NADIS disease bulletins are written specifically for farmers, to increase awareness of prevalent conditions and promote disease prevention and control, in order to benefit animal health and welfare.

Farmers are advised to discuss their individual farm circumstances with their veterinary surgeon.

Salmonella Abortion in Ewes

In the light of current concerns about the spread of foot and mouth disease, it almost seems superfluous to write about other sheep disease problems. Nevertheless, there have been several reports of abortion in ewes over the last few weeks, some of which have resulted in serious economic loss. In addition to the usual common causes of ovine abortion (chlamydial abortion, toxoplasmosis and campylobacteriosis), NADIS data indicate that salmonellosis has resulted in severe losses in some flocks. Abortion storms have been associated with Salmonella enterica serotypes Montevideo and Dublin.

Salmonella enterica serotype Montevideo

S. montevideo infection can result in abortions in more than 25% of a flock. Abortions can occur throughout the second half of pregnancy. In many cases the aborted foetuses are not found, but the first sign of the problem is the presence of a red vaginal discharge and hollow flanks in ewes. A small proportion of these ewes become sick and require antibiotic treatment, possibly due to retention of the placenta. When abortions occur during mid pregnancy, the foetuses are often fresh, but the placentas appear inflamed. When abortions occur during later pregnancy, aborted lambs are often rotten.

Salmonella enterica serotype Dublin

S. dublin outbreaks can also result in abortions in a high proportion of the flock. S. dublin infection often results in systemic illness and profuse diarrhoea in addition to abortion. Pregnant ewes may die as a result of systemic disease before aborting.

Diagnosis of salmonellosis

As with all ovine abortion problems, it is important to establish the cause promptly so that effective management practices can be employed. Salmonellosis should be suspected when abortion of fresh foetuses occurs in several mid to late pregnant ewes. The likelihood of other causes of abortion may be reduced on the basis of vaccination history, health scheme membership and the presence of systemic disease in some aborted ewes.

Whenever possible, aborted foetuses and placentae should be submitted for veterinary laboratory investigation, but if these samples are not available, vaginal swabs can be useful for the diagnosis of salmonellosis. The diagnosis is confirmed by the bacterial culture of Salmonella sp. from the placenta or foetal stomach contents.

Management of salmonella abortion outbreaks

Infection occurs several weeks before ewes abort, so by the time that salmonellosis has been identified, it will probably have spread throughout the group. Nevertheless precautions should be taken to limit the level of infection and prevent spread to other groups of animals -

- aborted ewes should be isolated from the flock

- products of abortion should be removed

- hygienic precautions should be taken to avoid spread of infection on clothing or equipment to other groups of sheep

Most biotypes of S. montevideo are sensitive to a wide range of antibiotics and whole flock treatment with a long acting injection of oxytetracycline is often recommended. In practice, treatment is often instigated before the diagnosis is confirmed. Treatment sometimes needs to be repeated after 7 – 10 days. While there are few data to support the efficacy of such treatment, practical experience suggests that it probably does reduce the severity of most outbreaks.

In common with other causes of ovine abortion, Salmonella sp. can cause disease in man, so sensible hygienic precautions should be observed when working with pregnant and aborted animals.

Prevention of salmonellosis