Cryptosporidium
Cryptosporidiosis is an acute, self-limiting diarrheal disease caused by the coccidian parasite Cryptosprodium parvum. Cryptosporidia have been implicated as a cause of diarrhea in travellers and of epidemic diarrhea in hospitals, daycare facilities, urban centers and other institutions worldwide. In immunocompromised persons Cryptosporidium infection may lead to a prolonged, life-threatening diarrheal illness. Cryptosporidium affects both man and animals such as poultry, fish, cats, dogs and livestock. This parasite is commonly found in lakes and rivers, especially with the water is contaminated with sewage and animal wastes. It was first identified as a disease that affects humans in 1976. Once thought to be a rare, opportunistic infection, Cryptosporidiosis is now recognized as a common cause of childhood diarrhea worldwide, accounting for 20% of all cases in developing countries.
Both the disease and the parasite are also known as “Crypto”. The parasite is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it very resistant to chlorine disinfection. During the past two decades, Crypto has become recognized as one of the most common causes of waterborne disease (drinking and recreational) in humans.
Cryptosporidia cause substantial illness throughout the world. The actual frequency of stool specimens found to be positive for Cryptosporidia varies according to the characteristics, including symptom status and immunologic function, of the population studied. The generally quoted prevalence of Cryptosporidia in stool specimens is 1% to 3% in Europe and North America and 5%to 10% in Asia and Africa. However, even in developed countries, where prevalence rates by stool examination have been found in 32% to 58% of adults.
It has been estimated that 30-35% of the U.S. population is seropositive to
Cryptosporidium. Seroprevalence rates in Europe and North America range from 25-35%but are believed to be considerable higher in less developed countries. There are 250-500 million cases of Cryptosporidiosis annually in Asia, Africa, and South America. As many as 7% of the children in developing countries may be suffering from Crypto.
In the spring of 1993 the largest documented waterborne disease outbreak in US history occurred in Milwaukee, Wisconsin. Cryptosporidium was identified as the cause, and more that 400,000 residents were infected and over 100 immunocompromised persons died after being infected with Crypto.
The first well-documented non-waterborne Cryptosporidiosis outbreak (160 cases) was traced to hand pressed apple cider.
In July 1997 there was an outbreak in Minnesota associated with a water sprinkler fountain at a zoo. Numerous outbreaks in the last 20 years have occurred in North America. These have been associated with drinking water, recreation water use, contaminated foods, contact with animals and childcare facilities.
In 1996 became notifiable in Ontario and 487 cases of crypto were identified in Ontario over a two year study period.
During the summer of 2000, five outbreaks of Cryptosporidiosis linked to swimming pools were reported to CDC.
Outbreaks have been reported from day-care centers in the United States, Great Britain, Australia, France, Portugal, Chile and South Africa.
Transmission of Cryptosporidium to humans may occur through direct or indirect contact with feces containing oocysts. Spread is by an oral-fecal route, including hand contact with the stool of infected humans or animals or with objects contaminated with stool. Transmission is also common from ingestion of food or water contaminated with stool, including water in the recreational water park and swimming pool settings. Person to person exposure is probably the most important route of transmission. The infectious dose for humans is low, perhaps fewer that 10 occysts. The cycle begins with ingestion of the oocyst, which breaks open and release sporozoites. The sporozoites invade and feed off the epithelial cells of the GI tract.
Symptoms of Cryptosporidiosis include, most commonly, watery diarrhea and cramps, sometimes severe. Loss of appetite, nausea, vomiting, weightloss and fever are also possible. Asymptomatic infection is also possible. Symptoms usually appear 2-10 days after infection. The severity of symptoms varies with the degree of underlying immunosuppression, with immunocompetent patients commonly experiencing watery diarrhea for a few days to 4 or more weeks and occasionally having a recurrence of diarrhea after a brief period of recovery. Patients with AIDS can have a large number of stools per day for months or even years. Pulmonary and tracheal Cryptosporidiosis in humans is associated with coughing and frequently a low-grade fever; these symptoms are often accompanied by severe intestinal distress.
There is generally no effective treatment. Oral rehydration therapy is to be recommended as infected individuals may at times suffer from voluminous diarrhea. Anti-diarrheal agents may be recommended for the reduction of fluid loss, but there is a question as to whether their use may prolong the infection. Treatment trials have been conflicting, but recently the use of paramomycin (Humatin) has been found to be effective in treating immunocompetent travellers with Crypto.
Chemical disinfectants (e.g.’ chlorine or iodine) are ineffective against oocysts. Alum and sand filtration reduce the number of oocysts, and seem to reduce their viability, but they do no eliminate them. Only water filters capable of removing particles less than 1 micrometer in diameter can reliably remove C. Parvum; this includes reverse-osmosis filters and 1-micron filters rated as “absolute”. Boiling water for 1 minute destroys the oocysts. Many, but not all brands of bottled water may provide a reasonable alternative to boiling tap water. Bottled water that is labeled distilled; reverse-osmosis or “1 micron absolute” is safe against Crypto.
Good hand washing after going to the toilet or changing diapers, and after touching farm animals, pets or wild animals. This is especially important before eating or preparing food.
Avoid using ice or drinking untreated water when traveling in countries where the water supply might be unsafe.
Avoid eating uncooked foods when traveling in countries with minimal water treatment and sanitation systems.
Boil water for at least 1 minute or filter water that has an absolute pore size of at least 1 micron or one that has been NSF-rated for “cyst removal:
Avoid uncooked food or drinks, which have been prepared with untreated water.
Unpasteurized milk or milk products should also be avoided.
Avoid swallowing recreational water.
Infected individuals should wash their hands frequently, especially before preparing food or after going to the toilet, and avoid close contact with anyone with a weakened immune system.
Infected individuals should avoid swimming in recreational water for at least 2 weeks after diarrhea stops.
Avoid fecal exposure during sex.
Nadine Parsons RN
Region of Waterloo Public Health
Waterloo, ON
519-8832006 (5271)
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http://www.cdc.gov/ncidod/dpd/parasites/cryptosporidiosis/factsht_cryptospoidiosis.htm