Cryptosporidium parvum, commonly known as “crypto,” is a microscopic parasite, (a single-celled protozoan organism) that can cause diarrhea in humans and animals.
Cryptosporidium are very similar parasites to coccidiosis, but unlike coccidiosis, crypto is a zoonosis in that it can infect people and has caused some large outbreaks of human disease in Canada and the United States. In some cases, it has infected thousands of people through contaminated water supplies.
There are many species of cryptosporidium parasites. Cryptosporidum parvum infects mammals including cattle, sheep, goats, pigs, horses, wildlife and humans.
There are also subspecies that may be specific to humans or restricted to cattle.
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 the spread of the disease.
People with compromised immune systems can be severely affected with this disease and symptoms may persist for long periods of time.
If you are dealing with an outbreak of crypto in your calves, you must wear protective clothing, wash your hands thoroughly and wash boots after handling infected calves.
Cryptosporidiosis has been identified as a common cause of neonatal diarrhea in young dairy calves and it 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, although cryptosporidium is sometimes not as well known. A U.S. Department of Agriculture National Animal Health Monitoring System (NAHMS) study collected samples from diarrheic beef calves from 69 operations, as well as samples from beef calves without diarrhea from another 141 operations.
About 20 percent of the calves with diarrhea were positive for cryptosporidium and 11.2 percent of the non-diarrheic calves were also positive.
The study showed that cryptosporidium is not just a disease of dairy calves. It is common on beef cow-calf farms and is something that producers should be aware of.
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 that include both viruses and cryptosporidium together.
Calves are often infected early in life and a high proportion of calves can be shedding the parasite in their feces by the second week of life.
The most common clinical sign is a mild to moderate diarrhea at five to 15 days of age, although cases can occur up to 30 days of age.
The duration of diarrhea tends to be a little longer than is typically seen in calves that are infected with viral or bacterial causes of diarrhea. It rarely causes severe dehydration and collapse, although calves may lose weight and can become significantly dehydrated. Crypto is often involved along with other viruses and calves may have a mixed infection, making their diarrhea more severe.
Your veterinarian can diagnose crypto by sending fecal samples from diarrheic calves to a diagnostic laboratory to identify the oocysts or eggs of the parasite under the microscope.
There are also commercial test strips available (Bovine Entericheck), which your veterinarian can use to help identify the cause of scours.
Some clinics will also be able to make smears on microscope slides and stain them with a specific acid-fast stain to identify the oocysts.
Unlike coccidiosis, we have few treatment alternatives available for crypto.
Calves with diarrhea caused by crypto may require fluid therapy, which might consist of oral fluids or intravenous fluids depending on the severity of the infection.
The only pharmaceutical product available that has been proven effective at reducing the severity of diarrhea and reducing the shedding of oocysts is an oral product called Halocur. The label dosage for Halocur is to give two millilitres per 10 kilograms of body weight orally every day for the first seven days of life. Unfortunately, while this treatment regimen has shown benefits in dairy calves, it is obviously much more logistically difficult to administer in a beef cow-calf operation.
It’s important not to overdose calves and to not use the product in calves that have significant clinical symptoms because Halocur can cause some significant side effects when used inappropriately.
Unfortunately, crypto is difficult to control because the parasite is highly infectious and it is also 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 it is resistant to many disinfectants. This makes it exceptionally difficult to control in dairy or beef operations once the premises are infected.
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 the infection pressure involves 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 calves get 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 applicable to minimizing the effect of cryptosporidiosis as well.