Analysis by regional veterinary laboratories shows toxoplasmosis and enzootic abortion (EAE) to be the leading causes of abortion in sheep.
“My advice to farmers is to always investigate the reasons for abortions. Contact your veterinary practitioner who will arrange for swabs to be sent to FarmLab Diagnostics in Elphin and for foetuses and placentae to be sent to the regional veterinary laboratory,” he said.
Paul is seeing an increase in the incidence of both toxoplasmosis and EAE on his clients’ farms this year, with a number of samples sent to the Sligo laboratory coming back as positive to either toxoplasmosis or EAE, or both.
A serious problem presented on a flock of 50 ewes where 15 aborted within a month of lambing. While the first foetuses sent to the laboratory did not test positive for either toxoplasmosis or EAE, later samples were positive for EAE.
“That can sometimes be the case, where it may take a second or a third submission before you get a positive result,” said Paul.
He has also dealt with a severe case of toxoplasmosis in an early lambing flock where around half of a group of 40 replacement ewes aborted. The farmer in question had planned to vaccinate before the ewes went to the ram, following previous investigations, but “didn’t get around to it”.
He said that while toxoplasmosis is not passed from ewe to ewe, EAE is highly infectious, with organisms passed from ewe to ewe in infected afterbirth, on new lambs and in vaginal discharges for up to three weeks after lambing.
“Where enzootic abortion is diagnosed, it is vital to keep aborted ewes separate from the rest of the flock and not foster lambs on to aborted ewes. Keeping bought-in ewes separate from the rest of the flock and segregating ewes into different age groups can also help.”
Paul is also actively involved with his father Colin in running the family sheep flock at The Rock, Dungannon, Co Tyrone.
They have a flock of 200 ewes, split half and half between pedigree Beltex and Charollais and a commercial flock. Paul also runs a flock of around 50 pedigree and commercial ewes at Strandhill, Sligo.
Progeny from their Beechtree pedigree flock are in strong demand in England and from farmers in both Northern Ireland and across the Republic of Ireland.
“We have been vaccinating against toxoplasmosis and EAE for the past eight to 10 years.
“While tests didn’t show positive to either disease, since we started vaccinating our barren rate is dramatically down and we have had no abortions,” said Paul.
“The one-shot vaccines available for toxoplasmosis and enzootic abortion (EAE) can be given to non-pregnant breeding ewes and lambs (from five months of age).
“Vaccination must be completed at least four weeks before sheep go to the ram,” advised Paul Barnes.
“Generally, just one shot of each vaccine is required during the lifetime of the ewe. It is important to get veterinary advice on the most appropriate vaccination strategy for your farm,” he added.
Swab tests help diagnosis
The FarmLab Diagnostics swab test pack for diagnosing toxoplasmosis and enzootic abortion.
FarmLab Diagnostics in Elphin, Co Roscommon, provides a test which can be used as a preliminary step in the diagnosis of both toxoplasmosis and enzootic abortion.
The test, which is provided through veterinary practitioners, consists of a pack which contains two FLOQ swabs. One should be used to sample the aborted placenta (cleanings). The second should be used to take a sample from the surface of the aborted foetus while still wet with birth fluids. Alternatively, this swab may be used to take a sample from the ewe’s vagina.
Both swabs should be placed inside the ziplock bag provided and, together with the completed form, given to the veterinary practitioner for submission to the laboratory. Test results are returned by email to both the farmer and veterinary practitioner.
A positive result for Chlamydia abortus or Toxoplasma gondii indicates that they are present in the samples submitted. FarmLab Diagnostics stresses that this does not necessarily mean that they are the actual or only cause of abortion. It recommends that foetal samples should also be sent to the one of the Department’s regional veterinary laboratories for post mortem examination and that farmers should avail of veterinary advice in determining the most appropriate course of action in dealing with abortion.
Causes and clinical signs of abortion
Toxoplasmosis, caused by a microscopic parasite Toxoplasma gondii (T. gondii), is most commonly caused by contamination due to cat faeces in feed, bedding or manure or directly on to pasture.
“A single cat dropping can contain enough eggs to infect more than 100 ewes and almost 75% of ewes are believed to come in contact with T. gondii during their lifetime,” said Sarah Campbell, veterinary advisor with MSD Animal Health.
She said clinical signs can include barren sheep, abortions, stillbirths, weakly lambs and mummified foetuses.
“Vaccination is the only way to effectively build uniform immunity to toxoplasmosis in the flock. Initially, the entire flock will require vaccination. In subsequent years, all replacements can be given a vaccine dose as they enter the flock.
An outbreak of enzootic abortion (EAE), caused by a bacterial organism called Chlamydophila abortus, can result in significant losses due to sheep aborting. The disease is usually introduced to the flock by bought-in replacement lambs, but it can also be spread by wildlife carrying infected placentae from farm to farm.
“When a ewe aborts, she sheds large numbers of organisms, which can infect any in-contact ewe or lamb. These newly infected sheep will not show any signs of infection.
“The organisms remain dormant in the body until the ewe becomes pregnant. In infected lambs, they can remain dormant for up to two years.
“About three weeks before lambing, the placenta becomes inflamed and abortion occurs,” she said.
“While ewes that aborted often continue to have a normal lambing in subsequent years, they are carriers of the disease and may still shed organisms, resulting in infection of other in-contact sheep and lambs
“Vaccination will effectively reduce the risk of enzootic abortion as part of a flock health plan. Because there is no test to identify latently infected sheep, it is important to vaccinate all breeding sheep in the first year. After that, only replacements need to be vaccinated,” explained Sarah.