This case study is an account of a recent outbreak of Salmonella on a client’s property.
At the beginning of January roughly 1.2% of the mob started dying over a period of about a week. Ewes that showed signs of sickness had drooping ears, were depressed and not wanting to eat or move. Some were scouring but others were not.
We had a strong suspicion for salmonella, but couldn’t rule out an unknown toxicity at this stage either. The farmer decided to grab salmonella vaccine (Salvexin B) on the presumption that that's what it was. He also got in contact with neighbouring farms, to let them know so they could be on the lookout for any illness in their own stock.
A day later the faecal samples came back positive for salmonella, so the decision to go ahead and vaccinate was a good one. The deaths decreased and stopped after a few days; as it can take up to 10 days for the vaccine to take effect, this was quite a quick response.
The farmer decided to vaccinate all the ewes and rams on the property, not just the affected mob. Consideration was paid to a couple of important points.
1. The start of mating is approaching. Sheep can be carriers of salmonella, and so the organism can often strike again weeks or months after the initial outbreak. There is a risk that ewes or rams in other mobs may become affected closer to mating.
2. The farmer did not have a quick and effective way to disinfect the sheep yards either, so there remained a risk of spreading the disease to other mobs of ewes and rams through the season.
Overall 4.8% of the ewes in that mob died from salmonella. Of the four sick ewes that were given antibiotic treatment, three survived. Prior to this outbreak, the farm hadn’t had a case of salmonella. Salmonella hindmarsh and brandenburg can cause significant losses of stock, and we see cases of both types every year. If you have any questions about the risk of salmonella in your flock, please contact VetSouth.