As many people have heard, or even experienced themselves, there has been a massive increase in the number of cows in the southern region affected by Salmonella.
This increase coincided with the wettest spring on record, and other factors such as changes in feed, waterlogged paddocks, cold weather, carrier cows and exceptional stress on cows (and farmers) all meaning some of these outbreaks were very severe.
Interim data (see Figure 1 below) has shown there was almost 10x more cases of Salmonella in Southland in 2024 compared to the previous seven years!
Figure 1. The number of Salmonella cases in Southland over the last eight years.
Source: MPI Animal Health Surveillance Team.
Salmonella Typhimurium is usually the most common type in cattle in the south.
Cases of Salmonella Bovismorbificans were very uncommon until 2024, when case numbers suddenly spiked – with 22 cases recorded between May and December.
S. Bovismorbificans has been associated with higher morbidity (sick cows) and mortality (dead cows) than S. Typhimurium, and there are also concerns about resistance to certain antibiotics developing more quickly.
As well as these trends, there have also been several cases of Salmonella Give in cattle in Southland, previously only found for the last three years in the Waikato and Taranaki.
In the majority of cases, herds were not previously fully vaccinated with Salvexin+B. This vaccine covers the four most common types of Salmonella, including S. Bovismorbificans and S. Typhimurium, but not S. Give.
Many dairy farmers are planning to implement preventative vaccination using Salvexin+B this autumn.
Timing-wise, we recommend the booster vaccination of Salvexin+B is given at least 2 weeks prior to dry-off, with a sensitiser dose given 4-6 weeks earlier. For most local spring calving herds working to a timeline of giving a sensitiser dose approximately 1st April and booster dose 1st May would be appropriate.
You can vary from this and give booster doses during the winter, however vaccinating early calving cows after mid-July should be avoided due to the possible metabolic effects in heavily pregnant animals.
