Flea Abundance, Species Composition, and Prevalence of Rickettsioses from Urban Wildlife in Orange County, California, 2015-2019

Fleas infesting urban wildlife have been epidemiologically linked to the transmission of flea-borne rickettsial pathogens in urban and suburban areas of Orange County, California. To understand the prevalence of flea-borne rickettsioses caused by either Rickettsia felis or R. typhi, a survey of fleas from wildlife was conducted to determine the flea species composition of host animals and prevalence of rickettsial pathogens in fleas on host animals. This study reports flea abundance, species composition, and infestation intensity on unowned domestic cats and wildlife (i.e., coyotes, opossums, rabbits, skunks, squirrels, raccoons, and commensal rodents) collected in urban neighborhoods of Orange County. The survey revealed presence of the northern rat flea on eastern fox squirrels, and widespread distribution of the human flea on skunks and coyotes in Orange County. The flea index and prevalence of flea-bone rickettsioses in fleas has been used by the Orange County Mosquito and Vector Control District to guide decisions regarding risk management and intervention strategies to reduce and prevent the transmission of flea-borne pathogens. The prevalence of R. felis and R. typhi in fleas in Orange County was 8.94% and 0.39%, respectively. Roof rats, eastern fox squirrels, and striped skunks had the highest diversity of flea species, while the Virginia opossum had the lowest, as determined by the Simpson’s Diversity Index. The sticktight flea was found to have the highest diversity of mammal hosts. It is not known how flea species composition on hosts impacts the maintenance and persistence of rickettsial and other pathogens in fleas from urban wildlife in Orange County.