Quantification of visits of wild fauna to a commercial free-range layer farm in the Netherlands located in an avian influenza hot-spot area assessed by video-camera monitoring.

Free-range poultry farms have a high risk of introduction of avian influenza viruses (AIV), and it is presumed that wild (water) birds are the source of introduction. There is very scarce quantitative data on wild fauna visiting free-range poultry farms. We quantified visits of wild fauna to a free-range area of a layer farm, situated in an AIV hot-spot area, assessed by video-camera monitoring. A total of 5,016 hr (209 days) of video recordings, covering all 12 months of a year, were analysed. A total of 16 families of wild birds and five families of mammals visited the free-range area of the layer farm. Wild birds, except for the dabbling ducks, visited the free-range area almost exclusively in the period between sunrise and the moment the chickens entered the free-range area. Known carriers of AIV visited the outdoor facility regularly: species of gulls almost daily in the period January-August; dabbling ducks only in the night in the period November-May, with a distinct peak in the period December-February. Only a small fraction of visits of wild fauna had overlap with the presence of chickens at the same time in the free-range area. No direct contact between chickens and wild birds was observed. It is hypothesized that AIV transmission to poultry on free-range poultry farms will predominantly take place via indirect contact: taking up AIV by chickens via wild-bird-faeces-contaminated water or soil in the free-range area. The free-range poultry farmer has several possibilities to potentially lower the attractiveness of the free-range area for wild (bird) fauna: daily inspection of the free-range area and removal of carcasses and eggs; prevention of forming of water pools in the free-range facility. Furthermore, there are ways to scare-off wild birds, for example use of laser equipment or trained dogs.