Someone I know recently became very sick with diarrhea, and was diagnosed with cryptosporidiosis. Cryptosporidiosis is caused by a protozoal parasite similar to coccidia. This parasite causes diarrhea in calves that leads to untold millions in lost production in both the dairy and beef industries. Since this disease has zoonotic potential, that is, it can be transmitted from animals to people, I think a discussion of the disease and control measures is needed.
The protozoal parasite responsible for the disease is Cryptosporidium parvum. The parasite exists in intestinal cells in multiple forms depending on stages of its life cycle. In the environment it can survive for days to weeks or even months, given the right conditions, in an encysted form. After it is ingested and passed through the stomach, it begins to develop, multiply and reproduce in the small intestine. It has the ability to reinfect calves through ingestion in a contaminated environment, and can reinfect calves within the small intestine without ever having to leave the body. An infected calf can shed as many as 10 billion organisms per day. Calves 5 to 21 days old are most susceptible to the disease. It only takes as few as 100 parasites to cause the disease.
Calves affected with the disease develop a watery diarrhea that is indistinguishable from other types of neonatal diarrhea (E. coli, Salmonella, rotavirus, Clostridium perfringens).
Initially, calves’ appetites remain good, but as dehydration develops, the calves become more depressed and appetite diminishes. Without aggressive fluid therapy, either oral or intravenous, the affected calves slowly deteriorate over 4 to 5 days, dying from severe dehydration and starvation. Calves that are stressed or immunosuppressed due to inadequate colostrum intake are much more at risk for developing life threatening disease.
Cryptosporidium are diagnosed by microscopic identification in feces.
Once diagnosed, control measures should be put in place to limit exposure to crypto. There is no antibiotic that will be effective to stop the disease. Research using various anticoccidial medications is ongoing; high doses of certain medications may help control the infection and increase survival rates. Environmental control is the most important feature of management. Keep a clean calving environment; calving areas should be as dry as possible, not crowded and cleaned and rebedded regularly. On the dairy, once calves are born, move them to individual housing as soon as possible. When calves are weaned, thorough cleaning is necessary of the calving pen before a new calf is placed there.
As I mentioned earlier, there is the potential for transmission of this parasite to people in contact with infected calves. For the average person, your immune system can combat the parasite and clinical symptoms (primarily diarrhea) are diminished. People at highest risk are immunosuppressed; the very young, the very old, people on immunosuppressive medication, and AIDS patients can suffer life-threatening disease. Make sure to use good hygiene when handling sick calves for your safety.
Mike Bloss, DVM, owns Countryside Animal Clinic with his wife, Kirstin Bloss, DVM, in Aurora, Mo.
