Bacterial pathogen emergence required more than direct contact with a novel passerine host
Infection and Immunity
American Society for Microbiology
© 2018 Staley et al. This is an openaccess article distributed under the terms of the Creative Commons Attribution 4.0 International license: https://creativecommons.org/licenses/by/4.0/
While direct contact may sometimes be sufficient to allow a pathogen to jump into a new host species, in other cases fortuitously adaptive mutations that arise in the original donor host are also necessary. Viruses have been the focus of most host shift studies, so less is known about the importance of ecological versus evolutionary processes to successful bacterial host shifts. Here we tested whether direct contact with the novel host was sufficient to enable the mid-1990s jump of the bacteriumMycoplasma gallisepticumfrom domestic poultry into house finches (Haemorhous mexicanus). We experimentally inoculated house finches with two genetically distinctM. gallisepticumstrains obtained either from poultry (Rlow) or from house finches at epizootic outbreak (HF1995). All 15 house finches inoculated with HF1995 became infected, whereas Rlow successfully infected 12 of 15 (80%) inoculated house finches. Comparisons among infected birds showed that, relative to HF1995, Rlow achieved substantially lower bacterial loads in the host respiratory mucosa and was cleared faster. Furthermore, Rlow-infected finches were less likely to develop clinical symptoms than HF1995-infected birds and, when they did, displayed milder conjunctivitis. The lower infection success of Rlow relative to HF1995 was not, however, due to a heightened host antibody response to Rlow. Taken together, our results indicate that contact between infected poultry and house finches was not, by itself, sufficient to explain the jump ofM. gallisepticuminto house finches. Instead, mutations arising in the original poultry host would have been necessary for successful pathogen emergence in the novel finch host.
This study was funded by a Natural Environment Research Council (NERC) grant to C.B. (NE/M00256X/1) and small research grants to M.S. from the Alabama Ornithological Society, American Ornithologists' Union, Birmingham Audubon Society, Society for Integrative and Comparative Biology, and Wilson Ornithological Society. Additionally, an Auburn University Cellular and Molecular Biosciences Peaks of Excellence Research Fellowship provided support for M.S. during this study.
This is the author accepted manuscript. The final version is available from American Society for Microbiology via the DOI in this record
Vol. 86 (3), article e00863-17
Place of publication