Avian Influenza in Wild Birds and Poultry: Dissemination Pathways, Monitoring Methods, and Virus Ecology

Abstract

Avian influenza is one of the largest known threats to domestic poultry. Influenza outbreaks on poultry farms typically lead to the complete slaughter of the entire domestic bird population, causing severe economic losses worldwide. Moreover, there are highly pathogenic avian influenza (HPAI) strains that are able to infect the swine or human population in addition to their primary avian host and, as such, have the potential of being a global zoonotic and pandemic threat. Migratory birds, especially waterfowl, are a natural reservoir of the avian influenza virus; they carry and exchange different virus strains along their migration routes, leading to antigenic drift and antigenic shift, which results in the emergence of novel HPAI viruses. This requires monitoring over time and in different locations to allow for the upkeep of relevant knowledge on avian influenza virus evolution and the prevention of novel epizootic and epidemic outbreaks. In this review, we assess the role of migratory birds in the spread and introduction of influenza strains on a global level, based on recent data. Our analysis sheds light on the details of viral dissemination linked to avian migration, the viral exchange between migratory waterfowl and domestic poultry, virus ecology in general, and viral evolution as a process tightly linked to bird migration. We also provide insight into methods used to detect and quantify avian influenza in the wild. This review may be beneficial for the influenza research community and may pave the way to novel strategies of avian influenza and HPAI zoonosis outbreak monitoring and prevention.

Temporal Dynamics of Influenza A(H5N1) Subtype before and after the Emergence of H5N8

“…This results in a strong economic burden through its huge impact on the poultry industry and culling of millions of birds. Both subtypes have been reported to transmit from wild aquatic birds to domestic poultry and vice versa [ 19 , 35 , 39 ]. Our findings provide evidence of the long-term persistence of H5 subtypes in natural reservoirs with the changing dominance of subtypes.…”

Surveillance of avian influenza viruses from 2009 to 2013 in South Korea

“…Anseriformes and Charadriiformes) more likely to carry AIVs across flyways than others 24 . Compositions of the population (e.g., frequency of juveniles), which is also influenced by timing and environmental factors, may also affect AIV diversity 25 , 26 . However, for this study, we did not identify the species sources of the fecal samples, so we could not know for certain whether the bird population at the time of sampling affected our AIV isolation rates.…”

Exploring surface water as a transmission medium of avian influenza viruses – systematic infection studies in mallards

“…As fecal–oral transmission chains are highly effective this would be theoretically sufficient to infect another 10 6 ducks assuming, conservatively, the minimal infectious dose per animal would amount to 10 3 –10 4 EID 50 [ 24 ]. Dispersion of virus-contaminated fecal matter and oropharyngeal excretions in surface waters is expected to potentiate transmission efficacy: (1) Depending on the AI virus strain but also on various physico-chemical properties of the water body such as temperature, pH, salinity, sedimentation rates, presence of biologic compounds and so on, the infectivity of virus particles shed into such water is retained for astonishingly long periods of up to several months [ 26 ]. Conversely, higher water temperatures (22°C), alkaline or acid pH and high salinity inactivate viral infectivity within hours to days [ 26–30 , 31 ].…”

“…Dispersion of virus-contaminated fecal matter and oropharyngeal excretions in surface waters is expected to potentiate transmission efficacy: (1) Depending on the AI virus strain but also on various physico-chemical properties of the water body such as temperature, pH, salinity, sedimentation rates, presence of biologic compounds and so on, the infectivity of virus particles shed into such water is retained for astonishingly long periods of up to several months [ 26 ]. Conversely, higher water temperatures (22°C), alkaline or acid pH and high salinity inactivate viral infectivity within hours to days [ 26–30 , 31 ]. Furthermore, the presence of invertebrate animals (clams, snails, shrimps, insects) may modulate the retention time of infectious AIV in surface water and sediments [ 26 , 32–34 ].…”