Lyme Disease and the Black-Tailed Deer on southern Vancouver Island
By Lynette Browne, DVM
Do you want to know about Lyme disease and the risk of getting this disease from ticks? For many of us that migrate here from Eastern Canada, we hear a lot more about Lyme disease as it is much more prevalent there, and actually on the increase. However, here in B.C., the rate of Lyme disease in humans remains consistently very low at less than 1% in adults (<0.5/100,000 population).
The ticks that transmit Borrelia burgdorferi, the bacterium that causes Lyme disease, fall into two main categories, Ixodes pacificus (Western Black-Legged Tick) on the West Coast of North America, and Ixodes scapularis (Black-Legged Tick) in the Northeastern U.S.A. and Canada. Unlike in Eastern Canada, the rate of Lyme disease remains low in B.C. for several main reasons:
- The prevalence of B. burgdorferi in ticks in B.C. has remained consistently low over time, with less than 1% of ticks tested carrying the bacteria. This is different than the Eastern portion of N. America where Lyme disease rates in both ticks and humans have increased over time along with climate change.
- The Western Black-Legged Tick are less capable of carrying B. burdorferi than the Black-Legged Tick in Eastern Canada and the U.S.A.
- The animals on which Ixodes ticks feed are different. In B.C., the ticks primarily feed on small rodents such as deer mice and dusky-footed woodrat. In Eastern Canada and the U.S.A., the ticks feed on white-footed mice and white-tailed deer.
- The vegetation and climate are different between B.C. and Eastern Canada (e.g. B.C. has mostly coniferous forests, whereas Eastern North Amercia has mostly leafy forests).
- Despite Ixodes ticks being present throughout southern and central B.C., including in most of the highly-populated areas, an expansion of the range of these ticks, which could occur with climate change, would not greatly increase the number of people exposed in B.C. since the expansion of the range would be to less-populated areas.
To sum it up, the risk of Lyme disease in B.C. is lower and more stable than it is in Eastern Canada and in the Northeastern U.S.A.
That said, it is always important to protect yourself from being bitten by ticks, especially while out hiking. Check out the BCCDC website for more information.
Out of concern for Lyme disease, some people have asked about the number of ticks seen on deer through the course of our research project. During the UWSS’s deer contraception project, there were very rare instances of ticks seen on the deer that were handled. In fact, none were seen during the latest Fall of 2020 portion of the project. So, though deer management is on the mind of many people in Greater Victoria, at least the risk of Lyme disease does not need to be part of the concern.