores larger than 0.2 microns - note the location of the decimal point, as it is important - will let bacteria through. The advantages of a filter are quick processing time (don't have to wait for the pot to boil or the iodine to do its work) and clean-tasting water (no iodine or vitamin C flavor). Some systems also contain a carbon filter which will remove chemical toxins. Finally, one system seldom used by hikers, but carried on seagoing boats and possibly sea kayaks, is the reverse osmosis, or RO filter. These systems are bulky, heavy, and expensive, but they will desalinate seawater - a useful thing to be able to do on a lifeboat, for example. Such filters will also remove all biological contaminants, including viruses (viruses are considerably larger than the exclusion limit of the RO filter). --What Might Hurt You Chemicals in water could include inorganic contaminants (arsenic and other heavy metals) or organic toxins (fertilizers and pesticides, for example). In general, it is a bad idea to trust any purification system to remove these, as even small quantit ies could ruin your day in a hurry. The good news is that water sources in the backcountry are seldom contaminated with appreciable levels of toxic chemicals. Take a good look at the stream you're about to get water from. Are there fish in it? Is there algae on the rocks? Crawdads on the bottom? Insects skimming the surface? Plants growing along the banks? If yes, the water is probably non-toxic, chemically speaking. If you're hiking in the desert, though, and a trickle of water etching a groove in the rock is bubbling sulfur from its barren depths, you should probably avoid it. There are a number of parasites, both multicellular and unicellular, which live in water. The most common ones in North America are _Giardia lamblia_ (see the CDC report later in this panel) and _Cryptosporidium_. A good filter will remove both, and boiling will kill them. Iodine is a reasonable second choice, but is a bit chancy in water carrying Crypto. In third-world countries, the number of parasites in the water is staggering, hence the hackneyed advice, "Don't drink the water." Amoebae can cause dysentery ("Montezuma's Revenge"), whipworm causes diarrhea and possible complications if not treated, and roundworms (_Ascaris lumbricoides_) can be unpleasant, to name a few. In some areas, such as the Philippines and Africa, you should tr y to avoid ANY contact with river water, including swimming or washing in unpurified water, as _Schistosoma_ sp. is prevalent in these areas. These tiny parasites bore directly into the skin, entering the bloodstream and eventually setting up shop in either the intestine or the bladder. If left untreated or incorrectly diagnosed (a common problem, as symptoms only become manifest weeks or months after contact), the complications can be severe. As with _Giardia_, though, all of these parasites ar e removed by filtration or killed by boiling. Bacteria are the second smallest pathogens in water, but they can still be removed by a 0.2 micron filter. One frequently hears about water being tested for _Escherichia coli_. While strains of this bacterium can be pathogenic, the vast majority are not, and it is, in fact, one of the species required in the intestine for digestion to occur (without bacteria, we would all die). Since it is present in large quantities in sewage, it is a good indicator strain to show when water has been contamina ted with sludge. There are plenty of other bacteria which are happy in the intestine, to the detriment of the host. All are sensitive to iodine treatment, are killed by boiling, and are removed by good filters. The smallest parasites are viruses (please direct pointless debates about whether or not they are "alive" to one of the sci.bio groups). In true wilderness areas, pathogenic viruses are seldom found in water, but the odds increase with population dens ity and poor sanitation practices. Ordinary filters DO NOT remove viruses - in fact, Louis Pasteur originally defined viruses as "filterable agents," meaning they traveled easily through a 0.2 micron ceramic filter. Filters which have an iodine matri x will kill viruses ("inactivate" them, if you prefer), and iodine treatment will also work. Boiling is the most reliable way to do away with viruses, though, and is strongly suggested in third-world countries. The specific viruses you should worry about in water are hepatitis A, rotaviruses, polioviruses, and echoviruses. All of these will cause diarrhea, intestinal cramps, and discomfort about 48-72 hours after contact, and complications could range from liver damage (for hepatitis) to aseptic meningitis and encephalitis (for echoviruses), and paralysis or death (for polio). Yes, everyone is vaccinated against polio these days, but if you were born before the vaccine, you could have problems with it. --Notes About This Introduction 1) Boiling your water is cheap and easy, and kills all known pathogens. If you can manage the extra fuel necessary, this is the preferred method. 2) In the United States, you will seldom encounter anything in drinking water which can kill you (make you sick, yes, but probably not kill you). Be careful, but don't have a heart attack if you accidentally swallow some unpurified stream water. The c hances are thousands of times greater that you will die in an automobile accident. 3) Anecdotal evidence which you see on the Net should largely be ignored, especially the "I've used X method for 20 years and never had a problem" variety. Since most water is not contaminated to begin with, just about any method could appear to work for quite awhile. 4) This introduction was written by Alan Dove and edited by Eugene Miya [well, I studied biological warfare] and Bill Tuthill. All three know the subject matter, but this information is intended only for general guidance. Anything that happens to you as a result of following or not following it is your own damned fault. ===== OCR'ed memo from the Centers from Disease Control: GIARDIASIS: By Dennis D. Juranek, Chief, Epidemiology Activity Parasitic, 1990 A majority of the people involved in the experiment which OCR'ed Dr. Juranek's memo in the early days before the web have agreed that it would be better to remove his older memo and instead point to the CDC's own web site's pages. The experiment was tried to see how much effort the r.b. community would attempt to work with existing sources of external information. Some of the results include the other parts of this panel as well as parts of the Lyme and poison ivy/oak panels. This panel continues to need work restructuring it. But the original contributors don't really have the time. Please see http://www.cdc.gov select the 'G' letter in the Index (currently top of the home page) and link "Giardia." The web site has a number of advantages including not only being more up to date but also having images which are a little harder to Usenet to transmit. Dr. Juranek himself has authored other memos and papers following 1990 and those are referenced on the CDC web page. Use the CDC's information which should be considered authoritative. The original text was moved to the end of this panel and will be completely removed at the end of 2009. Temporary Patch: Tinidazole (Tendamax) is now available in the US both in trademarked and generic form. It is now apparently the usual treatment for Giardia. This patch will also remain until end of 2009. =============== CRYPTOSPORIDIOSIS (Fact Sheet) What is cryptosporidiosis? Cryptosporidiosis is a disease caused by the parasite Cryptosporidium parvum, which as late as 1976 was not known to cause disease in humans. Until 1993, when over 400,000 people in Milwaukee, Wisconsin, became ill with diarrhea after drinking water conta minated with the parasite, few people had heard of either cryptosporidiosis or the single-celled intestinal protozoon that causes it. Since the Milwaukee outbreak, concern about the safety of drinking water in the United States has increased, and new attention has been focused on determining and reducing the risk for cryptosporidiosis from community and municipal water supplies. How is cryptosporidiosis spread? Cryptosporidiosis is spread by putting something in the mouth that has been contaminated with the stool of an infected person or animal. In this way, people swallow the Cryptosporidium parasite, which is too small to be seen with the naked eye. A person c an become infected by drinking contaminated water or eating raw or undercooked food contaminated with Cryptosporidium oocysts (an egg-like form of the parasite that is the infectious stage); direct contact with the droppings of infected animals or stool o f infected humans; or hand-to-mouth transfer of oocysts from surfaces that may have become contaminated with microscopic amounts of stool from an infected person or animal. What are the symptoms of cryptosporidiosis? Two to ten days after infection by the parasite, symptoms may appear. Although some persons may not have symptoms, others have watery diarrhea, headache, abdominal cramps, nausea, vomiting, and low-grade fever. These symptoms may lead to weight loss and d ehydration. In otherwise healthy persons, these symptoms usually last 1 to 2 weeks, at which time the immune system is able to stop the infection. In persons with suppressed immune systems, such as persons who have AIDS or recently have had an organ or bone marrow tr ansplant, the infection may continue and become life-threatening. What should you do if you suspect that you have cryptosporidiosis? See your physician. Since the routine stool examination used for most parasites usually fails to detect Cryptosporidium, a stool specimen should be examined using stains/tests available especially for this parasite. It is important for persons with a poor ly functioning immune system to seek medical attention early in the course of their disease. What is the treatment for cryptosporidiosis? No safe and effective cure is available for cryptosporidiosis. People who have normal immune systems improve without taking antibiotic or antiparasitic medications. The treatment recommended for this diarrheal illness is to drink plenty of fluids and to get extra rest. Physicians may prescribe medication to slow the diarrhea during recovery. Who is at risk? Persons at increased risk for cryptosporidiosis include child care workers; diaper-aged children who attend child care centers; persons exposed to human feces by sexual contact; and caregivers who might come in direct contact with feces while caring for a person infected with cryptosporidiosis at home or in a medical facility. Once infected, persons with suppressed immune systems, such as cancer chemotherapy patients, are at risk for severe disease. How can you prevent cryptosporidiosis? Avoid water or food that may be contaminated. Wash hands after using the toilet and before handling food. If you work in a child care center where you change diapers, be sure to wash your hands thoroughly with plenty of soap and warm water after every diaper change, even if you wear gloves. During communitywide outbreaks caused by contaminated drinking water, boil drinking water for 1 minute to kill the Cryptosporidium parasite. Allow water to cool before drinking it. HIV-infected persons should avoid drinking water directly from lakes or rivers; avoid unpasteurized milk or milk products; avoid exposure to calves and lambs and places where these animals are raised; wash hands after contact with pets; and wash hands aft er gardening or other contact with soil. Because any sexual activity that brings a person in contact with the feces of an infected partner greatly increases the risk for cryptosporidiosis, HIV-infected persons and AIDS