Enzootic Abortion in Sheep: Causes, Symptoms, and Control
Enzootic abortion of ewes (EAE), also known as chlamydial abortion, is a significant reproductive disease affecting sheep flocks worldwide. It is caused by the bacterium Chlamydia abortus and leads to late-term abortions, stillbirths, and the birth of weak lambs, resulting in substantial economic losses and welfare concerns.
Cause and Transmission
The causative agent, Chlamydia abortus, primarily infects the placenta of pregnant ewes. Transmission occurs through:
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Ingestion or inhalation of contaminated materials (placenta, uterine fluids, bedding).
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Close contact with infected ewes, especially around lambing.
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Carrier animals: Some ewes may carry the bacteria without showing clinical signs but can shed the organism during subsequent pregnancies.
Once infected, ewes typically do not abort in the current pregnancy but are likely to abort in the next one.
Clinical Signs
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Abortion in the last 2–3 weeks of gestation is the hallmark sign.
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Stillbirths or birth of weak lambs that may die shortly after birth.
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The placenta is often thickened, inflamed, and covered in a brown, necrotic exudate.
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Abortion storms may occur in naïve flocks, affecting up to 30% or more of pregnant ewes.
Diagnosis
Diagnosis is confirmed through:
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Post-mortem examination of aborted fetuses and placentas.
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Laboratory tests, including PCR, ELISA, or culture of Chlamydia abortus.
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Serology can be used for flock monitoring.
Treatment and Control
There is no specific cure for enzootic abortion, but control strategies include:
1. Vaccination
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Live vaccines are available and are the most effective prevention method.
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Vaccination is typically done before tupping (mating). However vaccines need to be given 4 weeks pre tupping in most cases. Check out handy calendar to confirm when you can vaccinate. Abortion Vaccination Window
2. Antibiotics
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Long-acting oxytetracycline injections may reduce the severity and spread if given during pregnancy, but this is not a long-term solution.
3. Biosecurity Measures
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Isolate aborting ewes for at least 3 weeks.
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Burn or deeply bury aborted materials and contaminated bedding.
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Wear gloves and disinfect lambing equipment regularly.
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Introduce new stock from reputable, disease-free sources.
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