Rocky Mountain spotted fever in Arizona: documentation of heavy environmental infestations of Rhipicephalus sanguineus at an endemic site.

A recent epidemiologic investigation identified 16 cases and 2 deaths from Rocky Mountain spotted fever (RMSF) in two eastern Arizona communities. Prevalence studies were conducted by collecting free-living ticks (Acari: Ixodidae) from the home sites of RMSF patients and from other home sites within the community. Dry ice traps and flagging confirmed heavy infestations at many of the home sites. Only Rhipicephalus sanguineus ticks were identified and all developmental stages were detected. It is evident that under certain circumstances, this species does transmit Rickettsia rickettsii to humans and deserves reconsideration as a vector in other geographic areas.