Infectious Causes of Abortion in Ewes - OSU Sheep Team

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December
2018

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Infectious Causes of Abortion in Ewes
Susan Schoenian, Sheep & Goat Specialist, University of Maryland Small
Ruminant Extension Program
(Previously published on the Maryland Small Ruminant Page)
There are many things than can disrupt a
healthy pregnancy in a ewe. While it is
common for about 25% of embryos to die
or be reabsorbed the first three weeks of
pregnancy up to the time of implantation,
these are the most crucial in establishing
healthy pregnancies. The nutritional
requirements of ewes during early
gestation is only slightly more than
maintenance requirements, but it is

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essential that the flock not be exposed to
any undue stresses.

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It appears normal for about 1.5 to 2.0% (up to 5%) of the ewes in a flock to
abort. Abortion rates significantly above this level cut into profit potentials, as
what may start out as a few isolated cases can quickly escalate into an
abortion “storm,” resulting in 20-30% percent abortions or as high as 80%
lamb mortality.
There are several infectious agents which are known to cause late-term
abortions in small ruminants. The most common are Campylobacter fetus
(also called Vibrio), Chlymidia psittach (also called EAE or Enzootic Abortion
in Ewes) and Toxoplasma gondii. Less common causes include Leptospirosis,
Brucella ovis (related to epididymitis in rams) , Q-fever, Border disease
(related to BVD in cattle) and Bluetongue virus. Non-infectious causes of
abortion include rough handling, fighting among animals, inadequate
nutrition, and plant poisons.
Ewes infected with Vibrio typically abort during the last 6-8 weeks of
pregnancy or give birth to weak or dead lambs. Once a ewe aborts, she is
immune to the disease. Vibrio abortions are usually introduced into a flock via
a carrier animal. A carrier is an animal that has aborted, but carries the
infectious bacteria. It is important to note that the bacterium that causes
Vibrio in cattle is different from the one that causes it in sheep.
Chlamydia abortions also occur during late pregnancy and may result in
stillborns or weak lambs that die shortly after birth. Chylamydia is also
associated with pinkeye, polyarthritis, and pneumonia. The spread of
enzootic abortion is believed to be primarily through contact with infected
fetuses, placenta or vaginal discharges, though there is evidence to suggest
that some “carrier” ewes may constantly shed the organism in their feces or
from their lungs.
Vaccines are available for both Vibrio and Chlamydia, often in the same
injection. They are designed for use at the beginning of the breeding season.
They are killed vaccines, thus two shots are required the first year. After a
ewe has received her initial two-vaccination series, only a single vaccination
needs to be given in subsequent years. Some large producers have achieved

Mt. Hope Auction, OH

good results simply by vaccinating replacement ewes.

Muskingum Livestock, OH

Toxoplasmosis is a common intestinal, protozoal infection in cats. It can cause
abortion in sheep at any stage of pregnancy, depending upon the stage
during which the ewe was infected. It is generally accepted that ewes

New Holland, PA
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become infected when they ingest feed or water which has been
contaminated with infected cat feces. Unfortunately, there is no vaccine
available in the U.S. to prevent toxoplasmosis. The best prevention is to
control cat populations by keeping cats away from pregnant ewes and/or
maintain a healthy adult cat population and to prevent contamination of feed
and water by nesting cats.
In order to develop a course of action and prevent abortion storms in
subsequent years, the specific cause of abortion must be determined.
Diagnosis is based on clinical signs and flock history, combined with
laboratory diagnostics. It is crucial that the proper samples (both the fetal and

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placental tissues) be submitted to a veterinarian or state diagnostic laboratory
in order to differentiate between abortion types. Tissues can be kept cold by
packing in ice in a leak-proof, insulated container until they can be delivered.
Blood sampling (before and after abortion) may also be warranted.
Controlling an abortion outbreak requires strict sanitation and separation of
aborting ewes. Infected fetuses, placental tissues, and bedding must be
properly disposed of (burned or buried). All aborting ewes or those with
vaginal discharges should be immediately isolated from the main flock.
Aborted ewes should not be used as foster mothers for female offspring,
unless infectious causes of abortion can be eliminated. Pregnant ewes
should never be fed on the ground. Breeding stock from flocks that have
experienced abortion storms should not be purchased.

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Immediate vaccination and the use of antibiotics may help lessen losses
during an outbreak. Ewes should be injected with an antibiotic (tetracyclines),
then started on a feed that contains antibiotics. Consult with a food animal
veterinarian for an appropriate course of action and if using any drug extralabel.
It is important to note that humans are susceptible to many of the same
abortion-causing agents as sheep. Care must be taken when assisting ewes
during lambing and when caring for weak lambs. Plastic gloves and other
protective clothing should be worn whenever contaminated material is
handled. Unpasteurized milk or cheese should not be consumed. Pregnant
women are especially susceptible to toxoplasmosis and should not handle
infected cats or aborted fetuses.

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Posted by Braden Campbell at 8:00am
Posted in Health and tagged Health, Management, Reproduction. Bookmark
the permalink.

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