Emerging Tick-Borne Pathogens in Central Canada: Recent Detections of <i>Babesia odocoilei</i> and <i>Rickettsia rickettsii</i>.

<b><i>Background:</i></b> The spread of emerging tick-borne pathogens has steadily increased in Canada with the widespread establishment of tick vectors and vertebrate hosts. At present, <i>Borrelia burgdorferi</i>, the bacterium causing Lyme disease, is the most common tick-borne pathogen in Canada and primarily transmitted by <i>Ixodes scapularis</i>. A low prevalence of other emerging tick-borne pathogens, such as <i>Anaplasma phagocytophilum</i>, <i>Babesia</i> species, <i>Borrelia miyamotoi</i>, and <i>Francisella tularensis</i> have also been detected through surveillance efforts in Canada. Although <i>Rickettsia rickettsii</i> has been historically detected in <i>Haemaphysalis leporispalustris</i> in Canada, the current prevalence and geographic extent of this pathogen is unknown. <b><i>Material and Methods:</i></b> In this study, we assessed the presence and prevalence of several emerging tick-borne pathogens in ticks and hosts collected through tick dragging and small mammal trapping in Central Canada. <b><i>Results:</i></b> Nested PCR testing detected three pathogen species in ticks, with <i>Babesia odocoilei</i> and <i>B. burgdorferi</i> in <i>I. scapularis</i> in addition to <i>R. rickettsii</i> in <i>H. leporispalustris</i>. Three pathogen species were detected in small mammals by nested PCR including <i>B. odocoilei</i> in <i>Blarina brevicauda</i>, <i>Babesia microti</i> in <i>Peromyscus leucopus</i>, and a <i>Hepatozoon</i> species in <i>P. leucopus</i> and <i>Peromyscus maniculatus</i>. <i>B. burgdorferi</i> and <i>Babesia</i> species were the pathogens most often detected in our samples, suggesting they are widely distributed across Central Canada. We also detected <i>B. odocoilei</i> and <i>R. rickettsii</i> beyond their known geographic distribution. <b><i>Conclusions:</i></b> Our results provide evidence that emerging tick-borne pathogens may be present outside defined risk areas identified by current surveillance efforts in Canada. As a result, emerging tick-borne pathogens introduced by the dispersal of infected ticks by migratory birds or maintained by hosts and vectors through cryptic transmission cycles may go undetected. More comprehensive testing including all tick life stages and additional tick-borne pathogens will help detect the spread and potential risk of emerging or re-emerging tick-borne pathogens for human and wildlife populations throughout Canada.