Cryptosporidiosis

Nature Notes by Dr. Frank Lang

As if Giardia were not enough, there is a new water-borne disease to watch out for, Cryptosporidiosis. It was first recognized as a cause of diarrhea in humans in 1976, although it has been recognized in animals much longer. It is thought by some to be the most overlooked cause of severe gastroenteritis in humans. We can get it from untreated surface water (watch out hikers and swimmers), in day care centers, (watch out diapered tots and handlers), and, maybe, from pets less than six months old (puppy’s or kitty’s revenge).

Symptoms include diarrhea, flatulence, abdominal pain, nausea, and in fewer cases, fever, vomiting, and bloating. In one study, symptoms lasted from five to 60 days with a median of 21 days. There is no effective therapy known; it is no fun at all. People whose immune systems have been ravaged by AIDS or leukemia are at serious risk from life-threatening dehydration. Children and babies can also become very ill.

The microorganism lives in the lower intestinal tract of mammals, especially calves and lambs, and a number of other animals including mice, snakes, rabbits, deer and young humans. It is passed from host to host by direct contact with bodily waste or contaminated water supplies. After ingestion, Cyptosporidium spores, called oocysts, become attached to the wall of the small intestine where they reproduce, causing the diarrhea. Excreted oocysts can remain viable for up to 18 months.

Because it is carried by domestic stock, there is a risk that Cryptosporidiosis could become yet another contaminate of wildland water supplies where open grazing is allowed. It should be emphasized, however, that only recently has drinking surface water been implicated in the transmission of the disease in humans, and more research is clearly called for.

Sampling surface water is difficult. A sample of at least 1,000 liters must be taken and then the oocysts concentrated by centrifugation. Diagnosis of infected individuals is a relatively simple laboratory procedure.

For those of us who hike and camp, Cryptosporidiosis requires that we use a filtration device or boil our drinking water for 30 minutes. This miserable organism is resistant to most commonly-used disinfectants such as chlorine and iodine. Needless to say, the relatively recent discovery of this parasite in water supplies has been a cause of concern among public health officials.

So if you end up with diarrhea after a trip in the woods and you came in contact with surface water, treated or not, your physician has yet another possibility to consider along with Giardia and all the rest. Cryptosporidiosis. Ugh.

Cryptosporidiosis showed up in Medford water in 1990. Hasn’t been seen since. Poor Medford, and poor Ashland, if it gets established in the watershed. Don’t worry about it though, it was just Ecological Catastrophe, the fifth Horseman of the Apocalypse’s horse pooping in our drinking water. And that tap, tap, tapping? Just one more nail in our ecological coffin.

— Dr. Frank Lang

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