Lyme disease has been found in ticks and in some humans much farther north than it was found a decade ago. Climate warming is suspected as a facilitator but how did it get there?
The cause of Lyme disease is the bacterium Borrelia burgdorferi but it depends for transmission on the black-legged tick Ixodes scapularis. Often called the deer tick, this tick uses many other wildlife hosts.
A team from the Redpath Museum of McGill University measured the occurrence of Lyme disease in southern Quebec. It was widespread in white-footed mice (very similar to deer mice). They used those records to construct a model that allowed prediction of the rate of spread of Lyme disease toward the north. That prediction was for northward advance of the disease by from 3.5 to 11 Kilometres per year under present conditions.
Other research has found ticks infected with Lyme disease attached to birds, which may indicate a way for the disease to jump longer distances and possibly establish colonies which could then spread and coalesce using mice as a vector.