In Indiana, Ixodes scapularis is an important tick in public health because it feeds on a variety of hosts including humans, and transmits Borrelia burgdorferi (Lyme disease), Anaplasma phagocytophilum (human granulocytic ehrlichiosis), and Babesia microti (babesiosis). Symbiotic, non-pathogenic Rickettsia found in Ixodes scapularis may play a role in excluding pathogenic species of Rickettsia from being transovarially transmitted. In order to investigate this idea further in Indiana, a total of 378 adult I. scapularis from 4 different counties (Jasper, Pulaski, Newton and Starke) were tested by polymerase chain reaction analysis (PCR) for the presence of Rickettsia sp. Four positive samples from the PCR (using Rocky Mountain spotted fever group specific primers to target the rOmpA gene; Rr190.70p and RH 90.602n) reactions were sequenced to verify identity. These four samples matched closest to the reference number AB002268 from GenBank which describes, I. scapularis endosymbiont DNA for rOmpA. A total of 62 engorged females were tested; 53 (85.5%) harbored the rickettsial symbiont. A total of 41 questing females were tested; 33 (80.5%) were positive. Of the 249 males tested, 14 (5.6%) were positive. A restriction digestion on some of the positive samples revealed that the 1 scapularis symbiont was different from R. montana and R. rickettsii. The second goal of this study was to identify the presence of B. microti. In I. scapularis ticks, this would be the first time this pathogen was identified in Indiana. To accomplish this goal 106, ticks were tested using the primers Babl and Bab4, which target the 18S rRNA gene specific for B. microti. Three tick samples were found to harbor B. microti as determined by sequencing. However, sequencing of amplification band in the negative control also yielded B. microti. Thus, the presence of B. microti in Indiana ticks could not be confirmed. A negative control was also sequenced and was identified as Babesia microti indicating that there was a contamination so it is not possible to conclude that B. microti was found in Indiana ticks. / Department of Physiology and Health Science