Sheep farmers are being urged to look out for signs of coccidiosis in young lambs, after the onslaught of unseasonal weather and delayed spring up and down the country.
The risk of the disease taking hold is increased when ewes and lambs are housed, turned out on poached pastures, or pasture previously used by earlier lambs.
Ian Jones, a vet with Powys-based Hafren Vets, says: “For anyone this year, the weather could mean management changes and ewes and lambs being kept in for longer to avoid excessive poaching in fields which are already saturated.
“There seems little doubt the coccidiosis challenge will be higher than ever.”
Young lambs aged between two and eight weeks of age are most at risk, which peaks when they are five to six weeks and grass is introduced into the diet.
Charlotte Read, farm animal account manager with pharmaceutical company Krka, says: “Orphaned, housed lambs being fed via a milk machine or bottle are also highly susceptible and should be carefully watched.
“Affected lambs may suffer from dullness, lack of appetite, diarrhoea, with or without blood, dehydration and weight loss, although symptoms are often unseen in host sheep.”
Veterinary diagnosis of coccidiosis is based on clinical findings plus the demonstration of large numbers of oocysts in faecal samples.
Mr Jones says the source of the initial outbreak is likely to be either residual contamination in the environment as oocysts can overwinter on pasture in low numbers, or low levels of oocyst shedding by other sheep.
“The level of the environmental infection, is probably the most important factor, but other factors, such as nutritional and climatic stress, may also be involved,” he says.
In the case of expected high oocyst challenge, preventative treatment should be administered about 10-14 days after turnout and only on farms with a confirmed history of coccidiosis.
Ms Read says: “Studies carried out on treating on the basis of expected high challenge has shown lambs to have reduced oocyst output, higher growth rates and less diarrhoea.
“Coccidia oocysts are extremely resistant to environmental stress, including exposure to disinfectants.
“Oocysts are, however, killed by heat, direct sunlight and drying, so housing should be cleaned at high temperatures to avoid the environmental build-up of sporulated oocysts.”