Survey of Fleas and Ticks for Rickettsia rickettsii and Rickettsia typhi in the El Paso Community and Other Areas in Texas, New Mexico, and Ciudad Juarez, Mexico

This survey was conducted with the aim of determining the public health risk of Rocky Mountain spotted fever and murine typhus in the urban and peri-urban areas of El Paso, as well as other areas in Texas, southern New Mexico, and Ciudad Juarez, Mexico. The approach was to assess the diversity of tick and flea species, determine if the ticks and fleas were infected with Rickettsia rickettsii and Rickettsia typhi (R. typhi), respectively, and assess previous human infection with Rickettsia species. Ticks and fleas were collected from domestic and wild animals and tested using a nested polymerase chain reaction assay. Human plasma samples were also tested for antibodies using an indirect fluorescence assay. Among 203 fleas, including Pulex irritans, Echidnophaga gallinacea, and Ctenocephalides felis (C. felis), collected from wild and domestic small mammals, only one pool of four C. felis collected from a dog in the El Paso community was positive for Rickettsia felis. All 194 Rhipicephalus sanguineus ticks collected from stray and domestic dogs in the El Paso community, southern Doña Ana County, and Ciudad Juarez were negative for Rickettsia spp. In Travis County, Texas, a total of 207 ticks collected from white-tailed deer, including 196 Ixodes scapularis and 11 Dermacentor albipictus, were negative for Rickettsia spp. pathogens. Among 375 archived human plasma samples collected in the El Paso community, only two were positive for R. typhi antibodies. These preliminary findings suggested that tick- and flea-borne diseases were not a major health risk in the El Paso community or the other areas included in this survey.