Salmonella Update
Recent research performed by the Aus-Vac company has shown some benefits of vaccinating against salmonella. The first benefit is that cows that are fully vaccinated before calving deliver a degree of immunity to the calf through the colostral antibodies. When these calves were exposed to salmonella bacteria they were less likely to become clinically affected than calves that did not receive antibodies. Secondly, vaccinated cows were shown to not shed salmonella organisms in their manure, even when they exhibited signs of clinical salmonellosis. This is an important feature as organisms shed by "carrier" cows act as the source of infection for the rest of the herd. If the level of bacterial shedding can be reduced the spread of infection will theoretically be reduced. Finally, when vaccinated animals were dosed with sufficient salmonella organisms to become sick, they recovered more quickly than unvaccinated animals. It is important to realise this is preliminary research on a small number of animals but the results give some weight to the effect of preventative vaccine. Lately we have seen very few large salmonella out breaks. Many of these are related to such events as upsets in feed intake or balance. This indicates that these cows probably had salmonella present in the gut prior to the outbreak.As a general recommendation we don't feel salmonella vaccination is a vital component of an animal health program. It is available for anyone who wishes to use it and the above research indicates some protection may be gained. Previous experience tells us that vaccinating in the face of an outbreak does not alter the course of that outbreak.
Clinically affected animals shed large numbers of salmonella bacteria in their milk. If you are treating cows with salmonella, it is advisable that the milk is discarded and NOT fed to calves. It is important to remember that salmonella can infect humans. The control of salmonella is important for the health of your stock and the people on your farm.
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