Toxoplasmosis is the number one cause of abortions on sheep farms, according to Teagasc’s Michael Gottstein.
The Teagasc Head of the Sheep Knowledge Transfer Programme said the disease is caused by sheep ingesting oocysts shed by cats on pasture or in contaminated feed, bedding or water.
Speaking at a recent Teagasc Better Sheep Farm walk in Co. Wexford, he said that the disease may go unnoticed in flocks during the early stages of pregnancy, but it may cause stillbirths, mummified lambs or the birth of a weak lamb in late pregnancy.
According to Teagasc, most sheep farms experience some abortions each year, but it can rise as high as 25% of the flock during an abortion storm.
Two of the most common causes of abortion are toxoplasma and enzootic abortion.
Gottstein said enzootic abortion is spread by sheep-to-sheep contact and farmers buying in replacement ewes should consider vaccinating against the disease in their flocks.
When ewes have not been vaccinated for the disease, it spreads to the womb and afterbirth of an unprotected sheep which kills the developing lambs causing abortion.
According to research, non-pregnant sheep, including newborn lambs can pick up the infection from aborting ewes and the disease will remain dormant in the animal until the animal is 90 days pregnant.
Identify the problem before vaccination
Gottstein said that the correct procedure to identify the disease causing the abortion in the flock is by sending foetal material, including the placenta to the laboratory.
He said that the use of blood tests to identify the disease is not accurate as rising blood titre levels are only indicative of the disease and are not accurate – certainly not in flocks that already have the disease circulating.
Once the cause of the abortion problem has been identified, he said the farmer can then develop a vaccination programme to control further outbreaks of the disease on their farms.