Identifying and managing pathways of AI transmission by wild birds on meat chicken farms in eastern Australia

Abstract

Conjecture surrounds the reservoir and bridge species potentially involved in introducing, maintaining and transmitting avian influenza (AI) on Australian meat chicken farms. This is mainly due to a lack of AI prevalence data and in-depth understanding of wild bird ecology on farms and across regions. For risk assessment purposes, we identified candidate species likely to be involved in AI maintenance and transmission during 68 bird surveys conducted across ten commercial meat chicken farms from Winter 2016 to Summer 2018 in southeastern Queensland. Using an AI-risk classification processes described in this paper, we speculate that 57 of the 139 species recorded in and around production facilities and nearby water bodies pose a medium to high risk, particularly on free range farms. On the farms with permanent waterbodies, resident and semi-resident dabbling ducks (Genus Anas ) could maintain AI indefinitely on-site, creating opportunities for these species and several bridge species to potentially infect poultry by being a vector between the dam/water habitat and poultry facilities. We suggest that other types of wild birds that may be involved in AI transmission including nomadic waterfowl, grazing ducks (Australian Wood Ducks and Plumed Whistling-duck), Waterhens, Lapwings, resident scavengers (corvids, ibis), birds of prey and mud nests builders (e.g. Fairy Martins). Disrupting AI maintenance cycles on farm dams would reduce the chances of transmission of environmental AI by potential bridge species. This may be achievable by proactively preventing higher risk waterfowl becoming resident and habituated on farms and deterring potential bridge species from accessing poultry houses. Targeted AI surveillance of suspected bridge species is required to determine the real risk. Ideally, this should occur on non-commercial poultry farms where AI transmission to poultry can be objectively investigated.