Prevalence, transmission and evolution of avian influenza viruses in Newfoundland and Labrador

Huang, Yanyan (2014) Prevalence, transmission and evolution of avian influenza viruses in Newfoundland and Labrador. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The island of Newfoundland is an important location for the breeding and wintering of millions of subarctic birds. The adjacency of the island to Greenland and western Europe indicates the possibility of inter-continental viral transmission by pelagic birds. In this thesis, the prevalence and transmission of avian influenza viruses (AIVs) in 3 major bird groups (duck, gull and murre) were investigated to shed light on AIV ecology and evolution at this region. The epidemiological study of AIVs in ducks (2008-2011) revealed an overall virus detection rate of 7.2%. The viral prevalence differed significantly by bird age and sampling season. Although the AIV detection rates were much lower in gulls (1.8%) and murres (3.9%) during 2009-2011, virus prevalence also displayed strong variability by bird age and season. In addition, serological study revealed a much higher frequency of AIV infection in ducks, gulls and murres compared to results by virus detection alone. The gene sequences of 30 duck AIVs (2008-2011) in Newfoundland and 79 reference duck AIVs (2006-2010) from the Atlantic bird flyway of North America were analyzed to reveal their genetic structure and the extent of gene flow. The genetic structure differed amongst the 8 viral segments with the highest diversity being found in the HA and NA segments. These viruses showed rare inter-continental transmission, but frequent reassortment, and frequent interspecies and North American inter-flyway distribution. The gull AIVs in Newfoundland (2009-2011) showed frequent inter-continental and cross-host group transmission. The study also revealed a larger than previously detected AIV gene reservoir in gulls in Atlantic Canada. The 21 H1N2 AIVs identified from Common Murre in summer 2011 belonged to 4 genotypes. The major genotype had been circulating in the murre population for a while before detection, as indicated by its genetic heterogeneity. The murre viruses displayed a mainly waterfowl-related gene pool with considerable inter-continental and avian-gull gene reassortments. The results of this thesis work provided a profile of AIV prevalence in Newfoundland, and increased our understanding of AIV ecology and evolution in wild birds of Atlantic Canada. Besides continuing the AIV surveillance in gulls, murres and dabbling ducks, future surveillance work should expand to include sea ducks and shorebirds, to better reveal the dynamics of AIV evolution and transmission in this region.

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