Refining estimation of antimicrobial use at national level: A quantitative surveillance study processing data from the Swiss national reporting system

Antimicrobials are frequently used in livestock, but imprudent antimicrobial use (AMU) has raised concerns about antimicrobial resistance and animal welfare. Recently, the Swiss government has established the national reporting system "Information System of Antimicrobials in Veterinary Medicine" (IS ABV) to monitor AMU. This study used IS ABV data to calculate AMU of finisher pigs and dairy cattle across 1500 farms using two different indicators. We calculated treatment incidence (TI, in defined daily doses [DDD] per animal and year), and number of treated animals per 1000 animals per day (NoTrA) at the population (_P) and at the farm (_F) level. For finisher pigs, at the population level, we estimated 0.74 DDD/finisher pig/year and 8.65 treated finisher pigs/1000 finisher pigs/day, with antimicrobials mainly prescribed on stock and administered parenterally. Median TI_F for finisher pigs was 0.05 DDD/finisher pig/year (1st quartile: 0.0; 3rd quartile: 0.54). For dairy cattle, at the population level, we estimated 6.09 DDD/cow/year and 13.23 treated cows/1000 cows/day, with most treatments being administered by intramammary route. Median TI_F for dairy cattle was 5.21 (2.73; 8.36). Penicillins were the most frequently used antimicrobial class for both production categories. This is the first study to calculate AMU using IS ABV data including prescriptions on stock in its calculations, underlining its potential for standardized data collection and comprehensive AMU estimation. While AMU in finisher pigs and dairy cattle aligns with Swiss guidelines for prudent use, concerns remain over prescriptions on stock due to insufficient recorded information. This highlights the need for improved data recording.