Sheep Infectious Abortion: Enzootic Causes and Control

Infectious abortion in sheep causes significant welfare harm to ewes and fetal lambs. Understanding the main causes enables targeted prevention programs.

Key Facts

Enzootic abortion caused by Chlamydia abortus is the most common cause of sheep abortion in the UK
Toxoplasma gondii is the second most common cause and is introduced via cat feces
Infected ewes may abort or deliver stillborn or weak lambs in the last few weeks of pregnancy
Vaccines against EAE and toxoplasmosis are available and highly effective when used correctly
Human health risks exist with EAE - pregnant women should not handle aborting ewes

Welfare Considerations

Infectious abortion causes welfare harm to ewes through systemic illness, painful fetal expulsion, and retained membranes. Repeated abortion in a flock creates ongoing welfare compromise for affected animals and distress from failed reproductive attempts. The welfare solution combines vaccination with good biosecurity: EAE and toxoplasmosis vaccines dramatically reduce abortion storm incidence when used proactively. Reactive treatment after an abortion storm limits spread but cannot reverse the welfare harm already caused. Prevention is both more effective and more welfare-positive than response.

What You Can Do

Vaccinate ewes against enzootic abortion and toxoplasmosis before the breeding season
Control cat access to sheep feed and silage to reduce toxoplasmosis exposure
Implement strict hygiene protocols during abortions to prevent spread within the flock
Work with your vet to investigate and confirm the cause of any abortion cluster promptly
Advise all farm workers of the human health risks of handling aborting ewes