Seasonality dynamics of avian influenza occurrences in Central and West Africa

Abstract

SUMMARY Understanding seasonal cycles of viruses originating in wildlife can provide insight into their likelihood of persistence in animal populations and inform policies to limit spillover to human populations. Avian influenza virus (AIV) is an important zoonotic agent causing seasonal occurrence of avian influenza (AI) in wild birds in temperate areas. Although the seasonality of AIV transmission in tropical birds is largely unknown, peaks of influenza activity in human populations in the tropics coincide with the rainy season. To assess the seasonality of AI in tropical birds, from 2010-14, we sampled 40,099 birds at 32 sites in Central Africa (Cameroon, Central African Republic, Congo-Brazzaville, and Gabon) and West Africa (Benin, Côte d’Ivoire, and Togo). Although AIV was not isolated by egg culture, in Central Africa, detection rates by real-time RT-PCR were 3.57% for passerine songbirds and 8.74% for Anatid ducks. RT-PCR positivity in resident birds increased when Palearctic migrants arrived in Central Africa. At sampling sites with two annual wet seasons, the positive rate in wild birds was greatest during the big rainy season in September – October. This study provides the first evidence that AI is present in Central African birds and identifies environmental factors associated with cases.

Migratory birds as vehicles for parasite dispersal? Infection by avian haemosporidians over the year and throughout the range of a long‐distance migrant

“…Migratory animals may be key players in the spread of parasites and in the structuring of assemblages (Altizer, Bartel, & Han, ; Garamszegi & Møller, ; Viana, Santamaría, & Figuerola, ). In particular, migratory birds may be vehicles for the dispersal of parasites among widely separated geographic areas (Altizer et al., ; Fourment, Darling, & Holmes, ; Rappole, Derrickson, & Hubálek, ; Waldenström, Bensch, Kiboi, Hasselquist, & Ottosson, ) and could play an important role in the transmission of parasites among species at breeding and wintering grounds (Cohen, Auckland, Marra, & Hamer, ; Fuller et al., ; Hellgren et al., ; Klaassen, Hoye, Nolet, & Buttemer, ; Levin et al., ; von Rönn, Harrod, Bensch, & Wolf, ; Valkiūnas, ; Waldenström et al., ). For example, in the Nearctic–Neotropical migratory system, millions of birds travel between temperate breeding and tropical nonbreeding areas, potentially allowing parasites to extend their geographical and host ranges (Durrant et al., ; Ricklefs, Fallon, Latta, Swanson, & Bermingham, ; Ricklefs et al., ); this may account for the broad distributions of some parasite lineages (Fallon, Fleischer, & Graves, ).…”

Remote Sensing and Ecological Variables Related to Influenza A Prevalence and Subtype Diversity in Wild Birds in the Lluta Wetland of Northern Chile

“…With respect to the meteorological variables evaluated in this study, none were significantly associated with IAV positivity to the virus in the wetland, although climatic variables such as temperature and precipitation have been described as important drivers of IAV in wild birds in other regions of the world [ 24 , 26 , 56 , 57 ]. This could be explained mainly because climatic conditions in the wetland are stable throughout the year.…”

Factores ambientales relacionados con la presentación de virus influenza A en aves silvestres

“…Estos resultados son similares a otros encontrados en el continente africano, en donde un incremento en la prevalencia estuvo relacionado con la temporada de arribo de migrantes (17,39). Además, Fuller et al (39) también determinó que las temporadas lluviosas estarían asociadas con un incremento en la prevalencia de VIA en humedales de África Central.…”

“…Estos resultados son similares a otros encontrados en el continente africano, en donde un incremento en la prevalencia estuvo relacionado con la temporada de arribo de migrantes (17,39). Además, Fuller et al (39) también determinó que las temporadas lluviosas estarían asociadas con un incremento en la prevalencia de VIA en humedales de África Central. Probablemente esto se deba a dos mecanismos: [1] que las precipitaciones desencadenan un aumento en la disponibilidad de alimentos y, por lo tanto, una mayor abundancia de aves y [2] que el inicio de la temporada lluviosa coincide con el inicio del periodo de reproducción de las aves, lo que favorece la congregación en los sitios aumentando la tasa de contacto.…”

“…Basados en estos resultados, los autores sugieren que las precipitaciones determinarían una oportunidad de reproducción, influenciando la estructura etaria dentro de la población (mayor cantidad de juveniles), lo que afecta la dinámica de infección del VIA (39). Esto es consistente con lo reportado por Van Dijk et al (12), quienes demostraron que el pico de prevalencia de VIA en Patos de collar (Anas platyrhynchos) en Holanda, estuvo relacionado con un aumento de los individuos jóvenes susceptibles durante fines de verano/principios de otoño.…”