Crypto parasite infectious, treatment options few

Cryptosporidium parvum, commonly known as crypto, is a microscopic parasite that can cause diarrhea in humans and animals.


This tiny single-celled organism has been the cause of large outbreaks of human disease in Canada and the United States, in some cases infecting thousands of people through contaminated water supplies. 


The parasite has a short life cycle and can reproduce within 12 hours inside the intestinal wall. It is spread from person to person, through animal to person contact or by ingestion of contaminated food or water. Poor hygiene is often a factor in spread of the disease.


Crypto can severely affect people with compromised immune systems, and symptoms may persist for long periods of time. 


It is a serious disease in AIDS patients and can sometimes be fatal.


Cryptosporidium parvum infects mammals, including cattle, sheep goats, pigs, horses, wildlife and humans. There are also subspecies that may be restricted to humans or restricted to cattle.


Cryptosporidiosis has been identified as a common cause of neonatal diarrhea in young dairy calves and is sometimes overlooked as a cause of diarrhea in young beef calves. 


Most producers are aware of coccidiosis as a cause of diarrhea in beef calves, but cryptosporidium is sometimes not as well known.


The parasite is highly infectious and is capable of long survival times in the environment. It does not multiply in the environment, but it is not destroyed easily by freezing or drying and is resistant to many disinfectants. 


Unfortunately, there is no specific treatment for cryptosporidiosis. Both humans and animals are treated with supportive therapy such as fluids to prevent dehydration.


Calves are often infected early in life, and a high proportion of calves can be shedding the parasite by the second week of life. 


The most common clinical sign is a mild to moderate diarrhea at five to 15 days of age. 


The duration of diarrhea tends to be a little longer than is typically seen in calves infected with viral or bacterial causes of diarrhea. It rarely causes severe dehydration and collapse, although calves may lose weight and be mildly dehydrated.


A National Animal Health Monitoring System study conducted by the U.S. Department of Agriculture collected samples from diarrheic beef calves from 69 operations as well as samples from beef calves without diarrhea from 141 operations. 


Twenty percent of the calves with diarrhea were positive for cryptosporidium, while 11.2 percent of the non-diarrheic calves were positive. 


The study showed that cryptosporidium is not just a disease of dairy calves. It is also common on beef cow-calf farms.


The study also showed that younger calves are more likely to be shedding cryptosporidium than older calves. 


We also know from other studies that many calves with diarrhea may have mixed infections, which include both viruses and cryptosporidium together.


A veterinarian can diagnose crypto by sending fecal samples from diarrheic calves to a diagnostic lab, which can identify the oocysts or eggs of the parasite under the microscope. 


Crypto is difficult to control be-cause it can survive in the environment and is resistant to many disinfectants. Reducing the number of oocysts ingested by calves will probably reduce the severity of the disease. 


Calves with diarrhea should be isolated from healthy calves and kept separate for several days after recovery.


The basic principles of reducing infection pressure are important in preventing the disease. These include maintaining a clean calving area, spreading cow-calf pairs out and using separate turn-out areas or some form of calving system that minimizes environmental infections.


Ensuring that calves receive adequate colostrum is critical, just as it is for almost all young calf diseases. Many of the biosecurity strategies that we apply to viral or bacterial calf scours are also applicable to minimizing the effect of cryptosporidiosis.


John Campbell is head of Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine.