Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

European Commission's Joint Research Centre, Ispra, Italy.
Emerging infectious diseases (Impact Factor: 6.75). 09/2007; 13(8):1139-43. DOI: 10.3201/eid1308.070319
Source: PubMed


The claim that migratory birds are responsible for the long-distance spread of highly pathogenic avian influenza viruses of subtype H5N1 rests on the assumption that infected wild birds can remain asymptomatic and migrate long distances unhampered. We critically assess this claim from the perspective of ecologic immunology, a research field that analyzes immune function in an ecologic, physiologic, and evolutionary context. Long-distance migration is one of the most demanding activities in the animal world. We show that several studies demonstrate that such prolonged, intense exercise leads to immunosuppression and that migratory performance is negatively affected by infections. These findings make it unlikely that wild birds can spread the virus along established long-distance migration pathways. However, infected, symptomatic wild birds may act as vectors over shorter distances, as appears to have occurred in Europe in early 2006.

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    • "Thus, even a nonlethal parasite or pathogen may still be a useful biocontrol if it decreases the hosts' rate of dispersal. The pathological effects of parasite infection could debilitate or energetically impoverish the host, resulting in reduced dispersal ability (Bradley and Altizer 2005; Fellous et al. 2011; Moretti et al. 2014; Van Gils et al. 2007; Weber and Stilianakis 2007). A large body of literature has investigated the links between parasites and host dispersal/migration, because the interaction has important ecological and evolutionary consequences for both participants (Altizer 2001; Altizer et al. 2011; Avgar et al. 2013; Iritani and Iwasa 2014; Lion et al. 2006; Møller et al. 2004; Pérez-Tris and Bensch 2005; Prugnolle et al. 2005). "
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    ABSTRACT: Translocation of native-range parasites to control invasive species is effective only if the parasite substantially impairs either the viability or dispersal rate of the invasive host. Lungworms (Rhabdias pseudosphaerocephala) of cane toads (Rhinella marina) were introduced to Australia from the toad’s native range, along with the toads, and have been suggested as a potential biocontrol of invasive toads due to various negative impacts on toad viability. We conducted two radio-telemetry studies on a tropical floodplain to specifically assess the parasite’s impact on toad dispersal. First, a retrospective correlative analysis of data from field-collected animals showed that toads infected with lungworms moved farther, not less, than uninfected conspecifics. Second, an experimental study (comparing movements of experimentally infected toads vs. uninfected controls) showed that lungworms did not modify rates of toad dispersal. In addition, experimental infection with lungworms did not elicit an immune response substantial enough to influence dispersal behaviour. Thus, we conclude that increasing lungworm densities at the invasion front as an attempt at biocontrol would not slow down the spread of cane toads.
    Biological Invasions 10/2015; DOI:10.1007/s10530-015-0993-1 · 2.59 Impact Factor
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    • "Novel areas might also contain pathogens with altered virulence (relative to the range core), as an adaptation to altered host density, or from spatial sorting on the pathogens themselves (Phillips & Puschendorf 2013). Fourth, the physical exertion of sustained, rapid movement through unfamiliar habitat is likely to produce tissue damage and elevated stress levels (Segerstrom 2007; Weber & Stilianakis 2007; Buehler et al. 2010). Under these conditions, immune responses may be modified to prevent autoimmune damage (Pedersen & Hoffman-Goetz 2000; Raberg et al. 2002; Brown & Shine 2014). "
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    Ecology Letters 11/2014; 18(1):n/a-n/a. DOI:10.1111/ele.12390 · 10.69 Impact Factor
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    • "In areas commonly affected by HPAI, poultry trade is regarded as the primary cause for the persistence and spread of HPAI (Gauthier-Clerc et al., 2007), and long-distance transportation of poultry products along with unregulated practices at poultry markets have been linked to outbreaks in many parts of Asia (Amonsin et al., 2008; Liu et al., 2003; Shortridge et al., 1998; Wang et al., 2006; Yu et al., 2007). Waterbirds (i.e., Anatidae and Charadriidae) have been identified as primary reservoirs for low pathogenic influenza viruses (Stallknecht and Shane, 1988), but with our limited knowledge about the distances infected birds migrate and connectivity among populations, the importance of HPAI transmission by wild birds remains an open question (Gaidet et al., 2010; Takekawa et al., 2010b; van Gils et al., 2007; Weber and Stilianakis, 2007). The potential of wild birds to spread HPAI is evident in the 2005 outbreak at Qinghai Lake in China that killed more than 6000 wild waterfowl. "
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    Ecological Indicators 10/2014; 45:266–273. DOI:10.1016/j.ecolind.2014.04.027 · 3.44 Impact Factor
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