Rhipicephalus sanguineus sensu lato infestation in an urban area in South Sacramento, California, USA.

backgroundThe brown dog tick, Rhipicephalus sanguineus sensu lato (Rh. sanguineus s.l.), is an important vector of Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever (RMSF), in western North America, with the most prominent tick infestations occurring in the Southwestern USA and Northern Mexico. RMSF is a significant public health threat in these regions, including in the state of California.

methodsIn 2024, the Sacramento-Yolo Mosquito and Vector Control District detected a brown dog tick infestation in a neighborhood in South Sacramento (CA, USA) that encompassed three adjoining properties. This infestation was unusual due to its location farther north than those in most recent reports. In partnership with the Laboratory of Infectious Disease Ecology at the University of California, Davis, a surveillance and abatement program was implemented. This included tick monitoring, residual spraying of acaricide, deployment of tick collars on dogs and bilingual public outreach.

resultsThe integrated intervention substantially reduced tick populations at the affected site. Both adult and immature stages of Rh. sanguineus s.l. declined following sequential treatments. Sustained suppression and elimination were achieved through continued control and outreach efforts.

conclusionsThis localized infestation of Rh. sanguineus s.l. in northern California highlights the potential for range expansion of RMSF vectors and underscores the need for continued surveillance, rapid response and community engagement to mitigate vector-borne disease risks.