patients should follow safer sex gui delines and avoid sexual practices that may result in contact with feces. If you are a caregiver of cryptosporidiosis patients, wash hands after bathing patients, emptying bedpans, changing soiled linen, or otherwise coming in contact with the stools of patients. If you have cryptosporidiosis, wash your hands often to prevent spreading the disease to other members of your household. For more information on cryptosporidiosis, see the following sources: Cordell RL, Addiss DG. Cryptosporidiosis in child care settings: a review of the literature and recommendations for prevention and control. Pediatr Infect Dis J. 1994;13(4):310-7. Dubey JP, Speer CA, Fayer R. Cryptosporidiosis of man and animals. Boston: CRC Press, 1990. LeChevallier MW, Norton WD, Lee RG. Giardia and Cryptosporidium spp. in filtered drinking water supplies. Appl Environ Microbiol 1991;57(9):2617-21. MacKenzie WR, Hoxie NJ, Proctor ME, Gradus MS, Blair KA, Peterson DE, Kazmierczak JJ, Addiss DG, Fox KR, Rose JB, Davis JP. A massive outbreak in Milwaukee of Cryptosporidium infection transmitted through the filtered public water supply. N Engl J Med 199 4; 331:161-7. Rose JB, Gerba CP, and Jakubowski W. Survey of potable water supplies for Cryptosporidium and Giardia. Environmental Science and Technology 1991;25(8):1393-1400. Smith PD, Quinn TC, Strober W, Janoff EN, Masur H. Gastrointestinal infections in AIDS. Ann Intern Med 1992;116:63-77. Centers for Disease Control and Prevention National Center for Infectious Diseases Division of Parasitic Diseases June 1995 =============== Back-country water treatment to prevent giardiasis. Jerry E. Ongerth, PhD, PE, Ron L. Johnson, Steven C Macdonald, MPH, Floyd Frost, PhD, and Henry H. Stibbs, PhD American Journal of Public Health December 1989, Vol 79, No 12, pp 1633-1637. Copyright 1989 AJPH 0090-0036/89$1.50 [used without permission] Abstract This study was conducted to provide current information on the effectiveness of water treatment chemicals and filters for control of Giardia cysts in areas where treated water is not available. Four filters and seven chemical treatments were evaluated fo r both clear and turbid water at 10C. Three contact disinfection devices were also tested for cyst inactivation. Filters were tested with 1-liter volumes of water seeded with 3x10^4 cysts of G. lamblia produced in gerbils inoculated with in vitro cultur ed trophozoites; the entire volume of filtrate was examined for cyst passage. Chemical treatments were evaluated at concentrations specified by the manufacturer and for contact times that might be expected of hikers (30 minutes) and campers (eight hours, i.e., overnight). Two of the four filter devices tested were 100 percent effective for Giardia cyst removal. Of the other two filters, one was 90 percent effective and the other considerably less effective. Among the seven disinfection treatments, the iodine-based chemicals were all significantly more effective than the chlorine-based chemicals. None of the chemical treatments achieved 99.9 percent cyst inactivation with only 30-minute contact. After an eight-hour contact each of the iodine but none of the chlorine preparations achieved at least 99.9 percent cyst inactivation. None of the contact disinfection devices provided appreciable cyst inactivation. Heating water to at least 70C for 10 minutes was an acceptable alternative treatment. -------------------------------------------------------------------------------- Introduction Giardia lamblia is the most commonly identified human intestinal parasite in the United States. Giardiasis is commonly transmitted between humans, especially among small children. lt is also transmitted in water, particularly in the mountainous regions of the U.S. Since 1965, over 80 waterborne outbreaks of giardiasis have occurred in community water systems, affecting more than 20,000 persons (1). Giardiasis in hikers and campers has also been documented (2,3); indeed, it is commonly considered a bac kpackers' illness. Giardia cysts in concentrations as high as four per gallon have been detected in untreated surface water in northeastern and western states (4). Concern over waterborne transmission of Giardia has led to development of a variety of chemical disinfectants and portable filters for individual use in the backcountry. Although some information on such methods has been reported (2,5,6), there is no com prehensive guide to their reliability in actually removing or inactivating Giardia cysts. We tested four commercially available portable filters and one contact disinfection device for their ability to remove Giardia cysts from water. We also evaluated the cysticidal effectiveness of seven chemical disinfectants and three contact disinfection devices. -------------------------------------------------------------------------------- Methods Cysts of G. lamblia were prepared for use in both the filtration and disinfection tests by propagation in gerbils inoculated with trophozoites from sterile culture. Trophozoites were of two isolates: one from a beaver (Be-4 isolate from Alberta) and one from a human (H-2 CSU isolate from Colorado). Cysts were concentrated from crushed, filtered gerbil feces by flotation on zinc sulfate (sp. gr. 1.18), cleaned, and stored in distilled water at 4C for up to 10 days before use. Similarly, G. muris cysts o f an isolate originally obtained from hamsters (7) were purified from feces of infected athymic (nu/nu) mice and stored before use. Cyst concentrations were determined with a Coulter Counter (Model ZBI, Coulter Electronics, Hialeah, FL) and a haemacytome ter. Except where noted, cysts were added to water samples in concentrations of about 3x10^4/ml. Cyst viability was assayed by fluorogenic staining (8) and in vitro excystation (7). In the former method, live cysts are distinguished by two fluorescing dyes. One dye is fluorescein diacetate (FDA), which when absorbed by cysts produces a fluorescent green only in live cysts; the second dye, either propidium iodide (Pl) or ethidium bromide (EB), is excluded efficiently by live cysts but absorbed by dead cysts, resulting in red fluorescence. Filter testing The following backpacker-type water filters were purchased from local retailers: First Need Water Purification Device (First Need), General Ecology Inc., Lionville, PA; { H2OK Portable Drinking Water Treatment Unit Model No. 6 (H2OK), Better Living Laboratories Inc., Memphis, TN; [potential errata: This firm maybe be defunct. Awaiting confirmation.] } Katadyn Pocket Filter (Katadyn), Katadyn Products Inc., Wallisellen, Switzerland; and Pocket Purifier, Calco Ltd, Rosemont, IL. Also noted in this category is the Water Tech Water Purifier (Water Purifier), Water Technologies Corp ., Ann Arbor, Ml. Although it is not advertised as a filter and was not specifically tested for Giardia cyst removal, we report qualitative observations made during disinfection testing (see below) because its configuration and mode of operation suggest that particle removal may occur. Physical and operating information provided in the filter packaging is summarized in Appendix A. Each device was tested when it was new. Devices that removed all cysts when new were retested after a period of use approx imating several months for a regular weekend user. Each filter was prepared for testing by filtering four liters of tap water to purge loose carbon particles or debris. The cyst removal performance of each filter was determined by filtering one liter of spring water, turbidity of 0.1 NTU, to which formal in-fixed G. lamblia cysts had been added. The entire filtrate volume was passed through a 25-mm dia., 5-um pore size, polycarbonate membrane (Nuclepore, Pleasanton, CA), stained with EB (100 ug/ml), and mounted under a cover slip. Cysts were counted at x250 magnification with the aid of epifluorescence microscopy. A representative portion of each filter was examined to quantify cyst recovery as described previously (9). The area examined was inversely proportional to the number of cysts found and ran ged from 3.5 percent of seeded positive control filters to 25 percent (one quadrant) of filters with cyst densities less than one per field. Total numbers of cysts present were estimated by extrapolation in direct proportion to the area examined. In ext ensive work on recovery of Giardia cysts using the procedures described above, cyst retention on the 5-um polycarbonate membrane in a single filtration step has routinely averaged 80 to 90 percent (Ongerth JE: unpublished). Accordingly, the ability to id entify high levels of cyst removal, which would result in passage of very few or no cysts, is excellent. This ability is unaffected by the factors that contribute to lack of precision in counting large numbers of cysts on filters; such inaccuracies usual ly occur when only small representative subareas are examined and the total numbers are estimated by extrapolation. A seeded positive control and an unseeded negative control were processed with each batch of filter evaluations. The cyst removal perform ance evaluation was replicated three times for each filter device, with results expressed as the arithmetic average and corresponding standard deviation. Contact Disinfection Testing The Water Purifier is described in packaging information as a contact disinfection device. Likewise, the {H2OK and} Pocket Purifier devices are described as providing disinfection as well as removing cysts by filtration. These devices were therefore teste d for their effect on cyst viability in addition to filtration efficiency. A single 500-ml sample for each device was seeded with approximately 2.5 x 10^4 cysts and passed through the device. Filtrate was collected and filtered as described above to rec over cysts. The viability of cysts was then assessed by FDA and EB staining as described below. Disinfectant Testing The cysticidal effects of seven commercially available and commonly used disinfectant preparations were tested with identical procedures. Four of the products were iodine based: Polar Pure Water Disinfectant (Polar Pure), Polar Equipment, Saratoga, CA; Coghlan's Emergency Germicidal Drinking Water Tablets (CEGDWT). Coghlan's Ltd, Winnipeg. Canada; Potable Aqua Drinking Water Germicidal Tablets (Potable Aqua), Wisconsin Pharmacal Inc., Jackson, WI; and 2 percent iodine prepared from I2 reagent grade (Baker, Phillipsburg, NJ). The remaining three products were chlorine-based: Sierra Water Purifier (Sierra), 4 in 1 Water Co., Santa Fe, NM; Halazone, Abbott Laboratories, North Chicago, IL; and commercial liquid bleach (5.25 percent sodium hypochlorite). Disinfectant solutions were characterized by pH and total halogen concentration (Appendix B), the latter being determined colorimetrically using the DPD method. Two water sources were used, one to reflect clear high-mountain conditions, the other to reflect downstream, more turbid conditions. Water sources were characterized by pH, turbidity, and free chlorine demand (Appendix C). The upstream source was from a small, spring-fed tributary to the Snoqualmie River near North Bend, Washington. Samples were taken from the stream approximately 50 yards downstream from the spring. The downstream source was the discharge from Lake Washington in Seattle, Washington. Samples were taken in midstream at the entrance to Portage Bay, adjacent to the University of Washington campus. Water samples were prepared for testing by adding disinfectant, according to manufacturers' instructions, to one liter of water in stoppered glass bottles (Appendix B). Cysticidal properties of the chemical treatments were determined as follows: 1) Water was put in 50-ml disposable plastic centrifuge tubes and placed in a 10C incubator. 