Influence of Body Condition on Influenza A Virus Infection in Mallard Ducks: Experimental Infection Data

Abstract

Migrating waterfowl are implicated in the global spread of influenza A viruses (IAVs), and mallards (Anas platyrhynchos) are considered a particularly important IAV reservoir. Prevalence of IAV infection in waterfowl peaks during autumn pre-migration staging and then declines as birds reach wintering areas. Migration is energetically costly and birds often experience declines in body condition that may suppress immune function. We assessed how body condition affects susceptibility to infection, viral shedding and antibody production in wild-caught and captive-bred juvenile mallards challenged with low pathogenic avian influenza virus (LPAIV) H5N9. Wild mallards (n = 30) were separated into three experimental groups; each manipulated through food availability to a different condition level (−20%, −10%, and normal ±5% original body condition), and captive-bred mallards (n = 10) were maintained at normal condition. We found that wild mallards in normal condition were more susceptible to LPAIV infection, shed higher peak viral loads and shed viral RNA more frequently compared to birds in poor condition. Antibody production did not differ according to condition. We found that wild mallards did not differ from captive-bred mallards in viral intensity and duration of infection, but they did exhibit lower antibody titers and greater variation in viral load. Our findings suggest that reduced body condition negatively influences waterfowl host competence to LPAIV infection. This observation is contradictory to the recently proposed condition-dependent hypothesis, according to which birds in reduced condition would be more susceptible to IAV infection. The mechanisms responsible for reducing host competency among birds in poor condition remain unknown. Our research indicates body condition may influence the maintenance and spread of LPAIV by migrating waterfowl.

Reassortant influenza A viruses in wild duck populations: effects on viral shedding and persistence in water

“…Such host-related variations may have direct implications in the transmission dynamics of IAV in wild duck populations. In addition, it may also affect long-distance virus dispersal during duck migrations [14,42,45] and be critical for the spread of HP viruses [21,22,24,46]. Compared with CL shedding, genotype-related differences may exist for OP shedding, as one of the five virus genotype we studied exhibited a significantly different pattern.…”

Demographic Parameters of Rural and Urban Adult Resident Canada Geese in Georgia

“…We divided time intervals into 3 periods (i.e. early, mid-, late winter) and calculated a body condition index (BCI) following Arsnoe et al (2011;Devries et al 2008). We conducted an ordinary least-squares regression of adjusted mass and an index of body size (principal component 1 of skull, culmen, and tarsus length) and then divided the residuals from the predicted mass to create a condition score for each bird.…”

Bridge hosts for avian influenza viruses at the wildlife/domestic interface: An eco-epidemiological framework implemented in southern Africa

“…Although the pathogenic effect of AIV infections on migrating bird is still debated (Arsnoe et al, 2011), the study of individual bird movements or waves of migrating populations in relation to the epidemiology of AIV in wild birds indicates that these hosts play a role in medium and large scale spread of LPAI and possibly (highly pathogenic) HPAI (Wang et al, 2008;Reperant et al, 2010). In addition, phylogenetic analyses of LPAI indicated intercontinental movements of strains across waterfowl populations (Koehler et al, 2008).…”