Salmonella Dublin

A calf-health threat has been found in Ontario. This bacteria can cause massive devastation to a herd and is transmissible to humans as well as other species. Frequently, this bacteria is antibiotic-resistant, making heightened biosecurity measures crucial to maintaining herd health status. Producers are urged to take precautions with new or sick calves on the farm.

In Quebec, Salmonella Dublin was first discovered in 2011. Since then, positive test results have been popping up province-wide, with 75% of the strains showing ampicillin, ampicillin-sulbactam, ceftiofur, and/or tetracycline resistance. In 2011, 13 veal farms were identified to have Salmonella Dublin infection. Salmonella Dublin is immediately notifiable in Ontario, meaning laboratory diagnoses are passed on to the Provincial government for the appropriate response.

The bacteria are shed through feces and milk. Some animals may become lifetime carriers of the infection. With a 50% mortality rate, Salmonella Dublin can cause severe devastation. Stress – from overcrowding, poor air quality, co-infections, transportation, or nutritional deficiencies – can trigger the symptoms of this bacterial infection. Testing and culling is the only eradication protocol currently suggested for infected herds. With proper biosecurity measures, detailed below, the spread of Salmonella Dublin can be limited.


Normal salmonellosis presents as a gastro-intestinal issue; however, Salmonella Dublin most often presents as a respiratory illness. Calves less than six months old are at the highest risk for infection, but the whole herd is at risk.

Calves will show signs through:

  • Fever
  • Coughing
  • Pneumonia
  • Diarrhea (especially terminally)
  • Dehydration
  • Septicemia
  • Unwillingness to eat
  • Abortion in cows

It is important to note that carrier animals may not display any symptoms, but continue to shed the organisms in manure and milk.

This bacteria can infect humans. Fecal-oral introduction and raw milk consumption are high-risk activities. Salmonella Dublin in humans can cause illness and death. If you or your family members are displaying the following symptoms, seek assistance immediately:

  • Fever
  • Delirium
  • Vomiting
  • Diarrhea (with or without blood)
  • Abdominal cramping

Very young or elderly people, those with weakened immune systems, and those who are pregnant have the highest risk of becoming infected.

Protecting the Herd

Ensuring that farm visitors are not carrying the bacteria is the first step to controlling spread. Farm-associated vehicles – including milk trucks, feed trucks, livestock transporters, and deadstock vehicles – all pose the risk of introducing Salmonella Dublin to the farm. Disinfection of trucks, boots, and clothing when moving between farms will help to keep your herd healthy.

New calves and cows should be quarantined upon arriving on the farm. Since stress often triggers this illness it is likely that the calf, if infected, will soon show symptoms. Feed and care for the quarantined animals last, and disinfect anything with fecal or oral contact after each use.

Identification & Treatment

Salmonella Dublin outbreaks become endemic in times of poor environmental management: provide comfortable, clean, well-ventilated areas for calves that are, or may become, ill. Disinfection of the environment requires dilute chlorine bleach, phenols, quaternary ammonium compounds or oxidizing agents (like Virkon-S). Follow the recommended use on the product’s label to ensure that the bacteria are not transmissible.

Fecal, lung tissue, and bulk milk tests are available to check the status of your herd. If a positive result is found, immediately isolate the infected animal(s). These tests are made available through your herd veterinarian.

Since Salmonella Dublin is multi-drug resistant, it is a difficult infection to treat. Some antibiotics may treat secondary infections but the problem still remains. This residual bacteria may continue to be shed, infecting more herd mates. Providing sick calves with proper nutrition, ample water supply, and good air quality, gives the calves the best chance of survival.

Dairy farmers should also exercise caution as the bacteria can be shed through the milk. If feeding milk to calves from infected dairy cows you will increase the likelihood of the spread of disease in your herd. Bulk milk tank testing is available.