2) G. lamblia cysts were added to each test sample at time zero. 3) Tubes were vortex-mixed, sampled, and returned to the incubator. 4) At each sampling time, i.e., time 0, 30 minutes and 8 hours, a 10-ml sample was withdrawn; a portion was used for measuring disinfectant concentration, and in the remainder the disinfectant was quenched with 0.1-mM sodium thiosulphate. 5) Cysts in the quenched sample portion were exposed to aqueous solutions of the viability indicators, FDA (25 ug/ml) and EH (100 ug/ml), filtered on to a 13-mm dia. 5-um pore-size filter membrane, and rinsed with distilled water (10 ml). 6) Filters were mounted on glass slides, sealed under coverslips and examined by epifluorescence microscopy at x250 magnification (Model 16, Carl Zeiss, Inc., Thornwood, NY) to enumerate proportions of red and green fluorescing cysts indicating dead and l ive status, respectively. The viability baseline of the cysts was established by running a control sample of untreated water seeded with cysts through each test, using procedures identical to those for disinfectant- treated samples. Data are presented i n terms of percent survival relative to the controls (Figure 2). The effectiveness of each disinfectant for killing cysts in both upstream and downstream water was determined in triplicate, with results expressed as the arithmetic average and correspondi ng standard deviation. The Water Tech Water Purifier, a contact disinfectant, was also tested as a chemical disinfectant. The test water was 100 ml of spring-source water seeded with Giardia cysts. The treated water was filtered, stained, and examined for cyst viability as de scribed in steps 5 and 6 above. Three replicates were assayed. Heat Inactivation Inactivation of G. lamblia and G. muris cysts by heating was established as follows. Cysts were added to distilled water in 15-ml glass test tubes. The seeded tubes were incubated for 10 minutes at temperatures ranging from 10C to 70C. Afterwards, cyst suspensions were cooled immediately by swirling in 10C water for one minute. Cyst viability was determined either by excystation or by staining. If by the latter, FDA and EB were added to the samples, the tubes were vortex-mixed, and a 1-ml aliquot was filtered through a 13-mm dia. 5-um pore-size filter membrane. Filters were rinsed, mounted, and examined as described above to enumerate the live and dead cysts. -------------------------------------------------------------------------------- Results Filter Device Tests The four filters differed significantly in their ability to remove Giardia cysts (Figure 1). The number of cysts recovered from water having passed through the filter devices ranged from zero to greater than 10^4 in individual tests. The performance of individual devices was consistent as indicated by the standard deviations for each of the three replicate test sets (Figure 1). The percentage of cysts removed by the devices, corresponding to 100 minus the percent of cysts recovered from the filtrate, w as 100 percent for the First Need and Katadyn filters and approximately 90 percent for the {H2OK filter}. The concentration of cysts in the Pocket Purifier effluent was not statistically different from the seed concentration. The First Need and Katadyn filters were then subjected to a period of moderate use and then retested. The volume of water processed during the simulated use period was not the same for the two filters owing to differences in their operation. The differe nce in volume had no apparent effect on performance of the two filters. A total of 88 liters of tap water (turbidity of 0.3 NTU) was filtered with the First Need. During the process it was back-flushed, as recommended in package instructions, because th e filtration rate decreased after 50, 71, and 75 liters had been filtered. After 88 liters had been processed, the filtration rate was about 25 percent lower than when the filter was new, and it was retested in that condition. The Katadyn filter was sub jected to use by filtering one liter of tap water four times a day for five days. At the end of each day, the filter was cleaned according to package instructions by disassembling, brushing the filter element, and allowing it to air-dry overnight before reassembly. After the respective periods of use, these two filters were tested in triplicate for efficiency of cyst removal. Performance of these filters was the same, 100 percent cyst removal, when they were retested. Cyst Inactivation Contact Disinfection Devices - The effect of each of the contact disinfection devices on G. lamblia cyst viability was limited. The Water Purifier inactivated about 15 percent of the cysts added in 100 ml of upstream (low turbidity) water; {the H2OK filter inactivated about 5 percent of the cyst challenge,} and the Pocket Purifier inactivated about 2 percent of the cyst challenge. Chemical Disinfectants - The effectiveness of seven disinfecting chemical preparations ranged from only a few percent to greater than 99.9 percent, depending on the chemical and its concentration, the contact time, and the disinfectant demand of the water (Figure 2). None of the disinfectants was more than 90 percent effective after a contact time of 30 minutes. After eight-hour contact, the four iodine-based disinfectants, each caused a greater than 99.9 percent reduction in viable cysts. The chlorine -based disinfectants were clearly less effective than the iodine-based ones at both contact times. Heating in Water - Experiments conducted with cysts of G. lamblia and of G. muris indicated that the two species have virtually the same sensitivity to inactivation by heating. Cysts at both species were completely inactivated by heating to 70C for 10 mi nutes. Heating to 50C and 60C for 10 minutes produced 95 and 98 percent inactivation, respectively (Figure 3). -------------------------------------------------------------------------------- Discussion To remove Giardia cysts from water, one must use a filter with sufficiently small pores to trap the cysts and sufficiently large capacity to produce a useful volume of treated water before backwashing or replacement is necessary. Although a number of man ufacturers advertise that their filters remove Giardia cysts, the only previously published account of filter performance was for the Katadyn unit (6). Our filter evaluation study showed that only the First Need and the Katadyn filters removed cysts with at least 99.9 percent effectiveness. Under the same test conditions, {the H2OK filter was approximately 90 percent} effective and the Pocket Purifier was less than 50 percent effective for cyst removal. The analysis of viability for the cysts collected i n the effluent of the Water Purifier, {H2OK,} and Pocket Purifier indicates that passage through the device did not significantly reduce the percentage of viable cysts. The current study showed that none of the chemical treatments could inactivate more than 90 percent of cysts with 30 minutes of contact time at 10C. At both 30 minutes and eight hours of contact time, the iodine-based disinfectants inactivated a higher f raction of cysts than did the chlorine-based products. All methods inactivated a lower percentage of cysts in cloudy or turbid water than in clear water. All disinfectants performed better with eight hours of contact time than with 30 minutes. Only the iodine-based compounds inactivated 99 to 99.9 percent of cysts, within eight hours of contact time for both turbid and clear water. As observed by Jarroll, et al (5), the 2 percent tincture of iodine was less effective than the other iodine preparations with 30 minutes of contact time, but it was as effective as the others at eight hours. Comparison of our results with those of Jarroll, et al (5), is complicated by differences between test conditions used. However, our results generally indicate more stringent requirements for effective inactivation of Giardia cysts. Differences between cyst populations used in the two studies could account for the observed differences, even though both were G. lamblia. Cysts produced in our trophozoite - gerbil sys tem had consistently high intrinsic viability (>80 percent), excysted efficiently when fresh (80 to 90 percent), and have appeared more resistant to halogen disinfectants than reported previously (Ongerth J.E.: unpublished). The results of heat inactivation in our study correspond to previous reports indicating that heating to between 60C and 70C kills Giardia cysts efficiently. In addition, our data illustrate the correspondence between the fluorogenic staining and in vitro excystation procedures for assessing cyst viability. When applied to cysts of the same condition. Staining indicates a slightly higher proportion of viable cysts than does excystation. Overall, however, the two procedures provide comparable informatio n. -------------------------------------------------------------------------------- Figure 1 - Effectiveness of Four Portable Water Filters for Removal of Giardia Cysts from One-Liter Volumes of Water Each containing approximately 3x10^4 Cysts (dotted line). [A bar chart showing the positive and negative controls and results from the fi lters, on a log scale. The First Need and Katadyn results and the negative control were all zero. The Pocket Purifier and the positive control were approximately the same - i.e. the Pocket Purifier did not remove cysts at all. {The H2OK results were somewhat below the positive control, actually -- due to the log scale -- indicating 90% removal.]} Figure 2 - Effect of Time and Disinfectant Concentration of Seven Chemical Disinfectants on Survival of G. lamblia Cysts in Turbid and in Clear Water. [A rather striking bar chart comparing chemical treatments under varying conditions. The chlorine comp ounds were basically ineffective, with no significant effect at 30 minutes; at 8 hours the Sierra was still totally ineffective, the bleach killed about half the cysts, and the Halazone killed 70- 90% of the cysts (better in clear water). The iodine comp ounds were poor at 30 minutes in turbid water (half killed), only a little better at 30 minutes in clear water (70-90% killed, with Potable Aqua the best), but completely effective (100% killed) after 8 hours.] Figure 3 - Inactivation of Giardia Cysts as a Function of Temperature (10-minute exposures) as Indicated by Ethidium Bromide Staining and by in vitro Excystation. [A line chart showing cyst survival at different temperatures. Four combinations of Giardi a species, source, and laboratory technique are shown, but all show approximately the same results. 