Salmonella brandenburg abortions were first seen in sheep in mid-Canterbury back in 1996. Since then a cyclical pattern has been seen, with outbreaks mainly in Otago and Southland. Cases in cattle have been sporadically seen, but recently we have seen a concerning trend of increasing numbers, culminating in around five of our farms this year having confirmed Brandenburg abortions in their cattle. The aborting cows typically present as off-colour for 1-3 days before calving a rotten calf (often with assistance). These have been up to 50 days early, and many of the cows aren't coming into milk . Scouring and death can also occur, and scours can also occur in calves. Salmonella is highly zoonotic (contagious to humans) so good hygiene should be maintained in any cases with suspicious signs. Individually affected cows should be treated with oxytetracyclines, anti-inflammatories, and fluids. Aborting animals will shed high numbers of bacteria, so are an important source of transfer and environmental contamination.
Transfer of Salmonella brandenburg onto new farms is likely to occur in one of three ways:
- Firstly infected cows can become non-clinical latent shedders. Purchase of these latent shedders can bring the disease onto your farm.
- Secondly environmental contamination of pasture/yards/waterways/trucks can lead to transfer. Salmonella is likely to last just 1 week in bright, exposed, sunny conditions, but can last between 4 months to 2 years in covered areas (including cattleyard dust).
- Finally it is thought that scavenger birds (such as seagulls) can transfer the bacteria between properties.
One of the main control measures currently being used is vaccination with Salvexin+B, along with picking up dead calves, reducing stress, and avoiding areas of high contamination (including cleaning trailers etc). Because Brandenburg is an emerging disease there is no research into vaccination in the face of an outbreak, however anecdotally it has been reported to decrease the incidence of abortions and death. The majority of interventions have had no ill effect on the cows, however there has been one incidence of downer cows post-vaccination so any decision to vaccinate should be discussed fully with your veterinarian to weigh up the pros and cons. As with any disease, vaccination prior to exposure is better than in the face of an outbreak, so future vaccination programmes will need to be implemented on at-risk farms.
If you are seeing any similar cases contact your prime vet to make a plan for diagnosis and control.