Enzootic Abortion and Toxoplasmosis in Ewes – Control by Vaccination

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As lambing time looms again, sheep keepers nationwide cross their fingers, look out their lucky socks, and bargain with the Gods of springtime, that we may be blessed with good weather and lively lambs this year.

Whilst the weather is certainly outwith our control, there are many things that can be done to increase the chances of a successful lambing period. One such action is to be aware of, and protect against, the main infectious causes of sheep abortion.

In the UK, over 80% of sheep abortion outbreaks are caused by just 3 infectious diseases, all of which are zoonotic (i.e. they may be passed to humans).

Infectious causes of sheep abortion

Enzootic Abortion of Ewes (EAE)

Caused by Chlamydophila abortus bacteria invading the placenta, causing abortions and the birth of very weak lambs.
Infection spreads to other ewes (and humans) by contact with infected birthing fluids, placenta or aborted/infected lambs.
Long lasting immunity occurs in previously infected or vaccinated ewes.

Toxoplasmosis

The single cell parasite Toxoplasma gondii is transmitted by cats. Infected young cats shed eggs in their faeces, which develop in the environment and can survive for years.
Sheep ingest infective stages through eating contaminated feed or grass, or drinking from infected water sources.
Disease occurs in the placenta and developing foetus, causing abortion, stillbirth, mummified foetuses, or the birth of infected live but weak lambs.
Long lasting immunity occurs in previously infected or vaccinated ewes.

Campylobacter

Campylobacter bacterial infection can cause abortion, stillbirth and weak live lambs but can also be responsible for high barren (non-pregnant) rates.
Spread is through contact with infected faeces, lambing fluids, products of abortion (fluid, placenta, lambs), bird droppings, and carrier sheep (that are infected but appear healthy).
Spread is greatest where sheep are in close contact (e.g. housed) or in dirty/muddy conditions.

These are all zoonotic diseases (i.e. can be transferred to humans). It is therefore especially important that pregnant women and any immunocompromised individuals are protected by avoiding contact with pregnant sheep, lambing equipment and clothing worn by those who are in contact with the sheep.

How to recognise abortion in ewes

Aborting ewes may be well in themselves with only a slight reddish brown vulval discharge to indicate a problem, so careful attention must be paid to identify abortion early.

Most aborting ewes will go on to deliver a dead or occasionally mummified foetus, or live but very weak lambs that cannot stand or suckle and sadly do not survive long.

Ewes expecting twins can abort one foetus and still deliver one live lamb so all aborting ewes should be examined carefully.

What to do if you suspect a ewe is aborting

Abortion in ewes can occur for various reasons however ALL abortions should be treated as infectious unless/until proven otherwise.

Isolate the ewe in an individual pen with constant free access to fresh food and water.
Prevent contact with other sheep (i.e. ensure others cannot reach through the pen sides to contact the aborting ewe, her feed, water or bedding.
Examine the ewe thoroughly – is she eating and drinking, does she appear poorly? Do not be tempted to reach for an antibiotic here – many ewes will abort without becoming unwell themselves so antibiotic use may not be necessary or appropriate. If you have any doubt, contact your vet for advice.
Adopt strict hygiene protocols, including wearing disposable gloves, and overalls and boots that can be thoroughly disinfected before contacting the rest of the flock.
Collect the products of abortion (foetus and placenta) and submit these promptly (same day) to the lab for testing. This is important from the first (and hopefully only) abortion through to the last. Early diagnosis is valuable in managing a disease outbreak but more than one infectious agent may be present and future control strategies depend on identifying all underlying causes.
Do not twin female lambs onto aborted ewes as they may themselves go on to abort in their first breeding year.
When the aborted ewe leaves the isolation pen, all bedding should be collected and disposed of carefully, preventing access by all other animals including livestock, farm dogs/cat, wildlife and birds, and avoiding water courses and grazing.
The pen and all associated equipment e.g. buckets and gates, should be disinfected thoroughly after use.
If lambing outside, consider bringing aborting ewes inside to minimise further disease spread.
Record the identity of any aborted ewes as they may or may not be kept for future breeding depending on the cause of abortion.

