Influence of porcine circovirus type 2 vaccination on the level of antimicrobial consumption on 65 Austrian pig farms

The administration of antibiotics to farm animals is an important contemporary topic. Veterinarians, pig producers, politicians, retailers and consumers all have a vested interest in reducing antimicrobial use on farm, while ensuring adequate health and welfare of food-producing animals. Vaccination programmes may be used to reduce the overall level of clinical disease in a population, subsequently leading to a decline in antimicrobial use. In 2008, a vaccination programme against porcine circovirus type 2 (PCV-2) was initiated in Austria. In the retrospective observational study presented here, farm medication records (2008–2011) from 65 conventional pig farms were evaluated. As PCV-2 has been shown to lead to generalised immunosuppression, enabling secondary bacterial infections to occur, the authors hypothesised that PCV-2 vaccination would decrease antimicrobial consumption at farm level. Firstly, we focused on the annual antimicrobial consumption expressed as the number of administered animal daily doses per kg liveweight (nADDkg/kg/year). Secondly, a linear mixed effects model was applied to evaluate the influence of PCV-2 vaccination on the antimicrobial consumption at farm level. The interaction between farm type and PCV-2 vaccination was found to be a highly significant factor (P=0.0002) influencing antimicrobial use at farm level. The estimated impact of PCV-2 vaccination revealed a highly significant (P<0.001) decline in total antimicrobial drug use from 1.72 ADDkg/kg/year to 0.56 ADDkg/kg/year on finishing farms, whereas only a negligible decline was detectable on farrow-to-finish farms.