Vet's view: How farmers can help prevent calf losses from coccidiosis

Conditions

COCCIDIOSIS is more common in intensive management systems, with high stocking rates, and can be seen either indoors or outdoors. It usually effects young cattle between one to two months old and a year of age.

Most outbreaks occur when the build-up of oocysts on contaminated pasture and bedding is overwhelming. It can also be associated with stress triggers such as a change in weather or feed.

Miss Williamson says: “In spring-calving herds, turnout is a high risk time. Crowding around feed and water troughs can cause the oocysts to be ingested. This is particularly likely if calves have been turned out onto the same pasture as the previous year.

“In all-year-round calving there is not a specific time frame when threat is at its greatest,” she adds.

Calving areas can often be highly contaminated and if calves are regularly seen with coccidiosis at three-weeks-old, due to the nature of the pathogen’s 21-day lifecycle, this means they were infected at birth.

Miss Williamson says: “The disease targets poor doers with compromised immune systems, those with concurrent enteric infections may be more severely infected.”

The pathogen

Coccidiosis is caused by an intracellular parasite, a protozoa, which are host specific, meaning they only infect one particular species, for example, cattle species only infect cattle.

The reproduction and development of the protozoa takes place in the intestines, and their rapid multiplication causes the cells lining the intestines to rupture.

Miss Williamson says: “Damage to the villi lining of the caecum and the large intestine causes a reduction in surface area so not enough nutrients are absorbed which leads to scour and reduced growth rates.”

As the coccidia develop in the animal, oocysts are produced and shed in large quantities in faeces onto pasture or bedding. These oocysts are highly resistant to environmental stress and when ingested by another animal, start their lifecycle all over again, rapidly multiplying and causing the burden to pasture or bedding to increase.

Miss Williamson adds: “The oocysts are naturally occurring and can survive for more than a year in favourable conditions making it tricky to control to disease.”

The lifecycle of the pathogen is about three weeks, which means calves will usually show symptoms of disease three to four weeks after exposure to oocysts.

Prevention

Miss Williamson says: “It is important to limit the build-up of the oocysts in the environment by reducing infection pressure.

“This can be achieved by avoiding over-stocking, regular clean bedding, and if animals are outside, change paddocks frequently.

“When feeding animals outside, troughs should be moved frequently, if they are fed in the same place week in and week out, the oocysts will build up and it becomes more likely they will be ingested,” she adds.

Practice an all-in all-out system with good cleaning and disinfectant between groups of calves, the same as for any disease.

“There is always a low level of the coccidia on farm, it is a case of preventing build up,” says Miss Williamson.

Treatment

Calves diagnosed with infection by coccidia should be separated from the rest of the herd to avoid further contamination of the environment.

They must also be treated with fluid therapy to replace fluids lost through diarrhoea. Treatment of the coccidiosis can be effective with the use of anti-protozoal drugs prescribed by a vet.

Calves can build up immunity after they have had been exposed to the disease, however, long-lasting damage has often already occurred and economic impacts will be seen so it is better to avoid exposure to the infection initially.

Miss Williamsons says: “Vet prescribed in-feed medication is a good way to control coccidiosis if you have problems on your farm.”