| Low pathogenic avian influenza (LPAI) viruses naturally circulate among wild birds, especially those inhabiting aquatic environments. Because of frequent contact with domestic poultry through shared areas, wild birds are believed to be responsible for the geographical spread of avian influenza. Although LPAI viruses cause little to no disease in their natural avian hosts, subtypes H5 and H7 mutate into high pathogenic forms (HPAI) when in chickens. For nearly two decades, HPAI outbreaks, especially subtype H5N1, occur frequently and with ferocity across the globe. Given that the origins of HPAI lie with LPAI, we must increase our understanding of the mechanisms governing the spread and persistence of LPAI viruses in their natural reservoir.;Here, we present four deterministic, compartmental models describing the indirect transmission and maintenance of LPAI viruses among wild birds, culminating in an age-structured model for a migratory species. For each model, we established positivity and boundedness of solutions as well as derived sufficient conditions for the local stability of the disease-free equilibrium. Numerical simulations allowed us to explore how varying environmental factors, such as temperature, and host conditions contribute to the endemicity of LPAI viruses. Supporting theoretical conjectures, we conclude that certain sub-populations and free-living virus surviving in the environment drive disease dynamics, but the extent of influence for both species differs between resident and migratory birds. |
