J. L. Goelz, D.V.M.
International SheepLetter
November 2000

Abortions can occur sporadically or as an outbreak. Generally we classify abortions due to and infectious cause or due to a non-infectious cause. Non-infectious abortions can be caused by trauma to the ewe by rough handling or by other ewes such as fighting for feed bunk space or piling through a narrow barn door. Even in poorly managed flocks with bad facilities the incidence of non-infectious abortions will be less than 5%. Steps can be taken to minimize non-infectious abortions, however from a production or economic standpoint it is infectious abortions that are potentially catastrophic. If the incidence of abortions is greater than 5% be suspicious of an infectious cause and steps should be taken to determine the cause and minimize the abortion losses to the flock.

The first step is to determine the infectious cause. There are three primary causes of abortion that we see every winter and spring. These are Chlaymida psittici, Campylobacter (vibrio), and Toxoplama gondii. Often the history of your flock may be suggestive of a potential cause. For example, if the abortions are occuring in ewe lambs or young ewes it is likely that the infectious cause is Chlaymida. Remember that not all abortion storms follow the textbook and even if we suspect Chlamydia we need to confirm the diagnosis. In fact, we often get surprised once the infectious cause if finally determined.
The best way to determine the exact infectious cause is to submit fresh aborted fetuses and placenta to a veterinary diagnostic laboratory. The fetus must be as fresh as possible and either driven or sent next day delivery to the closest diagnostic laboratory. Don't forget to also send a portion of the placenta as often the lesions are only present in the placenta and not in the fetus. The fetus and placenta should be chilled with ice packs but not frozen. Your local veterinarian can help you with shipping and packaging of samples.

Since it may take up to a week for results from the diagnostic lab you must attempt to stop the abortion storm while you are waiting for results. Unfortunately, we often are left with the "shotgun" approach for therapy while diagnostic lab results are pending. However, we can at least make sure that we are pointed in the right direction. First of all, since the aborted fetus and placenta are considered infectious it is critical that they are removed from the pen immediately. Any aborting ewes should be isolated from the gestating ewes as they present a risk of infecting other pregnant ewes and causing them to abort. Secondly, if the cause of abortion is Chlamydia we can stop the abortions by treating the ewes with tetracycline. This can be administered in the feed (500mg per head per day) or by injecting oxytetracycline such as LA-200 or Biomycin 200 (5ml per 100# of body weight repeated every 7 days). If the cause of the abortions is Campylobacter (Vibrio) about half of the isolates that we see are sensitive to tetracycline. Therefore we have a pretty good chance at stopping the abortion storm while we are waiting for diagnostic lab results. In cases of Campylobacter (Vibrio) isolates that are resistant to tetracycline a good second choice of antibiotics is Sulfadimethoxine (Albon) administered through the drinking water. In cases were neither tetracycline nor sulfa are effective we have to rely on the diagnostic lab sensitivity to tell us which antibiotics will be effective.

Unfortunately, in cases of Toxoplasma abortions everything that we have discussed so far will be ineffective. This is due to the fact that Toxoplasma is not a bacteria but is rather a protozoan parasite. The importance of this difference is in the manner in which ewes are infected. Toxoplasma is a parasite of cats and rodents. In the winter months we often find stray cats taking up residence in the sheep barn and using the feed as a litter box. These stray cats, especially young ones, shed Toxoplasma into the environment and when ingested by the ewe the Toxoplasma causes abortions. The only treatment is prevention. The shepherd needs to: 1) Cover stored feed to prevent cats from using it as a litterbox, 2) Discourage stray cats from taking up residence in the sheep barn, 3) Feed a coccidostat such as Rumensin or Deccox. Rumensin, although not approved by the FDA for sheep is effective in preventing Toxoplasma abortions if fed 15 to30 mg. per head per day. Deccox is approved for sheep however the level that you need to feed to prevent Toxoplasma abortions is four times the FDA approved level. Either of these should be thoroughly mixed into the feed as the inclusion rates are small and adequate consumption is important.

There are many management steps that can be employed to prevent infectious abortions in your flock. Vibrio and Chlamydia are often introduced into non-infected flocks but the addition of purchased ewes or rams. All new flock additions should be scrutinized along with their flock of origin. Any pregnant ewes that are added should be penned separately for as long as possible, preferable until they lamb. The same goes for replacement ewe lambs within the flock. Since they have not been exposed to the mature ewe flock they should be gestated separately from the mature ewes. In many Midwestern flocks Chlamydia is present and goes relatively unnoticed until the ewes are confined before lambing. We can prevent abortions if we begin feeding the ewes 250 mg. of tetracycline per head per day as soon as the ewes are drylotted. This has been a very effective way of controlling Chlamydia abortions in flock with historical Chlamydia problems. Additionally, it is critical that ewes are not fed on the ground. The transmission of both Chlamydia and Vibrio oral ingestion of feed contaminated with fecal material from ewes that are shedding or contact with fetal and placental fluids. If the ewes are fed in a bunk this will decrease the probability of oral ingestion of the bacteria. Any aborted fetuses should be removed from the pen immediately to prevent other ewes from coming into contact with the fetus. Be sure to wear disposable gloves when handling the fetus as all of the pathogens that cause abortions in sheep can be spread to humans. Finally, vaccination for both Chlamydia and Vibrio are an important part of a flock health program. Every lambing season we talk with Shepherds who have never vaccinated for Chlamydia or Vibrio and have never had abortion problems. Unfortunately, the reason why they called is that their luck ran out and they now are experiencing an abortion storm. Vaccine is cheap insurance against disaster.