Hookworm disease
Hookworm disease is an illness caused by one of two types of S-shaped worms that infect the intestine of humans (the worm's host): Necator americanus and Ancylostoma duodenale. The two species cause illness by attaching themselves to the lining of the small intestine and sucking a person's blood.
Both types of hookworm are similar. The adult worm of both is about 10 mm long, pinkish-white in color, and curved into an S-shape or double hook. The females produce about 10,000-20,000 eggs per day. These eggs are passed out of the host's body in feces. The eggs enter the soil, where they incubate. Afterabout 48 hours, the immature larval form hatches out of the eggs. These larvae take about six weeks to develop into the mature larval form that is capableof causing human infection. If exposed to human skin at this point (usuallybare feet walking in the dirt or bare hands digging in the dirt), the larvaewill bore through the skin and ride through the lymph circulation to the right side of the heart.
An itchy, slightly raised rash called "ground itch" may appear around the area where the larvae first bored through the skin. The skin in this area may become red and swollen. This lasts for several days and commonly occurs betweenthe toes.
The larvae are then pumped into the lungs. There, they bore into the tiny airsacs (alveoli) of the lungs. Their presence within the lungs usually causesenough irritation to produce coughing, fever, and wheezing. However, some people have none of these symptoms.
The larvae are coughed up into the throat and mouth, and are then swallowed and passed into the small intestine. Within the intestine that they develop into the adult worm. Hookworms cause trouble for their human host when they attach their mouths to the lining of the small intestine and suck the person's blood.
Once established within the intestine, the adult worms can cause pain,decreased appetite, diarrhea, and weight loss. The worms suck between0.03-0.2 ml of blood per day. When a worm moves from one area of the intestine to another, it detaches its mouth from the intestinal lining, leaving an irritated area that may continue to bleed for some time. This results in evenfurther blood loss. A single adult worm can live for up to 14 years in a patient's intestine. Over time, the patient's blood loss may be significant. Anemia is the most serious complication of hookworm disease, progressing over months or years. Children are particularly harmed by such anemia and cansuffer from heart problems, mental retardation, slowed growth, and delayed sexual development. In infants, hookworm disease can be deadly.
To diagnose hookworm disease, a stool sample is examined under a microscope for hookworm eggs. Counting the eggs in a specific amount of feces allows thehealthcare provider to estimate the severity of the infection. Minor infections are often left untreated, especially in areas where hookworm is very common. If treatment is required, the doctor will prescribe a three-day dose of medication. One to two weeks later, another stool sample will be taken to see if the infection is still present. Anemia is treated with iron supplements. Insevere cases, blood transfusion may be necessary. Two medications, pyrantelpamoate and mebendazole, are frequently used with good results.
The prognosis for patients with hookworm disease is generally good. However,reinfection rates are extremely high in countries with poor sanitation. Preventing hookworm disease involves improving sanitation and avoiding contact with soil in areas with high rates of hookworm infection. Children shouldbe required to wear shoes when playing outside in such areas, and people whoare gardening should wear gloves.
Ancylostoma duodenale is found primarily in the Mediterranean, the Middle East, and throughout Asia. Necator americanus is common in tropical areas including Asia, parts of the Americas, and throughout Africa. Research suggests that at least 25% of all people in the world have hookworm disease. In the United States, 700,000 people are believed to be infected with hookworms at any given time.
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