The cold, snowy spring this year made for an especially challenging calving season.
Many producers experienced sick calves and substantial loses.
One of the culprits during this tough spring was a parasite called Cryptosporidium. Cryptosporidiosis is a common cause of diarrhea in young calves. This nasty parasite attaches to and damages the intestinal lining, causing abnormal absorption and high volume, watery diarrhea.
Neonatal calves become infected within the first few days after birth. Feces containing eggs are a major source of infection, but calves may also spread the parasite through direct contact. Since the eggs survive well in the environment, calves can also pick up infections from water, feed and soil. In addition to calves, crypto affects other young animals including piglets, lambs, kid goats, foals and fawns (farmed deer).
Diarrhea caused by crypto usually manifests in calves between five and 15 days of age. Older cattle and those that were previously infected with crypto are usually resistant to reinfection.
Although an unpleasant affair, the diarrhea caused by crypto parasites is often self-limiting and leads to short-term illness and weight loss that last about one week. Stressors such as inadequate milk consumption, cold weather and wind may also play an important role in determining how severe the infection will be and how long it will last.
Calves with crypto do not typically experience severe diarrhea, dehydration or profound weakness. This is an important feature that distinguishes it from other pathogens, which tend to cause more severe illness. Calves with diarrhea could be affected by more than one infectious agent at time, leading to synergistic and additive effects.
The diagnosis is confirmed by laboratory testing that identifies the presence of the parasite in the feces. Treatment is often limited to supportive care: keeping calves warm, hydrated and fed. Scouring calves should be isolated from the rest of the herd whenever possible to limit the spread. And since it is a parasite rather than a bacterium, antibiotics will not help this infection.
Crypto is challenging to control because of its hearty environmental resistance and the lack of vaccines. An important approach to control is to ensure every calf consumes adequate colostrum. This first milk contains essential immune system components that help fight infections like crypto. It is also important to maintain calf-pen hygiene. Millions of parasite eggs are present in just one gram of feces, so during outbreaks, it can become widespread in pens and pastures. The eggs survive well in the environment, especially under cool, moist conditions that often occur in spring. Extreme temperatures, both freezing and heat, are effective at killing the eggs outside the animal. Keeping pens clean and dry is helpful to controlling this disease. Any equipment used to feed calves, such as tubes and bottles, should also be carefully cleaned and disinfected.
As with many of the infectious agents that cause scours in calves, crypto is a zoonotic pathogen, meaning it can be transmitted from animals to people. People treating scouring calves should take precautions to avoid infecting themselves. This includes wearing protective clothing such as coveralls and gloves, washing hands and carefully avoiding cross-contamination. Children, the elderly and individuals with poorly functioning immune systems, such as those on immunosuppressive medications, are susceptible to infection so they should not have contact with sick calves. Outbreaks in people are also associated with fecal contamination in water sources, as was the case in the 2001 North Battleford, Sask., outbreak that affected thousands of people.
In addition to crypto, other causes of calf scours include viruses, Salmonella and E. coli bacteria, so it is important to determine the cause to direct treatment and control measures.
Dr. Jamie Rothenburger is a veterinarian who practices pathology and is an assistant professor at the University of Calgary’s Faculty of Veterinary Medicine.