Gitler-Mangan-URF25-MU

Introduction

Cycle of Lyme Disease infection through different hosts as the tick grows from a larva to an adult. The cycle includes mice, human and deer as additional hosts of the infection.

Lyme disease is the most prevalent vector-borne illness in the United States, caused by the bacterium Borrelia burgdorferi. Its transmission occurs primarily through the bite of the deer tick, Ixodes scapularis, which acquires the bacteria during its early stages of feeding on mammalian hosts. Once infected, I. scapularis becomes a vector for B. burgdorferi, perpetuating a cyclic pattern of transmission to other susceptible hosts, a mechanism similar to a positive feedback loop.

Map of Northern Michigan, highlighting Benzie County with a red circle to show infected mice. Circles show areas where mice were trapped for research. A red dotted line shows the farthest northern spread of Lyme Disease in white-footed mice.

The white-footed mouse, Peromyscus leucopus, typically inhabits forested regions of the Midwest but historically faced challenges establishing populations in northern areas due to harsh winters. However, global warming has led to a northward expansion of its range. In the life cycle of Ixodes scapularis, ticks target hosts of varying sizes; P. leucopus stands out as the most persistent host. It can harbor the bacteria long-term, facilitating transmission to subsequent generations of ticks, earning it the title of "reservoir host" for Lyme disease in the Midwest.

Peromyscus leucopus mouse

We are exploring genetic and demographic data from mice in Michigan to understand whether the observed variations in B. burgdorferi infection rates could stem from certain mouse families displaying predispositions to the bacterial infection. We specifically looked at data from Benzie County because it is the area closest to the northern boundary of infected mice, with a mixture of infected and uninfected animals. Our genetic analysis utilizes microsatellite markers and Genemapper fragment analysis, allowing for detailed genetic scrutiny. Meanwhile, our demographic evaluation covers a spectrum of factors including sex, age, weight, ear size, and rates of B. burgdorferi infection.

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