A recent article by Jonathan Runstadler in Science* highlighted the risk of avian influenza H5 clade 2.3.4.4b to wild bird, terrestrial and aquatic mammalian populations. Although losses to commercial poultry have been quantified, the magnitude of mortality among diverse avian taxa is unknown. According to the Convention on The Conservation of Migratory Species of Wild Animals and the Food and Agricultural Organization, avian influenza is a panornitic that has affected as many as 500 species of wild birds since 2020. Reflecting the situation in commercial poultry, avian influenza in wild and migratory avian species is less seasonal and now ye
ar-round in incidence. A number of endangered species have been highlighted in attempts at understanding the magnitude of infection. Obviously, the California condor is at extreme risk and the small remaining population justified capture and vaccination. Other species including the Barnacle Goose, Dalmatian Pelican, Northern Gannet and Roseate Tern populations have been severely diminished.
Emergence of H5N1 in marine mammals along the Pacific littoral demonstrates susceptibility of a wide range of seal and sea lion species with obvious animal-to-animal transmission.
The article stressed that “avian influenza in wild birds extends beyond classic epidemiologic principles of contact and incorporates the effects of climate change, habitat destruction and host species behavior.” The article called for enhanced surveillance of wildlife populations and developing an understanding of the factors contributing to infection.
It is evident that frequent and extensive outbreaks in poultry are contributing to infection of domestic resident birds including scavenger species such as black vultures and raptors. Persistence of avian influenza H5N1 and possibly other emerging H5 and H7 serotypes will perpetuate outbreaks among commercial poultry. This suggests the need for protective vaccination given that extreme biosecurity does not provide absolute protection. Evidence that close contact with infected flocks and dairy herds can result in zoonotic infection is obviously of concern as recombinant events and mutations may result in a more pathogenic or even contagious strain impacting the human population.
*Runstadler, J., (2024) Global Influenza Threatens Conservation, Science 336:618-619