40C kills no cysts; 50C kills a lot of cysts, 60C kills most cysts, 70C kills all cysts.] -------------------------------------------------------------------------------- Acknowledgements References to commercial products shall not be construed to represent or imply the approval or endorsement by project investigators or sponsors. Grant support was provided in part by the REI Environment Committee which assumes no responsibility for the content of research reported in this manuscript. -------------------------------------------------------------------------------- References (1) Craun GF: Waterborne outbreaks of giardiasis: current status. In: Erlandsen SL, Meyer EA (eds): Giardia and Giardiasis. New York: Plenum Press, 1984; 243- 262. (2) Kahn FH, Visscher BR: Water disinfection in the wilderness. West J Med 1975; 122:450-453. (3) Barbour AG, Nichols CR, Fukushima T: An outbreak of giardiasis in a group of campers. Am J Trop Med Hyg 1980; 25:384-389. (4) Ongerth JE, Butler R, Donner RG, Myrick R, Merry K: Giardia cyst concentrations in river water. In: Advances in Water Treatment and Analysis, Vol 15. Denver: Am Water Works Assoc, 1988; 243-261. (5) Jarroll EL, Bingham AK, Meyer EA: Giardia cyst destruction: effectiveness of six small quantity water disinfection methods. Am J Trop Med Hyg 1980; 29:8-11. (6) Schmidt SD, Meier PG: Evaluation of Giardia cyst removal via portable water filtration devices. J Freshwater Ecol 1984; 2:435-439. (7) Schaefer FW III, Rice EW, Hoff JC: Factors promoting in vitro excystation of Giardia muris cysts. Trans R Soc Trop Med Hyg 1984; 78:795-800. (8) Schupp DG, Erlandsen SL: A new method to determine Giardia cyst viability: correlation of fluorescein diacetate and propidium iodide staining with animal infectivity. Appl Environ Microbiol 1987; 53:704-707. (9) Ongerth JE, Stibbs HH: Identification of Cryptosporidium oocysts in river water. Appl Environ Microbiol 1987; 53:672-676, (10) American Public Health Assoc: Chapter 408E In: Standard Methods for the Examination of Water and Wastewater, 15th ed. Washington, DC: Am Public Health Assoc, 1980; 309-310. -------------------------------------------------------------------------------- Appendix A: Water Filter characteristics Listed by Manufacturers on Packaging or Instruction Insert [Manufacturer column omitted. See text for this information.] Name Filter Type Operating Operating Useful Restrictions Mode Rate Life /Limitations First Need 0.4 um microscreen hand pump 1 pt/min up to 800 A plus absorber pints {H2OK 6 um mesh, 3 in. gravity 1 qt/min 2000 gal A, B activated carbon w/Ag} Katadyn 0.2 um ceramic, hand pump 1 qt/min many years A Pocket Ag-impregnated Filter Pocket 10 um (nominal), halo- mouth - - A Purifier genated resin (38% I), suction Ag-impregnated carbon Water Pur- Polystyrene resin bed gravity - 100 gal A, C ifier (a) (46% I2 as I5) A - Does not desalinate; not for saltwater or brackish water. B - Pretreat with I2 for bacterially contaminated water. C - Not for use with muddy water. (a) Not described as a filter by package information. -------------------------------------------------------------------------------- Appendix B: Characteristics of Disinfectant Preparations [Manufacturer column omitted. See text for this information.] Name Active Chemical Recommended Application Total Halogen pH Concentration (b) (a), (mg/liter) Polar Pure Crystalline iodine, 1-7 capfuls per quart 2.4 (1 6.1 99.5% depending on temperature cap/quart) CEGDWT Tetraglycine hydro- 1 tablet per liter or 4.5 (1 5.6 periodate 16.7% (6.68% quart tab/quart) titrable iodine) Potable Tetraglycine hydro- 1 tablet per liter or 5.3 (1 5.6 Aqua periodate 16.7% (6.68% quart tab/quart) titrable iodine) 2% Iodine Iodine 0.4 ml per liter 4.5 6.5 Sierra Calcium hypochlorite & 100 crystals (50 mg) 11.6 6.7 hydrogen peroxide Ca(OCl)2 + 6 drops H2O2 per gallon Halazone p-dichloro-sulfamoyl 5 tablets per quart 7.5 6.7 benzoic acid, 2.87% Chlorine sodium hypo-chlorite, 5 ml per gallon 3.9 7.1 bleach 5.25% (a) As prepared according to package instructions. (b) In water treated according to package instructions. -------------------------------------------------------------------------------- Appendix C: Characteristics of Disinfectant Test Water Source pH Turbidity (NTU) Chlorine Demand (a) (mg.liter) Spring-fed 6.8 0.09 0.3 Lake Washington 7.1 0.75 - 0.80 0.7 (a) 30 minutes, free chlorine demand (5). -------------------------------------------------------------------------------- The authors Address reprint requests to Jerry E. Ongerth, PhD, PE, Assistant professor, Department of Environmental Health, SB-75, University of Washington, School of Public Health and Community Medicine, Seattle, WA 98195. Dr. Stibbs is with the Department of Patho biology, also at the School, and Mr. Macdonald is with the Department of Medical Education, School of Medicine, both at the University of Washington; Mr. Johnson is with the Department of Biological Chemistry, Johns Hopkins School of Medicine, Baltimore; Dr. Frost is with the Office of Environmental Programs, Department of Social and Health Sciences, Olympia, WA. This paper, submitted to the Journal January 12, 1289, was revised and accepted for publication June 22, 1989. =============== AU XIAO LH; HERD RP TI EPIDEMIOLOGY OF EQUINE CRYPTOSPORIDIUM AND GIARDIA INFECTIONS SO EQUINE VETERINARY JOURNAL. V0026 N1. JAN 1994. pp. 14-17. AB Prevalence and infection patterns of Cryptosporidium and Giardia infections in horses were studied by a direct immunofluorescence staining method. Faecal examinations of 222 horses of different age groups revealed Cryptosporidium infection rates of 15- 31% in 66 foals surveyed in central Ohio, southern Ohio and central Kentucky, USA. Only 1 of 39 weanlings, 0 of 46 yearlings, and 0 of 71 mares were positive. Giardia infection was found in all age groups, although the infection rates for foals were highe r (17-35%). Chronological study of infection in 35 foals showed that foals started to excrete Cryptosporidium oocysts between 4 and 19 weeks and Giardia cysts between 2 and 22 weeks of age. The cumulative infection rates of Cryptosporidium and Giardia in foals were each 71%. Some foals were concurrently infected with both parasites and excretion of oocysts or cysts was intermittent and long-lasting. The longest duration of excretion was 14 weeks for Cryptosporidium and 16 weeks for Giardia. Excretion of C ryptosporidium oocysts stopped before weaning, while excretion of Giardia cysts continued thereafter. Infected foals were considered the major source of Cryptosporidium infection in foals, whereas infected mares were deemed the major source of Giardia inf ection in foals. The high infection rate of Giardia in nursing mares suggested a periparturient relaxation of immunity. The results indicated that Cryptosporidium and Giardia infections are common in horses. AD Reprint: OHIO STATE UNIV,DEPT VET PREVENT MED,1900 COFFEY RD/COLUMBUS//OH/43210. =============== Pointer to CDC Web page on Giardia: http://www.cdc.gov/ncidod/dpd/giardias.htm =============== =============== Pointer to FDA Web page on Giardia: http://vm.cfsan.fda.gov/~mow/preface.html =============== ===== REI Water Filter Chart (also available at http://www.rei.com/) [Sources: REI Product Information Guide on Water Filters, Fall 1997 plus Campmor, SweetWater, and MSR Web pages ] pore field carbon weight pump L/min pumps filter cost size clean? (oz) force flow per L life (micron) (lbs) rate (gal) Pur Pioneer $ 30 .5 no no 8.4 2 1.0 59 20 SwtWtr Walkabout $ 35 .2 yes yes 8.5 ? .7 ? 100 Pur Hiker $ 55 .3 rinse yes 11.0 8 1.5 48 200 SwtWtr Guardian $ 60 .2 yes yes 11.0 2 1.0 60 200 MSR Miniworks $ 65 .3 yes yes 14.3 8.5 .6 100 1000 1st Need Deluxe $ 70 .1 no lots 15.0 6 1.7 45 100 Pur Voyageur $ 70 .3 + I rinse yes 11.5 12 1.3 53 200 Pur Scout $ 80 .3 + I rinse option 12.0 11 1.0 60 200 SwtWtr Guardian+ $ 80 .2 + I yes yes 15.0 3 .9 60 200,90 MSR Waterworks 2 $125 .2 yes yes 16.6 12 .8 76 1000 Pur Explorer $130 .3 + I self option 24.8 5 1.4 43 400 Katadyn Mini $139 .2 yes no 8.2 13 .5 120 1000 Katadyn Combi $185 .2 + I yes yes 29.2 ? 1.2 50 14000,60 Katadyn PF $295 .2 yes no 22.7 20 .7 82 15000 Notes: cost reflects lower of Campmor or REI retail price pore size must be < .3 micron to filter out small bacteria activated carbon can reduce toxic chemicals and heavy metals pumping force can increase considerably as filter clogs output rate can decrease substantially as filter clogs capacity as rated by manufacturer, might not be accurate with silty water First Need clogs more rapidly than Pur Hiker models labeled "+I" use iodine to neutralize viruses and bacteria MSR filters do not include cost of handy stainless steel screen Katadyn Mini requires frequent cleaning because of small size under filter life, numbers after comma indicate iodine longevity only Explorer is self cleaning-- others require disassembly CHANGES IN PROGRESS For room reasons I left off two filters. Its specs are in order: Basic Designs 1.0 absolute, 12 oz., 2, Granular active carbin & ceramic, $.07, 1000, 60 MINUTES!, $40.00, $60.00. Timber Line: 2.0 absolute, 6 oz., 1, Spun Polypro, $.30, 100, 70 Seconds, $? ?.??, $30.00. The filtering times are probably based on a new unit. Some units are easy to clean, one can't be properly, and one can be cleaned on the fly. Lower prices can be found elsewhere than REI. REI charges list mostly. Notes: 1st Need, Timberline, and Basic Designs require iodine to treat bacteria and viruses. Katadyn and MSR require iodine to treat viruses. Only PUR requires no additional iodine. With carbon elements, only MSR, 1st Need, and Basic Designs remove harm ful chemicals. =============== From: alanmalk@netcom.com (Alan Malkiel) Subject: Review-Katadyn Mini Filter Equipment Review - Katadyn Minifilter Specifications: weight 8.2 oz., filters to 0.2 microns, pump force 13 lbs., output 0.5 liters per minute, cost $150. Specifications taken w/o permission from REI catalog. Personal observations: My wife and I used the Katadyn Minifilter on a 4 day backpack trip to Colorado. Most of the trip was just below tree line. It did not rain during this period. As the primary pumper, let me say I possess reasonable upper body str ength. (Prior to the trip I built a wood fence using hand tools and a hand post hole digger.) The first time I used the filter I tossed the intake screen into a fast moving, clear trout stream. The intake settled onto what I thought was a clean rock, and I began pumping. After dozens of strokes without pumping a drop I speculated that the filter was defective. After disassembly and inspection I concluded the metal intake screen had clogged and the ceramic element had a thick "gunk" coating. My "clean" rock was covered with a thin layer of brown algae which plugged the system on the first strok e. Disassembly was quick, requiring a half turn of the outlet spout. The cleaning tool is actually a metal file which scrapes off a layer of ceramic, exposing a fresh surface. The instructions claim 100 cleanings are possible. A measuring device (included ) determines when the remaining ceramic material is worn away. The plugged metal screen was cleaned with a finger nail. Reassembly was equally quick but no effort was made to keep unfiltered water from contaminating the "clean area". For the next attempt, I filled a 2 quart pot and dropped in the intake hose. Contaminated water from the first dozen strokes was discarded. Pumping one quart required an average of 150 strokes. Relative effort was high, requiring a "death grip" on the f ilter body to aim the stream of filtered water into the canteen. Average time to filter a quart was 5 minutes. Averages were computed over the 4 day period, during which time 3 additional cleanings were necessary while filtering 6 to 8 quarts per day. Other observations: The intake screen jumped 2 inches on each stroke and tended to "walk" out of the pot. A clothes pin would have been handy here. Of greater concern was the single drop of unfiltered water leaking from around the pump shaft after ever y 10 to 20 strokes. Holding the pump at the wrong angle would allow this water to drip into the canteen. As a precaution I added Polar Pure iodine at half strength and doubled the waiting period. Finally comment - it took my wife about 10 minutes to pu mp a quart, including rest periods. Conclusion. The Katadyn Minifilter is acceptable only if: A - Filtration is the preferred method of water treatment. B - Weight and small size is critical. C - Intended use is by one or two people, max. Cleaning is necessary after pumping 6 quarts of water with no visible particulates (except for 10 inch trout), bringing the estimated cost to $0.25 per quart. Compare this to less than a penny per quart for Polar Pure. Pumping effort will work up a swea t and preventing unfiltered water from contaminating filtered water is problematic. The