| Summary: | The ecology and epidemiology of Rocky Mountain Spotted fever and typhus fever pathogens are poorly understood along the United States–Mexico border, especially in the far Southwestern region of Texas. The objective of this dissertation was to understand the prevalence and distribution of Rickettsia rickettsii and Rickettsia typhi and associated tick and flea species and the prevalence of these Rickettsiae in domestic and feral mammals in urban and rural areas of the El Paso community and other areas of Texas. Also, the goal was to determine if humans are being infected by R. rickettsii and R. typhi in the El Paso community. The methods for the collection of ticks included dragging, flagging and direct collection by hand from the animals. Flea trapping consisted of a commercial adhesive trap with an intermittent green light and direct collections by hand from the animals. The collected ticks and fleas were identified morphologically using taxonomic keys. Ticks and fleas were sorted by species, sex and/ or life stage and prepared in pools of 7 specimens. The testing of ticks and fleas for Rickettsiae was performed by first grinding individual pools in phosphate buffered saline (PBS), 200 μl per pool. The nucleic acid was extracted using a Qiagen DNeasy blood and tissue kit and then tested for spotted fever group Rickettsia by a nested polymerase chain reaction (PCR) assay. The genus specific primers use in the PCR included the 17kDa lipoprotein gene which amplified a 434- bp DNA fragment, gltA and ompA genes. If samples were positive for Rickettsia, they were further tested by Sanger dideoxy sequencing to determine the Rickettsial species. A total of 56 pools consisting of 223 fleas were collected in and around the El Paso community, including 40 pools of Pulex irritants, 11 pools of Echidnophaga gallinacea and 5 pools of Ctenocephalides felis. All of these fleas were collected by hand from small mammals including, Canis latrans (coyotes), Procyon lotor (racoons), Urocyon cinereoargenteus(foxes), Canis lupus ...
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