15 March 2002

Restocked ewes can bring abortion risks

FARMS which have restocked with sheep from a number of sources following foot-and-mouth culling may have a dangerous mix of ewes infected with chlamydia organisms – which cause enzootic abortion – and uninfected ones.

According to vet Matt Colston, of Frame, Swift & Partners, Penrith, there will also be ewes which are immune, but still shedding the organism responsible for the disease.

Producers with bought-in sheep may not know their current status and face uncertainty about abortion risk this year, where vaccination was not carried out, he adds.

"Its important to act quickly if you start getting abortions, stillbirths or weak lambs. The first step is to isolate aborting ewes and disinfect the local area to reduce the risk of infection spreading. The second step is to identify the cause of abortion with your vet."

If unaffected ewes are vaccinated quickly at the start of an enzootic abortion storm, losses can be minimised.

According to vaccine maker Novartis, trials show that whole flock vaccination protects animals that are uninfected and increases the number of live lambs born to ewes already infected with chlamydia. &#42