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Changing perspectives on prudent drug use

The theme of this year’s CanWest veterinary conference sponsored by the Alberta Veterinary Medical Association was prudent drug use and antimicrobial resistance. Approximately 750 veterinarians, animal health technicians and human health professionals attended.

The meeting provided several key messages about antimicrobial use. First, this is a complex issue and there are no easy answers. In Europe, antimicrobial resistance (AMR) has been the source of much study and debate over several decades. North America is now fully engaged.

Secondly, concern about AMR in humans is real. Within the span of one lifetime, the emergence of antibiotics as wonder drugs degenerated to a furor over use, abuse and possible ineffectiveness. These concerns were heightened by urbanization and the issues urbanization generated for agriculture and its use of antimicrobials in the production of food. In 1931, 31 per cent of Canada’s population was engaged directly in agriculture. Today it is about two per cent.

According to Dr. Bill Cox at the B.C. Ministry of Agriculture, this trend necessitates intensive agriculture practices making antimicrobials a necessary part of livestock production. It is the way we use the few antimicrobials available that will have to be optimized.

Dr. Gail Cunningham notes consumer demand and forces far removed from the farm often drive the debate on antibiotic use rather than the long-term impacts of policy on animal welfare and producer security.

A third conference theme was the challenge of effectively communicating risk at both ends of the spectrum — the real risk to human health of staying the course on antimicrobial use in agriculture, and real risk to animal health of curtailing antimicrobial use.

Conflict between the medical and veterinary professions surrounding antimicrobial use in agriculture only intensifies the communication gap. How can the average citizen unacquainted with the background respond rationally to the debate on antimicrobial use and resistance? The default position about prudent use of antibiotics in animal agriculture becomes indisputable in the absence of understanding! The link between animal health and human health is incontestable and maintaining health on both sides becomes an essential component of food production.

Regardless of whether antimicrobials are used to treat disease directly, or promote growth, safeguards are in place to ensure food remains safe. The first safeguard comes with the responsibility given veterinarians to oversee health decisions for farm animals, including the types and amounts of medicines that should be given for specific diseases — especially antibiotics. A second safeguard is the strict approval process that all drugs used in animals go through, including drug efficacy, drug safety (human and animal), and manufacturing. As a part of the approval process, withdrawal times are established governing the time it takes the medicine to sufficiently clear the animal’s system before it is allowed to enter the food supply. Herein lies a growing challenge for industry.

The concept of a Food Animal Residue Avoidance Database (FARAD) was established in 1982 as a co-operative project between four U.S. veterinary colleges and the U.S. Department of Agriculture’s Food Safety and Inspection Service as a way to reduce the rate of residue violations in animal products through education and information. FARAD encouraged development of a Canadian databank to suit specific needs here. The Canadian gFARAD (CgFARAD) became a reality in 2002. Clinical pharmacology residents under the supervision of Dr. Patricia Dowling and Dr. Sarah Parker handle requests for service at WCVM. In 2011, a new eastern centre at the Ontario Veterinary College opened, supervised by Dr. Ron Johnson.

The CgFARAD provides expert-mediated decision support for inquiries related to drug or chemical residues in food animals. The purpose of the CgFARAD is not to promote extra-label drug use, but rather to protect public safety when it is necessary for licensed veterinarians to use approved drugs in this manner. CgFARAD withdrawal recommendations are not official withdrawal times.

Responsibility for residue violations remains with the prescribing veterinarian.

The bulk of the 14,700 requests since 2002 concern withdrawal times related to the extra-label use of drugs in poultry and swine feeds. CgFARAD is often assisted by the Canadian Food Inspection Agency’s Centre for Veterinary Drug Residues, that provides information on analytical methods and limits of detection for many veterinary drugs.

Dr. Dowling was adamant in reminding veterinarians that withdrawal recommendations are only provided for approved drugs used in species for which they are intended. Withdrawal times for approved drugs are based on maximum residue levels (MRLs) established by regulatory agencies. It is critical for veterinarians and producers to clearly understand that MRLs do not reflect limits of detection, which are often calculated in parts per billion and moving toward parts per trillion as technology advances. Detectable limits of many drugs last months; some persist for years. The use of non-approved drugs, including antimicrobials can have huge legal and financial implications for those who intentionally walk the line.

— Dr. Ron Clarke prepares this column on behalf of the Western Canadian Association of Bovine Practitioners. Suggestions for future articles can be sent to Canadian Cattlemen ([email protected]) or WCABP ([email protected]).

About the author


Dr. Ron Clarke

Dr. Ron Clarke prepares this column on behalf of the Western Canadian Association of Bovine Practitioners. Suggestions for future articles can be sent to Canadian Cattlemen ([email protected]) or WCABP ([email protected]).



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