Surveilling hard tick diversity and Spotted Fever Rickettsia Group prevalence in North-Central WV throughout 2023

Abstract

The Spotted Fever Rickettsia Group (SFRG) causes dangerous, albeit rare, infections in West Virginia, with an untreated mortality rate of approximately 25% in the United States. The bacterial causes of SFRG are gram-negative, obligate intracellular Rickettsia species that infect human vascular endothelial cells. They are transmitted primarily during the blood meal of a colonized American Dog tick (Dermacentor variabilis) but can also be transmitted by Asian Longhorn (Haemaphysalis longicornis), Lone Star (Amblyomma americanum), and other less frequently detected ticks. The aim of this project is to survey hard tick (Ixodidae) diversity and SFRG incidence rates in collected D. variabilis samples. Tick samples were collected year-round from veterinarian clinic donations and throughout May, June, and July by tick drags conducted across Upshur and Lincoln Counties, WV. Of 563 ticks collected in 2023, Ixodes species were most prevalent (48.8%), followed by Dermacentor (25.6%) and Haemaphysalis (24.9%), and only 0.5% of the collection consisted of Amblyomma specimen. Following identification and photography, ticks were cut in half for cryopreservation at -80^oC and DNA extraction. 145 D. variabilis total-DNA samples were analyzed via quantitative real-time Polymerase Chain Reaction (qPCR) for a conserved Rickettsia genus gene (17kDa Outer Membrane Antigen). Preliminary results suggest an infection rate of 5.52%. Ongoing investigation includes confirming positive samples through gel electrophoresis and species-specific sequencing. Overall, these data underscore the importance of understanding the diversity and pathogen colonization rate of West Virginia hard ticks to predict and map vector-borne disease trends.