Problems of Rams, Ewes, and Lambs - Raising Sheep - page 240

■ Salmonellosis
■ Toxoplasmosis
■ Vibriosis
Feed that contains mold spores can infect and destroy the placenta. This
in turn cuts off nourishment to the fetus.
Injury is often a cause of abortion, such as when a ram is running with the
pregnant ewes and bumps them away from hay or feed. Narrow doorways,
where sheep rush through for feed, are dangerous, especially as pregnancy
progresses and the ewes become large. Dog attacks nearly always cause abor-
tions among the ewes that have been injured or chased.
Certain diseases are another obvious cause of abortion, and these dis-
eases are more well defi ned than ever. When abortion occurs and there is
any chance that it is disease related (see the most common disease in North
America below), hygiene is critically important. Aborting ewes should be
quarantined from the rest of the fl ock, and aborted lambs, placentas, and the
bedding should be destroyed.
Enzootic Abortion of Ewes
Enzootic abortion of ewes (EAE) is caused by Chlamydia psittaci, which causes
late-term abortions, stillbirths, and weak lambs. It is the most common cause
of abortion in North American fl ocks. C. psittaci is not the same species of
Chlamydia that causes respiratory diseases, epididymitis in rams, conjunc-
tivitis (pinkeye), or arthritis in sheep; however, in fl ocks where C. psittaci is
enzootic, other problems, such as pneumonia, often arise.
C. psittaci is spread to susceptible ewes by contact with aborting ewes,
infected fetal membranes, uterine discharges, or a dead fetus. Susceptible
ewes thus infected will most likely abort their next lamb unless they become
infected early during gestation, in which case it would happen with the cur-
rent pregnancy. When the organism is fi rst introduced to a clean fl ock, abor-
tions can reach as high as 60 percent, but after a year or two, as the fl ock
develops immunity, they drop to about 5 percent.
Vaccinations are available, but they cannot help during an outbreak. Since
the signs of vibriosis (see below) and EAE are similar, laboratory analysis
must be used to identify the exact cause of an abortion. The EAE-vibrio vac-
cine protects from both and should be given 60 days prior to breeding, then
repeated at 30 days prior. Once a fl ock has been vaccinated, an annual single
dose will keep the animals protected.