Ontario cattle health update and biosecurity practices

By Dr. Cynthia Miltenburg on behalf of the Ontario Animal Health Network

In Ontario, the bovine Ontario Animal Health Network meets on a quarterly basis to review data collected from laboratory submissions and field veterinarians’ observations. Regular review of this information allows our network to communicate with veterinarians and industry on changing animal health risks in Ontario. This article will share a few highlights from our last year of surveillance for cattle in Ontario and review some best practices to avoid the introduction of new disease pathogens.

Salmonella Dublin

Salmonella Dublin (S. Dublin) continues to be a challenge for cattle producers with regular detections in diagnostic laboratory samples and new premises becoming infected. In 2024, there have been 25 detections of S. Dublin between January and October. Detections are clustered in the summer and fall months. The network hypothesizes this may be associated with calving patterns and pressure on calf housing, ambient temperatures, and typical fall respiratory disease risk factors. In 2023, lab detections were estimated to represent 16 disease outbreaks on 14 unique farms. For nine farms (two veal, four dairy, and three beef), this is believed to be the first time S. Dublin was detected on the farm.

S. Dublin has become the most frequently identified Salmonella species on laboratory submissions from cattle farms. In 2023 and 2024, three-quarters of bovine Salmonella detections were S. Dublin.

Bovine viral diarrhea virus

Testing for bovine viral diarrhea virus (BVD) occurs weekly at the provincial diagnostic lab. Approximately 2.5 per cent of cattle samples tested over the last year were positive for BVD. Samples tested are a mix of samples from suspect cattle with clinical signs that are consistent with BVD as well as samples collected as part of routine herd screening programs. Given the regular detection of positive results each month, BVD remains a risk in the province.

Neonatal diarrhea

Calf diarrhea is an ongoing challenge for calves in the preweaning period. Laboratory testing in Ontario shows that Rotavirus, Cryptosporidium and Coronavirus have high test positivity on submissions from calves in the zero-to-six weeks of age group. In 2024, there has been a trend for a higher number of positive submissions with E. coli compared to previous years.

Practical biosecurity

Given this information, preventing the introduction of new disease pathogens continues to be a priority for calf raisers. Disease can be introduced by the purchase of animals carrying a pathogen, or on contaminated vehicles, equipment or footwear from other premises. Biosecurity can work to minimize the risk of introduction of disease and reduce spread within an operation if introduced. Biosecurity is a big topic that includes practices around cattle purchase, manure management, sanitation, and others. To minimize risk, a few elements producers are encouraged to consider include:

1. Limiting purchase and isolating new additions – Herds purchasing animals have a greater risk of becoming positive for. S. Dublin. Purchasing from negative dairy herds as evidenced by a negative bulk tank test and negative individual blood test can reduce risk. New additions to dairy farms should be isolated for three to four weeks. This includes animals that leave for another farm or site and return to the home farm. For veal, sourcing from as few herds as possible can reduce risk. Segregating newly received calves from the general barn population upon arrival and maintaining stable groups (all in/all out) can reduce disease transmission.
2. Biosecurity for visitors – Many diseases are transmitted via the fecal-oral route so contaminated boots, clothing, trailers, and vehicles are a risk for introduction. Ideally, do not have visitors enter cattle housing unless necessary and ensure all visitors wear clean coveralls and boots to reduce the risk of contaminated manure entering the cattle housing area.
3. Shared equipment – The low infective dose of some diseases means an increased risk of becoming infected if your neighbour has a positive disease status due to the movement of people and equipment between properties. Ensure shared equipment is cleaned and disinfected, including livestock trailers. Bringing cattle out to transporters will minimize the need for their entry into cattle housing areas.
4. Biosecurity between cattle age groups – Designated boots for the calf area only on dairy farms can reduce movement of material from adult housing to calf housing and protect youngstock. Washing and disinfecting boots between age groups on veal farms can limit spread, particularly to new, naïve calves.

Producers can use industry program checklists or review their biosecurity with herd advisors to find gaps that can be targeted. High standards for yourself and others that visit your farm will protect animal health and livelihoods.