Chlamydial (Enzootic) Abortion

Chlamydial abortion (also known as enzootic abortion of ewes (EAE), ovine enzootic abortion (OEA), or kebbing) is a major cause of lamb mortality across the world and the most common infectious cause of abortion in sheep and goats in the UK. It is caused by the bacteria Chlamydia abortus which invades the placenta during pregnancy which can lead to abortion or the birth of weak lambs.

Infection with C. abortus has both a direct and indirect effect on the developing lamb. Growth of the organism directly damages the placenta and the destructive effect of the inflammation its presence induces affects the transport of nutrients to the developing lamb and the production of the hormones which control pregnancy. In addition the organism may also cross the placenta and cause a degree of inflammation in the lamb’s internal organs.

Abortions due to C. abortus typically occur in the last few weeks of pregnancy. Work at Moredun has shown that regardless of when sheep become infected, the organism does not actively cause disease until after 80-90 days of pregnancy.

A high level of environmental contamination by infected ewes in lambing pens or fields is an important link in the spread of disease.  Infected lambs, placentas and excretions provide a source of infection to other susceptible ewes through ingestion and inhalation.

C. abortus is also a zoonotic pathogen and therefore can be passed from animals to humans posing a particular risk to pregnant women.  It is important that pregnant women and immune-compromised individuals should avoid contact with ewes during lambing time and should not handle contaminated clothing from those working with lambs.