Canids in the Lyme Light: The Effects of Canid Predators on Lyme Disease Ecology

As Lyme disease spreads and incidence increases, understanding the factors fueling its rise is urgent. A growing body of research has attributed the increase of Lyme-infected ticks to the abundance of small mammal hosts. With large-scale changes to canid predator communities in the American Northeast and Midwest over the past century, small mammal populations may have been affected, in turn influencing tick populations and the prevalence of the Lyme disease causing bacteria, Borrelia burgdorferi. Recently, studies have sought to correlate certain predators with trends in Lyme disease prevalence. To observe predator effects on tick abundance and Lyme occurrence, I applied a three-pronged approach: 1) direct observation in the field, 2) spatial and temporal correlations of Lyme disease cases and predators from state hunting and trapping metrics, 3) a mathematical model of small mammals hosts, predators, and ticks. My observation and analyses found little support for the significant influence of canid predators on tick populations or resulting Lyme disease cases. While the model predicted some slight negative effects of canids on Lyme prevalence, it may be useful for quantifying the effects of other, more significant small mammal predators, such as raptors and mustelids, on Lyme disease incidence. Although changes to predator communities may have rippling effects that influence the spread of zoonotic diseases, these results suggest that correlations found by earlier studies may be overstated.