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.

A Review of Avian Influenza A Virus Associations in Synanthropic Birds

“…As such, IAV infections and exposures have been commonly detected in a broad diversity of hawks, eagles, owls, and vultures, e.g., [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. Farms are frequently used by a number of species in these groups for foraging opportunities, and these birds are regularly observed at poultry facilities, including foraging on carcasses ([ 21 , 22 ], personal observations).…”

“…However, other virus subtypes are sometimes isolated from gulls, and many gull species exhibit synanthropic behavior, so these species might play a role in the spillover of IAVs of consequence to poultry. Black-headed gulls ( Chroicocephalus ridibundus ) were commonly observed on a poultry farm in Switzerland [ 21 ], and black-headed gulls and lesser black backed gulls ( Larus fuscus ) were frequent visitors to poultry farms in the Netherlands [ 22 ]. Additionally, an epidemiological assessment of risk factors associated with HP IAV outbreaks on ostrich farms in South Africa showed that the presence of gulls was associated with an increased likelihood of an outbreak [ 28 ].…”

“…are often associated with farms, with several studies documenting their consistent presence in Canada, Germany and the Netherlands [ 21 , 69 , 70 ]. In Germany, carrion crows ( C. corone ) and ravens ( C. corax ) were both commonly detected on farms [ 21 ], and in the Netherlands magpies ( Pica pica ), carrion crows and jackdaws ( C. monedula ) were all observed on a poultry farm, with specific observations of these species overlapping with free-ranging poultry and foraging on eggs [ 22 ]. An epidemiologic investigation of risk factors for predicting HP H5N1 outbreaks on farms in Bangladesh identified the presence of dead house crows ( C. splendens ), a common synanthropic resident throughout Bangladesh known for its scavenging behavior, on or near farms as the most predictive risk factor associated with IAV outbreaks [ 71 ].…”

“…Starlings were only occasionally observed on poultry farms in Germany [ 21 ], and were moderately common on a poultry facility in the late summer in the Netherlands, where they were often observed foraging [ 22 ]. In contrast, starlings were one of the most abundant birds observed on poultry farms in Canada and were identified as a high priority species for further study to assess IAV spillover risk [ 69 ].…”

Detection of Low Pathogenic Avian Influenza Virus Subtype H10N7 in Poultry and Environmental Water Samples During a Clinical Outbreak in Commercial Free-Range Layers, Netherlands 2017

“…This water-rich area provides a good habitat for wild (water) birds, which live in large quantities near the farm. Elbers and Gonzales (42) monitored the free-range area of this particularly farm with video-cameras for 1 year and reported various visits of wild birds to the freerange area (42). No direct contact between hens and wild birds was observed, and it is hypothesized that wild birds infected with AIV probably contaminate the environment-soil and water present in the free-range area-with AIV.…”