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

Abstract

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.

Keywords: avian influenza; ducks; free-range poultry; gulls; water pools; wild fauna.

Figure 1

Aerial map of location of free‐range layer farm (source: Google Earth Pro, 2019). A: free‐range area on north‐side of poultry barn; B: free‐range area on south‐side of the poultry barn; C: ditch with surface water; D: ditch with surface water; E: ditch with surface water; F: canal with surface water; G: wide canal with surface water; H: neighbour free‐range layer farm; I: poultry barn; J: a few small trees (fenced) in free‐range‐area; K: a few large trees around the private house of poultry farmer

Figure 2

North‐side of the fenced free‐range area, on the right side the poultry barn

Figure 3

Distribution of the total daily wild fauna visits (unit of measurement: total daily wild fauna visits) to the free‐range area of the layer farm by month (fat dark line in the box: median; lower end of the box: 25% quantile; higher end of the box: 75% quantile; highest bullet or high end of the vertical line coming out of the box: highest value; lowest bullet or low end of vertical line coming out of the box: lowest value). A wild fauna visit was defined as one or more of wild birds from the same species landing, or wild animals (e.g. rat, mouse) entering, and subsequent staying for a continuous time period in the free‐range area (or sitting on the fence) until departing

Figure 4

Distribution of total daily bird counts (unit of measurement: total daily bird count) of members of the order Anseriformes, Charadriiformes and Passeriformes visiting the free‐range area of the layer farm by month (fat dark line in the box: median; lower end of the box: 25% quantile; higher end of the box: 75% quantile; highest bullet or high end of the vertical line coming out of the box: highest value; lowest bullet or low end of vertical line coming out of the box: lowest value)

Figure 5

Mosaic plots (graphs on the left side) and correspondence analysis plots (graphs on the right side) displaying: (a) the frequency of visits (mean number of visit per month), (b) number of wild birds visiting the outdoor facility and (c) exposure time, which is the number of birds visiting the outdoor facility times the duration of their visit (bird hours)

Figure 6

Total precipitation (in mm) by month from an official KNMI weather station located approximately 1 km from the free‐range layer farm in this study (source: Royal Netherlands Meteorological Institute (KNMI); https://www.knmi.nl/nederland-nu/klimatologie-metingen-en-waarnemingen)

Figure 7

Water pools in the free‐range area of the layer farm (second half of November)