Event Date
MIC (Microbiology Course) 291: Selected Topics in Microbiology
Work-in-Progress Seminars
Speaker: Lark L. Coffey, Ph.D., Professor of Pathology, Microbiology & Immunology, UC Davis Weill School of Veterinary Medicine
Dr. Coffey presents: “A Comeback in the Wild West: Re-emergence of Human-Pathogenic St. Louis Encephalitis Virus”
Abstract: The mosquito-borne human pathogen St. Louis encephalitis virus (SLEV) reemerged in the western United States in 2015 after more than a decade of apparent absence and has since spread throughout California, maintaining sustained transmission each year. This shift from sporadic SLEV activity observed prior to 2003 raises questions about whether contemporary genotype III SLEV strains differ in fitness in mosquito vectors or vertebrate hosts compared to historic strains. To test whether enhanced mosquito fitness contributed to reestablishment, we compared vector competence of five genotype III SLEV strains detected in California between 2016 and 2023 with a genotype V strain isolated in 2003. Infection, dissemination, and transmission were evaluated in Culex quinquefasciatus and Culex tarsalis, the two primary SLEV vectors in California. Multiple genotype III strains exhibited equal or greater infectivity in Cx. quinquefasciatus, whereas fitness differences in Cx. tarsalis were less consistent. Substantial inter-strain variability together with SLEV genome comparisons suggests phenotypic differences are not explained by shared amino acid substitutions alone. We also tested whether vertebrate competence of reemerging SLEV has increased. In collaborative cross outbred mice, SLEV strains produced similar viremia magnitude and kinetics; however, some contemporary strains disseminated more efficiently to peripheral tissues and exhibited greater neuroinvasion. These findings suggest that stable or enhanced fitness in vector mosquitoes and vertebrates support SLEV persistence and spread in California.. Ongoing work is evaluating whether avian reservoir dynamics and reduced cross-protection by related West Nile virus contribute to sustained SLEV transmission since 2015.
For more information about Dr. Coffey's research.
Host: Scott Dawson