These black-legged ticks, Ixodes scapularis, are found on a wide range of hosts including mammals, birds and reptiles. Black-legged ticks, I. scapularis are known to transmit Lyme disease, Borrelia burgdorferi, to humans and animals during feeding, when they insert their mouth parts into the skin of a host, and slowly take in the nutrient-rich host blood. (Photo credit: Wikipedia)
Lyme disease is becoming a problem in Canada, most likely due to climate change. Borrelia burgdorferi (B. burgdorferi) bacteria are the causative agents of the disease. Most commonly in Canada, the black-legged tick (Ixodes scapularis) and the white-footed field mouse (Peromyscus leucopus) spread the bacteria to humans. The white-footed mouse and the black-legged tick are expanding their ranges northward. Ticks hatch from eggs as larvae, then become nymphs, and at last become adults in a 2½ to 3-year cycle. Each life stage transition requires blood from a host.
The authors studied climate and landscape factors to estimate the northern limits of Lyme disease by the year 2050. The spread of disease occurs faster in disturbed and fragmented landscapes. As temperatures increase, disease-spreading bacteria (and the hosts which spread them) are moving toward the north and south poles, as well as to higher elevations. Ticks are moving north faster than white-legged mice, partly due to being carried by migratory birds.
Extensive collecting was done of mice and ticks in the northeastern limits to test for the presence of B. burgdorferi. The abundance of ticks correlated with increased temperatures, while the abundance of mice was limited by the length of winter and average winter temperature. B. burgdorferi was most commonly found at sites where white-footed mice and black-legged ticks were both found.
This study predicts a 150 km expansion northward, beyond the present northern range of B. burgdorferi by 2050 in southern Quebec. The limit of the ranges is believed to move from 3.5-11 km per year for the coming 40 years. Mice limit the spread of Lyme disease, and the first case of Lyme disease in a human in Quebec was in 2008. Cases continue to increase.
CONCLUSION: Knowledge of the future range of Lyme disease should be useful in order to deal with the disease in areas in which it has not previously occurred. This study confirms previous knowledge that climate change determines species distribution.
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PMID: 25469157.
Summary #686.
