Within-host dynamics of mycoplasma infections: Conjunctivitis in wild passerine birds

The host–pathogen interaction drives infectious disease dynamics at the individual, population and community levels. Here I present and analyze a model of the vertebrate immune response to mycoplasma infections, and use it to identify which pathogen and host immune characteristics drive patterns of Mycoplasma gallisepticum (MG) infections in the house finch (Carpodacus mexicanus) and other passerine birds. I also address which host and pathogen characteristics most affect host infectiousness and survival. These results imply that much of the observed variation in the house finch likely arises from variation among birds in the effectiveness of their non-specific immune response to MG, and that the host and pathogen characteristics most likely to influence host infectiousness and survival are the intrinsic pathogen growth rate, the strength and efficiency of the non-specific immune response and characteristics affecting the effectiveness of the specific response. These findings suggest that molecular-level study of how MG and other mycoplasmas interact with a host's non-specific and inflammatory responses should reveal much about the relationships between host infectiousness, pathogen load, and disease symptoms in these systems.

► I model a naive host's immune response to bacterial infection and compare with data.
► I extend a previously published model to include the specific immune response.
► Model and analytical results likely apply to other parasites in vertebrate hosts.
► Results suggest observed dynamics arises from non-specific immune variation.
► Characteristics most likely to affect host and parasite fitness are identified.