Passive Tick Surveillance and Detection of <i>Borrelia</i> Species in Ticks from British Columbia, Canada: 2002–2018

Abstract

Lyme disease, caused by <i>Borrelia burgdorferi sensu lato</i> (s.l.) complex, is the most common vector-borne disease in North America. This disease has a much lower incidence in western compared with eastern North America. Passive tick surveillance data submitted over 17 years from 2002 to 2018 were analyzed to determine the occurrence of tick species and the prevalence of <i>Borrelia</i> spp. in ticks in British Columbia (BC), Canada. The BC Centre for Disease Control Public Health Laboratory received tick submissions from physicians, veterinarians, and BC residents. Ticks were identified to species, and all ticks, except <i>Dermacentor andersoni</i>, were tested using generic <i>B. burgdorferi</i> s.l. primer sets and species-specific PCR primer sets for <i>B. burgdorferi sensu stricto</i> (s.s.). Tick submission data were analyzed to assess temporal and geographical trends, tick life stages, and tick species. Poisson regression was used to assess temporal trends in annual tick submissions. A total of 15,464 ticks were submitted. Among these, 0.29% (<i>n</i> = 10,235) of <i>Ixodes</i> spp. ticks and 5.3% (<i>n</i> = 434) of <i>Rhipicephalus sanguineus</i> ticks were found carrying <i>B. burgdorferi</i> s.s. <i>B. burgdorferi</i> s.s. was primarily detected in <i>Ixodes pacificus</i> (52%; <i>n</i> = 16) and <i>Ixodes angustus</i> ticks (19%; <i>n</i> = 6) retrieved from humans (<i>n</i> = 5) and animals (<i>n</i> = 26). <i>B. burgdorferi</i> was found in ticks submitted throughout the year. <i>Ixodes</i> spp. ticks were primarily submitted from the coastal regions of southwestern BC, and <i>D. andersoni</i> ticks were primarily submitted from southern interior BC. The number of human tick submissions increased significantly (<i>p</i> < 0.001) between 2013 and 2018. The annual prevalence of <i>B. burgdorferi</i> in ticks remained stable during the study period. These findings correspond to those observed in US Pacific Northwestern states. Passive tick surveillance is an efficient tool to monitor long-term trends in tick distribution and <i>B. burgdorferi</i> prevalence in a low endemicity region.