Theses and Dissertations

Date of Award


Document Type


Degree Name

Master of Science (MS)



First Advisor

Dr. Christopher Vitek

Second Advisor

Dr. Erin Schuenzel

Third Advisor

Dr. Rupesh Kariyat


Rhipicephalus sanguineus is a common tick species in the lower Rio Grande Valley of both human and veterinary concern. Two lineages of R. sanguineus have been described across the United States known as the tropical and temperate lineage. Both lineages can be differentiated morphologically, genetically, biologically, and by vector competence. The species name for both lineages has not been well established therefore this thesis will utilize their widely used identification. Both lineages have been identified in Texas. While the distribution of these lineages has been well-defined in some regions across the world, recent studies have observed sympatric populations in certain areas, suggesting a need for further investigation into their distribution and potential overlap. The aim of this study is to explore the genetic variation among different populations in the lower Rio Grande Valley by conducting a sequence analysis of the 12S rRNA mitochondrial gene. The presence of one or both lineages in the Rio Grande Valley may help predict the relative risk of some tick-borne diseases. Collections were conducted weekly for five months. A sample size of 250 R. sanguineus ticks were utilized in this study. The sequence analysis of 12S rRNA indicated only the presence of the tropical lineage, confirming previous studies that only found that lineage in this region.


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