A small amount of abortions are inevitable in all flocks, but once they exceed 2 per cent, investigations should be made.
Occasional abortions are inevitable in all flocks. However, once the incidence exceeds 2 per cent, particularly if several cases occur close together, it suggests an infectious agent may be present.
Caroline Robinson, veterinary investigation officer at SAC, says investigation should be carried out to determine the cause and instigate any appropriate control measures.
“The most comprehensive way to investigate an abortion is to submit the entire product of the abortion to your nearest SAC Consulting, APHA disease surveillance centre, or other local post mortem facility,” she says.
“If there has been more than one abortion, submission of material from several ewes will increase the chances of a swift diagnosis. Material from different ewes should be submitted in different bags to avoid contaminating the material and clouding the results – more than one cause of abortion could be at work in your flock.
“Ensuring collection of placentae to accompany lambs, where possible, greatly increases the chance of detecting some infectious agents: some causes of abortion act directly on the placenta, restricting its ability to provide essential life support in the womb but leaving little evidence in the lambs. Enzootic abortion [EAE] is a good example.”
Farmers can be badly overstretched at lambing time, and submission of abortion material to a laboratory is sometimes delegated to another member of the family or farm staff.
In these cases, write a brief history for the laboratory, including details of what has been happening, numbers involved, the size of the group at risk and any vaccines used (particularly those against EAE and toxoplasma). Mrs Robinson also advises noting whether the affected animals are home-bred or bought-in, the ages affected and whether they are sick or well. Supplying a telephone number on which the lab will be able to reach you with any further questions when the lambs arrive is also worthwhile.
If you are too far from a post-mortem facility for submission of lambs to be feasible, your own vet may be able to help by taking the range of samples needed from aborted lambs during a farm visit or from abortion material dropped at the practice, says Mrs Robinson.
Samples sent to laboratories need to comply with international regulations for packing of infectious substances, so farmers should not submit samples by post themselves. Even if you are taking material directly to a laboratory, it is recommended to let your own vet know you suspect a problem and are investigating so they can advise on the best way to proceed.
The pattern of abortions seen so far may result in your vet recommending a particular action or treatment while you wait for your results. Your vet may also recommend blood sampling the ewes in some situations.
Mrs Robinson says: “If you do not reach a diagnosis with your first submission, it is worth submitting material from further abortions, if there are any. Causative organisms can die before they reach the lab, becoming unidentifiable; mummified lambs may not yield all the samples necessary for diagnosis; or sometimes the first submission has been incomplete.
While waiting for the results, all aborted ewes should be marked and, if possible, isolated away from all other sheep until the abortion discharges have dried up, says Mrs Robinson. Keep any aborted ewes well away from ewes which are still to lamb.
“It should always be remembered many infectious causes of abortion in sheep can be transmitted to humans. This is particularly of concern for pregnant women or women of childbearing age, who should not come into contact with lambing ewes, placentae, discharges or abortion material.”