| Summary: | Influenza is caused by influenza A virus, a single stranded RNA virus of the orthomyxoviridae family. In humans, it causes yearly outbreaks with high morbidity and excess fatality rates as a direct effect. Placed in its ecological niche however, in dabbling ducks, avian influenza virus (AIV) induce quite mild disease. It is when the virus crosses the species barrier that pathogenic traits are attributed to infection. Also infection of close relatives to dabbling ducks, the domestic chicken, cause morbidity and may in some cases change the virus into a highly pathogenic variant with nearly 100% fatality rate. Being a very adaptable virus, these spill-over events are frequent, and numerous species are susceptible to influenza virus. When a subtype of influenza which has not previously infected humans crosses the species barrier, adapts to humans and spread easily, a pandemic event is imminent. There is no cure for influenza infection, and vaccination is a cumbersome endeavor, so currently the strategy when a pandemic strikes is damage control. In this thesis, I have been involved in a surveillance project, to increase our knowledge of how influenza travels across the globe with its natural host. We have also used animal models to investigate the pathological effects in mallard ducks and their susceptibility to re-infection. Furthermore, we have evaluated the effect and the potential risk of frivolous use of the anti-viral agent oseltamivir, and also investigated a novel approach to the classic virus isolation method of growing virus in embryonated chicken eggs (ECE's). Indication was found in northern Alaska that prevalence of influenza is probably not lower here than in other breeding areas for dabbling ducks, as has been previously suggested. As these birds travel over the Bering Strait, the reason for the genetic isolation of Eurasian and North American influenza A strains remains unclear. Inoculation of mallards equipped with subcutaneous data transmitters indicated very little effect on the host and no stress ...
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