Enzootic Abortion of Ewes: Chlamydial Abortion in Sheep
- See your vet immediately if a ewe aborts, delivers weak lambs, or has a retained placenta late in pregnancy.
- Enzootic abortion of ewes is usually caused by Chlamydia abortus and most often shows up in the last 2 to 3 weeks of gestation.
- The placenta and birth fluids carry a high infection risk for other sheep and for people, especially pregnant women.
- Diagnosis usually depends on testing the placenta, fetus, and sometimes blood samples rather than signs alone.
- Flock control often includes isolation, careful disposal of contaminated materials, cleaning, and vet-directed antibiotic or vaccination plans.
What Is Enzootic Abortion of Ewes?
Enzootic abortion of ewes, often shortened to EAE or OEA, is a contagious reproductive disease of sheep caused by Chlamydia abortus. It is best known for causing late-term abortions, stillbirths, and weak lambs. In many flocks, a ewe may look normal for most of pregnancy and then suddenly abort near the end of gestation.
This disease matters because it can spread quietly through a flock before obvious losses appear. Some ewes become infected earlier in life and do not show problems until a later pregnancy. During an outbreak, the placenta, vaginal discharge, and lambing environment can expose many other sheep.
It is also a zoonotic disease, which means people can become infected. Pregnant women are at especially high risk for severe illness and pregnancy loss after contact with infected ewes, placentas, or birth fluids. If abortions are happening in your flock, use gloves, dedicated clothing, and strict hygiene, and keep pregnant people away from lambing areas until your vet helps identify the cause.
Symptoms of Enzootic Abortion of Ewes
- Late-term abortion, usually in the last 2 to 3 weeks of pregnancy
- Stillborn lambs or lambs born weak and unable to nurse well
- Retained placenta or heavy vaginal discharge after abortion or lambing
- Placenta that looks thickened, inflamed, or dark red-brown
- Fresh-looking fetus with little decomposition despite abortion
- Mild depression, reduced appetite, or fever in some ewes
Call your vet promptly for any abortion in late pregnancy, and treat multiple abortions as an urgent flock problem. Cornell notes that an infectious cause should be strongly suspected when more than 2% of the flock aborts. Keep the ewe, fetus, and placenta separate from the rest of the flock until your vet advises next steps.
Do not handle placentas or aborted lambs with bare hands. Pregnant people should not enter the lambing area or help with affected ewes. Even if the ewe seems bright afterward, the flock-level risk can still be significant.
What Causes Enzootic Abortion of Ewes?
Chlamydia abortus is the main cause of enzootic abortion of ewes. Sheep are usually exposed through infected placentas, birth fluids, vaginal discharge, contaminated bedding, and lambing areas. The organism can also spread through carrier animals, and rams may play a role in venereal transmission.
One frustrating part of this disease is timing. A ewe may become infected well before she shows any reproductive problem. Then, at the next pregnancy, she may abort late in gestation or deliver weak lambs. Afterward, many ewes do not abort again, but they may remain infected and continue to shed the organism around breeding and lambing.
Outbreaks are more likely when replacement animals are introduced without quarantine, when lambing areas are crowded, or when contaminated materials are not removed quickly. Because several infectious diseases can cause abortion in sheep, your vet will also consider other causes such as campylobacteriosis, toxoplasmosis, listeriosis, Q fever, salmonellosis, and leptospirosis.
How Is Enzootic Abortion of Ewes Diagnosed?
A diagnosis is usually made by combining flock history with laboratory testing. Your vet will want to know when abortions started, how many ewes are affected, whether new animals were added, and what stage of pregnancy losses occurred. Late-term abortions with placental inflammation raise concern, but signs alone are not enough to confirm chlamydial abortion.
The most useful samples are the placenta, fetal tissues, and sometimes blood from the ewe. Merck Veterinary Manual notes that definitive diagnosis can be made with tests such as PCR, ELISA, fluorescent antibody testing, or organism isolation. Placental smears may show chlamydial bodies, but those findings are not specific enough to rule out every other cause.
If possible, refrigerate but do not freeze the fetus and placenta unless your vet or diagnostic lab tells you otherwise. Keep samples clean, bagged separately, and away from dogs, cats, wildlife, and other sheep. Fast sample submission improves the odds of getting a useful answer and helps your vet build a practical flock plan.
Treatment Options for Enzootic Abortion of Ewes
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Farm call or flock consultation with your vet
- Immediate isolation of aborting ewes
- Removal and secure disposal of placenta, bedding, and aborted materials
- Basic PPE and hygiene plan for handlers
- Targeted treatment plan for in-contact ewes if your vet recommends oxytetracycline under a valid veterinary-client-patient relationship
- Monitoring of the rest of the flock for additional abortions
Recommended Standard Treatment
- Veterinary exam and flock risk assessment
- Diagnostic submission of placenta and fetus for PCR and/or necropsy-based abortion workup
- Isolation and biosecurity protocol for lambing areas
- Vet-directed flock medication plan when appropriate
- Record review of bred ewes, replacements, and recent abortions
- Follow-up prevention plan that may include vaccination strategy where available and appropriate
Advanced / Critical Care
- Multiple diagnostic submissions during an outbreak
- Necropsy and histopathology through a veterinary diagnostic lab
- Culture or additional rule-out testing for mixed or competing abortion causes
- Repeated flock visits during an abortion storm
- Supportive care for sick ewes with metritis, retained placenta, dehydration, or systemic illness
- Whole-flock outbreak response plan covering quarantine, culling decisions, breeding management, and future lambing protocols
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Enzootic Abortion of Ewes
Bring these questions to your vet appointment to get the most out of your visit.
- Which samples should I collect right now, and how should I store and transport them?
- Based on this ewe's stage of pregnancy and placental changes, how likely is Chlamydia abortus compared with other abortion causes?
- Should the in-contact ewes be treated, and if so, which animals should be included?
- What biosecurity steps matter most today to protect the rest of the flock?
- Do I need to separate replacement ewe lambs, recently purchased animals, or the ram?
- Is vaccination appropriate for this flock, and if so, when should it be given relative to breeding?
- Which people on the farm should avoid the lambing area because of zoonotic risk?
- What records should I keep so we can track whether this is becoming a larger flock outbreak?
How to Prevent Enzootic Abortion of Ewes
Prevention starts with biosecurity and flock management. Quarantine new additions before mixing them with bred ewes, and avoid buying replacements from flocks with an unclear abortion history. During lambing, remove placentas and contaminated bedding promptly, clean pens between ewes when possible, and keep feed and water away from manure and birth fluids.
If an abortion happens, isolate that ewe right away and keep dogs, cats, wildlife, and unnecessary foot traffic out of the area. Use gloves, dedicated boots, and washable outerwear. Cornell recommends isolating aborting females and completely disposing of materials associated with abortions and normal births, because more than one infectious cause may be active in a flock.
Vaccination can be part of prevention in some regions and management systems. Merck notes that C. abortus bacterins are available and reduce abortions, though vaccine products and protocols vary by country and practice setting. Your vet can help decide whether vaccination, strategic medication, culling of repeat problem animals, or changes to replacement sourcing make the most sense for your flock.
Because this disease is zoonotic, prevention also protects people. Pregnant women should not handle pregnant sheep, aborted fetuses, placentas, or contaminated bedding when abortion disease is suspected.