[Intramammary use of antibiotics in dairy farms in the canton of Ticino before, during and after Staphylococcus aureus genotype B elimination].

The aim of the study was to evaluate the use of intramammary antibiotics before, during and after the elimination of Staphylococcus aureus genotype B (SAGTB). Data on intramammary antibiotic use was collected in 65 dairy farms as part of a pilot project for SAGTB elimination in the canton of Ticino from 2017 to 2019. The investigated farms were divided into 46 affected farms (with at least one SAGTB-positive animal) and 19 control farms (SAGTB-free farms). Data on antibiotic use were requested from veterinarians and treatment incidence, as a measure of antibiotic use, was calculated based on medical records and veterinary prescriptions. In addition, the treatment incidence was calculated for 47 farms during alpine farming period. In 2018 (elimination year), the mean incidence of treatment during lactation in the SAGTB-positive farms was significantly higher than in the control farms (p=0,003). In 2019 no significantly lower antibiotic use during lactation or dry period was detected between 2017 (before elimination) and 2019 (after elimination). Alpine farming places where only S. aureus genotype B-negative animals had access to had a significantly lower antibiotic use during lactation (p=0,004). The new federal database (Antibiotics Information System in Veterinary Medicine, IS ABV) should allow continuous monitoring and to confirm the reduction of antibiotic use in the coming years.