unit is mechanically rugged and will probably survive greater abuse than - for example - the First Need. Access to critical parts is very good. Reviewer - Alan Malkiel =============== *A warning about iodine toxicity* (some individuals appear to be susceptible to this, while many are not). %J Animal Health Newsletter %I University College of Veterinary Medicine %D July 1995 %K Canine Giardia, According to "Understanding Nutrition" by Whitney, Hamiltion and Rolfes (a nutrition text book), iodine is "a component of the thyroid hormone thyroxin which helps to regulate growth, development, and metabolic rate." "Excessive intakes of iodine can als o cause an enlargement of the thyroid gland... [and] depressed thyroid activity. this goiterlike condition can be so severe as to block the airways in infants and cause suffocation..." Average consumption in [the U.S.] rose from 150 micrograms per day i n 1960 .. to an all-time high of over 800 micrograms per day in 1974. It has since decline to about 200 to 500..." "The toxic level at which detectable harm results is thought to be over 2,000 micrograms per day for an adult..." Now to the tablets.. . My bottle of "Potable Aqua" (which I carry as a back-up for the broken filter) has a net contents of 0.21 ounces for 50 tablets. Here are the calculations: 0.21 oz/50 tablets ==> 0.0042 oz/tablet = 0.1191 gram/tablet; each tablet is 6.68% Iodi ne, thus 0.0668 * 0.1191 * 1,000,000 = 7,956 micrograms of iodine per tablet. Note that this is PER TABLET. One tablet treats a quart of water. For Giardia control, or if the water is cold or of poor quality, the directions say to use 2 tablets per qu art. (Who doesn't want to control giardia ?!!) The average backpacker should be drinking a gallon a day (varies widely). One gallon treated with iodine at the rate of 1 tablet per quart would contain about 31,800 micrograms of iodine. At the rate of 2 tablets per quart, it would be 63,600 micrograms. These levels exceed the *believed* toxicity level by a mile. This is the reason that prolonged use of iodine isn't recommended, and the reason (in addition to taste/smell) that *I* switched to a fi lter. As for short term use I guess the relevant question is, "How's your thyroid feeling?" Medicine for Mountaineering, 3rd edition: "Ingested iodine is absorbed as iodide, and an average adult requires 150 to 200 micrograms per day. Daily consumption of one to two liters of water disinfected with 8 mg/L of iodine would provide 30 to 80 times that amount, but such quantities would not affect most individuals with normal thyroid function. Almost all patients who have developed iodide goiter after consuming excess iodide have consumed far larger amounts for six months to more than 5 years." > A) What is the effect, if any, of standard, household dish detergent > on Giardia? No effect. > B) What is the effect, if any, on Giardia which has been subjected to > the temperatures of a standard hot water heater for several hours? The FAQ said "Giardia is killed in less than a minute at 176 F (80 C)" and most household hot water heaters are not cranked above 140 F. This is a stupid question. People should not drink hot water-heated water because it often contains high concentrations of lead and/or PVC leached from pipes. The hot water heater question is interesting in one sense, i.e. if you had no other choice and were principally worried about infectious agents, hot tap water would be better than cold. However, that situation is pretty contrived, and it doesn't seem like there are any data to support a recommendation specific to Giardia. > C) How long does Giardia survive on dry plates and utensils which were > rinsed in water that might contain Giardia? Weeks? Months? Years? I don't know-- cysts are quite durable. The answer to the third question is very important-- unfortunately I don't know. Can't Giardia cysts survive on dry plates for months? The final one is, as far as I know, an open question. In sunlight, it would probably be killed in under an hour on a clean, dry surface. On a plate stuffed into a backpack? Who knows? The cysts can survive for years in soil, but that's a different situation. Bill's answers are as complete as any I could provide. Giardia can be killed by household bleach, but not at concentrations you would want to drink. Date: Fri, 20 Mar 1998 10:09:03 -0800 (PST) From: Bill Tuthill <tut@netcom.com> Message-Id: <199803201809.KAA07296@netcom16.netcom.com> To: ad52@columbia.edu, eugene Subject: Re: Summary of revamps Eugene, I've made it easy for you. A) What is the effect of ordinary dish detergent on Giardia? It has no effect. To kill Giardia cysts, you must rinse dishes in an iodine solution, or in hot water above 80 C (176 F). B) What is the effect, if any, on Giardia subjected to the temperatures of a standard hot water heater for several hours? Most household water heaters cannnot heat water above 60 C (140 F), which is not hot enough to kill Giardia. To kill bacteria and viruses, water must be even hotter. Moreover, it is a bad idea to drink hot tap water because it often contains high concentrations of lead and/or PVC leached from pipes. C) How long does Giardia survive on dry plates and utensils rinsed in water that might contain Giardia? This is an open question. In sunlight, Giardia cysts are probably killed in under an hour on a clean, dry surface. On a plate stuffed into a backpack, who knows? Cysts can survive for years in soil, but that's a different situation. [1] Meyer, EA (ed), Giaridasis (1990), Human Parasitic Diseases, Volume 3, Elsevier, Amsterdam [2] Erlandsen, SL, and Meyer, EA (1984), Giardia and Giardiasis, Plenum Press, NY [3] Frame, JD (1984), Amebiasis and Giardiasis. In: Ellner, PD (ed), Infectious Diarrheal Diseases, pp. 117-140, Marcel Dekker, NY Prevalence of Giardia spp. and Cryptosporidium spp. on dairy farms in southeastern New York state. Prev Vet Med. 2003 May 30;59(1-2):1-11. Risk of giardiasis in Aucklanders: a case-control study. Int J Infect Dis. 2002 Sep;6(3):191. A comparative study of the intestinal parasites prevalent among children living in rural and urban settings in and around Chennai. J Commun Dis. 2002 Mar;34(1):35-9. Pathogen survival in swine manure environments and transmission of human enteric illness--a review. J Environ Qual. 2003 Mar-Apr;32(2):383-92. Factors associated with the likelihood of Giardia spp. and Cryptosporidium spp. in soil from dairy farms. J Dairy Sci. 2003 Mar;86(3):784-91. Faecal contamination of greywater and associated microbial risks. Water Res. 2003 Feb;37(3):645-55. Microbial agents associated with waterborne diseases. Crit Rev Microbiol. 2002;28(4):371-409. Review. Giardia in beaver (Castor canadensis) and nutria (Myocastor coypus) from east Texas. J Parasitol. 2002 Dec;88(6):1254-8. ARSENIC references Chwirka, J. D. Removing Arsenic from groundwater Journal of the American Water Works Association v92, no3, pp. 79-88 Focazio M. J. A retrospective analysis of the occurrence of arsenic in ground water resources. USGS Water resources investigation report 99-4279. http://www.yosemite.org/naturenotes/Giardia.htm http://www.journals.uchicago.edu/CID/journal/issues/v34n3/010954/010954.html http://www.latimes.com/travel/outdoors/la-os-giardia26jul26,0,4844133.story http://chppm-www.apgea.army.mil/wpd/CompareDevices.aspx *** Diseases Branch Division of Parasitic Diseases Centers for Disease Control Transmission and Control Introduction During the past fifteen years giardiasis has been recognized as one of the most frequently occurring waterborne diseases in the United States (1). Giardia lamblia have been discovered in the United States in places as far apart as Estes Park, Colorado (ne ar the Continental Divide); Missoula, Montana; Wilkes-Barre, Scranton, and Hazleton, Pennsylvania; and Pittsfield and Lawrence, Massachusetts just to name a few. In light of recent large outbreaks of waterborne giardiasis, it seem timely to present reliab le information on the way in which giardiasis is acquired, treated, and prevented. Giardiasis: Prevalence and Symptoms Giardiasis is a disease caused by a one-celled parasite with the scientific name Giardia lamblia. The disease is characterized by intestinal symptoms that usually last one week or more and may be accompanied by one or more of the following: diarrhea, abdo minal cramps, bloating, flatulence, fatigue, and weight loss (see Table 1). Although vomiting and fever are listed in Table 1 as relatively frequent symptoms, they have been uncommonly reported by people involved in waterborne outbreaks of giardiasis in t he United States. Table 1 also suggests that 13 percent of patients with giardiasis may have blood in their stool. Giardia, however, rarely causes intestinal bleeding. Therefore, blood in the stool of a patient with giardiasis almost always indicates the presence of a second disease. While most Giardia infections persist only for one or two months, some people undergo a more chronic phase, which can follow the acute phase or may become manifest without an antecedent acute illness. The chronic phase is characterized by loose stools, an d increased abdominal gassiness with cramping, flatulence and burping. Fever is not common, but malaise, fatigue, and depression may ensue (2). For a small number of people, the persistence of infection is associated with the development of marked malabso rption and weight loss (3). Similarly, lactose (milk) intolerance can be a problem for some people. This can develop coincidentally with the infection or be aggravated by it, causing an increase in intestinal symptoms after ingestion of milk products. Some people may have several of these symptoms without evidence of diarrhea or have only sporadic episodes of diarrhea every 3 or 4 days. Still others may not have any symptoms at all. Therefore, the problem may not be whether you are infected with the pa rasite or not, but how harmoniously you both can live together, or how to get rid of the parasite (either spontaneously or by treatment) when the harmony does not exist or is lost. Medical Treatment Three drugs are available in the United States to treat giardiasis: quinacrine (Atabrine*), metronidazole (Flagyl*), and furazolidone (Furoxone*). All are prescription drugs. In a recent review of drug trials in which the efficacies of these drugs were co mpared, quinacrine produced a cure in 93% of 129 patients, metronidazole cured 92% of 219, and furazolidone cured 84% of 150 patients (4). Quinacrine is generally the least expensive of the anti-Giardia medications but it often causes vomiting in children younger than 5 years old. Although the treatment of giardiasis is not an FDA-approved indication for metronidazole, the drug is commonly used for this purpose. Furazolidone is the least effective of the three drugs, but is the only anti-Giardia medicatio n that comes as a liquid preparation, which makes it easier to deliver the exact dose to small children and makes it the most convenient dosage form for children who have difficulty taking pills. Cases of chronic giardiasis refractory to repeated courses of therapy have been noted, one of which responded to combined quinacrine and metronidazole treatment (5). (*) Use of trade names is for purposes of identification only. Etiology and Epidemiology Giardiasis occurs worldwide. In the United States, Giardia is the parasite most commonly identified in stool specimens submitted to state laboratories for parasitologic examination. From 1977 through 1979, approximately 4% of 1 million stool specimens sub mitted to state laboratories were positive for Giardia (6). Other surveys have demonstrated Giardia prevalence rates ranging from 1 to 20% depending on the location and ages of persons studied. Giardiasis ranks among the top 20 infectious diseases that ca use the greatest morbidity in Africa, Asia, and Latin America (7); it has been estimated that about 2 million infections occur per year in these regions (8). People who are at highest risk for acquiring a Giardia infection in the United States may be placed into five major categories: 1) People in cities whose drinking water originates from streams or rivers and whose water treatment process does not include filtration, or filtration is ineffective because of malfunctioning equipment. 