By Becky Adamczyk BVetMed MRCVS, St Columb Practice
Sheep are here to challenge us and from tupping to lambing, these challenges appear greatly increased. From getting a good working ram and making sure the ewes are in good body condition, to stopping dog worrying and having a clean and usable lambing shed, there are already enough problems without the worry of infectious abortion.
Although the list of causes of abortion are extensive, there are 3 infectious causes that are the most common and mostly preventable. These have been well documented previously, but a quick overview here will help to refresh the memories of last years’ meetings and articles.
Campylobacter is the most common bacterial cause of abortion, resulting in late abortion or stillbirths. It is easily spread by poor hygiene as the is bacteria commonly found in sheep dung and can spread from ewe to ewe at lambing if equipment is poorly sterilised, or abortion material not cleaned up. Firebreak treatment with antibiotics can help reduce spread in an outbreak but in the UK we have no vaccine available. The bug can also cause the aborted sheep to be ill with a uterine infection requiring further antibiotic treatment.
Toxoplasma is a parasite causing abortion in sheep and is spread by infected cats defecating on sheep’s feed. The parasite uses sheep as an intermediate host and causes them to abort in late pregnancy or absorb the foetus if sheep are infected early in pregnancy, but has no effect on the health of the ewe. Sheep will develop immunity once infected, but an abortion storm can cause widespread havoc in an unvaccinated flock. Once vaccinated, a ewe is protected for a large proportion of her reproductive life. Importantly, removal of abortion material will help reduce the spread in an outbreak.
Enzootic abortion (EAE) is caused by the bacteria Chlamydophila abortus and abortion occurs in the last 2-3 weeks of pregnancy, no matter when the ewe was exposed in that period. Once infected, a ewe carries the bug for life and will shed around ovulation, providing a perfect tool to infect a working ram. This then becomes a venereal disease, basically a sheep STD, and will spread to other ewes being served by that ram. Protection prior to service by vaccinating can help prevent spread of the disease and without feeling like a parrot repeating myself, hygiene of aborting animals is of the upmost importance.
As well as the above, Border disease, Salmonella, Listeria and Schmallenberg can all lead to lamb losses and ultimately profit. The best way to determine the cause of abortion is to provide your vet with the placenta and potentially a whole foetus for investigation, but only if it is fresh as rotting tissue will not give useful results. This along with a good history of the flock, including ram or bought in replacement vaccination status is needed for a useful prevention plan. Some of the above diseases are avoidable and some also treatable with vaccination, so knowing the cause can help reduce the spread in an outbreak.
Most importantly there is zoonotic potential of some of these diseases i.e. the ability to spread to humans and cause illness. Campylobacter and Salmonella are well known to cause illness in humans and hygiene will again play an important role in keeping everything and everyone on the farm healthy. It is well documented that Toxoplasma can cause abortions; but less well documented is the spread of Chlamydia to humans, which has reportedly caused abortion in pregnant women. Ensuring dirty work wear is removed prior to entering the house and put in the washing machine yourself will keep the bug away from pregnant women. Keeping pregnant and immune compromised adults, children and sick people away from lambing sheep is paramount.
Another non-infectious cause of abortion is dog worrying. This was widely covered in the news in 2013 and a campaign headed by the National Sheep Association promoted dog walkers to keep their animals under control. Ewe nutrition will also affect her ability to hold to term and sudden diet changes can compromise the pregnancy. Worming and fluke treatment will also have a part to play as a ewe riddled with parasites will struggle to produce a healthy, live lamb.
Ultimately there are two salient points; vaccination can prevent the disease and good hygiene will both prevent the disease causing abortion in the first place and prevent the spread within a flock. If at any point during pregnancy abortions are seen, steps can be taken to minimise losses if you contact your vet as soon as problems are noted.