Ewe blood tests reveal hidden diseases

MILTON KEYNES, UK, August 14 2015 – An underlying disease was a significant cause of barrenness or abortion in ewes last year according to an analysis of the latest diagnostic results released by MSD Animal Health (known as Merck Animal Health in the United States and Canada).Blood samples from 500 UK sheep farms were tested during 2014 when the EXPERTISTM Barren EweCheck and FlockCheck diagnostic services (subsidised by MSD Animal Health) were made available to vets.

According to the data, more than 81 percent of the flocks tested showed evidence of exposure to the parasite Toxoplasma gondii, which causes toxoplasmosis. The data also show that 52 percent of flocks had been exposed to Chlamydophila abortus bacteria, the organism causing enzootic abortion (EAE); 43 percent of flocks 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 Animal Health technical manager John Atkinson MRCVS.

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

“Toxoplasmosis can cause abortions, barrenness, reabsorptions, mummified foetuses, stillbirths and weakly lambs. 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,” Mr Atkinson says.

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 percent of ewes. Once a flock has the disease it is likely it will never disappear due to its persistence in carrier sheep. 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 recorded a flock barren rate greater than 2 percent last season to talk to their vet for advice, even if diagnostic blood samples have not been taken. Ask for help too if any ewes aborted lambs during lambing, he says.

“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, conveniently, can be given up until three weeks before tupping.

“The ENZOVAX® vaccine 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 advises.