Coccidiosis in Calves

The NADIS disease forecast is based on detailed Met Office data, and regional veterinary reports from 37 farm animal practices and the large animal units at six UK veterinary colleges.

NADIS data can highlight potential livestock disease and parasite incidences before they peak, providing a valuable early warning for the month ahead.

NADIS disease bulletins are written specifically for farmers, to increase awareness of prevalent conditions and promote disease prevention and control, in order to benefit animal health and welfare. Farmers are advised to discuss their individual farm circumstances with their veterinary surgeon.

NADIS Cattle Disease Focus – September 2005

Coccidiosis is probably the second most important cause of diarrhoea in calves (after rotavirus). The reports from NADIS vets show that most cases of coccidiosis are seen in late summer, with additional peaks in November and January. However cases can occur at any time of year, so it’s important to be aware of coccidiosis throughout the season.

What is Coccidiosis?

Coccidiosis is caused by single-celled parasites (not bacteria) known as coccidia. There are several species in cattle, not all of which cause disease. The species that cause disease are primarily found in the large intestine, and the diarrhoea results from damage to the cells lining it.

Coccidiosis is seen in animals up to two years old, and is particularly common in calves between three weeks and six months of age. Infection can spread directly between calves but the majority of infection spreads via a contaminated environment. Infected calves pass out large numbers of the egg stage of the parasite (known as the oocysts). These oocysts are designed to survive for very long periods in the environment being resistant to heat and cold and many disinfectants. So unless the environment is thoroughly cleaned between batches of calves infection can easily spread between calves. This can happen either indoors on bedding, or outdoors when stocking density is high.

Clinical Signs

The most common sign is a watery diarrhoea, which because the coccidia damage the large intestine is often accompanied by straining (which can become very severe), mucous and blood. Other signs can include depression, loss of appetite, weight loss, and, much more rarely than with diarrhoea in milk-fed calves, dehydration. Death is rare. Infections that fail to produce diarrhoea can, nevertheless, result in reduced growth and weight gain. This sub-clinical infection is very common, with up to 95% of cases being of this type. In fact the major economic loss associated with coccidiosis is its effect on weight gain.


  • On the clinical signs described above
  • Get several samples of scour examined for oocysts. These results require interpretation so ask your vet for advice


  • Most cases will recover without treatment.
  • If calves become dehydrated then electrolytes should be given
  •  Once high numbers of oocysts are found, then treatment is unlikely to be of any benefit
  •  Treatment is better given to in-contact animals that have not yet started showing signs, or to combat secondary infection. A large number of products are available for treatment, but only two are licensed. Specific recommendations should be obtained from your veterinarian.
  • All calves with diarrhoea should be separated from clinically normal calves, to reduce contamination of environment with oocysts.
  • If possible, during an outbreak stressful procedures, such as dehorning, castration and weaning should be avoided

To achieve effective control of coccidia, good management and hygiene is vital. This should include:

1) Reducing stocking density
2) Regularly moving feed and water troughs
3) Preventing faecal contamination of feed and water troughs, by raising or covering
4) Increasing the bedding to reduce contamination
5) Avoid mixing different ages of calves
6) Clean and disinfect all buildings between groups of calves. It is important to use a disinfectant that claims effectiveness against coccidial oocysts
7) Mass medication can be used as a preventative, but it is no substitute for improving management.

Copyright © NADIS 2005

While every effort is made to ensure that the content of this forecast is accurate at the time of publication, NADIS cannot accept responsibility for errors or omissions.
All information is general and will need to be adapted in the light of individual farm circumstances in consultation with your veterinary surgeon


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