12 February 2025

Investigating abortion in ewes - causes, prevention and management

Lambing is fast approaching for many mid-season lambing flocks. Sheep Specialist at Teagasc, Damian Costello takes a closer look at the various causes of abortion in sheep, preventative measures and critical management tasks if abortion is suspected.

Ovine abortion primarily occurs for two reasons: 1). non-infectious causes; or 2). infectious causes.

Non-infectious causes of abortion

Non-infectious causes usually present with lower abortion rates, typically under 2%. Ewe injury is the most common reason, thus highlighting the importance of providing adequate feeding space and taking extra care when handling pregnant ewes when carrying out routine management tasks in advance of lambing.

Another significant factor responsible for non-infectious abortions is inappropriate nutrition, leading to metabolic conditions such as twin lamb disease and milk fever. Both conditions can cause abortion and stillbirths if not properly managed or the ewes’ nutritional needs are not being met in the latter stages of pregnancy.

Infectious causes of abortion

A higher than normal barren rate at scanning; greater than 2% of ewes aborting in the weeks before lambing; and lambs being born weak or stillborn are all indicators that infectious abortion may be an issue in the flock. If this is the case, take swift action and investigate.

Among the most prevalent infectious causes of abortion in Ireland are toxoplasmosis and enzootic abortion (EAE). Other, less common but still important, causes include E. coli, Campylobacter, Salmonella, Listeria, and the Schmallenberg virus.

Where infectious abortion is suspected, expect the worst but hope for the best. Most importantly, speak to your vet to identify the root cause and implement an effective management and control plan. Their input and guidance in collecting samples for testing at your local Regional Veterinary Laboratory may prove valuable in finding the cause.

Pro tip: Prompt investigation is crucial in any abortion outbreak to prevent further spread and to reduce losses.

Some key actions to take include:

Promptly isolate the affected ewe to avoid potential spread of infection to the rest of the flock and clearly identify the ewe in case follow up blood tests are required;
Collect aborted foetus/lamb and afterbirth in a clean plastic bag and contact your vet, providing relevant flock information that may assist in the diagnosis and also to organise submission of the sample to the Regional Veterinary Laboratory (RVL);
Sending a number of clean fresh samples to the RVL for analysis increases the chances of getting a diagnosis;
Clean out bedding from the pen where aborted material was collected and thoroughly disinfect the area;
Discuss the next steps with your vet.

Where the cause of the abortion has been identified, a further discussion is then required with your vet to limit its impact in future lambing seasons. Vaccinations are available for both toxoplasmosis and enzootic abortion, but these must be administered at the correct time pre-mating to ensure an effective immune response is achieved. Some farmers and vets reported difficulty in securing adequate supplies of enzo vaccines last autumn, so speak to your vet if this was the case on your farm.

Safety

Many of the infectious ovine abortion agents can be transmitted to humans and great care should be taken to use gloves when handling ewes during and after lambing. Expectant mothers should completely avoid contact with sheep around the lambing period.

More from Teagasc Daily: Sheep farmers’ views on labour wanted