Prevalence of Infection and Co-Infection and Presence of Rickettsial Endosymbionts in Ixodes scapularis (Acari: Ixodidae) in Connecticut, USA

Abstract

<i>Ixodes scapularis</i> is currently known to transmit 7 pathogens responsible for Lyme disease, anaplasmosis, babesiosis, tick-borne relapsing fever, ehrlichiosis, and Powassan encephalitis. <i>Ixodes scapularis</i> can also be colonized by endosymbiotic bacteria including those in the genus of <i>Rickettsia</i>. We screened 459 <i>I. scapularis</i> ticks submitted to the Connecticut Agricultural Experiment Station Tick Testing Laboratory with the objectives to (1) examine differences in infection prevalence of <i>Borrelia burgdorferi</i>, <i>Anaplasma phagocytophilum</i>, <i>Babesia microti</i>, and <i>Borrelia miyamotoi</i>, (2) evaluate whether prevalence of co-infections occur at the same frequency that would be expected based on single infection, and (3) determine the presence of rickettsial endosymbionts in <i>I. scapularis</i>. The prevalence of infection in <i>I. scapularis</i> was highest with <i>Bo. burgdorferi</i> sensu lato (nymph = 45.8%; female = 47.0%), followed by <i>A. phagocytophilum</i> (nymph = 4.0%; female = 6.9%), <i>Ba. microti</i> (nymph = 5.7%; female = 4.7%), and <i>Bo. miyamotoi</i> (nymph = 0%; female = 7.3%). We also identified rickettsial endosymbionts in 93.3% of <i>I. scapularis</i>. Nymphs were significantly more likely to be infected with <i>Bo. burgdorferi</i> if they were infected with <i>Ba. microti</i>, whereas adult females were significantly more likely to be infected with <i>Bo. burgdorferi</i> if they were infected with <i>A. phagocytophilum</i>. Our study suggests that the infection prevalence of <i>Bo. burgdorferi</i> is not independent of other co-circulating pathogens and that there is a substantially higher infection of <i>Bo. miyamotoi</i> in <i>I. scapularis</i> females compared with nymphs in this study. High prevalence of infection and co-infection with multiple pathogens in <i>I. scapularis</i> highlights the public health consequences in Connecticut, a state endemic for Lyme and other tick-borne diseases.