Cryptosporidium parvum regularly associated with diarrhea in Ontario calves

By Dr. Cynthia Miltenburg on behalf of the bovine Ontario Animal Health Network

The bovine Ontario Animal Health Network (OAHN) regularly monitors data from laboratory submissions to look for trends among bovine disease in Ontario. Data from samples submitted for post-mortem analysis and other diagnostic tests helps us understand the most common disease challenges producers and veterinarians are facing.

Undoubtedly among young calves, the most common disease work up is for diarrhea. There are several different pathogens that can cause diarrhea in calves, and diagnostic testing is important to show which diarrhea-causing agents are involved. One pathogen, Cryptosporidium parvum, commonly referred to as Crypto, is an ongoing concern for calf raisers. Last year, 43 per cent of 469 calf fecal samples tested were positive for Cryptosporidium parvum at the Animal Health Laboratory. It is worth noting that many diarrhea cases are mixed infections and other pathogens may also be present in addition to Cryptosporidium parvum in some of these cases. Calf diarrhea with multiple agents is more complex to control and working with a veterinarian is important.

Lab data only represents cases where a veterinarian chose to submit samples for diagnostics, which may represent more severe or difficult to treat cases, and highlights that this may be a challenging disease agent. But other research studies tell a similar story. When a sample of 500 calves from 51 different Ontario dairy farms with a history of diarrhea were tested in 2005, 40.6 per cent of calves were found to be infected in Cryptosprodium parvum, with anywhere from zero to 70 per cent of calves infected in individual herds.

Cryptosporidium parvum is an internal parasite found in calves in their first month of life. Calves become infected when they ingest parasite oocysts shed in the feces of other infected calves. The parasite is then released from the oocyst and invades cells in the intestine where it undergoes several more life stages before ultimately producing millions more oocysts that are shed back into the environment. The infective dose has been shown in research to be only 25 oocysts, and the higher the dose a calf receives, the more ill the calf becomes. This low dose for infection and extremely high shedding pattern creates a heavily contaminated environment that puts all calves at risk and can cause a major breakdown on-farm.

Infected calves suffer from diarrhea and severe dehydration, quickly becoming weak, and in severe cases, death can occur. Recovered calves may suffer from a delay in growth. For calves affected with cryptosporidiosis, fluid and electrolyte replacement is critical to prevent dehydration along with nutritional support. Use of an anti-inflammatory such as meloxicam can also be beneficial for calves with diarrhea. Antibiotics are ineffective at treating Cryptosporidium parvum and should only be used as per your veterinary protocol for neonatal diarrhea.

Like calves, humans are susceptible to infection from this parasite as well. Anyone handling an animal with cryptosporidiosis should take great care to practice good hygiene to avoid becoming ill themselves or other members of their family. Children and people with other health conditions may be more susceptible and develop more serious disease. Handling ill animals last, proper handwashing, and not bringing barn clothes outside of the barn can help protect calf caregivers. If you have concerns about your own health, it is best to speak to your health care practitioner.

Our main points of control for this disease are general sanitation measures to prevent infection of naïve calves. Cryptosporidium parvum can persist in the environment for a long time, particularly during high summertime temperatures and humidity. Having a diagnosis of cryptosporidiosis can guide how to manage calves. Cryptosporidium parvum is resistant to many disinfectants but some are still useful to reduce overall pathogen load in the facilities. Keeping bedding fresh and minimizing overcrowding will also support lower pathogen load. The herd veterinarian may also recommend an anti-protozoal solution called Halofuginone lactate for calves at risk as part of the overall strategy to lower shedding and new infections. Supporting a robust immune system of calves with delivery of colostrum at birth and a high plane of nutrition will also help. When naïve calves were experimentally challenged with Cryptosporidium parvum, a high plane of nutrition supported maintenance of hydration, faster resolution of diarrhea, and growth.

Cryptosporidium parvum is a common challenge for dairy and veal producers; working with the herd veterinarian when diarrhea occurs to get a diagnosis will help tailor management to best support calf health.

Key facts for control and prevention in calves:

• House unaffected calves away from affected calves
• Minimize group size
• Remove manure and replace bedding frequently
• Clean and disinfect housing between calves and let rest. Chlorine dioxide has been shown to have efficacy at reducing overall environmental load
• Feed calves at least 20 per cent of body weight on milk or milk replacer feeding programs

References available upon request.

The Bovine Ontario Animal Health Network is a group of veterinarians and specialists working in government, university research and laboratory, and in beef, dairy, and veal practice who meet regularly to monitor and discuss disease trends in Ontario. Our goals are to facilitate coordinated preparedness, early detection, and response to animal health and welfare in Ontario. For our recent reports or more information visit www.oahn.ca.