Detection of Rickettsiae, Borreliae, and Ehrlichiae in Ticks Collected from Walker County, Texas, 2017–2018

Abstract

Cases of tick-borne diseases, including spotted fever rickettsioses, borreliosis, babesiosis, anaplasmosis and ehrlichiosis, in the United States and territories have more than doubled from 2004 to 2016 and account for 77% of all vector-borne disease reports. In an effort to inform control efforts, the presence of tick-borne pathogens and their vectors was assessed in a recreational park in Walker County, Texas. Here we report data from questing ticks collected on three dates from June 2017 to June 2018. The majority of ticks collected were Amblyomma americanum (96.69%) followed by three additional tick species: Dermacentor variabilis (2.59%), Ixodes scapularis (0.52%), and A. maculatum (0.21%). Ticks were pooled and tested for molecular evidence of bacterial and viral pathogens, respectively. All of the 68 pools of A. americanum had molecular evidence of the spotted fever group rickettsia, Rickettsia amblyommatis. Additionally, six (8.82%) of the A. americanum pools contained sequences matching Ehrlichia chaffeensis, the pathogen responsible for human monocytotropic ehrlichiosis, and 11 (16.18%) for E. ewingii. Three of the A. americanum pools demonstrated evidence of Borrelia lonestari. The presence of etiologic agents of known human disease in this study merits the continued surveillance efforts of ticks and their pathogens in areas where they could pose risks to public health.