2) Hikers/campers/outdoorspeople. 3) International travelers 4) Children who attend day-care centers, day-care center staff, and parents and siblings of children infected in day-care centers. 5) Homosexual men. People in categories 1, 2, and 3 have in common the same general source of infections, i.e., they acquire Giardia from fecally contaminated drinking water. The city resident usually becomes infected because the municipal water treatment process does not i nclude a filter that is necessary to physically remove the parasite from the water. The number of people in the United States at risk (i.e., the number who receive municipal drinking water from unfiltered surface water) is estimated to be 20 million. Inte rnational travelers may also acquire the parasite from improperly treated municipal waters in cities or villages in other parts of the world, particularly in developing countries. In Eurasia, only travelers to Leningrad appear to be at increased risk. In prospective studies, 88% of U.S. and 35% of Finnish travelers to Leningrad who had negative stool tests for Giardia on departure to the Soviet Union developed symptoms of giardiasis and had positive tests for Giardia after they returned home (10,11). With the exception of visitors to Leningrad, however, Giardia has not been implicated as a major cause of traveler's diarrhea. The parasite has been detected in fewer than 2% of travelers who develop diarrhea. Hikers and campers risk infection every time they drink untreated raw water from a stream or river. Persons in categories 4 and 5 become exposed through more direct contact with feces of an infected person, e.g., exposure to soiled diapers of an infected child (day-care center-associated cases), or through direct or indirect anal-oral sexual practices i n the case of homosexual men. Although community waterborne outbreaks of giardiasis have received the greatest publicity in the United States during the past decade, about half of the Giardia cases discussed with staff of the Centers for Disease Control in the past 2 to 3 years have a day-care center exposure as the most likely source of infection. Numerous outbreaks of Giardia in day-care centers have been reported in recent years. Infection rates for children in day-care center outbreaks range from 21 to 44% in the United states and from 8 to 27% in Canada (12,13,14,15,16,17). The highest infection rates are usually observed in children who wear diapers (l to 3 years of age). In one study of 18 randomly selected day care centers in Atlanta (CDC unpublished data), 10% of diapered chi ldren were found infected. Transmission from this age group to older children, day-care staff, and household contacts is also common. About 20% of parents caring for an infected child will come infected. It is important that local health officials and managers of water utility companies realize that sources of Giardia infection other than municipal drinking water exist. Armed with this knowledge, they are less likely to make a quick (and sometimes wrong) assumption that a cluster of recently diagnosed cases in a city is related to municipal drinking water. Of course, drinking water must not be ruled out as a source of infection when a larger than expected number of cases are recognized in a community, but the possibility that the cases are associated with a day-care center outbreak, drinking untreated stream water, or international travel should also be entertained. Parasite Biology To understand the finer aspects of Giardia transmission and the strategies for control, one must become familiar with several aspects of the parasite's biology. Two forms of the parasite exist: a trophozoite and a cyst, both of which are much larger than bacteria (see Figure 1). Trophozoites live in the upper small intestine where they attach to the intestinal wall by means of a disc-shaped suction pad on their ventral surface. Trophozoites actively feed and reproduce at this location. At some time during the trophozoite's life, it releases its hold on the bowel wall and floats in the fecal stream through the intestine. As it makes this journey, it undergoes a morphologic transformation into an egglike structure called a cyst. The cyst, which is about 6 t o 9 micrometers in diameter x 8 to 12 micrometers (1/100 millimeter) in length, has a thick exterior wall that protects the parasite against the harsh elements that it will encounter outside the body. This cyst form of the parasite is infectious for other people or animals. Most people become infected either directly by hand-to-mouth transfer of cysts from the feces of an infected individual, or indirectly by drinking feces-contaminated water. Less common modes of transmission included ingestion of fecall y contaminated food and hand-to-mouth transfer of cysts after touching a fecally contaminated surface. After the cyst is swallowed, the trophozoite is liberated through the action of stomach acid and digestive enzymes and becomes established in the small intestine. Although infection after the ingestion of only one Giardia cyst is theoretically possible, the minimum number of cysts shown to infect a human under experimental conditions is ten (18). Trophozoites divide by binary fission about every 12 hours. What this means in practical terms that if a person swallowed only a single cyst, reproduction at this rate would result in more than 1 million parasites 10 days later, and 1 billion parasites by day 15. The exact mechanism by which Giardia causes illness is not yet well understood, but is not necessarily related to the number of organisms present. Nearly all of the symptoms, however, are related to dysfunction of the gastrointestinal tract. The parasite rarely invades other parts of the body, such as the gall bladder or pancreatic ducts. Intestinal infection does not result in permanent damage. Transmission Data reported to the CDC indicate that Giardia is the most frequently identified cause of diarrheal outbreaks associated with drinking water in the United States. The remainder of this article will be devoted to waterborne transmission of Giardia. Waterbo rne epidemics of giardiasis are a relatively frequent occurrence. In 1983, for example, Giardia was identified as the cause of diarrhea in 68% of waterborne outbreaks in which the causal agent was identified (19). From 1965 to 1982, more than 50 waterborn e outbreaks were reported (20). In 1984, about 250,000 people in Pennsylvania were advised to boil drinking water for 6 months because of Giardia-contaminated water. Many of the municipal waterborne outbreaks of Giardia have been subjected to intense stud y to determine their cause. Several general conclusions can be made from data obtained in those studies. Waterborne transmission of Giardia in the United States usually occurs in mountainous regions where community drinking water is obtained from clear ru nning streams, is chlorinated but is not filtered before distribution. Although mountain streams appear to be clean, fecal contamination upstream by human residents or visitors, as well as by Giardia-infected animals such as beavers, has been well documen ted. It is worth emphasizing that water obtained from deep wells is an unlikely source of Giardia because of the natural filtration of water as it percolates through the soil to reach underground cisterns. Well-water sources that pose the greatest risk of fecal contamination are those that are poorly constructed or improperly located. A few outbreaks have occurred in towns that included filtration in the water treatment process, but the filtration was not effective in removing Giardia cysts because of def ects in filter construction, poor maintenance of the filter media, or inadequate pretreatment of the water before it was filtered. Occasional outbreaks have also occurred because of accidental cross-connections between water and sewerage systems. One can conclude from these data that two major ingredients are necessary for waterborne outbreak. First, there must be Giardia cysts in untreated source water and, second, the water purification process must either fail to kill or fail to remove Giardia cysts from the water. Although beavers are often blamed for contaminating water with Giardia cysts, it seems unlikely that they are responsible for introducing the parasite into new areas. It is far more likely that they are also victims: Giardia cysts may be carried in untrea ted human sewage discharged into the water by small-town sewage disposal plants or originate from cabin toilets that drain directly into streams and rivers. Backpackers, campers, and sports enthusiasts may also deposit Giardia-contaminated feces in the en vironment that are subsequently washed into streams by rain. In support of this concept is a growing amount of data that indicate a higher Giardia infection rate in beavers living downstream from U.S. National Forest campgrounds compared with a near zero rate of infection in beavers living in more remote areas. Although beavers may be unwitting victims in the Giardia story, they still play an important part in the transmission scheme, because they can (and probably do) serve as amplifying hosts. An amplifying host is one that is easy to infect, serves as a good habitat for the parasite to reproduce, and, in the case of Giardia, returns millions of cysts to the water for every one ingested. Beavers are especially important in this regard because they tend to defecate in or very near the water, which ensures that most of the Giardia cysts excreted are returned to the water The contribution of other animals to waterborne outbreaks of Giardia is less clear. Muskrats (another semiaquatic animal) have been found in several parts of the United States to have high infection rates (30 to 40%) (2l). Recent studies have shown that m uskrats can be infected with Giardia cysts obtained from humans and beavers. Occasional Giardia infections have been reported in coyotes, deer, elk, cattle, dogs, and cats, but not in horses and sheep, encountered in mountainous regions of the United Stat es. Naturally occurring Giardia infections have not been found in most other wild animals (bear, nutria, rabbit, squirrel, badger, marmot, skunk, ferret, porcupine, mink, raccoon, river otter, bobcat, lynx, moose, bighorn sheep) (22). Removal from Municipal Water Supplies During the past 10 years, scientific knowledge about what is required to kill or remove Giardia cysts from a contaminated water supply has increased considerably. For example, it is known that cysts can survive in cold water (4 deg C) for at least 2 month s and that they are killed instantaneously by boiling water (100 deg C) (23,24). It is not known how long the cysts will remain viable at other water temperatures (e.g., at 0 deg C or in a canteen at 15-20 deg C), nor is it known how long the parasite wil l survive on various environment surfaces, e.g., under a pine tree, in the sun, on a diaper-changing table, or in carpets in a day-care center. The effect of chemical disinfection, such as chlorine, on the viability of Giardia cysts is an even more complex issue. It is clear from the number of waterborne outbreaks of Giardia that have occurred in communities where chlorine was employed as a disin fectant that the amount of chlorine used routinely for municipal water treatment is not effective against Giardia cysts. These observations have been confirmed in the laboratory under experimental conditions (25,26,27). This does not mean, however, that c hlorine does not work at all. It does work under certain favorable conditions. Without getting too technical, one can gain some appreciation of the problem by understanding a few of the variables that influence the efficacy of chlorine as a disinfectant. 