Salmonellosis in sheep

Enteric Salmonellosis is a disease we see regular cases of in our area and, every four to five years, tend to see widespread outbreaks also occurring.

While losses due to Salmonella can occur anytime, the majority of our cases occur during the February to May period. Problems tend to be worse in years with good grass growth as this provides a food source for the bacteria to replicate in the gut.

Deaths from Salmonella are classically in well conditioned mixed aged ewes. Often, but not always, affected animals are found near a water source such as dams, creeks or troughs and, if not simply found dead, are obviously sick and have profuse khaki green smelly diarrhoea. Deaths tend to occur in one of two patterns - either five or so sheep dead at once OR a slow trickle of deaths over a week to 10 days. To quote one of my farmers "normally you don't see dead sheep as they die in the gullies, when you have Salmonella they are dead in the gateway".

As a general rule Salmonella is uncommon in two-tooths and younger stock. Diagnosis is commonly made by post-mortem (PM) examination and is best done on freshly dead (within six to 12 hours) animals. The classic PM signs include a very red and inflamed abomasum combined with watery contents in the large intestine and rectum.

Annual vaccination of two-tooths (AND rams) helps to minimise the impact of Salmonella on a property. Two vaccinations four to six weeks apart are required and are best done over the December to January period. This timing works well in our area as it ensures vaccinations take place prior to pre-tupping vaccinations. Delayed action can result in having to vaccinate during mating which is not ideal as there is potential for impact on reproductive performance. Vaccination can, in some cases, make sheep go off their food for a few days and be not right for up to a week, so I recommend that rams are left out for an extra 10 days... however a slightly longer mating period rather than increased ewe deaths due to not vaccinating is preferable in my mind. A dry ewe is worth more than a dead ewe!

For further information don't hesitate to give your vet a call.