Statewide surveillance of tick-borne pathogens in ticks collected in Delaware using novel multiplex PCR assays

Tick-borne pathogens are responsible for most vector-borne human diseases in the United States. With the growing recognition of tick-borne diseases and the expanding range of ticks, it is imperative to understand which pathogens, and in what prevalence, are carried by tick species in areas populated by humans. Few studies exist surveying the presence and distribution of tick-borne pathogens in the state of Delaware. The goal of this study was to create multiplex real-time PCR assays to identify Borrelia burgdorferi sensu stricto, Babesia microti, Anaplasma phagocytophilum, Ehrlichia chaffeensis, and Ehrlichia ewingii from their respective tick vectors collected across the state of Delaware.

Two multiplex, real-time PCR assays were developed and tested on 1027 ticks comprising Ixodes scapularis and Amblyomma americanum, two species of ticks commonly encountered in Delaware. The results showed that in a sample of 500 Ixodes scapularis ticks, 30.20 % were positive for Borrelia burgdorferi, 2.60 % were positive for Babesia microti, and 1 % were positive for Anaplasma phagocytophilum. Testing of 527 A. americanum ticks showed that 4.74 % were positive for E. chaffeensis and 1.14 % were positive for E. ewingii. These findings suggest that these five tick-borne pathogens are present across the state of Delaware and therefore pose a risk to the public.