LPAI Risicofactoren (WOT-01-003-060)

A case-control study was conducted to identify risk factors for the introduction of low pathogenic avian influenza (LPAI) virus at free range layer farms in the Netherlands. Forty farms with a known LPAI virus introduction in the past five years (cases) were compared with 81 farms without a known introduction of LPAI virus in the past five years (controls).

A questionnaire was developed to collect information about potential risk factors and was filled in at the farm during a farm visit. First the data were examined by univariate analysis (mainly by a chi-square test) to detect possible risk factors. Subsequently a multivariate logistic regression analysis was performed with the possible risk factors that were identified by the univariate analysis.

The analyses showed that the risk of introduction of an LPAI virus at free range layer farms is more than three times higher when wild ducks are seen in the free range at least once a week compared to layer farms where wild ducks are seen less frequently (once a month or less).  

The analysis also showed that free range layer farms on clay soil have a six times higher risk of introduction of LPAI virus than free range layer farms on soil other than clay.

The multivariate analysis identified no risk factors that were associated with farm management or hygiene.