Cryptosporidia: A cause of illness in calves and people too


One of the germs that contributes to calf scours cases is cryptosporidia, or “crypto”. Crypto is a one-celled protozoa that is normally present in small numbers in the digestive tract of cows and calves. As such, it’s not an organism you can eliminate from a farm. Calves pick this bug up from manure on their mother or in their pen. It’s a very hardy germ; in cool temperatures it can survive for weeks or months. Illness results when calves get exposed to enough of the organism, or if their immune system is weakened by factors like poor colostrum intake or cold wet weather stress.

Crypto in Calves

Baby calves usually get their first exposure to crypto soon after they’re born, but the effects of the germ don’t show up until about 7 days of age. Once a calf gets to be about a month old, they’re pretty resistant to the effects of crypto. 

The crypto organism invades the tips of the cells lining the intestines and significantly impairs digestion. There is an impaired ability to absorb fluids from milk, and the increased load of intestinal content further sucks water into the gut. Diarrhea is the result, sometimes mild and sometimes very watery. Often the manure from a calf with crypto has a pudding-like consistency, sometimes with a spot of blood in it. The resulting dehydration and metabolic derangements like low blood pH give rise to a calf that is slow, droopy, and uncoordinated. Many times crypto works in conjunction with other viruses or bacteria to cause calf scours. 

There are no approved vaccines or specific treatments for crypto. Veterinarians have tried different medications with varying degrees of success. Supportive treatments like oral or intravenous fluids are pretty much all we have. When it comes to prevention, producers work on managing the calves’ exposure to large quantities of crypto by calving in clean lots or pens and managing weather and nutritional stresses.

Crypto in Humans

If its effects on calves weren’t bad enough, crypto can also make people sick. Over 100 human cases of crypto were reported in South Dakota last year. Many of these human illnesses can be traced back to contaminated water. But a recent report estimated that about 1 out of every 6 human crypto cases came from animals; calves (both beef and dairy) are the most common animal sources there are. 

Crypto in people can cause some pretty uncomfortable symptoms:

  • Stomach cramps
  • Diarrhea
  • Vomiting

In a few severe cases, people can end up in the hospital to be treated for dehydration or other complications. Manure from sick calves—and often normal calves as well—is the material that harbors the cryptosporidia. Taking care to avoid contact with calf manure, changing boots and overalls, wearing latex gloves, and washing hands with soap and water are all measures one should take when working with calves.
As cattle producers work through scours issues this spring, crypto should be on the list of possibilities. Working with a local vet is the best way to start formulating a plan to prevent or work through a scours outbreak due to crypto.

Source: Russ Daly, DVM, DACVPM

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