We document the presence of blacklegged ticks, Ixodes scapularis, in the Grand River valley, Centre Wellington, Ontario. Overall, 15 (36%) of 42 I. scapularis adults collected from 41 mammalian hosts (dogs, cats, humans) were positive for the Lyme disease bacterium, Borrelia burgdorferi sensu lato (.). | Detection of lyme disease bacterium, Borrelia burgdorferi sensu lato, in blacklegged ticks collected in the Grand River valley, Ontario, Canada