Salmonella is a common and bothersome disease organism in livestock production. But the species Salmonella Dublin is of particular concern.
Cattle are the host species for S. Dublin, which is highly contagious and difficult to treat. On dairy farms, it is most likely to cause severe clinical disease in calves. It also is classified as a zoonotic disease, meaning it can be transferred from animals to humans through consumption of raw milk and undercooked meat (and accidentally ingested feces and saliva) from infected animals.
Michigan State University Veterinary and Extension educators Angel Abuelo and Faith Cullens recently published a new bulletin on Salmonella Dublin in dairy calves. They noted that this particular strain of Salmonellahas typically been thought of as a problem primarily on dairies in the western United States, but it is gaining a foothold in the Midwest and Northeast. For example, from 2015 to 2019, S. Dublin represented 20.8% of all Salmonella species isolates in bovine samples at Michigan State’s veterinary diagnostic laboratory.
Calves are the most likely population on the farm to succumb to the infection because of their naïve immune systems. “Silent carrier” animals can shed the organism via colostrum, milk, saliva, urine, semen and vaginal secretions. Thus, newborn calves often are infected via vertical transmission from their dams or other adult cows on the farm. If they survive the disease, they may shed the bacteria intermittently throughout their own lifetimes. Calving often increases shedding loads, because cows have lower immunity in late pregnancy.
While most Salmonella infections cause diarrhea in calves, S. Dublin usually presents as respiratory disease in calves 2 to 12 weeks of age. Clinical signs include:
- Off feed
- Respiratory distress (coughing and/or labored breathing)
- Bloody diarrhea
Protecting calves from S. Dublin infections requires a multi-faceted approach, including:
- Calving pen management – Remove calves from dams within 2 hours of birth, and prevent calves from nursing dirty teats. Limit the number of cows present in the calving pen, replenish bedding frequently, and disinfect regularly. Avoid using the calving area as a hospital pen, and do not group newborns in warming rooms, which can become incubators for the disease.
- Colostrum management – Avoid pooling colostrum, and use practices to harvest and store colostrum to prevent bacterial growth.
- Calf nutrition – Delivering calves an adequate plane of nutrition to promote healthy immune-system development will help them fight the disease. If feeding waste milk, pasteurization or acidification is recommended to destroy the organism.
- Housing environment – The stand-by practice of clean, dry and comfortable bedding applies. Avoid overcrowding calves, and prevent exposure of calves to manure from adult calves. Power washing of calf facilities is not recommended, as this practice can aerosolize and spread bacteria.
- Feeding sanitation – Routine protocols to clean and sanitize feeding equipment are necessary to prevent disease spread. Most classes of disinfectants used on dairy farms (aldehydes; alkalis; biguanides [chlorhexidine]; halogens [sodium hypochlorite, iodines]; and quaternary ammonium compounds) are effective. However, removing organic material must always precede use of the disinfectant product.
The University of Wisconsin Veterinary Diagnostic Laboratory provides these guidelines for cleaning facilities – including calf housing, maternity pens, livestock trailers and more – if contamination by any species of Salmonella is suspected or confirmed.
The Michigan State authors advise consulting your herd veterinarian if you are experiencing a high number of respiratory infections in calves that do not respond well to treatment.