Maximizing the number of weaned lambs per ewe exposed to the ram is a production goal for most sheep producers. Abortions are only the "tip of the iceberg" relating to reproductive causes of production loss; infertility, early embryonic death and weak lambs may actually be the larger portion of production losses from the same disease that caused the abortions. An increase of abortions above 2% of the herd warrants an investigation.
In sheep the three most common causes for abortion are:
Toxoplasmosis,Chlamydiosis(EAE-enzootic abortion of ewes) and Campylobacteriosis. The relative importance of each of these agents varies according to geographic locale. Toxoplasmosis is the most frequent abortifacient agent in north central US where as EAE is the most frequent in England. Salmonella is also a known cause of abortion as are other agents such as Border Disease Virus, Coxiellasp.(Q fever),Liste-ria, and A. pyogenes.
It is important to remember the public health significance/zoonotic potential of many of these agents: Chlamy-dia, Toxoplasmosis,Salmonella. Listeria and Q. fever!
In attempting to reach a diagnosis for the cause of abortion in sheep the following factors are important to consider:
Rules of Thumb
1. Regard all abortions as infectious until proven otherwise! HANDLE WITH CARE.
2. Record history on the ADDL submission form - Number of animal(s) affected, which group is affected, previous abortion history, etc.
3. Tissues to submit: Ideally} fresh, clean, fetus and placenta (including cotyledons), chill, but do not freeze!
Minimally; Fresh and formalin fixed lung, brain, kidney, liver and placenta including cotyledon (preferably with gross lesion). Collect stomach contents aseptically in a syringe. Recording gross lesions seen at time of the necropsy is extremely helpful.
Collect serum from aborted ewe, but freeze it in your clinic for future reference, if needed. Following the above recommendations will greatly enhance the success of diagnosing abortions in sheep.
Daniel Ronen, Class of '94 (Edited by: W.G.VanAlstine)