1) Water pH: at pH values above 7.5, the disinfectant capability of chlorine is greatly reduced. 2) Water temperature: the warmer the water, the higher the efficacy. Thus, chlorine does not work well in ice-cold water from mountain streams. 3) O rganic content of the water: mud, decayed vegetation, or other suspended organic debris in water chemically combines with chlorine making it unavailable as a disinfectant. 4) Chlorine contact time: the longer Giardia cysts are exposed to chlorine , the more likely it is that the chemical will kill them. 5) Chlorine concentration: the higher the chlorine concentration, the more likely chlorine will kill Giardia cysts. Most water treatment facilities try to add enough chlorine to give a free ( unbound) chlorine residual at the customer tap of 0.5 mg per liter of water. The five variables above are so closely interrelated that an unfavorable occurrence in one can often be compensated for by improving another. For example, if chlorine efficacy is expected to be low because water is obtained from an icy stream, either the chlorine contact time or chlorine concentration, or both could be increased. In the case of Giardia-contaminated water, it might be possible to produce safe drinking water with a chlorine concentration of 1 mg per liter and a contact time as short as 10 m inutes if all the other variables were optimal (i.e., pH of 7.0, water temperature of 25 deg C, and a total organic content of the water close to zero). On the other hand, if all of these variables were unfavorable (i.e., pH of 7.9, water temperature of 5 deg C, and high organic content), chlorine concentrations in excess of 8 mg per liter with several hours of contact time may not be consistently effective. Because water conditions and water treatment plant operations (especially those related to water r etention time and, therefore, to chlorine contact time) vary considerably in different parts of the United States, neither the U.S. Environmental Protection Agency nor the CDC has been able to identify a chlorine concentration that would be safe yet effec tive against Giardia cysts under all water conditions. Therefore, the use of chlorine as a preventive measure against waterborne giardiasis generally has been used under outbreak conditions when the amount of chlorine and contact time have been tailored t o fit specific water conditions and the existing operational design of the water utility. In an outbreak, for example, the local health department and water utility may issue an advisory to boil water, may increase the chlorine residual at the consumer's tap from 0.5 mg per liter to 1 or 2 mg per liter, and, if the physical layout and operatio n of the water treatment facility permit, increase the chlorine contact time. These are emergency procedures intended to reduce the risk of transmission until a filtration device can be installed or repaired or until an alternative source of safe water, s uch as a well, can be made operational. The long-term solution to the problem of municipal waterborne outbreaks of giardiasis will involve improvements in and more widespread use of filters in the municipal water treatment process. The sand filters most commonly used in municipal water treatmen t today cost millions of dollars to install, which makes them unattractive for many small communities. Moreover, the pore sizes in these filters are not sufficiently small to remove a Giardia (6 to 9 micrometers x 8 to 12 micrometers). For the sand filter to remove Giardia cysts from the water effectively, the water must receive some additional treatment before it reaches the filter. In addition, the flow of water through the filter bed must be carefully regulated. An ideal prefilter treatment for muddy water would include sedimentation (a holding pond where the large suspended particles are allowed to settle out by the action of gravity) followed by flocculation or coagulation (the addition of chemicals such as alu m or ammonium to cause microscopic particles to clump together). The large particles resulting from the flocculation/coagulation process, including Giardia cysts bound to other microparticulates, are easily removed by the sand filter. Chlorine is then add ed to kill the bacteria and viruses that may escape the filtration process. If the water comes from a relatively clear source, chlorine may be added to the water before it reaches the filter. The point here is that successful operation of a complete water treatment facility is a complex process that requires considerable training. Troubleshooting breakdowns or recognizing potential problems in the system before they occur often requires the skills of an engineer. Unfortunately, most small water utilities that have a water treatment facility that includes filtration cannot afford the services of a full-time engineer. Filter operation or maintenance problems in such systems may not be detected until a Giardia outbreak is recognized in the community. The bot tom line is that although, in reference to municipal systems, water filtration is the best that water treatment technology has to offer against waterborne giardiasis, it is not infallible. For municipal water filtration facilities to work properly, they m ust be properly constructed, operated, and maintained. Water Disinfection in the Out-of-Doors Whenever possible, persons in the out-of-doors should carry drinking water of known purity with them. When this is not practical, and water from streams, lakes, ponds, and other outdoor sources must be used, time should be taken to disinfect the water bef ore drinking it. Boiling Boiling water is one of the simplest and most effective ways to purify water. Boiling for 1 minute is adequate to kill Giardia as well as most other bacterial or viral pathogens likely to be acquired from drinking polluted water. Chemical Disinfection Disinfection of water with chlorine or iodine is considered less reliable than boiling for killing Giardia. However, it is recognized that boiling drinking water is not practical under many circumstances. Therefore, when one cannot boil drinking water, chemical disinfectants such as iodine or chlorine should be used. This will provide some protection against Giardia and will destroy most bacteria and viruses that cause illness. Iodine or chlorine concentrations of 8 mg/liter (8ppm) with a minimum contact time of 30 minutes are recommended. If the water is cold (less than 10 deg C or 5O deg F) we suggest a minimum contact time of 60 minutes. If you have a choice of disinfectants, use iodine. Iodine's disinfectant activity is less likely to be reduced by un favorable water conditions, such as dissolved organic material in water or by water with a high pH, than chlorine. Below are instructions for disinfecting water using household tincture of iodine or chlorine bleach. If water is visibly dirty, it should first be strained through a clean cloth into a container to remove any sediment or floating matter. Then the water sh ould be treated with chemicals as follows: IODINE Tincture of iodine from the medicine chest or first aid kit can be used to treat water. Mix thoroughly by stirring or shaking water in container and let stand for 30 minutes. Tincture of Iodine Drops* to be Added per Quart or Liter Clear Water Cold or Cloudy Water** 2% 5 10 * 1 drop = 0.05ml ** Very turbid or very cold water may require prolonged contact time; let stand up to several hours or even overnight. CHLORINE Liquid chlorine bleach used for washing clothes usually has 4% to 6% available chlorine. The label should be read to find the percentage of chlorine in the solution and the treatment schedule below should be followed. Drops* to be Added per Quart or Liter Available Chlorine Clear Water Cold or Cloudy Water** 1% 10 20 4% to 6% 2 4 7% to lO% 1 2 Unknown 10 20 * 1 drop = 0.05ml ** Very turbid or very cold water may require prolonged contact time; let stand up to several hours or even overnight. Mix thoroughly by stirring or shaking water in container and let stand for 30 minutes. A slight chlorine odor should be detectable in the water; if not, repeat the dosage and let stand for an additional 15 minutes before using. Filters Newcomers in the battle against waterborne giardiasis include a variety of portable filters for field or individual use as well as some household filters. Manufacturers' data accompanying these filters indicate that some can remove particles the size of a Giardia cyst or smaller and may be capable of providing a source of safe drinking water for an individual or family during a waterborne outbreak. Such devices, if carefully selected, might also be useful in preventing giardiasis in international travelers, backpackers, campers, sportsmen, or persons who live or work in areas where water is known to be contaminated. Unfortunately, there are yet few published reports in the scientific literature detailing both the methods used and the results of tests employed to evaluate the efficacy of these filters against Giardia. Until more published experimental data become avai lable, there are a few common sense things that a consumer should look for when selecting a portable or household filter. The first thing to consider is the filter media. Filters relying solely on ordinary or silver-impregnated carbon or charcoal should be avoided, because they are not intended to prevent, destroy, or repel micro-organisms. Their principal use is to remove undesirable chemicals, odors, and very large particles such as rust or dirt. Some filters rely on chemicals such as iodide-impregnated resins to kill Giardia. While properly designed and manufactured iodide-impregnated resin filters have been shown to kill many species of bacteria and virus present in human feces, their efficacy a gainst Giardia cysts is less well-established. The principle under which these filters operate is similar to that achieved by adding the chemical disinfectant iodine to water, except that the micro-organisms in the water pass over the iodide-impregnated d isinfectant as the water flows through the filter. While the disinfectant activity of iodide is not as readily affected as chlorine by water pH or organic content, iodide disinfectant activity is markedly reduced by cold water temperatures. Experiments on Giardia indicate that many of the cysts in cold wa ter (4 deg C) remain viable after passage through filters containing tri-iodide or penta-iodide disinfectants (28). As indicated earlier, longer contact times (compared to those required to kill bacteria) are required when using chemical filters to proces s cold water for Giardia protection. Presently available chemical filters also are not recommended for muddy or very turbid water. Additionally, filters relying solely on chemical action usually give no indication to the user when disinfectant activity ha s been depleted. The so-called microstrainer types of filters are true filters. Manufacturer data accompanying these filters indicate that some have a sufficiently small pore size to physically restrict the passage of some micro-organisms through the filter. The types of filter media employed in microstraining filters include orlon, ceramic, and proprietary materials. Theoretically, a