Sheep Abortion Diseases: Enzootic Abortion and Flock Welfare

Infectious abortion diseases are a major welfare and economic problem in sheep. Understanding their causes and prevention protects both ewe welfare and flock productivity.

Key Facts

Enzootic abortion of ewes (EAE), caused by Chlamydia abortus, is the most common cause of infectious abortion in UK sheep, causing up to 30% of ewes in naive flocks to abort.
Toxoplasmosis (Toxoplasma gondii) is the second most common cause of ovine abortion in the UK, typically causing mid-to-late gestation fetal death.
Other abortion causes include Salmonella, Campylobacter, border disease virus, and Listeria.
EAE is a zoonosis — pregnant women who handle aborted material are at serious risk of infection causing miscarriage or stillbirth.
EAE vaccination is available and highly effective — it is recommended for all naive ewes entering affected flocks.
Toxoplasmosis prevention relies on cat control around sheep feed stores and vaccination.
Abortion storms in naive flocks cause extreme levels of welfare suffering — ewes carrying dead fetuses, dead and dying lambs, and systemic illness.

Welfare Considerations

Ovine abortion diseases cause significant welfare suffering. Ewes that abort in late gestation experience the physical and metabolic burden of fetal death and expulsion, often accompanied by systemic illness in bacterial infections like Salmonella. Ewes carrying dead fetuses may become systemically ill as toxins from the decomposing fetus enter the circulation. The lambing unit during an abortion storm is a scene of acute welfare crisis — the scale and speed of losses, and the suffering of affected ewes, creates welfare emergencies that overwhelm farm resources. Prevention through vaccination and hygiene is far preferable to outbreak management. Stockperson safety is also a welfare concern — EAE is a significant human health risk during lambing, and protective measures are essential.

What You Can Do

Vaccinate ewes against Chlamydia abortus (EAE) before the breeding season — this is the most effective preventive measure.
Control cat access to sheep feed, bedding, and water to reduce toxoplasmosis risk.
Wear gloves and protective clothing when handling aborted material — report suspected abortion storms to your vet immediately.
Test aborted material to identify the cause — this guides specific treatment and prevention for the flock.
Isolate ewes that have aborted from the main flock during lambing to reduce pathogen shedding.
Pregnant women must not handle aborted ewes or lambing material during an EAE or toxoplasmosis episode — this is a serious public health risk.