How Has the Prescription-Only Regulation Affected Antibiotic Use and Resistance Canada’s Cow-Calf Herds?

Background

Since December 2018, Canada’s cattle producers have required a valid veterinary-client-patient relationship and a veterinary prescription before they can obtain antibiotics for their cattle. Since then, many veterinarians have encountered cattle producers who previously purchased their over-the-counter antibiotics from farm supply stores. The ensuing conversations may have resulted in changes to which antibiotics are being purchased and used in cow-calf operations.

Objectives

To describe

• Antibiotic use and reasons for use in Canadian cow-calf herds to monitor impacts of the 2018 changes in regulations,

• changes in access to and cost of antibiotics for treating sick animals and producer awareness of antibiotic stewardship and the importance of antibiotic resistance,

• frequency of antibiotic use within cow-calf herds and examine factors associated with variation in frequency among and within herds using individual animal treatment records,

• antibiotic resistance in fecal indicator organisms from cows and calves from spring and fall for comparison to national antibiotic resistance surveillance data collected at feedlots, packing plants, retail locations and in other livestock commodities, and

• cow-calf veterinarians’ prescribing practices, experiences and information needs following the December 2018 changes in prescribing regulations.

What they did

They surveyed approximately 150 cow-calf producers from in the Canadian Cow-Calf Surveillance Network (C3SN) about on-farm herd and animal-level antimicrobial use (AMU) practices as well as their attitudes about antimicrobial use and resistance and changes to antimicrobial regulations.

Antimicrobial resistance (AMR) data was also collected from 50 herds in western Canada. Fecal samples were collected at random from 10 calves and 10 cows in the spring and fall of 2021. Isolates of E. coli and Enterococcus were obtained and analyzed for AMR prevalence. Enterococcus samples were also analyzed using Whole Genome Sequencing (WGS).

They also surveyed veterinarians to determine changes in veterinary prescribing practices, veterinary and producer attitudes and their perspectives on producer information needs.

What they did

Most cow-calf herds reported using antimicrobials in their herds to treat at least one animal. However, the frequency of antimicrobial use in cow-calf herds was relatively low, with most herds treating <5% of animals. The most common reasons for treatment included respiratory disease and diarrhea in calves, and lameness in adult cows.

Most producers reported being aware of initiatives to improve antimicrobial stewardship and indicated that AMR was an issue of importance to them personally as well as to the beef industry. Since the regulatory changes in 2018, most producers reported no changes to antimicrobial use practices, access, or costs. Producers reported using veterinarians as their primary source of information regarding antimicrobials.

Antimicrobial resistance (AMR) was seen in both E. coli and Enterococcus from calves in cows in both the spring and fall. The prevalence of resistance in E. coli is quite low (only 16% of isolates being resistant to at least one of the tested antimicrobials) and relatively unchanged from previous work. Antimicrobial resistance in Enterococcus was higher (85% of isolates were resistant to at least one antimicrobial) but this is not all related to AMU. Enterococcus has widespread intrinsic resistance (i.e., resistance that occurs naturally, even without exposure to antimicrobials). The whole genome sequencing (WGS) of Enterococcus casseliflavus revealed vanC-type intrinsic vancomycin resistance genes. The only observed association was between AMU and AMR was between macrolide use and macrolide resistance for Enterococcus spp.

Most veterinarians reported acquiring more clients, more cow-calf clients requiring prescriptions, and having spent more time supporting client needs since the regulatory change to prescription-only status came into place. The increased time required by veterinarians is generally billed as professional time, especially at client onboarding. The move to prescription only status for antimicrobials was reported by veterinarians as leading to some changes in the types of antimicrobials prescribed and used in the cow-calf sector.

What it means

Since the imposition of more stringent regulations in December of 2018, there have been very minimal changes to antimicrobial use practices. Both producers and veterinarians recognize the importance of proper antimicrobial use practices and the impact of antimicrobial resistance in their herds, and to the industry as a whole. Antimicrobial stewardship initiatives are important to keep producers, veterinarians, and the public working together to continually improve antimicrobial use practices. Developing regulations that work for all levels involved is essential to protecting the health and welfare of animals, while also reducing the risk of antimicrobial resistance.