Reconstructing an annual cycle of interaction: natural infection and antibody dynamics to avian influenza along a migratory flyway

Abstract

Migratory animals may play an important role in connecting disparate ecosystems, including the introduction of various pathogens. Th e incidence of these pathogens may vary over time and space, such that events along the entire migratory fl yway are likely to be important in the interaction between pathogens and their migratory hosts. On this premise, the annual cycle of a naturally occurring host-pathogen system was reconstructed by examining infection with and antibodies to avian infl uenza virus along the fl yway of a long-distance Arctic migrant, the Svalbard-breeding pink-footed goose Anser brachyrhynchus . A highly-localized transmission period was identifi ed in winter, in contrast to the north -south decline expected from dabbling ducks, indicating the dynamics of infection may diff er among host species. In spring, 63% (95% CI: 57.1, 68.9) of adults had detectable antibodies to the nucleoprotein of avian infl uenza virus, compared to just 15% (95% CI: 8.7, 23.4) of juveniles, suggesting inter-annual antibody maintenance. Nevertheless, adult seroprevalence declined by approximately 30% from spring to late summer, indicating signifi cant seroreversion in the population. Integrating these fi ndings in an epidemiological model, detectable antibodies to nucleoprotein were estimated to persist for just 343 days (95% CI: 221, 607); considerably shorter than for other wildlife diseases in long-lived bird species. Th e investigation of wildlife diseases in migratory populations is an inherently complex task, yet, by integrating disease incidence and seroprevalence along a migratory fl yway, our fi ndings suggest that the ecological interactions and life history of the host, as well as the life-history of the pathogen, can infl uence the dynamics of infection and host immune response.

Contact between bird species of different lifespans can promote the emergence of highly pathogenic avian influenza strains

“…There is both observational and experimental evidence that a variety of domestic and wild avian species produce specific hemagglutination-inhibiting and neutralizing antibodies against HA, although opinion is divided as to their efficacy and duration, and there are some mechanistic reasons (such as the existence of truncated variants of IgY among ducks) that could prevent certain species from mounting an effective immune response (41)(42)(43). Nonetheless, AIV prevalence tends to decline with age whereas seroprevalence increases (9,(44)(45)(46), suggesting that some form of functional, long-term immunity is acquired upon exposure. We also present here an analysis of published data from a large, multiannual survey of influenza prevalence in wild birds in The Netherlands (47) showing that virus prevalence decreases with lifespan ( Fig.…”

Identifying crucial gaps in our knowledge of the life-history of avian influenza viruses—an Australian perspective

“…Antibody titre has been seen to increase rapidly as a result of re-infections, and is thought to be responsible for the decreased shedding period seen in re-infected individuals (Kida et al 1980;Fereidouni et al 2009Fereidouni et al , 2010Jourdain et al 2010). However, there is very little knowledge on how long these antibodies persist, with current estimates somewhere between a few months to a year (Nishiura et al 2009;Fereidouni et al 2010;Hoye et al 2010a). …”

“…Prevalence levels of antibodies are thus considerably higher than prevalence levels of virus and investigation of seroprevalence is potentially an effective means to screen for potential host species (Hoye et al 2010b). Beyond the identification of host species, analysis of seroprevalence, combined with information on contemporary infection (sampling virus directly) can shed considerable light on the temporal dynamics of infection (Hoye et al 2010a). Laboratory kits for this type of work have been developed for poultry and some species of waterfowl.…”

Variation in postsampling treatment of avian blood affects ecophysiological interpretations

“…Disease ecologists and veterinarians also rely on blood samples to measure specific antibodies that indicate prior infection with particular pathogens (e.g. Hoye et al 2011). Furthermore, the concentrations of various stable isotopes in blood samples can also be used to reconstruct the composition of an individuals' diet and determine its trophic position , as well as assess reproductive investment strategies (Klaassen et al 2001), patterns of habitat occupancy and migration routes and timing (Hobson & Norris 2008).…”