Ticks on migrating birds also may carry the bacteria and some common bird species are potential hosts for Lyme bacteria. All aspects of Lyme disease, including methods of transmission, are being intensively investigated. In Alberta, Lyme disease is most likely to occur in the foothills, mountains, and aspen parkland areas where arthropods are most common. The tick found on moose in the winter is not likely to carry the bacteria but ticks on rabbits, hares, ground squirrels, white-footed mice, deer, elk, bighorn sheep, and mountain goats could be involved in the cycle. Small rodents, usually white-footed mice or deer mice, are the best hosts for Lyme bacteria.
Larval ticks pick up the bacteria when they take blood from infected mice.
These animals could be ground squirrels, rabbits, hares or people. After feeding, the nymphs drop off, moult to adults, and then attach to bigger animals, such as deer. Thus the greatest chance of people being infected occurs when they walk bare-legged through brush and tall grass in spring and summer when tick nymphs are most active. Remember, the number of ticks, if any, carrying Lyme disease in Alberta probably is very small. In a survey of ticks collected in southern Alberta in 1991, no infected ticks were found nor was there any evidence of infection in dogs, deer, or mice that had been exposed to ticks.