Enzootic abortion, brucellosis and other conditions can seriously reduce the lambing rate. It’s crucial to act swiftly to bring these diseases under control
Abortion, which can occur at any stage of gestation, is the result of a disturbance in the functioning of the afterbirth (placenta). This causes premature loss of the foetus.
Many conditions can cause abortion in sheep and goats.The most frequent are the infectious types: enzootic abortion, brucellosis, Rift Valley fever and Wesselsbron disease.
Enzootic abortion (chlamydiosis) is a contagious disease in sheep and goats caused by Chlamydophila abortus (previously Chlamydia psittaci).It can even induce abortions in pregnant women who handle sick sheep or lambs.The disease is usually spread during lambing.
Livestock also pick up the bacteria by mouth when grazing an area contaminated by infected afterbirth or uterine fluid.The infection can remain dormant in the ewe lamb until its first pregnancy. An outbreak invariably occurs within a year or two of infected sheep arriving on the farm.The more intensive the sheep-farming enterprise, the more likely it is that the disease will spread.
An infected ewe will not appear ill; blood spots above the udder and on the hocks may be the only signs of abortion.A newly-infected flock may have an abortion rate of up to 70%. Abortion can occur as early as three months, in which case the foetus is usually resorbed, or as late as the last month of pregnancy.The ewe may even give birth to a small, weak lamb that dies shortly after birth.
Treatment and prevention
Treatment involves a prolonged, high dose of antibiotics, but this is seldom practical or affordable.Onderstepoort Biological Products (OBP) produces an oil-based, inactivated vaccine to prevent abortion caused by chlamydial infection.Pregnant ewes can be safely inoculated.It is essential to vaccinate before the breeding season, as the vaccine will not provide protection against abortion once the foetus has been infected.The ideal time is four to six weeks beforehand.
Brucellosis
This is caused by the bacterium Brucella melitensis.A high percentage of the infected ewes will abort, and infected humans develop Malta fever, a disease characterised by fever, joint pain, headaches and sweating.Lambs may be born alive, but die soon afterwards. Such lambs, as well as foetal fluid and afterbirth of the infected ewes, contaminate the grazing, spreading the disease further.The bacteria also contaminate the milk of the infected ewe, and the animal may show symptoms of mastitis.She may not look especially ill, but will appear weak and in poor condition. After the abortion, she will discharge a thick, dark-red fluid from the vulva.Treatment and prevention
Vaccination is an option in countries where there is a high incidence of the disease.In South Africa, however, vaccination is not permitted; instead, the authorities aim to eradicate brucellosis by destroying all infected animals and removing all traces of infected material from the lambing area.
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