Ohio’s Lyme Risk: Beyond the Border

The susceptibility to contracting Lyme disease, transmitted by infected ticks, is comparable in Ohio to that of Northeastern states with decades of documented Lyme disease prevalence, according to recent empirical findings.

This investigation builds upon a 2014 assessment that identified Ohio’s initial established population of blacklegged ticks, the vectors for Lyme disease-causing bacteria, in Coshocton County during 2010.

At that juncture, the presence of infectious bacteria was noted in 2.4% of sampled blacklegged ticks. Furthermore, antibodies signifying prior encounter with the pathogen were identified in 20% of white-footed mice, a predominant small mammal species serving as an infection reservoir for ticks in their immature stages.

The subsequent research conducted by a team from The Ohio State University revealed a significant escalation in pathogen presence. The infection rate among captured ticks escalated to as much as 47.6%, while infected small mammals showed a prevalence of up to 60.4%.

Our hypothesis posited that within a decade, with the proliferation of suitable host species within Ohio’s ecological landscape, this pathogen vector system would become firmly entrenched and demonstrate exponential growth. This study substantiates that very outcome.”

Risa Pesapane, senior author, associate professor of veterinary preventive medicine at Ohio State

“Consequently, Ohio now mirrors the risk profile of endemic Northeastern regions. This finding may surprise many, as the common perception is that while ticks and some hosts are present, Ohio is not analogous to Connecticut. However, in certain areas of Ohio, the situation is now virtually identical to that of Connecticut.”

Dr. Pesapane highlighted that the risk of infection is not uniform across Ohio, registering highest in the wooded terrains of the eastern and southern portions of the state. Despite this localized variability, blacklegged ticks have been documented in all 88 counties.

“It is imperative to communicate to the public, concerning both personal safety measures and the medical community’s awareness, that the probability of acquiring Lyme disease in Coshocton, Ohio, and comparable locales with conducive habitats, is on par with that in Lyme, Connecticut.”

The findings of this study were recently disseminated in the publication, *Journal of Medical Entomology*.

Blacklegged ticks, also referred to as deer ticks, are extensively distributed throughout the eastern United States and are recognized vectors for the *Borrelia burgdorferi* bacterial strains responsible for the majority of North American Lyme disease cases in humans and canines. These ticks also harbor *Anaplasma phagocytophilum*, the causative agent of anaplasmosis.

Ningzhu Bai, a doctoral candidate within the Environment and Natural Resources Graduate Program at Ohio State, spearheaded this research as part of her master’s thesis. The investigative team collected 654 ticks exhibiting questing behavior and successfully trapped 106 small mammals. Ticks acquire infectious bacteria from small mammals, which act as reservoir hosts, subsequently infecting the ticks that feed on them.

While deer do not play a direct role in the early-stage infection cycle within ticks, they are significantly associated with blacklegged ticks as they serve as the primary hosts for adult ticks seeking blood meals and mates.

Genomic DNA was extracted from 368 ticks and from mammal tissue and blood samples to conduct analyses for the presence of *Borrelia burgdorferi* and *Anaplasma phagocytophilum*.

“It was striking to observe the infection prevalence increase from 2.4% for *Borrelia burgdorferi* sensu lato to nearly 50% within a ten-year span,” stated Bai. “Furthermore, the prevalence for *Borrelia burgdorferi* sensu stricto was also exceptionally high, with over 40% of ticks carrying that particular pathogen.”

The prevalence of the anaplasmosis pathogen in ticks registered at 15.5%. Six out of the eight tested mammal species demonstrated positive results for infectious bacteria, with infection rates of 60.4%, 19.8%, and 11.9% for the respective pathogens. White-footed mice and eastern chipmunks were identified as the most frequently infected host species.

“A key takeaway I emphasize is that, in Ohio, approximately one out of every two ticks encountered could potentially be infected,” remarked Dr. Pesapane, who also holds a faculty position in Ohio State’s School of Environment and Natural Resources.

The current study furnishes essential ecological data to strategically guide public health interventions, pinpointing areas where efforts to mitigate tick-borne disease transmission would yield the greatest impact. A future research endeavor is planned to assess the efficacy of tick-exterminating acaricides on small mammal reservoirs at the Coshocton study sites.

“Implementing effective ecological interventions presents considerable challenges. Consequently, we continue to advocate for personal protective measures, which have proven exceptionally effective,” Dr. Pesapane advised. These measures encompass the use of tick repellents, the wearing of long sleeves and trousers, tucking pant legs into socks when outdoors, conducting thorough tick inspections upon returning indoors, showering promptly, and utilizing preventive treatments for companion animals.

According to Dr. Pesapane, undertaking these protective actions in Ohio is highly beneficial. “Observing the period from 2010 to the projected 2025, there has been a remarkable 48-fold increase in reported Lyme disease cases within Ohio, and the state is anticipated to be classified as a high-incidence region moving forward.”

In addition to ongoing systematic collection and analysis of medically significant ticks across Ohio, Dr. Pesapane encourages public participation by facilitating the submission of ticks to her laboratory. She also serves as the faculty director for the Buckeye Tick Test, an Ohio State initiative that offers pathogen testing for submitted ticks, including those causing Lyme disease, for a nominal fee.

These public submissions, coupled with her own research endeavors, underscore the fact that tick-borne threats are not confined to warmer weather conditions.

“Even on days with snow cover, provided the ambient temperature remains above freezing, blacklegged ticks will actively seek hosts and will bite indiscriminately any individual they encounter,” she elucidated. “Therefore, the risk of tick exposure persists throughout the entire year.”

Andreas Eleftheriou from Ohio State also contributed as a co-author to this study. The research received financial support from the U.S. Department of Agriculture’s National Institute of Food and Agriculture.