A baseline survey of antimicrobial use and health issues in the freshwater salmonid industry in France

International organizations encourage the monitoring of antimicrobial use and resistance in bacteria to manage and minimize further development of antimicrobial resistance. In France, the public policy plan Ecoantibio has underlined the need to collect data on antimicrobial use in all livestock production chains from direct, on-farm studies. To gain better knowledge on antimicrobial use in the aquaculture industry, we therefore conducted a cross-sectional study in 2014–2015 on a representative sample of 100 French freshwater salmonid farms. The health issues and medicinal products used during the reference year (full year preceding the visit, 2013 or 2014), were recorded by administering an on-farm questionnaire and by consulting documents, feed mills and prescribing veterinarians. Rainbow trout fry syndrome (RTFS), the most frequently reported disease, affected 41% of the fish farms at least once in the previous year. Parasitic diseases were also a cause of major concern, and finally furunculosis affecting 20% of the farms. Two-thirds (65%) of the farmers used antimicrobials at least once during this preceding year. Florfenicol was the most frequently used antimicrobial, mainly to treat outbreaks of RTFS, but it represented less than 20% of the treated fish biomass. Antimicrobials regarded as critical for public health reasons were used only exceptionally.