CONICET | Buscador de Institutos y Recursos Humanos

Aquatic birds are considered to be the natural reservoir of all influenza viruses. Low Pathogenic Avian Influenza viruses have been isolated from at least 36 species of ducks, 8 species of geese, 10 species of shorebirds, 9 species of terns, and a few additional waterfowl species. Prevalence of influenza A virus is higher in fall than in spring in all studies of ducks and gulls from Europe and North America. This temporal pattern of prevalence was attributed to the higher proportion of immunologically naive juveniles during fall migration. In contrast, the seasonal prevalence of influenza viruses in shorebirds of North America showed a different picture, found that prevalence of avian influenza in shorebirds in Delaware Bay area was 14.2% during northward spring migration, but only 0.9% (15 times lower) during southward fall migration. To explain this pattern, it has been proposed that an undetermined reservoir of influenza viruses exists in South America where shorebirds may be exposed during the non-breeding season, and subsequently carry virus back north during spring migration. Different hypotheses for the mechanisms of perpetuation of AI viruses have been proposed. Viruses could survive in frozen lakes with reinfection of birds the following spring; or influenza virus gene pool in aquatic birds is perpetuated by low-level transmission among waterfowl throughout the year. Finding avian influenza viruses in shorebirds at wetlands that become frozen in winter, or at the coast of Patagonia would support the hypothesis of a South American reservoir. We present the results from165 shorebirds sampled in fresh water wetlands and the coast of Chubut and Santa Cruz in southern Argentinean Patagonia. In this region breeding and post-breeding Neotropical shorebirds and waterfowl are found in mixed flocks with non-breeding Nearctic shorebirds.

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