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Enzootic Abortion of Ewes
(Chlamydial Ovine Abortion, EAE)
Douglas A. Anderson,
DVM
Staff Veterinarian
Technical Service
In previous
issues of Vet’s Corner, we have discussed ovine abortion and
campylobacteriosis (vibrionic abortion of ewes).
The following article references another common cause
of ovine abortion, chlamydial ovine abortion, or more commonly
known as enzootic abortion of ewes (EAE).
Chlamydia psittaci (Antigenic type 1) is the
organism responsible for the disease.
It is an unique gram negative, spheroidal bacterium
that replicates similarly to a virus.
They normally require special microscopic techniques to
confirm or identify their presence.
Infected ewes
may appear sick for several days before they abort late in
their pregnancy (last month).
They may also deliver stillborn, weak, or premature
lambs. In
unexposed flocks, the abortion rate may reach 30-50% of the
ewes. The
abortion may occur the following year, if the exposure occurs
after the ewes are pregnant.
Ewe lambs exposed prior to weaning may harbor the
disease and abort during their first pregnancy. In enzootic
areas (area where the disease is commonly present) abortions
will continue each season in the yearling and recently added
ewes. Infected
rams will show very few symptoms, but breeding will result in
a reduced conception rate and possible uterine infections in
the ewe.
The aborted
fetus is usually well preserved, in contrast to an autolytic
(already showing signs of decomposition) fetus in
campylobacteriosis or vibrionic abortion of ewes.
The fetus may be covered with a light beige or a clay-coloured,
flaky material. The
placenta exhibits variable areas of inflammation with
hyperemic (reddened) margins and necrotic (decomposing)
cotyledons. The
areas between the cotyledons will be thickened, granular, and
leathery appearing. Following
the abortion, a brown uterine discharge is common.
The placenta may also be retained and require
additional medical attention.
In rare cases, mortality of the ewe may result from an
unexpelled, mummified fetus.
Surviving ewes may become carriers.
This disease is contagious and normally
spreads through oral or nasal contact, ingestion, or
inhalation of contaminated material.
The fetus, placenta, birth fluids, and vaginal
discharge from the ewe are all sources of infection.
Isolate the aborting ewes immediately and consult with
your veterinarian on recommended treatment, proper disposal of
the aborted fetus/placenta, and disinfection procedures.
The veterinarian may also want to perform a necropsy or
take samples for an accurate diagnosis.
Prevent the
disease from spreading by limiting access to the aborted
materials by wild birds and wild or domestic mammals, which
may spread the organism.
Take measures to assure that the water supply, drinking
area, and feeding area do not become contaminated with the
aborted material, or vaginal discharges.
The use of ‘quarantine’ areas, separate boots,
coveralls, and plenty of disinfection is highly recommended
and cannot be stressed enough.
Cleanliness is absolutely essential.
Great care should be exercised to prevent human
exposure.
This disease
can be controlled with the use of a vaccine like CHLAMYDIA
PSITTACI BACTERIN, from Colorado Serum Company.
Vaccinate all incoming and unvaccinated ewes sixty days
prior to breeding season and again thirty days later.
Follow up with a booster every year just prior to
breeding season. Chlamydial
polyarthritis and conjunctivitis are caused by Chlamydia
psittaci (Antigenic type 2) and does not allow for
adequate cross protection.
As always, consult with your veterinarian for the
program that best fits your needs.
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