Lyme disease in British Columbia: Are we really missing an epidemic?

224 ABSTRACT: The risk of Lyme disease depends on climate, geography, the abundance of specific insect vectors, and human interaction with these. In BC, Ixodes pacificus, the primary tick vector for the causeative spirochete, Borrelia burgdorferi, has consistently been found in low numbers in populous areas, and rates of infection in this tick remain at less than 1%. Correspondingly, rates of human cases of Lyme disease in BC are less than 0.5 per 100 000 per year; this is similar to rates reported in US states with environmental epidemiology like BC’s and considerably less than in high endemic areas of the eastern United States (29 per 100000). There is no evidence to support an epidemic of Lyme disease in BC. Responses to a recent survey indicate that physicians generally are aware of the low but real risk of Lyme disease, know to treat patients with clinical symptoms, and understand that Lyme disease is preventable and treatable. Public health authorities will continue to remind residents and visitors to BC of the simple measures they can take to prevent tick bites and ex posure, as well as which early signs and symptoms should lead them to seek appropriate medical treatment. L yme disease is a tick-borne zoonosis caused in North America by infection with the spirochete Borrelia burg dorferi. Humans acquire Lyme disease through the bite of an infected tick.1 The principal tick vector in BC is the Pacific black-legged tick, Ixodes pacificus,2 which is found throughout the highly populated areas of southern BC. This situation is in contrast to eastern Canada and the US, where the tick Ixodes scapularis is the most common vector. The low incidence of Lyme disease in BC may be explained by the fact that I. pacificus is a less competent vector than I. scapularis, is less abundant, and is less likely to feed on deer mice.3-5 Studies have shown that infectivity rates are lower in areas where I. pacificus predominates than in areas where I. scapularis predominates. Lyme disease advocacy groups in BC have expressed concern that an Lyme disease in British Columbia: Are we really missing an epidemic?