Download ovine-abortion-cliffe

OVINE ABORTION
Infectious abortion remains one of the major flock health problems faced by sheep farmers and can
have a significant impact on production. Costs are variably quoted as between £40 and £65 per
aborted ewe, but will be more when lamb prices are high.
Sporadic losses do occur, but once the abortion rate starts to become more than 2% (or sudden
clusters) it is very suggestive that an infectious organism is involved and further investigation by
post-mortem and blood sampling is strongly recommended.
The two main pathogens diagnosed are Chlamydophila abortus (Enzootic abortion (EAE) and
Toxoplasma gondii. According to MSD Animal Health Flock Check results for 2010-2011, 86% of the
blood samples submitted tested positive for Toxoplasmosis; 62% for EAE, with 43% testing positive
for both.
Enzootic abortion
EAE usually causes the birth of a stillborn lamb in the 2-3 weeks prior to the expected lambing date.
Other ewes will get infected by ingestion of infected material (vaginal discharge, afterbirth).
Normally, ewes that abort become immune but occasionally a ewe can retain the organism and
excrete this at the next oestrus cycle/lambing. Ewe lambs born to infected ewes can become
infected and abort in their first pregnancy. Vaccination at least four weeks prior to tupping remains
the best way of preventing the disease alongside general biosecurity measures. Whenever an
abortion is seen it is important to isolate the aborted ewe and dispose of all infected material. In the
face of an outbreak, treatment with an Oxytetracycline antibiotic can be used to reduce the number
of abortions. This will not reverse the damage already done to the placenta in those ewes that are
very close to lambing. Even though Oxytetracycline can’t save these lambs, lambs from healthy ewes
can be fostered onto these ewes. It is vital that these are not kept as replacements.
Toxoplasma
Toxoplasma is one of the most successful organisms in the world as it is capable of infecting most
warm blooded animals (including humans). The sheep is an intermittent host that can get infected
by ingesting oocysts (eggs) shed by the definite host, the cat. Even just a brief visit from an infected
cat can significantly contaminate barns and pastures. One cat dropping contains enough oocysts to
infect over a hundred ewes. These oocysts can survive in the environment for up to 12-18 months.
It causes resorption, abortion and birth of mummified or weakly lambs, with early infections causing
infertility in the ewes. Investigation is still ongoing as to whether the infection can be vertically
transferred from mother to foetus, but this is felt to be a very minor route of infection
This disease can be prevented by using the available vaccine up to 3 weeks prior to tupping. Both
vaccines last for several years and are usually given once.
Other infections
Other causes of abortion include Campylobacter, Salmonella, Listeria, Border disease and Q-fever.
Campylobacter is particularly seen in intensively managed flocks at the end of lambing when heavy
contamination and unhygienic environments occur. The main source of infection is carrier sheep
with risks from wild birds being another source. Salmonella is mostly associated with abortion and
death in ewes.
As several of the organisms involved cause a significant zoonotic risk (especially in pregnant women)
adhering to strict personal hygiene methods whilst handling sheep is very important.
Recommended flock biosecurity and biocontainment measures include:
 Isolate aborted ewes to prevent infection from vaginal discharges (eg. Chlamydia can remain
in discharges for up to 2 weeks), this includes ewes that gave birth to full-term death or
weakly lambs
 Remove all infected material like bedding (Chlamydia can survive in bedding for up to 6
weeks)
 If possible, keep the flock closed or if buying in replacements try and source them from a
flock with a high health status.
 When buying in replacements from an unknown source vaccination for EAE and
Toxoplasmosis is recommended
 Tag all ewes affected for future blood sampling or culling
 If more than 2% of the flock is affected submit samples to the lab for further diagnosis.
 Do not keep ewe lambs fostered onto aborted ewes.