Poster Presentation 64th International Conference of the Wildlife Disease Association 2015

Discoveries and Lessons Learned from Twenty Years of Sampling Wild Birds for Mycoplasma gallisepticum (#168)

David H Ley , Wesley M Hochachka , Andy P Dobson , Steven J Geary , Meghan May , Dana M Hawley , André A Dhondt

Mycoplasma gallisepticum was a well characterized bacterial pathogen of chickens and turkeys worldwide and apparently relatively host-specific, until 1994 when an outbreak was identified in Eastern USA house finches. The opportunity to collect samples and study this emergent disease with a multi-institutional, multi-disciplinary team has yielded a wealth of knowledge and been a model of collaborative research. Key to the success and productivity of this effort has been isolation of M. gallisepticum spanning the wild bird host, temporal, and geographic ranges of the disease from emergence to endemicity. Faced with the challenges and costs of sample collection for mycoplasma culture from remote locations over time, we tried various protocols to arrive at a practical optimum. Wild bird sampling for mycoplasma culture allowed us to identify M. sturni associated with conjunctivitis in cliff and barn swallows, and M. corogypsi associated with polyarthritis and tenosynovitis in black vultures. M. gallisepticum isolates in experimental infections of house finches showed evolution of virulence with parallel patterns of increased virulence in both western and eastern isolates. Phylogenetic studies using isolates from wild birds and poultry suggested multiple host transfers from poultry to house finches, but only one successful lineage accounting for the continent-spanning epidemic. Genomics showed extensive variation in surface lipoprotein gene content, phenotypic plasticity, and genomic changes associated with virulence evolution. Using serology and PCR, we recently found that a diverse range of wild bird species may carry or have been exposed to M. gallisepticum in the USA, as in Europe and Asia. This evidence for a diverse wild bird host range exposed to M. gallisepticum exemplifies a transmissible subclinical mycoplasmosis: achievement of an ideal host/parasite relationship. Emergence of a pathogenic M. gallisepticum strain in house finches may actually be the exception that has allowed us to identify the broader epidemiologic picture.