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Minor differences in body condition and immune status between avian influenza virus-infected and noninfected mallards: a sign of coevolution?

van Dijk JG, Fouchier RA, Klaassen M, Matson KD - Ecol Evol (2014)

Bottom Line: The degree of virus shedding from the cloaca and oropharynx was not associated with body mass.Hp concentrations were higher in LPAIV-infected juveniles and females compared to infected adults and males.These results may support the role of mallards as asymptomatic carriers of LPAIV and raise questions about possible coevolution between virus and host.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW) Droevendaalsesteeg 10, 6708 PB, Wageningen, The Netherlands.

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.

No MeSH data available.


Related in: MedlinePlus

Male mallard (Anas platyrhynchos; picture taken by D.J. Brown).
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fig01: Male mallard (Anas platyrhynchos; picture taken by D.J. Brown).

Mentions: The aim of our study was to investigate the extent to which LPAIV infection and shedding were associated with body condition and immune status in free-living mallards (Fig.1). We comprehensively sampled mallards on their wintering grounds during the autumn LPAIV infection peak. Autumn is generally the period that LPAIV infection in mallard populations is the highest in the northern hemisphere (van Dijk et al. 2014a; Latorre-Margalef et al. 2014). In our investigation of the interactions between body condition and immune status, we considered effects of bird age, sex, and migratory strategy. Our study population consists of both migratory and resident birds (throughout Europe mallards are partially migratory; Scott and Rose 1996). Effects of LPAIV infection in juveniles may be more profound than in adults, because juveniles are immunologically naïve and immunity to LPAIV is likely acquired with age (Munster et al. 2007; Latorre-Margalef et al. 2009a). Due to sex differences in body condition, immune status, and physiology in general, effects of LPAIV infection may differ between males and females (Zuk and McKean 1996). Males are less likely to have anti-NP antibodies than females, although LPAIV infection and shedding are similar between the sexes (Munster et al. 2007; van Dijk et al. 2014a). Effects of LPAIV infection may also differ between migratory and resident birds, because energetic demands of migration may compromise immune function and nutritional status in migratory birds (Owen and Moore 2006). Indeed in autumn, migratory mallards were more frequently infected with LPAIV than residents, although virus shedding was similar, and migrants had low anti-NP antibodies (van Dijk et al. 2014a).


Minor differences in body condition and immune status between avian influenza virus-infected and noninfected mallards: a sign of coevolution?

van Dijk JG, Fouchier RA, Klaassen M, Matson KD - Ecol Evol (2014)

Male mallard (Anas platyrhynchos; picture taken by D.J. Brown).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4314274&req=5

fig01: Male mallard (Anas platyrhynchos; picture taken by D.J. Brown).
Mentions: The aim of our study was to investigate the extent to which LPAIV infection and shedding were associated with body condition and immune status in free-living mallards (Fig.1). We comprehensively sampled mallards on their wintering grounds during the autumn LPAIV infection peak. Autumn is generally the period that LPAIV infection in mallard populations is the highest in the northern hemisphere (van Dijk et al. 2014a; Latorre-Margalef et al. 2014). In our investigation of the interactions between body condition and immune status, we considered effects of bird age, sex, and migratory strategy. Our study population consists of both migratory and resident birds (throughout Europe mallards are partially migratory; Scott and Rose 1996). Effects of LPAIV infection in juveniles may be more profound than in adults, because juveniles are immunologically naïve and immunity to LPAIV is likely acquired with age (Munster et al. 2007; Latorre-Margalef et al. 2009a). Due to sex differences in body condition, immune status, and physiology in general, effects of LPAIV infection may differ between males and females (Zuk and McKean 1996). Males are less likely to have anti-NP antibodies than females, although LPAIV infection and shedding are similar between the sexes (Munster et al. 2007; van Dijk et al. 2014a). Effects of LPAIV infection may also differ between migratory and resident birds, because energetic demands of migration may compromise immune function and nutritional status in migratory birds (Owen and Moore 2006). Indeed in autumn, migratory mallards were more frequently infected with LPAIV than residents, although virus shedding was similar, and migrants had low anti-NP antibodies (van Dijk et al. 2014a).

Bottom Line: The degree of virus shedding from the cloaca and oropharynx was not associated with body mass.Hp concentrations were higher in LPAIV-infected juveniles and females compared to infected adults and males.These results may support the role of mallards as asymptomatic carriers of LPAIV and raise questions about possible coevolution between virus and host.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW) Droevendaalsesteeg 10, 6708 PB, Wageningen, The Netherlands.

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.

No MeSH data available.


Related in: MedlinePlus