Spring is in full swing in Roscommon, with the usual range of spring-related illnesses and problems. One such problem which recurs every year is that of abortion in sheep.

Sometimes this may present as a ewe losing lambs before she reaches full term, but sometimes it can result in a ewe giving birth to weak or unviable lambs at full term.

Last week, I carried out a caesarean section on a ewe which had passed a waterbag, but had not dilated properly. The ewe was scanned for two lambs, appeared to be full term and upon examination I could feel at least one live lamb through the ewe’s partially open cervix. Therefore, the decision was made to operate on the ewe.

The caesarean section resulted in the delivery of one weak live lamb and one dead lamb, which appeared to be underdeveloped. This raised the question as to whether an infection could have caused this problem to occur.

We took a sample from the placenta (cleanings) and the lambs. Analysis of the sample gave a positive result for chlamydia abortus. C.abortus is the causative agent for enzootic abortion of ewes (EAE). This is a relatively common disease which enters flocks through the purchase of infected ewes.

Ewes may be infected at any stage of their lives by coming in contact with the birth fluids/ placenta of other infected ewes, thus the lambing shed is the usual location for spread of infection. We subsequently got similar results from other ewes in the same flock. Therefore, we have advised the farmer to inject any remaining pregnant ewes with long-acting antibiotics.

We have also advised the farmer to vaccinate all ewes before going to the ram next year in order to boost their immunity to the disease. Ewes which have given positive results for EAE should also be culled.

People say you need to be lucky to have good results with sheep, but identifying the causes of weak lambs or abortions and taking steps to control EAE if diagnosed can improve your chances of being lucky.

John Gilmore is a practising vet and managing director at FarmLab Diagnostics, an animal health testing laboratory. Visit www.farmlab.ie.