The effects of avian influenza viruses on free-living mallards

Running period: 
2010 to 2014

Avian influenza has become one of the most dangerous infections for animals and humans at present. Around the world, surveillance programs are initiated to detect avian influenza in wild birds, providing an early warning system for the global spread of highly pathogenic avian influenza (HPAI) virus. However, the epidemiology of HPAI and low pathogenic avian influenza (LPAI) virus, including the effects of the pathogen on individuals and host populations, has only received little attention. We particularly investigate the ecological processes underlying the epidemiology of LPAI viruses in wild birds, by studying the interactive ecology of avian hosts with LPAI virus in a natural setting.

We focus on mallards (Anas platyhrynchos), as mallards are believed to be a major reservoir for LPAI viruses contributing importantly to the global spread of LPAI viruses. Many surveillance programs are focused on single seasons, while intensive year-round sampling schemes, measuring both current and past infection, are needed to enhance our knowledge on temporal dynamics of LPAI virus infections. We therefore conduct a year-round surveillance at a duck decoy (“eendenkooi”) in the Netherlands. Besides measuring current (through viral shedding) and past LPAI virus infection (through antibodies presence) we also study host susceptibility, which is a key element when studying the spread and distribution of an infectious disease. With hydrogen-stable isotope analysis on feathers, determining the origin and hence the distinction between resident and migratory individuals, we try to identify whether migrants or residents are predominantly responsible for the spread of LPAI virus, which is a subject of considerable debate. We also study the effect of infection on host fitness by monitoring the effects of LPAI virus infection on reproduction of free-living mallards. The assessment of the effect of a ‘natural’ (ecologically relevant) disease in wild, free-living birds will be a significant addition to our understanding of disease ecology in general, and the effects of a LPAI virus infection in particular.