Dehydration and malnutrition are the most common effects of cryptosporidiosis, an infection of the intestine by microscopic parasites known as Cryptosporidia.

First identified in 1976 as a cause of disease in humans, Cryptosporidia are normally passed in the feces of infected persons and animals in the form of cysts. The cysts can remain in the ground and water for months, and when ingested produce symptoms after maturing in the intestine and the bile ducts. The most common sources of infection are other humans, water supplies, orreservoirs. These are contaminated by animals that defecate in these areas. An outbreak in Milwaukee in 1993 in which over 400,000 persons were affected was traced to the city's water supply. Cysts of Cryptosporidia are extremely resistant to disinfectants commonly used in water treatment plants andare incompletely removed by filtration.

Most persons who experience significant symptoms have altered immune systemsand diseases such as AIDS or cancer. However, as shown in the Milwaukee outbreak, even those with normal immunity can experience symptoms.

Human-to-human transmission (such as occurs in day-care centers or through sexual behavior) is also an important cause.

Many individuals can be infected without any illness, but the major symptom is diarrhea, which is often watery and incapacitating. Dehydration, low-gradefever, nausea, and abdominal cramps are frequent.

In those with a normal immune system, the disease usually lasts about ten days. For patients with altered immunity (immunocompromised), the story is quitedifferent, with diarrhea becoming chronic, debilitating and even fatal.

In about 20% of AIDS patients, bile duct infection also occurs, causing symptoms similar to gallbladder attacks. Eighty percent or more of those with infection of the bile ducts die from the disease. The lungs and pancreas are alsosometimes involved. Cryptosporidia are just one cause of the diarrheawasting syndrome in AIDS, which results in severe weight loss and malnutrition.

Diagnosis is based on either finding the characteristic cysts in stool specimens, or on tissue samples from an infected organ, such as the intestine.

The first aim of treatment is to avoid dehydration. Oral rehydration solutionor intravenous fluids may be needed. Medications used to treat diarrhea by decreasing intestinal movement, such as loperamide or diphenoxylate, are alsouseful but should only be used with the advice of a physician.

Treatment aimed directly at Cryptosporidia is only partially effective, and rarely eliminates the organism. The medication most commonly used is paromomycin (Humatin), but others are presently under evaluation.

Cryptosporidia rarely cause a serious disease in persons with normal immune systems. Replacement of fluids is all that is usually needed. On the other hand, those with altered immune systems often suffer for months to years.Paramomycin and other drugs have been able to improve symptoms in over halfof those treated. Unfortunately, many organisms are resistant, and subsequentinfections are common.

The best way to prevent cryptosporidiosis is to minimize exposure to cysts from infected humans and animals. Proper hand washing technique, especially inday care centers is recommended.

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