Abortion in ewes has many causes. Some are infectious like enzootic abortion of ewes (EAE)/chlamydiosis (Chlamydia psittaci), vibriosis/campylobacteriosis (Campylobactre fetus), brucellosis (Brucella spp.), toxoplasmosis (Toxoplasma gondii), listeriosis (Listeria monocytogenes), and salmonellosis (Salmonellaspp.). Others are toxic like hellebores (Veratrum spp.), kale (Brassica spp.), locoweed (Oxytropis spp.), poison/milk vetch (Astragalus spp.), broomweed (Gutierrezia microcephala), coumarins (rat poison, moldy grass or sweet clover), and mycotoxins (usually those that mimic the hormone estrogen). Still other diseases and toxic plants can cause abortions under certain conditions. Malnutrition, abrupt nutritional changes, and heat stress have been implicated and several more causes are currently under investigation.

In most cases of abortion, the actual cause is long gone by the time the abortion actually occurs, making a positive diagnosis difficult. A decomposed fetus or contaminated area further complicates the diagnostic efforts. Some toxins require extensive testing at special laboratories. In reality, due to the variety of causes (etiologies) and diagnostic hurdles, as many as 40-50% of all ovine abortions may go undiagnosed. This often explains why a plan that might work for one flock has no effect in a second flock.

While the odds may not look promising, establishing at least a presumptive diagnosis is necessary to take corrective action or develop a preventative plan. Isolate the aborting ewe and aborted fetus from the rest of the flock. These materials may be infectious and can be transmitted to the other ewes. Call your veterinarian as soon as possible. They can advise you on how to handle the material before they arrive to collect samples. After the examination, dispose of the fetus and aborted tissues properly and disinfect the area very well. Care must be taken while handling the material because some of the infectious agents are also contagious to man.

Two of the most common causes of ovine abortion are EAE (enzootic abortion of ewes) and vibriosis/campylobacteriosis. If these diseases are confirmed or suspected, a preventative plan should include vaccination of the flock and all future new arrivals to the breeding program.

At Colorado Serum Company, we carry a full line of sheep vaccines, which include two specifically developed to prevent ovine abortion.


  • For the prevention of enzootic abortion of ewes (EAE) caused by Chlamydia psittaci.

  • Vaccinate ewes sixty days prior to breeding with a booster dose thirty days later. Revaccinate yearly prior to breeding.


  • For the prevention of vibrionic abortion of ewes (vibriosis/campylobacteriosis) caused byCampylobactre fetus subspecies jejuni (type I) and subspecies intestinalis (type V).

  • Vaccinate ewes thirty days prior to breeding with a booster dose sixty to ninety days later. Revaccinate yearly around breeding time.

As always, read and follow label instructions.

For help with your flock health program, feel free to give our veterinary staff a call.