Investigating Avian Influenza Infection Hotspots in Old-World Shorebirds

Abstract

Heterogeneity in the transmission rates of pathogens across hosts or environments may produce disease hotspots, which are defined as specific sites, times or species associations in which the infection rate is consistently elevated. Hotspots for avian influenza virus (AIV) in wild birds are largely unstudied and poorly understood. A striking feature is the existence of a unique but consistent AIV hotspot in shorebirds (Charadriiformes) associated with a single species at a specific location and time (ruddy turnstone Arenaria interpres at Delaware Bay, USA, in May). This unique case, though a valuable reference, limits our capacity to explore and understand the general properties of AIV hotspots in shorebirds. Unfortunately, relatively few shorebirds have been sampled outside Delaware Bay and they belong to only a few shorebird families; there also has been a lack of consistent oropharyngeal sampling as a complement to cloacal sampling. In this study we looked for AIV hotspots associated with other shorebird species and/or with some of the larger congregation sites of shorebirds in the old world. We assembled and analysed a regionally extensive dataset of AIV prevalence from 69 shorebird species sampled in 25 countries across Africa and Western Eurasia. Despite this diverse and extensive coverage we did not detect any new shorebird AIV hotspots. Neither large shorebird congregation sites nor the ruddy turnstone were consistently associated with AIV hotspots. We did, however, find a low but widespread circulation of AIV in shorebirds that contrast with the absence of AIV previously reported in shorebirds in Europe. A very high AIV antibody prevalence coupled to a low infection rate was found in both first-year and adult birds of two migratory sandpiper species, suggesting the potential existence of an AIV hotspot along their migratory flyway that is yet to be discovered.

A social–ecological approach to landscape epidemiology: geographic variation and avian influenza

“…At the same time, assumptions that are derived from any single region must be considered as working hypotheses until they have been validated in other systems. For example, widely held assumptions based on northern hemisphere findings about the importance of migratory ducks or large congregation sites of shorebirds (Krauss et al 2010) as the primary sources of AIVs were not substantiated for Africa Gaidet et al 2012b) despite clear evidence of a Eurasian origin for AIVs entering Southern Africa (Abolnik et al 2006). Regional differences combined with geographic connectivity emphasize the need for a global-to-local approach to disease surveillance and control, because a failure to respond appropriately in one region can have consequences for other regions.…”

Rôle des oiseaux sauvages dans la transmission et la dispersion des virus de l’influenza aviaire : apport de l’éco-épidémiologie dans les écosystèmes afro-tropicaux

“…(Cappelle et al, 2011 ;Caron et al, 2011). Une circulation lors de différentes saisons a également été détectée dans le site de Mauritanie où les canards sont absents toute l'année, suggérant la contribution d'autres groupes d'hôtes sauvages à la persistance des VIA (Gaidet et al, 2012a). Globalement, dans ces écosystèmes africains, la circulation des VIA existe à un niveau faible, avec des niveaux plus élevés chez les anatidés et pendant les saisons où les migrateurs eurasiatiques sont présents ( 2.3 Déterminants écologiques influençant la transmission des VIA au sein des communautés de canards sauvages L'analyse des données collectées à l'échelle continentale sur environ 8 400 anatidés sauvages dans 16 sites afrotropicaux révèle que les variations de taux d'infection VIA sont associées à plusieurs facteurs écologiques, soit à l'échelle de l'hôte (le groupe taxonomique), soit à l'échelle de la communauté (densité locale d'anatidés, saison d'hivernage des anatidés migrateurs) (Gaidet et al, 2012b).…”

“…En Afrique, aucun hot spot de circulation de VIA chez les laro-limicoles n'a été détecté, malgré la vaste étendue géographique et taxonomique des oiseaux échantillonnés (69 espèces de laro-limicoles appartenant à dix familles distinctes échantillonnées dans 25 pays), en particulier dans les grands sites de concentration de laro-limicoles sur les sites d'hivernage ou de migration (delta du Nil-Égypte, banc d'Arguin-Mauritanie, delta du Sénégal, delta du Niger-Mali, plaines de la Kafue-Zambie) (Gaidet et al, 2012a). De plus, les variations de taux d'infection entre sites et saisons n'ont pu être associées avec l'abondance locale des laro-limicoles.…”

Avian Influenza in Wild Birds from South America: Review, Implications and Perspectives

“…11,28 However, because the avian communities of South America are vastly different from those of the Northern Hemisphere, caution is advised not to presume that AIV epidemiology in the Neotropics will be identical to that observed in other well-studied continents. Other aquatic birds that may live in close proximity with Anseriformes and Charadriiformes should be investigated as they could potentially be involved in the maintenance and transmission of AIV.…”