Pembrokeshire's sheep producers can expect to confront another potentially expensive problem as lambing gets underway.

Toxoplasmosis ranks alongside enzootic abortion as one of the major causes of abortion in sheep flocks, according to National Animal Disease Information Service vet, Mike Howe.

Mr. Howe, who is based in Pembrokeshire, admits precise losses due to toxoplasmosis are difficult to assess because, as well as causing identifiable late abortions, it can result in foetal loss at any stage of pregnancy.

The toxoplasma gondii is primarily an intestinal parasite of cats and has a wide range of intermediate hosts, including sheep and mice. Research suggests that one cat has the ability to infect a large number of sheep.

A report written by NADIS vet, Neil Sargison, and sponsored by the Meat and Livestock Commission, Elanco Animal Health and Intervet, suggests that aborted ewes remain clinically normal and may not be diagnosed until lambing time when they appear as barren ewes.

"The classic picture of toxoplasmosis is of a late aborted lamb alongside a brown-coloured mummified lamb and placenta," said Mr. Sargison. In the face of a late abortion storm, injectable or oral sulphanomide antibiotics can be used to reduce losses.

Measures should be taken to limit cat breeding and maintain a healthy adult cat population.

Mike Howe said farmers should seek the advice of their vets about the control of toxoplasmosis in their flocks.

Following exposure to toxoplasmosis, ewes develop a life-long immunity, therefore if they are exposed to a contaminated environment prior to their first pregnancy they don't abort.

But this situation is difficult to reproduce in practice, so vaccination appears to be the most obvious method of control.

"Toxovax is very effective in the control of ovine toxoplasmosis," said Mr. Howe. "It has a very short shelf life and must be handled carefully. A single injection effectively gives life-long protection."