Toxoplasmosis and enzootic abortion (EAE) are the two most common causes of sheep abortion that are diagnosed from post-mortem submissions by the Animal Plant and Health Agency (APHA) (Figure 1). Sheep abortion results in considerable economic loss to the flock and increases stress during lambing.

Both diseases can cause abortion (lambs are often mummified with toxoplasmosis), stillbirths and the birth of weakly lambs that may die shortly after birth or are more likely to succumb to neonatal disease (Figure 2). Occasionally abortion storms may occur, whereby a large proportion of the flock aborts. Toxoplasmosis can additionally result in high barren rates and low scanning percentages. Toxoplasmosis is caused by the protozoan parasite, Toxoplasma gondii, with ingestion of feed contaminated with cat faeces containing toxoplasma oocysts (eggs) being the main source of infection. EAE is caused by the bacteria, Chlamydophila abortus, and it is most commonly introduced to a naïve flock by buying-in ewes that carry the bacteria.

Ovine Abortion
Ovine Abortion

Screening for disease

Annually, through the FlockCheck scheme, MSD Animal Health subsidise the laboratory fees to test ewes for exposure to toxoplasmosis and EAE. Six to eight blood samples will be taken from unvaccinated ewes that have either aborted, are barren or have produced weakly lambs. Subsidised blood testing is only available until 30th June 2020 so take advantage of it now!

Controlling and preventing abortion

There are a number of important measures to control and prevent Toxoplasmosis and EAE in your flock; some of these measures are specific to each disease but the preventative step common to both diseases is vaccination. Toxovaxâ (Toxoplasmosis vaccine) should be given at least three weeks prior to tupping and is known to provide protection for at least two lambing seasons. Enzovaxâ (EAE vaccine) should be given at least four weeks prior to tupping and is known to provide protection for at least three lambing seasons. Enzovaxâ and Toxovaxâ can be given together.

Please get in touch with the practice for more information.


  1. Veterinary Record. 30th January 2020. Surveillance Focus: investigating abortions in small ruminants.
  2. Abortion – MSD Animal Health Republic of Ireland [Internet]. MSD Animal Health Republic of Ireland. 2020. Available from: