No one wants their calves to be infected with Salmonella, but the serotype Dublin is an especially ominous threat, and it’s not going away.
According to Angel Abuela, veterinarian and instructor of Large Animal Clinical Sciences at Michigan State University’s College of Veterinary Medicine, Salmonella Dublin has become substantially more prevalent in dairy and calf-rearing facilities in the U.S. and Canada since 2012.
At the 2025 Recent Graduate Conference of the American Association of Bovine Practitioners, Abuela briefed young veterinarians on the characteristics and challenges presented by S. Dublin.
While Salmonella is most often associated with scours in calves, he notes S. Dublin usually causes pneumonia, respiratory distress and fevers instead. Calves appear listless, anorexic, dehydrated and can also suffer from septicemia and arthritis. Bloody scours are possible but not very common.
Acute infections of S. Dublin typically strike calves at 2 to 12 weeks of age, and sudden death within one to two days after onset of illness can occur due to endotoxic shock. Data from S. Dublin outbreaks shows up to about one-third of infected calves became clinically sick, and about a quarter of calves with confirmed S. Dublin diagnosis died.
For those that survive, lingering effects can include poor growth rate, ill thrift, lameness due to arthritis, and loose stools. It is less common in adult animals, but when infected, those older cattle can experience a sudden drop in milk production, slight fever, mild diarrhea and abortion. Persistent infection with intermittent fecal shedding during times of stress is also possible in adult cows.
In addition to its critical impacts on cattle health, two distinct characteristics of S. Dublin make it a high-level concern: its multi-drug resistance properties and its potential effects on human health.
“In the U.S., S. Dublin has become one of cattle’s most important multi-drug-resistant (MDR) bacteria,” Abuela notes. “The MDR has complicated the treatment of clinically sick animals and has become a threat to human medicine.”
S. Dublin is resistant to many common antibiotics used to treat bacterial infections in animals and humans. Currently, there are no approved antibiotics for veterinary use to treat S. Dublin. Abuela notes the only therapeutic tools are supportive care, including fluid therapy to correct dehydration and electrolyte imbalances, along with anti-inflammatory therapy.
As a zoonotic disease, it is possible for S. Dublin infections to spread from ill animals to humans, causing severe digestive illness and bacterial infections of the bloodstream. While uncommon, S. Dublin infections in humans are most likely to occur in the individuals caring for sick animals, including farm personnel and veterinarians who might accidentally ingest infected animal feces or fluids.
Abuela recommends the following on-farm offense strategies to help minimize the transmission of S. Dublin infections in cattle:
- Providing clean, dry calving pens and avoiding large group-calving areas.
- Removing calves from contact with their dams’ feces as soon as possible after birth.
- Placing calves in a clean environment, where they have no contact with other calves or adult cattle.
- Maintaining strict control of colostrum management.
- Feeding pasteurized, rather than raw, milk to calves.
- Identifying and isolating newly sick cattle immediately and ensuring that farm personnel handle sick cattle separately.
- Sanitizing and disinfecting all equipment used between animals.
- Ensuring personnel wash hands, boots and any common equipment used between groups of animals.
A herd veterinarian should investigate suspected cases of S. Dublin for a full diagnostic work-up, treatment and prevention plan.
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