Black-legged ticks

I. pacificus

Black-legged ticks, I. pacificus (shown) and I. scapularis are known vectors for the zoonotic spirochetal bacteria Borrelia burgdorferi, which is the pathogen responsible for causing Lyme disease. The ticks, inoculated with the bacterium when they bite infected mice, squirrels, and other small animals, subsequently pass the pathogens to their human victims when they obtain a blood meal. B. burgdorferi bacteria infect several body parts, producing different symptoms at different times.