Abstract
Wildlife pathogens can alter host fitness. Low pathogenic avian influenza virus (LPAIV) infection is thought to have negligible impacts on wild birds; however, effects of infection in free-living birds are largely unstudied. We investigated the extent to which LPAIV infection and shedding were associated with body condition and immune status in free-living mallards (Anas platyrhynchos), a partially migratory key LPAIV host species. We sampled mallards throughout the species' annual autumn LPAIV infection peak, and we classified individuals according to age, sex, and migratory strategy (based on stable hydrogen isotope analysis) when analyzing data on body mass and five indices of immune status. Body mass was similar for LPAIV-infected and noninfected birds. The degree of virus shedding from the cloaca and oropharynx was not associated with body mass. LPAIV infection and shedding were not associated with natural antibody (NAbs) and complement titers (first lines of defense against infections), concentrations of the acute phase protein haptoglobin (Hp), ratios of heterophils to lymphocytes (H:L ratio), and avian influenza virus (AIV)-specific antibody concentrations. NAbs titers were higher in LPAIV-infected males and local (i.e., short distance) migrants than in infected females and distant (i.e., long distance) migrants. Hp concentrations were higher in LPAIV-infected juveniles and females compared to infected adults and males. NAbs, complement, and Hp levels were lower in LPAIV-infected mallards in early autumn. Our study demonstrates weak associations between infection with and shedding of LPAIV and the body condition and immune status of free-living mallards. These results may support the role of mallards as asymptomatic carriers of LPAIV and raise questions about possible coevolution between virus and host.
Highlights
Wildlife pathogens can alter host fitness, for instance, by affecting an animal’s ability to grow (Burthe et al 2008), reproduce, or survive (Burthe et al 2008; Mayack and Naug 2009)
Viral prevalence differed between months (GLM: v2 = 38.92, P < 0.001; Fig. 3A), with no monthly difference in the degree of virus shedding from the cloaca and oropharynx
Studying the physiological effects of Low pathogenic avian influenza virus (LPAIV) infection in waterfowl is important for generating better perspectives on their potential role as asymptomatic carriers of this virus
Summary
Wildlife pathogens can alter host fitness, for instance, by affecting an animal’s ability to grow (Burthe et al 2008), reproduce (de Crespigny and Wedell 2006), or survive (Burthe et al 2008; Mayack and Naug 2009). Disease outbreaks can have detrimental effects on population numbers, as exemplified by the historic outbreaks of rinderpest in African ungulates at the end of the 20th century (Plowright 1982), and canine distemper in lions and seals in the late 1990s and early 2000 (Roelke-Parker et al 1996; Kuiken et al 2006). Pathogens can have more subtle effects which may impair host fitness, such as reduced foraging or decreased activity (Bradley and Altizer 2005; Venesky et al 2009). Susceptibility to pathogen infection may differ between hosts.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
