An insidious infectious disease such as toxoplasmosis was likely to be the cause of barrenness or abortion in ewes seen earlier this year, according to vets.
Blood samples from sheep farms across the United Kingdom were tested between February 2021 and June 2021.
According to data from 375 farms, 66% of units had one or more ewes testing positive for the productivity-damaging parasite Toxoplasma gondii.
The parasite causes toxoplasmosis, and it remains a key cause of barrenness and abortion in sheep flocks across the country.
It also causes reabsorptions, mummified fetuses, stillbirths and weakly lambs, and as a result of the range of different disease pictures that can manifest, its impact on flock profits is often significantly underestimated.
MSD Animal Health livestock veterinary adviser Dr Kat Baxter-Smith said the continued high exposure of sheep to Toxoplasma gondii highlights the importance of vaccinating ewes.
“Each year we consistently see about two thirds of UK sheep units testing positive for this serious, productivity-limiting parasite," she explained.
"Consequently, we urge all sheep producers to discuss their individual farm situation with their vet, well in advance of the upcoming autumn tupping season.
“Toxoplasmosis is so widespread that the industry focus should be on preventing infection in breeding ewes and the best way to do that is to vaccinate replacements well before they go to the ram.
"The clear industry advice is to ensure every ewe is vaccinated before she breeds.”
According to Dr Baxter-Smith, sheep pick up the infection from the environment and so normal biosecurity measures are not enough to control the disease.
Infected cats are one of the ways this parasite spreads to sheep, they shed toxoplasma eggs in their faeces and sheep become infected when they ingest these eggs from contaminated pasture, feed and water.
“EAE is caused by Chlamydophila abortus bacteria,” said Dr Baxter-Smith. “The disease can cause devastating abortion storms affecting approximately 30% of ewes.
"Once a flock has the disease it is likely it will never disappear due to its persistence in carrier sheep. The disease often arrives on farm through bought-in replacements and is passed on from ewe to ewe at lambing time.
"If an unvaccinated ewe is infected, she will more than likely abort in the next pregnancy,” she warned.
Sheep producers who recorded a flock barren rate greater than 2% during the 2021 lambing season are being urged to talk to their vet for advice.