Biosecurity risk factors associated with outbreaks of high pathogenicity avian influenza (HPAI) on poultry farms in Lower Saxony (Germany) – A case-control-study

Biosecurity is an essential component when considering risk factors for high pathogenicity avian influenza (HPAI) and may be an explanation for the phenomenon that not all poultry farms are equally affected by outbreaks - despite similar conditions in terms of location, surroundings and size as well as type of poultry and production. In a case-control study, the association of biosecurity measures with the risk of outbreaks of HPAI in poultry farms in Lower Saxony, Germany, was investigated. In total 15 case farms with at least two previous outbreaks of HPAI and 26 control farms without such were examined during farm visits using a specially developed biosecurity checklist. In the univariable logistic regression analysis, the following factors showed a significant association with the outbreak status in poultry farms: longer distance to nearest federal highways, not short-cut grass areas around the stables, no dedicated facilities for removing carcasses from the stables, using trays instead of mats for shoe disinfection as well as feed, litter and manure storage in such a way that suppliers have to enter the clean area. In the multivariable analysis with backward stepwise regression only the variables not short-cut grass areas and no dedicated facilities for removing carcasses from the stables were identified as factors having a significant association with the HPAI outbreak status of a poultry farm. Taking these factors into account could contribute to reducing the risk of HPAI on poultry farms.