Keep Enzootic Abortion Out Of Your Flock

Around half of the 400,000 infectious abortions in sheep each year are estimated to be from EAE. Learn more about enzootic abortion and how to keep it out of your flock.

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What Is Enzootic Abortion?

Abortion continues to be a major worry during the lambing season. There are many causes, but the most common is enzootic abortion of ewes (EAE), which is the result of infection by the bacteria Chlamydophila abortus. Around half of the 400,000 infectious abortions in sheep each year are estimated to be from EAE. Typical abortion storms average 13% losses, but figures can reach 50%.

What Does Enzootic Abortion Do To My Flock?

EAE causes abortion in late pregnancy or the birth of very weak lambs. The infected afterbirth and vaginal discharges are highly contagious and spread the infection very rapidly round the rest of the flock. The bacteria can remain in the environment for around six weeks. If ewes are infected when they are less than 6 weeks away from their due date, or after lambing, the infection lies dormant but re-emerges in the next pregnancy, causing abortion the following year. Ewes are often well in themselves at the time of abortion and will develop an immunity to it in the future.

How Does Infection Happen?

The major reason for infection is simply that many sheep are not vaccinated. If your flock is genuinely closed and EAE-free, this may be justified. However, there is still a biosecurity risk from animals transferring infected material from neighbouring farms. Having the odd abortion is often accepted by shepherds, but if 2-3% of the flock are aborting due to EAE it is likely that the problem will escalate in subsequent years. When you buy in replacement stock you can’t guarantee their disease status unless they are blood tested, but the test can’t distinguish between vaccinated and infected animals. The safest bet is to buy from a reputable source and, unless proof of vaccination is available, immediately have new stock vaccinated.

How Can I Stop The Spread Of Infection?

Control measures have to be put into place immediately in the face of an EAE outbreak. Post mortems of aborted lambs and their placentas are vital to get a definitive diagnosis. Aborted ewes need to be isolated. Afterbirths and bedding they have been in contact with must be removed and destroyed, and the area disinfected thoroughly. Treatment of ewes with a long-acting oxytetracycline in the face of an outbreak can help reduce the incidence of abortion but this will not reverse any damage already done in the uterus. It may delay the abortion until the ewe is nearer term, able to produce more milk and can foster a lamb, but any lambs reared on a ewe that has aborted must not be kept as replacements.

How Can I Avoid The Problem In The First Place?

Prevention is by far the most effective way to control enzootic abortion and a specific vaccination is widely available. It cannot be given to ewes during pregnancy, so the usual protocol is for sheep to be vaccinated one or two months prior to tupping, which needs to be planned during the summer. Lambs can actually be vaccinated from five months of age, which has the advantage of reducing the risk of disease to followers over the spring and summer months. It also means you will have one less job to deal with before the tups go in during the autumn.

The cost of vaccination with live vaccines is offset by the protection, which in many flocks is a one-off cost per ewe. Saving just 14 abortions in 500 ewes can make vaccination economically viable. It is recommended that the whole flock should be vaccinated in the first year and all replacement stock in subsequent years.

Even if there are no signs of abortion in your flock you could still be at risk. Ceva Animal Health, manufacturers of the Cevac Chlamydia EAE vaccine, are running Assure Ewe, a subsidised enzootic abortion blood testing programme which allows you to monitor and prevent enzootic abortion in your flock whether you’ve experienced abortions or not. Scarsdale would like to support you in controlling abortion on your farm.

Please call the practice on 01332 294929 for more information and to find out more.

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