Influenza virus is a RNA virus that exists as different types and subtypes. Influenza A virus strains are known to cause disease in several bird and mammalian species. Wild birds are believed to constitute the natural reservoir for influenza A virus. In humans, influenza A virus causes yearly seasonal influenza epidemics of respiratory disease resulting in high morbidity and severe economic consequences. This thesis includes five articles where data are presented that add new knowledge on this subject. We add proof that wild ducks are indeed the host for most influenza A virus subtypes by presenting data from a meta-analysis on all published screening data from wild birds and by presenting data from a four year screening of migratory ducks that were caught and sampled at Ottenby Bird Observatory. Our investigations have shown that the prevalence of influenza virus in the wild duck population of western Eurasia shows temporal differences in comparison to the results found in studies…
Contents
1.0 Introduction
1.1 History and scientific progress
1.2 Structure and function
1.3 Genetic variability
1.4 Host specificity
1.5 Persistence and modes of transmission
1.6 Influenza A virus in man
1.7 Influenza A virus in other mammals
1.7.1 In pigs
1.7.2 In horses
1.7.3 In canines
1.7.4 In felines
1.7.5 In mink and ferrets
1.7.6 In seals and whales
1.8 Influenza A virus in domestic birds
1.9 Influenza A virus in wild birds
1.9.1 The wild bird reservoir
1.9.2 Geographic constraints
1.9.3 Species preference
1.9.4 Modes of transmission
1.9.5 Clinical picture and immunity
1.9.6 Enzootic cycle
1.9.7 Spread by wild birds
2.0 Aims of the study
3.0 Study design, populations and localities
3.1 Populations
3.2 Trapping methods
3.3 Measurements and sampling
4.0 Methodological considerations
4.1 Screening for influenza A virus;RNA-isolation and virus detection
4.2 Isolation of influenza A virus
4.3 Characterization of influenza A virus
4.3.1 Hemagglutinin and neuraminidase-inhibition tests
4.3.2 Serology
4.3.3 Immunization
4.3.4 Double immunodiffusion assays
4.3.5 Nucleotide sequencing and phylogenetic trees
5.0 Results and Discussion
5.1 Influenza A virus in different species of wild birds
5.2 Subtype distribution in wild birds
5.3 Seasonality and perpetuation in the wild bird reservoir
5.4 Geographic differences between wild bird populations
5.5 Relation between wild birds and outbreaks in poultry
6.0 Concluding remarks
Epilogue
Acknowledgements
Reference list
Author: Wallensten, Anders
Source: Linköping University
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