THE National sheep flock is, literally, sitting on a disease time-bomb because of underlying issues which are causing significant losses through barrenness in ewes.

Both toxoplasmosis and chlamydia have been highlighted during analysis of the latest diagnostic results released by MSD Animal Health following the promotion of its Barren EweCheck and FlockCheck diagnostic services.

This involved blood samples from 500 UK sheep farms tested during 2014 when the tests were made available to vets.

According to the data, more than 81% of those tested showed evidence of exposure to the parasite toxoplasma gondii, which causes toxoplasmosis and 52% of flocks had been exposed to chlamydophila abortus bacteria, the organism causing enzootic abortion (EAE). Some 43% had been exposed to both organisms.

"These latest diagnostic results highlight the continuing widespread prevalence of these financially damaging diseases in the national flock and we urge all sheep producers to discuss their individual farm situation with their vet, well in advance of the autumn tupping season," says MSD's technical manager, John Atkinson.

Toxoplasmosis remains a key cause of barrenness as well as infectious abortion in UK sheep flocks. The disease is a real drain on profits, he said.

"Toxoplasmosis can cause abortions, barrenness, reabsorptions, mummified foetuses, stillbirths and weakly lambs," said Mr Atkinson.

"Sheep pick up the infection from the environment and so normal biosecurity measures are not enough to control the disease. Infected cats shed toxoplasma eggs in their faeces and sheep become infected when they ingest these eggs from contaminated pasture, feed and water."

Another underlying disease problem that often manifests itself as significant early lamb losses is enzootic abortion (EAE).

"EAE is caused by chlamydophila abortus bacteria. The disease can cause devastating abortion storms affecting approximately 25% of ewes. Once a flock has the disease it is likely it will never disappear due to its persistence in carrier sheep," he added.

"The disease usually arrives on farm through 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.

"Vaccination of already infected ewes reduces the risk of abortion and bacterial shedding thus reducing the chance of transmission to their lambs and the rest of the flock."

Mr Atkinson urges any sheep producers who saw a barren rate greater than 2% last season to talk to their vet, even if diagnostic blood samples have not been taken. Farmers should also ask for help if any ewes aborted.

"If either toxoplasmosis or EAE has been diagnosed in a flock, vaccination is the most effective way to help protect against these diseases for future years. The Toxovax vaccine is known to protect the ewe against toxoplasmosis for at least two lambing seasons and can be given up until three weeks before tupping.

"Enzovax helps protect the ewe for at least three years against EAE and can be given to ewe lambs intended for breeding from five months of age. Animals should be vaccinated at least four weeks prior to tupping," Mr Atkinson advised.