Abortion in ewes has a serious economic impact on lambing flocks and losses can be at least £85 per affected ewe, the National Animal Disease Information Service (NADIS) has warned.
The five most common bacterial causes of abortion are: Chlamydophila abortus (enzootic abortion of ewes, toxoplasmosis; salmonella serotypes; campylobacter fetus intestinalis; and listeria monocytogenes. 
Such infectious causes of abortion are most common after day 100 of pregnancy and an abortion rate in excess of 2% is suggestive of an infectious cause.
Enzootic abortion of ewes, toxoplasma gondii and campylobacter species cause more than 70% of all abortion outbreaks, and the cost of abortion is variably quoted as £85 per aborted ewe.

Diagnosis of abortion
The minimum requirements for laboratory submissions collected by your veterinary surgeon for abortion diagnosis include the foetus(es) or foetal stomach contents, a piece of placenta, a maternal serum sample. Flockowners should continue to submit aborted material during the outbreak, as more than one agent may be present.

For Chlamydial abortion, Chlamydophila abortus, enzootic abortion of ewes (EAE): 

  • Disease is transmitted by ingestion following exposure of susceptible sheep to high levels of infected uterine discharges and aborted material. 
  • Infection remains latent in the sheep until the subsequent pregnancy then causes abortion 
  • Abortion/birth of fresh dead and/or weak lambs during the last three weeks 
  • The ewe is not sick
  • Live lambs rarely survive more than a few hours despite supportive care 
  • Lambs fostered on to aborted ewes should not be retained for future breeding 
  • Vaccination offers an excellent means of control 
  • The ‘gold standard’ approach would be to purchase accredited stock and vaccinate them against C abortus 


  • Toxoplasmosis results from infection of susceptible sheep with the protozoan parasite toxoplasma gondii. 
  • The sexual part of the life cycle takes place in cats 
  • Infection during early pregnancy may be manifest as embryo/early fetal loss with an increased barren rate
  • Toxoplasma infection during mid-pregnancy results in abortion or production of weakly live lambs near term often with a small mummified fetus 
  • The mummified fetus has a dark brown leathery appearance and is about 10cm long
  • All sheep feed should be stored in vermin-proof facilities to prevent contamination by cats and other vermin 
  • Vaccination provides excellent immunity


  • Campylobacter fetus, subspecies fetus and campylobacter jejuni are common causes of abortion, particularly where sheep are managed intensively leading to heavy contamination and unhygienic environments during late gestation 
  • The main source of infection is purchased carrier sheep 
  • The common presentation is abortion during late gestation
  • Treatment options are limited because infection has already spread rapidly through the group by the time the first abortions are recognised 

Salmonella abortion

  • Salmonella Montevideo, salmonella Dublin and salmonella typhimurium cause abortion and death in pregnant ewes 
  • Sheep may simply be found dead with rotten lambs still present in the womb 
  • Feedstuffs and watercourses, sewage effluent overflow, carrier cattle, and carrion are potential sources 
  • There is a significant zoonotic risk from suspected/confirmed cases salmonellosis, so it is essential that strict personal hygiene methods are used during and after handling sick sheep
  • Minimise the number of people with contact with such sheep 
  • Remove and disinfect outer clothing after handling 
  • Wash and clean thoroughly hands, arms and face after handling

Prevention and control – biosecurity

  • Reduce/prevent the introduction of new diseases onto your farm from outside sources
  • Freedom from most infectious causes of abortion is best achieved by maintaining a closed clean flock.
  • Biocontainment within your flock – vaccinate sheep where appropriate reduce and or prevent the movement of infectious diseases on your farm. Aborted ewes must be isolated and aborted material and infected bedding must be removed and destroyed to prevent spread of the disease throughout. Ewes that give birth to dead/weakly full-term lambs should also be isolated as soon as possible 
  • Ewe lambs fostered on to aborted ewes should not be retained for future breeding in the flock or sold for breeding
  • The potential of many abortificacient agents to infect humans (zoonotic infection) must be stressed to everyone attending sheep on your farm 
  • Appropriate hygiene precautions must also extend to all households where infection could arise from contact with farm workers’ contaminated clothing and footwear