The extensive variation in the amount of harm that pathogens cause their hosts has intrigued biologists for centuries, but there have been surprisingly few opportunities to test theoretical predictions in non-laboratory systems. We propose work on a tractable and well-studied wildlife-pathogen system, the house finch and its bacterial pathogen, Mycoplasma gallisepticum, in which we have already documented the independent evolution of increasing virulence since the emergence of the pathogen in two distinct parts of the host's range. We hypothesize two ecological conditions that underlie the observed patterns of increasing virulence evolution detected to date: 1) imperfect acquired host immunity, akin to vaccination, has selected for higher rates of within-host pathogen replication and associated higher virulence;and 2) higher contact rates, such as caused by anthropogenic feeding of birds, have resulted in increased virulence by minimizing the pathogen's risk of killing its host before it successfully transmits. The proposed work involves integration of theoretical virulence models with proposed experiments. First, formal within- and between-host models describing the two hypotheses will identify information needed for model refinement and validation;second, targeted experiments will quantify key parameters;and, third, these data will feed back to evaluate whether the models'assumed conditions explain observed field patterns. The empirical data will come from controlled infection and transmission experiments, which are unusually tractable in our study system, in order to characterize within- and between-host dynamics for partially immune versus immunologically naive hosts and at high and low between-host contact rates. Supplementing these model-focused experiments will be DNA.sequence and expression data from multiple field and experimental isolates of the bacteria, where our knowledge of gene function in M. gallisepticum will allow us to identify which genes may underiie the detected virulence changes. These data will serve as an independent test of the partial immunity hypothesis by addressing whether bacterial genes responsible for evading host immune systems are systematically changing in vivo and in vitro under selection due to acquired immunity, consistent with our hypothesis.

Public Health Relevance

'ons): Understanding the mechanisms that drive virulence evolution has far-reaching implications for public health measures such as imperfect vaccination that may inadvertently drive increases iri virulence for human pathogens. Our work will also shed light on the role of anthropogenic feeding and alterations of host contact rates via urbanization on the evolution of virulence in zoonotic pathogens.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM105245-02
Application #
8545883
Study Section
Special Emphasis Panel (ZRG1-IDM-U (55))
Program Officer
Eckstrand, Irene A
Project Start
2012-09-15
Project End
2016-08-31
Budget Start
2013-09-01
Budget End
2014-08-31
Support Year
2
Fiscal Year
2013
Total Cost
$530,189
Indirect Cost
$54,668
Name
Virginia Polytechnic Institute and State University
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
003137015
City
Blacksburg
State
VA
Country
United States
Zip Code
24061
Rogers, Krysta H; Ley, David H; Woods, Leslie W (2018) Mycoplasmosis of House Finches ( Haemorhous mexicanus) and California Scrub-Jays ( Aphelocoma californica) in a Wildlife Rehabilitation Facility with Probable Nosocomial Transmission. J Wildl Dis :
Hawley, Dana M; Moyers, Sahnzi C; Caceres, Johanel et al. (2018) Characterization of unilateral conjunctival inoculation with Mycoplasma gallisepticum in house finches. Avian Pathol 47:526-530
Fleming-Davies, Arietta E; Williams, Paul D; Dhondt, André A et al. (2018) Incomplete host immunity favors the evolution of virulence in an emergent pathogen. Science 359:1030-1033
Vinkler, Michal; Leon, Ariel E; Kirkpatrick, Laila et al. (2018) Differing House Finch Cytokine Expression Responses to Original and Evolved Isolates of Mycoplasma gallisepticum. Front Immunol 9:13
Dhondt, André A; Dhondt, Keila V; Hochachka, Wesley M et al. (2017) Response of House Finches Recovered from Mycoplasma gallisepticum to Reinfection with a Heterologous Strain. Avian Dis 61:437-441
Pflaum, K; Tulman, E R; Beaudet, J et al. (2017) Attenuated Phenotype of a Recent House Finch-Associated Mycoplasma gallisepticum Isolate in Domestic Poultry. Infect Immun 85:
Adelman, James S; Mayer, Corinne; Hawley, Dana M (2017) Infection reduces anti-predator behaviors in house finches. J Avian Biol 48:519-528
Thomason, Courtney A; Mullen, Nathan; Belden, Lisa K et al. (2017) Resident Microbiome Disruption with Antibiotics Enhances Virulence of a Colonizing Pathogen. Sci Rep 7:16177
Dhondt, André A; Dobson, Andrew P (2017) Stress Hormones Bring Birds, Pathogens and Mosquitoes Together. Trends Parasitol 33:339-341
Leon, Ariel E; Hawley, Dana M (2017) Host Responses to Pathogen Priming in a Natural Songbird Host. Ecohealth 14:793-804

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