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Salmonella in Sheep

(Enteric disease in sheep) A bacterial disease of the intestines which usually occurs as an outbreak involving large numbers.

Symptoms of the Disease/Condition

Caused by Salmonella hindmarshS. typhimurium and S.bovis morbifications but the clinical symptoms are the same for each.

S.typhimurium is the most common cause of acute diarrhoea in adult dairy cows but infection in beef cattle is rare.

This is a zoonosis, meaning humans can contract the disease from animals!

The disease is carried by normal healthy sheep all year so regard all ewe flocks as having the potential for an outbreak which may occur sometime after some form of “stress” such as:

  • Sudden feed changes.
  • Short periods without food and/or water (yarding, transport, empty water troughs).
  • Crowding associated with intensive rotational grazing.
  • Oral zinc dosing (facial eczema prevention).

The disease tends to be more common:

  • In adult sheep two tooth and older.
  • During December – June period.

However, outbreaks can occur without a history of any of the “classical” stress factors and you should expect salmonellosis to occur anytime during the year.

Affected sheep become very depressed, develop severe diarrheoa, and usually die within a few days.

Diagnosis is based on clinical signs and history, confirmed by autopsy and culture of intestinal contents.

Cost/Impact on Herd/Farm Revenue

Outbreaks can be dramatic with a high death rate in a short time but many outbreaks tend to be innocuous with “the odd ewe dying” until numbers are large enough for the farmer to become concerned. These outbreaks commonly end up with far more dead ewes than the farmer thought he had.

Death rate is usually 1-2% but can get up to 5%.

Apart from the deaths, salmonellosis can play havoc with normal management especially close to mating.

Management and Control.

Prevention is best achieved by vaccination.

Vaccination in the face of the outbreak will most likely reduce losses, whether the ewes have been sensitised or not. It is very easy to put vaccinating off because of the cost and it means mustering and yarding which is a risk to spreading the disease.

Cost is around $80/100 ewes. If ewes are worth $150, vaccination needs to save 2% of the ewes.