DAO prepress abstract  -  DOI: https://doi.org/10.3354/dao03219

A pharmaco-epidemiological study of antibacterial treatments and bacterial diseases in Norwegian aquaculture for the 6 yr period 2011 to 2016

Atle Lillehaug*, Christine Børnes, Kari Grave

*Email: atle.lillehaug@vetinst.no

ABSTRACT: Sales of antibacterials for use in Norwegian fish farming, and prescribing patterns for various fish species and production phases, as well as diseases causing treatment in the years 2011 to 2016, are described. The study is based on data of sales of antibacterials from wholesalers, pharmacies and feed mills, and prescription data obtained from a register of all prescriptions of antibacterials used in farmed fish, giving details on each treatment. The results demonstrate that the fish-farming industry uses very small volumes of antibacterials. In 2016, a total of 212 kg was sold for use in farmed fish, the only antibacterial substances sold were florfenicol and oxolinic acid. The total volume corresponded to 0.16 mg kg–1 fish slaughtered, or to approximately 0.14% of the fish produced this year being treated with antibacterials. A majority of the prescriptions is for non-specific bacterial infections, specific diseases are largely under control by vaccination. Most prescriptions for salmonid fish are in early production stages. However, due to higher biomasses of fish, the highest volumes of antibacterials were prescribed during the seawater production phase of Atlantic salmon Salmo salar. An increasing part of the prescriptions are for cleaner fish used for salmon lice control, in 2016 the major proportion of prescriptions were for this fish category. Due to the negligible use of antibacterials in Norwegian aquaculture, in particular for on-growers, the risk of development of antimicrobial resistance, and thus transmission of such resistance, to humans through fish meat is considered negligible.