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.