Surveillance and Biosecurity - Active engagement with Salmonella Dublin

To date, in 2015 and 2016, there have been almost 40 isolations of Salmonella Dublin from Ontario herds at the Animal Health Laboratory (AHL) in Guelph. Until 2012 the infection had never been identified in Ontario cattle. The positive samples have come from calf mortalities in about 10 veal and two dairy operations. This doesn't sound like a lot but judging by what has happened in New York State and Quebec over the last 10 years, this could be the beginning of a larger invasion.

Outbreaks of disease with S. Dublin can be very severe. Typically calves between the ages of 2 weeks and 4 months are most affected. In some reports 40 to 50% of exposed calves die. In most Ontario situations the most visible sign has been pneumonia. Diarrhea is far less prominent than one would expect. In young calves the S. Dublin bacteria enter the blood stream and circulate to a variety of organs such as the lungs, liver, spleen, joints and stomach lining. A very poor response to antibiotic treatment and an increase in calf deaths is what prompts herd owners and their vets to submit samples to the lab.

A concerning aspect of the current S. Dublin isolates is the multi-drug resistance (MDR) of the current strain. So far the Ontario isolates, like the ones in New York and in Quebec, are resistant to most antibiotics available for calf treatment. Few calves that become sick during a S. Dublin outbreak are successfully treated.

Cattle movement is how S. Dublin enters a dairy, beef or veal operation. Typically the infection moves from farm to farm via carriers, infected yearling or mature cattle that show no signs, or in young calves that are already infected but not yet showing signs. As over 70% of Ontario dairy producers reported introducing cattle into their herds over a recent five year period we suspect that more herds are infected than those who have had disease detected in laboratory submissions so far.

S. Dublin can infect people as well as cattle. And in people as in cattle, S. Dublin infection is both invasive and multi-drug resistant. On farms where S. Dublin could be present everyone working with cattle should take basic biosecurity precautions to avoid infection. Biosecurity practices should be reviewed. Frequent hand cleaning or gloves, protective clothing that stays in the barn, sanitation of feeding and handling equipment and so on will help to protect people and calves. Young, immunocompromised and older people are more vulnerable to infection. People access to the calf area should be restricted, especially if calves have been sick.

As part of the provincial disease surveillance strategy, a bovine health network group has been formed to communicate with industry, government, researchers and laboratory services regarding important cattle disease issues. The group has recently initiated a project to investigate calf health and, in particular, S. Dublin. The project has two parts. In Part One a dairy producer can sign up to have a bulk tank milk sample tested for antibody to S. Dublin to check for carrier cows. Testing bulk tank milk is a first step to evaluate how prevalent S. Dublin is within Ontario's dairy herd population.

In Part Two, project funding offsets the charges for veterinarians to do, or submit, calves from dairy, veal or cow-calf farms for post-mortem examination. PM's can be done by the herd vet at the farm, with samples submitted to the lab, or the entire calf can be submitted to the Animal Health Laboratories in Guelph or Kemptville.

If you are interested in participating in the calf PM part of the project, contact your herd veterinarian to find out how to enroll in this surveillance project. Project details are also available from Ann Godkin ( or 519 846 3409).

This project is funded by the OMAFRA-University of Guelph Strategic Partnership, under the Disease Surveillance Plan, which is a joint federal-provincial Growing Forward 2 project.

For more information:
Toll Free: 1-877-424-1300