Coccidiosis in dairy calves – your help needed to influence our advice

With the busy spring calving season in full flow, it’s time to focus on coccidiosis, a disease which continues to be a concern on many calf-rearing farms.

Coccidiosis mainly causes clinical disease in calves from three weeks to nine months of age. The most recent all-Island Animal Disease Surveillance Report details the percentage of samples submitted to Regional Veterinary Laboratories returning positive results for coccidial oocysts.

Coccidia are excreted in the dung and are ingested by a susceptible calf in dung-contaminated bedding, feed or water. A single ingested coccidia oocyst develops into thousands of new parasites, each of which destroys the calf’s gut lining resulting in very rapid and severe damage to the gut and which can lead to diarrhoea, dysentery (bloody diarrhoea), dehydration, straining, loss of condition and possible death.

The summary of their results, presented in Figure 1, shows a rise in the proportion of samples testing positive for coccidial oocysts throughout the spring, reaching a peak in May. This reflects the infection pressure of increasing numbers of calves in spring-calving herds, especially while the calves are housed.

Figure 1: Number of bovine faecal samples (all ages) tested for coccidiosis oocysts in 2020 (n=4,133)

 Infective coccidia oocysts are highly resistant to environmental conditions, both in housing and on pasture, so premises and fields can remain contaminated for a year or more. Calves are commonly infected through ingestion of coccidia oocysts from bedding or pasture, which previously have carried infected cattle (possibly including adult cows). Stressors, such as weaning, turnout, change of diet and poor weather may precipitate outbreaks of disease. As warm, damp conditions are necessary to allow oocysts to become capable of infecting animals, it is important to avoid dampness in bedding or around water bowls/drinking or feeding troughs. A lot of the damage and clinical signs can be seen in calves before coccidia oocysts appear in the faeces. So sampling of a number of calves in the affected group including contemporaries which have not yet developed clinical disease is important. This might help in the detection of coccidia oocysts and in the diagnosis of the cause of the clinical signs seen.

The Department of Agriculture, Food and the Marine’s Regional Veterinary Laboratories, Teagasc and UCD are carrying out research on coccidiosis in dairy calves. The research will find out what dairy farmers are currently doing to control, prevent and treat coccidiosis. You can participate in the study by clicking here and completing the survey. This survey will take approximately three minutes to complete and it is entirely anonymous. The results of this research will influence future Teagasc advice on how to control coccidiosis on dairy farms.

This article was originally published in January/February edition of Today's Farm.