filter having an absolute pore size of less than 6 micrometers might be able to prevent Giardia cysts of 8 to 10 micrometers in diameter fr om passing. However, when used as a water sampling device during community outbreaks, portable filters in the 1- to 3- micrometer range more effectively removed Giardia cysts from raw water than filters with larger pore sizes. For effective removal of bac terial or viral organisms which cause disease in humans, microstraining filters with pore sizes of less than 1 micrometer are advisable. However, the smaller the pores, the more quickly the filters will tend to clog. To obtain maximum filter life, and as a matter of reasonable precaution, the cleanest available water source should always be used. Keep in mind, however, that even sparkling, clear mountain streams can be heavily contaminated. Secondly, because infectious organisms can be concentrated on the filter element/media, it is important to consider whether the filter element can be cleaned or replaced without posing a significant health hazard to the user. Properly engineered portable filters should also minimize the possibility of contaminating the "clean water side" of the filter with contaminated water during replacement or cleaning of the filter element. This is especially important for filters used in the field where they are ofte n rinsed or "cleaned" in a stream or river that may be contaminated. Ongerth (29) recently evaluated four filters (First Need, H20K, Katadyn, the Pockett Purifier) for their ability to remove Giardia cysts from water. Only the First Need and Katadyn filters removed 100% of the cysts. Conclusion In conclusion, during the past fifteen years, giardiasis has been recognized as one of the most frequently occurring waterborne diseases in the United States. The most common sources of water contamination include improperly treated municipal sewage, infe cted animals, and indiscriminate defecation by outdoorsmen. Chlorine concentrations in the 0.1 mg per liter to 0.5 mg per liter range are largely ineffective against Giardia at the contact times commonly employed by municipal water utilities. The long-term solution to the problem of municipal waterborne outbreaks of giardiasis will involve appropriate pretreatment combined with improvements in and more widespread use of filters in the municipal water treatment process. While both micrometer- and submicrom eter-rated filters are being employed on a limited scale for personal or household use, further evaluation of the efficacy of filters distributed by different manufacturers is needed to enable individuals and public health personnel to distinguish those that are safe and effective from those that are not. TABLE I Percentage Number of Patients Symptoms Diarrhea* 84 516 Malaise 80 56 Weakness 72 324 Abdominal cramps 63 412 Weight loss (O.5 - 1 1 kg) 63 412 Greasy, foul smelling stools 59 412 Nausea 57 444 Headaches 53 92 Anorexia 49 156 Abdominal bloating 45 380 Flatulence 41 388 Constipation 25 88 Vomiting 24 488 Fever 22 32 Physical finding Abdomen tender to palpitation 66 92 Laboratory findings Blood Anemia 15 124 Leukocytosis 9 32 Stool Increased mucus 56 32 Increased neutral fats 50 32 Blood 13 156 * Index symptom; may be biased (upward) TABLE 1 - Based on data from Fifty diseases: Fifty Diagnoses, by M.G. Periroth and D.J. Weiland. Year Book Medical Publishers, Inc., Chicago, 1981, pp. 158-159. Reprinted by special arrangement with Year Book Publishers, Inc. References 1. Craun, Gunther T. Waterborne Giardiasis in the United States: A review. American Journal of Public Health 69:817-819, 1979. 2. Weller, Peter F. Intestinal Protozoa: Giardiasis. Scientific American Medicine, 1985 3. Id. 2. 4. Davidson, R.A. Issues in Clinical Parasitology: The treatment of Giardiasis. Am J. Gastroenterol. 79:256-261, 2984 5. Id. 2. 6. Intestinal Parasite Surveillance, Annual Summary 1978, Atlanta, Centers for Disease Control, 1979. 7. Walsh, J.D. Warren K. s. Selective Primary Health Care: An Interim Strategy for Disease Control in developing countries. N. Engl. J. Med., 301:967-974, 1979. 8. Walsh, J.A. Estimating the Burden of Illness in the Tropics, In Tropical and Geographic Medicine, Edited by K.S. Warren and A.F. Mahmoud, McGraw-Hill, New York, 1981, pp 1073-1085. 9. Weniger, B.D., Blaser, MlJ., Gedrose, J., Lippy, E.C., Juranek, D.D. an Outbreak of Waterborne Giardiasis Associated with Heavy Water Runoff due to Warm Weather and Volcanic Ashfall. Am. J. Public Health 78:868-872, 1983. 10. Brodsky, R.E., Spencer, H.C., Schultz, M.G. Giardiasis in American Travelers to the Soviet Union. J. Infect Dis. 130:319-323, 1974. 11. Jokipii, L., Jokipii, A.M.M. Giardiasis in Travelers: A prospective Study. J. Infect. Dis., 130:295-299, 1974. 12. Black, R.E., Dykes, A.C., Anderson, K.E., Wells, J.G., Sinclair, S.P., Gary, G.W., Hatch, M.H., Gnagarosa, E.J. Handwashing to Prevent Diarrhea in Day-Care Centers. Am. J. Epidemiol. 113:445-451, 1981. 13. Pickering, L.K., Woodward, W.E., DuPont, H. L., Sullivan, P. Occurrence of Giardia lamblia in Children in Day Care Centers. J. Pediatr. 104:522-526, 1984. 14. Sealy, D.P., Schuman, S.H. Endemic Giardiasis and Day Care. Pediatrics 72:154-158, 1983. 15. Pickering, L.K., Evans, D.G., DuPont, H.L., Vollet, J.J., III, Evans, D.J., Jr. diarrhea Caused by Shigella, Rotavirus, and Giardia in Day-care Centers: Prospective Study. J. Peidatr., 99:51-56, 1981. 16. Keystone, J.S., Yang, J., Grisdale, D., Harrington, M., Pillow, L., Andreychuk, R. Intestinal Parasites in Metropolitan Toronto Day-Care Centres. Can J. Assoc. J. 131:733-735, 1984. 17. Keystone, J.S., Kraden, S., Warren, M.R. Person-to-Person Transmission of Giardia lamblia in Day-Care Nurseries. Can. Med. Assoc. J. 119:241-242, 247-248, 1978. 18. Rendtorff, R.C. The Experimental Transmission of Human Intestinal Protozoan Parasites. II. Giardia lamblia cysts Given In Capsules, Am. J. Hygiene 59:209-220, 1954. 19. Water-related Disease Outbreaks Surveillance, Annual Summary 1983. Atlanta, Centers for Disease Control, 1984. 20. Craun, G.F. Waterborne Outbreaks of Giardiasis--Current Status in Giardia and Giardiasis, edited by S.L. Erlandsen and E.A Meyer. Pleunu Press. New York, 1984, pp 243-261. 21. Frost, F. Plan, B., Liechty, B. Giardia Prevalence in Commercially Trapped Mammals. J. Environ. Health 42:245-249. 22. Id. 21. 23. Id. 18. 24. Bingham, A.K., Jarroll, E.L., Meyer, E.A. Radulescu, S. Introduction of Giardia Excystation and the effect of Temperature on cyst Viability compared by Eosin-Exclusion and In Vitro Excystation in Waterborne Transmission of Giardiasis. Edit ed by J. Jakubowski and H. C. Hoff, U.S. Environmental Protection Agency, Washington, DC, 1979, pp. 217-229. EPA-600/9-79-001. 25. Jarroll, E.L., Bingham, A.K., Meyer, E.A. Effect of Chlorine on Giardia lamblia Cyst Viability. Appl. Environ. Microbiol. 41:483-487, 1981. 26. Jarroll, E.L., Jr., Bingham, A.K. Meyer, E.A. Inability of an Iodination Method to Destroy completely Giardia Cysts in Cold Water. West J. Med. 132:567-569, 1980. 27. Jarroll, E.L., Jr., Bingham, A.K., Meyer, E.A. Giardia Cyst Destruction: Effectiveness of Six Small-Quantity Water Disinfection Methods. Am. J. Trop. Med. Hygiene 29:8-11, 1980. 28. Marchin, B.L., Fina, L.R., Lambert, J.L., Fina, G.T. Effect of resin disinfectants--13 and --15 on Giardia muris and giardia lamblia. Appl Environ. Microbiol. 46:965-9, 1983. 29. Ongerth JE, Johnson RL, Macdonald SC, Frost F, Stibbs HH. Back-country water treatment to prevent giardiasis. Am J Public Health 1989;79(12):1633-7. -- Looking for an H-912 (container). ------------ And now a word from our sponsor ---------------------- For a quality mail server, try SurgeMail, easy to install, fast, efficient and reliable. 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[l/m 9/30/2009] Water filters & Giardia Distilled Wisdom (9/28) XYZ
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Putin the actual glitz: gorgeous Russian soldiers take centre stage (moreover selfies) At massive wining Day parade of 13,000 troops, Tanks and rockets as Moscow strongman warns the lessons of WW2 'are relevant once again'Vladimir Putin forced to cancel military flypast over Red Square at the last minute over fears of bad weatherThreat of thunder and cloud over Moscow saw the huge Victory Day display of military powergroundedDespite cancellation Russian president pledged to 'guarantee the high drives of our armed forces'By Chris Dyer For Mailonline and Will Stewart In Russia and Afp and Reuters
issued: 10:14 BST, 9 May 2019 recently: 18:10 BST, 9 probably 2019
Russian lead designer Vladimir Putin took a defiant tone at Moscow's annual military Victory Day parade in Red Square, Declaring that the country continues to strengthen its armed forces.
The Kremlin strongman observed on as 13,000 troops and more than 130 pieces of weaponry were paraded through the capital in a show of Russian military power.
discussing his country's battle with Nazi Germany, Putin then warned 'the lessons of the past war are relevant once again' as he made his case for 'guaranteeing the high faculties of our armed forces'.
Russia's ties with the West soured correct its annexation of Crimea from Ukraine in 2014, And Moscow has continued to challenge the nation through its staunch support for Syrian President Bashar al Assad and Venezuela's President Nicolas Maduro.
Among the hundreds of pieces of military hardware paraded in front of veterans and dignitaries was Russia's Yars mobile global nuclear missile launcher and its advanced S 400 air defence missile system, Which Moscow has deployed in Syria guard its forces and Putin's new 120,000 4.4 lite V 8 ragtop limousine.
have been also regiments of glamorous female soldiers on display who were pictured smiling as they filed past Mr Putin.
It also included military equipment, Ranging from a T 34 tank renowned for its toughness in World War II to lumbering Yars ICBM launch units, Ground to air rocket missile parts and Russian Armata tanks.
Russian female military servicemen march during the Victory Day parade on Red square in Moscow on Thursday afternoon
Smiling Russian naval cadets were pictured marching in perfect step as they filed past Putin the actual Victory Day parade
Russian Armata tanks roll down Red Square the particular Victory Day military parade to celebrate 74 years since the victory in WWII in Red Square in Moscow
Russian Ground Forces commander in Chief, Colonel common Oleg Salyukov salutes the troops from Putin's new 120,000 collapsible limousine during the Victory Day military parade today
Russian President Vladimir Putin delivers a speech face to face with St. Basil's Cathedral during the Victory Day parade i which he pledged to'guarantee the high performance of our armed forces'
Russian Yars RS 24 intercontinental ballistic missile systems roll through Red Square during the Victory Day military parade in downtown Moscow today
Vladimir Putin kisses his class teacher at school Vera Gurevich during a certified reception marking 74 years since the victory in WWII, doing Kremlwearing
Russian military law enforcement stand in formation [url=https://medium.com/@oli.t2017/everything-you-need-to-know-ukrainian-women-956bb3bae17a]single ukraine ladies[/url] during a Victory Day Parade in the city of Grozny, Chechen Republic
Former Soviet chief Mikhail Gorbachev (core) Is in the middle of his assistants as he arrives to attend the Victory Day military parade in Red Square today
Crowds of people carry portraits of their relatives who fought in World War II as they have fun playing the Immortal Regiment march on Tverskaya Street in Moscow
Russian Pacific Fleet leader, Admiral Sergei Avakyants compares the troops in a vintage car during the Vi (...)