Impact of body condition on influenza A virus infection dynamics in mallards following a secondary exposure

Authors

Nicholas G. Dannemiller, Colorado State University
Colleen T. Webb, Colorado State UniversityFollow
Kenneth R. Wilson, Colorado State UniversityFollow
Kevin T. Bentler, USDA, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research CenterFollow
Nicole L. Mooers, USDA, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research Center
Jeremy W. Ellis, USDA, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research CenterFollow
J. Jeffrey Root, USDA/APHIS/WS National Wildlife Research CenterFollow
Alan B. Franklin, USDA, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research CenterFollow
Susan A. Shriner, USDA/APHIS/WS National Wildlife Research CenterFollow

Date of this Version

2017

Citation

Dannemiller NG, Webb CT, Wilson KR, Bentler KT, Mooers NL, Ellis JW, et al. (2017) Impact of body condition on influenza A virus infection dynamics in mallards following a secondary exposure. PLoS ONE 12(4): e0175757.

Comments

This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

Abstract

Migratory waterfowl are often viewed as vehicles for the global spread of influenza A viruses (IAVs), with mallards (Anas platyrhynchos) implicated as particularly important reservoir hosts. The physical demands and energetic costs of migration have been shown to influence birds' body condition; poorer body condition may suppress immune function and affect the course of IAV infection. Our study evaluated the impact of body condition on immune function and viral shedding dynamics in mallards naturally exposed to an H9 IAV, and then secondarily exposed to an H4N6 IAV. Mallards were divided into three treatment groups of 10 birds per group, with each bird's body condition manipulated as a function of body weight by restricting food availability to achieve either a -10%, -20%, or control body weight class. We found that mallards exhibit moderate heterosubtypic immunity against an H4N6 IAV infection after an infection from an H9 IAV, and that body condition did not have an impact on shedding dynamics in response to a secondary exposure. Furthermore, body condition did not affect aspects of the innate and adaptive immune system, including the acute phase protein haptoglobin, heterophil/lymphocyte ratios, and antibody production. Contrary to recently proposed hypotheses and some experimental evidence, our data do not support relationships between body condition, infection and immunocompetence following a second exposure to IAV in mallards. Consequently, while annual migration may be a driver in the maintenance and spread of IAVs, the energetic demands of migration may not affect susceptibility in mallards.