Coccidiosis

Who is this for?

This guide is essential reading for anyone rearing young calves, whether on a dairy, beef or mixed farm. It covers the disease cycle, risk factors and the management practices that reduce exposure. 

• Dairy farmers
• Beef farmers
• Calf rearers
• Farm managers
• Veterinarians
• Agricultural advisors

What this guide covers

Coccidiosis is caused by a common parasitic organism called coccidia, which is present on most farms. Young calves become infected by ingesting oocysts from the environment, typically through contact with infected faeces. The disease develops over 12 to 21 days after ingestion, with coccidia maturing in the small intestine before moving to the large intestine and eventually being shed back into the environment through faeces. 

The key challenge with coccidiosis is timing. By the time clinical signs appear, significant gut damage has already occurred. Affected calves scour, sometimes with blood, and may be seen straining. Weight loss can be severe, and in serious outbreaks, deaths or chronic poor-doers are not uncommon. 

What causes outbreaks 

Outbreaks occur when young calves encounter high numbers of the parasite. Several common management practices increase this risk: poor disinfection of pens between batches, overcrowding, insufficient or poor-quality bedding, grouping calves of different ages together, using pens on a continuous basis, and allowing faecal contamination of feed or water. Forage fed on the floor or concentrates in low-level troughs are particularly common sources. 

Preventing coccidiosis 

Prevention is the only effective strategy – discuss control with your vet. Once clinical signs appear, gut damage has already been done. The most effective approach is to reduce the risk of young calves coming into contact with infected faeces through strict hygiene and management protocols. 

Key prevention steps 

Frequently asked questions

What are the signs of coccidiosis in calves? 

Affected calves typically scour, sometimes with blood in the faeces, and may strain when passing dung. Weight loss is common and can be significant. In severe cases, calves may die or become chronic poor-doers that never reach their potential. 

How does coccidiosis spread between calves? 

Coccidia spread through infected faeces. Calves ingest oocysts from contaminated bedding, feed or water. The parasite then develops over 12 to 21 days before oocysts are shed back into the environment, continuing the cycle. 

When should I treat calves for coccidiosis? 

By the time clinical signs appear, gut damage has already been done. Treatment can address the symptoms but cannot reverse the intestinal injury. Prevention is far more effective than treatment, which is why management practices to reduce exposure are so important. 

What pen management practices reduce the risk of coccidiosis? 

All-in, all-out calf management with thorough disinfection between batches is the most effective measure. Avoid grouping calves of different ages together, prevent faecal contamination of feed and water, maintain good bedding quality, and do not run pens on a continuous basis without cleaning. 

Does coccidiosis affect later performance in cattle? 

Yes. Calves that experience coccidiosis take longer to reach target weights for finishing or first calving. Severe infection can result in chronic poor-doers that never recover their growth trajectory, with a direct impact on farm profitability. 

Should I discuss coccidiosis control with my vet? 

Yes. If you suspect coccidiosis is affecting your herd, speak to your vet as soon as possible. They can help confirm the diagnosis, advise on a control programme and recommend any preventive treatment options appropriate for your farm.