Salmonella is likely under-diagnosed in herds due to its range of clinical signs. Whilst infections are well-known to be associated with signs such as diarrhoea, abortion and septicaemia, Salmonella is rarely investigated in cases of calf pneumonia or milk drop in adult cattle.
Salmonella is a public health concern as a zoonotic disease, however, how should we go about diagnosing and screening herds for Salmonella infection? And if we find it, what do we do next?
Diagnosis and screening
Effective screening methods for Salmonella include:
Youngstock serology - test calves >3 months old for antibody presence. Ensure all management groups are included.
Bulk tank - repeated bulk tank antibody testing improves test sensitivity
Pneumonia and scour outbreaks - include Salmonella culture when investigating pneumonia and scour outbreaks in youngstock.
Prevention
Salmonella is most commonly transmitted by the faeco-oral route generally from the environment. Strict biosecurity measures should be followed to prevent introduction of disease onto the farm.
Examples include:
Keep a closed herd where possible
Ensure staff, visitors and equipment are disinfected before entering the farm
If animals must be bought in, consider testing before purchase and buy from low risk herds carrying out regular Salmonella screening
To prevent transmission to calves, similar management controls to Johne's prevention plans should be followed.
Calving pen
Do not house sick cows in calving/dry cow pens
Clean calving pens regularly (every 3 weeks)
Remove calves from dam and calving pen environment ASAP
Neonatal calf
Follow high standards for colostrum management
Pre-weaned calf
Efforts should be made to reduce Salmonella contamination of milk and the calf environment in general
Whilst cattle can be persistently infected with Salmonella, management of these animals to control endemic disease is often unrewarding. Prevention of calf infection and maximising calf immunity are key when reducing the effects of Salmonella infection in a herd.
Vaccination
Vaccination will not prevent infection, but can be used to reduce the clinical signs of Salmonella infection and reduce the risk of abortion. The effect of vaccination in dry cows for protection in calves is unknown.
As a rule, management efforts should be put in place before considering vaccination.
Summary
Screen for Salmonella to find out your herd status. If infection is not found, prevent introduction of the disease by following strict biosecurity measures.
Implementing management protocols on farm is the most effective way of controlling Salmonella. Vaccination is only a small part of Salmonella management and is mostly used to reduce severity of clinical signs and reduce the risk of abortion.
Holschbach, C. L., & Peek, S. F. (2018). Salmonella in Dairy Cattle. The Veterinary clinics of North America. Food animal practice, 34(1), 133–154. https://doi.org/10.1016/j.cvfa.2017.10.005