Sheep farmers urged not to panic over abortion jab

Published on Sunday 16 May 2010 20:20

SHEEP farmers should not panic and abandon their established use of vaccinating their flocks against enzootic abortion, even if, as it has been revealed, the vaccines they have been using could themselves cause abortion.

That was the advice given by NFU Scotland vice-president, Nigel Miller to the startling news that has emerged from the world rated Moredun Research Institute in Edinburgh.

Miller, who is himself a vet as well as being a livestock farmer, advised "Do not over-react. The vaccines that we have been using have helped reduce the incidence of abortion in flocks."

Enzootic abortion is a major cause of lamb mortality across the world and accounts for 44 per cent of diagnosed infectious abortions in UK sheep. More than 50 years have elapsed since the causal organism was first identified at Moredun.

The most effective way to control enzootic abortion in sheep flocks is through the use of vaccines. Without vaccination abortion levels can be between 5 per cent and 10 per cent, with "abortion storms" of up to 25 per cent not uncommon. With flocks that have been vaccinated, abortions come down to 2 per cent or less.

No vaccine is ever 100 per cent effective and, although it is uncommon, sheep that have been vaccinated with a chlamydial vaccine can still abort at the next lambing. This may be because the ewe was already infected before she was vaccinated, or because of incorrect storage or administration of the vaccine.

The news that the vaccines could be causing some cases of the disease came to light following laboratory work at Moredun. They had been looking at tissue samples from aborted foetuses and after most of these were found to be infected with the abortion organism, it was also picked up that a number of the infections came from sheep that had been vaccinated. The scientists then identified a link between the vaccine strain and the probable cause of abortion.

Professor Julie Fitzpatrick, director of Moredun, echoed Miller's call that farmers should continue to use the vaccines that were available.

She said: "Although our findings are important, our message to farmers about controlling enzootic abortion remains the same. We would encourage farmers who have a vaccination strategy for enzootic abortion to continue vaccinating, as this is the most effective way to safeguard sheep from disease.

"If farmers receive a positive abortion result from a vaccinated ewe which has aborted, we would encourage them to work with their vet and contact the vaccine provider, who will investigate the situation."