When infectious abortion outbreaks do occur, the consequences can be devastating, with high lamb losses, poorly ewes, increased treatment costs and production losses, not to mention the human health risks and significant negative impact on emotional wellbeing. Talk to your vet to put strategies in place for getting through this tough time.

Diagnosing infectious causes of abortion in sheep

Submitting aborted lambs and placentae to the lab is the best way to reach a diagnosis during an abortion outbreak. Confirming the presence of an infectious agent(s) in these samples, indicates active disease in the flock.

High barren (non pregnant) rates at scanning or lambing should also be investigated as they may represent early embryonic loss (i.e. ewes who have been pregnant but reabsorbed the foetus(es) early on). This can be investigated using blood samples, however care must be taken in selecting which sheep to sample and in interpreting the results so work with your vet to get the best from testing.

Preventing abortion in sheep

Ideally, start with a disease-free flock and then keep disease out!

When establishing a new flock, or purchasing additional animals, consider whether suitable EAE accredited animals are available.
If not, consider blood testing purchased sheep before they join your flock.
Once your flock is established, aim to keep homebred replacement females rather than buying in ewes from other farms.

To further reduce the risk of abortions:

Avoid feed contamination by preventing access by cats or birds.
Where possible, avoid using high risk fields for pregnant ewes. Fields near to housing areas may be higher risk as they are more likely to be visited by cats.
Keep neutered adult cats on the farm to discourage other young cats from visiting.

Vaccinations

Whilst these actions can significantly reduce the risk of infectious abortions, it cannot be eliminated all together. Fortunately, vaccines are available to protect against EAE and Toxoplasmosis in the UK. They are considered to be:

Highly effective
Cost effective
Easily administered – usually, a single dose given 4 weeks to 4 months prior to breeding.
Long lasting – Protection after vaccination appears to last several years so most commercial flocks will only vaccinate young sheep prior to their first breeding season, and any bought in females. In flocks where ewes are retained longer, a booster vaccination may be required 2-4 years down the line.
Permitted in organic farming systems.

A campylobacter vaccine is available only under Special Import Certificate and this is usually carried out on a farm specific basis, after diagnosis has been confirmed.

Handling and administering vaccines to sheep

Vaccines are usually refrigerated and must be used on the same day they are opened. MSD animal health have a wealth of resources available regarding vaccination on their On My Farm site, including top tips on how to store and administer sheep vaccines. If you are uncertain, speak to your vet for advice.

Vaccine shortages

Unfortunately, in recent years there have been some abortion vaccine shortages. When this occurs, preventative actions such as securing feeds and maintaining a closed flock will still be valid, however if your flock are at high risk and cannot be vaccinated, speak to your vet to discuss if any other options are available.

In-feed medication during pregnancy or the very carefully considered use of antibiotics may be appropriate in some high-risk flocks, but neither strategy is ideal.

Conclusion

So, whether this year’s lambing finds you wearing a smile or a frown, in shorts or snow boots, in delight or despair … or most likely all of the above at some point!

Mind Your Head and #KeepTalking. Lambing can be a challenging time so keep talking to friends, family and supporters of agriculture (see more links below).
Young farmers are often involved at lambing time and support is available for them too – it can be worth asking #AreEweOk?
Keep recording what is happening, the good the bad and the downright ugly! Various apps are available, or ask your vet for a simple tally sheet. Recording births and losses in this way can really help pinpoint any issues or room for improvement.
Keep learning by seeking reputable advice. Following some of the links below and speak to your vet.
Your vet is there to help, whether you have 2 ewes or 2000, so don’t be afraid to get in touch for advice and support anytime. Once lambing is over, arrange a review meeting or phone call, or draw up a flock health plan to put preventative measures against sheep abortion in place for next year.