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Antibiotic resistance in the swine industry
Antimicrobials are important tools for ensuring the health, welfare and productivity of food animals. Societal concerns about the use of antimicrobials in food animals increased greatly in recent years, and substantial regulatory changes to oversight of antimicrobial use are underway in the USA. Even greater restrictions are likely in the future. These changes are likely to impact animal health, welfare, and productivity of swine production, and the economic viability of some farms, particularly smaller farmers. From a scientific perspective, two important unanswered questions are: 1) to what extent does antimicrobial use in food animals contribute to problems of clinical treatment failure in humans resulting from resistance; and 2) Which patterns of antimicrobial use in animals are of greatest concern with respect to selection of resistant bacteria? Without this knowledge, arguments that restricted use of antimicrobials in food animals will measurably benefit public health, and that particular modes of use are more harmful rest more on belief than evidence.
Momentum for regulatory changes in the USA has been inherited from changes implemented in the EU over the last 15 years. Most notably, banning of antimicrobial growth promotants in Denmark in 2000, and across the EU in 2006, gave great impetus to the recent changes in FDA regulations. The changes in the EU were initially motivated by specific concerns about antimicrobial resistance in foodborne pathogens (e.g., Salmonella, Campylobacter), where the link between animal antimicrobial use and human health is most direct. However, any resultant reduction in resistance in these organisms has been questionable. As we traverse the spectrum of ‘treatment-control-prevention-growth promotion’ uses, societal support for antimicrobial use in animals will understandably decline. Assuming any reduction of antimicrobial use is desirable (i.e., less is better) it seems logical to eliminate uses that are ‘less necessary’ or less justifiable in terms of benefits to animal health and welfare. However, it is ominous that recent developments to reduce antimicrobial use in food animals in the EU are almost completely divorced from any assessment of trends of resistance in bacteria or in clinical antimicrobial resistance in humans. An EU directive for mandatory recording and analysis of antimicrobial use in food animals is now being implemented, and better systems for accurately quantifying use in the USA are to be expected. Of greater concern are calls to eliminate preventive uses of antimicrobials, which appear to pay no heed to likely impact on animal health and well-being.
Keywords: Antimicrobial, resistance, use