315 A 99-year journey on the evolution of food safety in Canadian livestock production

Abstract Almost 100 yr ago, food safety concerns in Canadian livestock were very different than they are today. In the 1920s Brucella spp. which causes ‘undulant fever’ in humans was a major zoonotic pathogen. The main route of transmission of Brucella spp. was through consumption of unpasteurized milk, often from the family milk cow. By the 1940s transmission was more by slaughter-house workers and others handling cattle as Canada started a brucellosis eradication program which led to Canadian cattle being declared brucellosis-free in 1985. Another major zoonotic disease in the 1920s was bovine tuberculosis (TB) which was also transmitted by unpasteurized milk or through meat and was often fatal to the young children consuming the milk. Testing of cattle TB was spear-headed by the province of Manitoba, with the first general TB testing occurring in that province in 1923. The first Canada-wide TB test of cattle was not completed until 1961, with 400,000 reactors identified. By 1974 TB-infected herds were required to be quarantined and by 1997 after some years of depopulation of TB-positive animals, Canada was recognized by the USDA as having TB-free status. In the 1980s as brucellosis and tuberculosis no longer were food safety concerns, they were replaced by Salmonella spp., Campylobacter spp. and pathogenic strains of E. coli. These remain organisms of food safety concern in livestock production today. As livestock are often intermittently colonized with these pathogens and only neonates exhibit signs of infection, the cull positive animals plan which worked for brucellosis and TB is not an effective strategy. Instead, the focus has been on improving antimicrobial hurdles in Canadian slaughter plants and improving detection of these organisms to prevent the release of contaminated food to consumers. Physical and chemical antimicrobial interventions such as washing hide-on carcasses with caustic soda and spraying carcasses with organic acid or hot water are widely implemented at processing facilities. Improved detection has included incorporation of molecular methods such as PCR and whole genome sequencing (WGS), with WGS becoming in 2018 the standard technology for identification of and traceback of sources of food-borne disease by the Public Health Agency of Canada. With these improvements, we are better able to prevent outbreaks of human disease than at any time in the past. Accordingly, cases of Salmonellosis, the leading food-borne illness in Canada and a major concern in poultry products, have declined by approximately one-third since 2019. It is the collaboration of a huge team of researchers, regulatory bodies, food processors, and farmers across Canada that have led to the improvements in food safety in Canada over the past 99 yr. Challenges still remain, but work continues to ensure that Canadian food is among the safest in the world.