A43 Modeling the ecology and evolution of H13 and H16 avian influenza A subtypes in black-headed gulls to understand influenza disease dynamics

Wild birds of the orders Anseriformes (ducks, geese, swans) and Charadriiformes (gulls, terns, shorebirds) are the natural hosts for all avian influenza A viruses and act as the reservoir source for influenza viruses that can cause epidemics and even pandemics in mammalian hosts. The ecology, epidemiology, and evolution of influenza A viruses in wild migrating birds are still poorly understood due to extreme complexity resulting from numerous virus host species that are hard to study during part of their annual cycle and infection with multiple virus subtypes. To increase our basic understanding of avian influenza A virus (AIV) epidemiology, evolution, and ecology, we will use viruses of the H13 and H16 subtypes in black-headed gulls (Chroicocephalus ridibundus) as a model system. Black-headed gulls are an ideal model species to increase this understanding owing to the fact that they are fairly easy to study year-round, are only infected routinely with two subtypes (H13 and H16), and are affected by annual epidemics in breeding colonies. Since 2006, black-headed gulls have been intensely sampled for influenza A viruses during the breeding period in four breeding colonies in the Netherlands (Griend, Blauwe Stad, De Kreupel, Veluwemeer; >5,000 samples) and year-round out with the breeding colonies (>8,000 samples). This has provided evidence of annual peak prevalence spikes of H13 and H16 virus infections in first-year birds (mostly fledglings) on the breeding colonies but low prevalence outside of the breeding period in fledged birds and in adults. To date, of a total of 258 H13 and 129 H16 virus isolates, we have sequenced 125 viruses using next generation sequencing methods. We anticipate that the sequence data, ecological data, and additional metadata, along with state-of-the-art phylogenetic analyses will lead to the development of the first quantitative epidemiological models for AIV in gulls —a first step towards modeling influenza viruses in other wild bird species such as ducks.