People are exposed to ticks across diverse outdoor environments, from backyard gardens to backcountry wilderness. To limit tick-borne diseases, we can discourage ticks from biting us by wearing protective clothing, using repellants, and checking our bodies after outdoor activities. And we can reduce tick abundance by managing vegetation and applying pesticides. Project ITCH (Is Tick Control Helping?) aims to improve approaches for controlling ticks on residential properties, where people are likely to encounter them.
Project ITCH is a collaboration between households in the Northeast and scientists from New England Center of Excellence in Vector-borne Diseases (NEWVEC), which is based at UMass Amherst. With permission, NEWVEC conducts surveys of eligible residential properties to learn which ticks are present and then tests collected ticks for bacteria that cause Lyme disease and other illnesses. A study published in the May 2025 issue of Ticks and Tick-borne Diseases reports an unexpected finding from this collaboration between citizens and scientists: rabbit ticks in Maine carry a previously uncharacterized strain of bacteria that might cause illness in people.
Rabbit ticks (Haemaphysalis leporispalustris) rarely bite people, so they get less attention than the deer ticks that transmit Lyme disease and dog ticks that frequently bite people and pets. But rabbit ticks can be reservoirs for disease-causing bacteria and can contribute to their eventual transmission to humans. Dog ticks, for example, attach to three separate hosts during their life cycle, so they could pick up bacteria from an infected rabbit and pass it along to a human.
Between 2020 and 2024 Project ITCH collected nearly 300 rabbit ticks from counties across Maine. Of these, about 6 percent tested positive for a gene that scientists originally thought existed only in the bacteria Rickettsia rickettsii. These bacteria cause Rocky Mountain Spotted Fever (RMSF) in humans, a disease that is fatal in about 5 percent of cases in the United States. Cases of RMSF are apparently increasing in the United States, but remain uncommon in the Northeast; the disease is most prevalent in North Carolina, Tennessee, Missouri, Arkansas, and Oklahoma.
The story became more complicated when the researchers sequenced four other bacterial genes from the collected ticks. These genes were 97 to 99 percent identical to genes from R. rickettsii. Thus, the bacteria in Maine rabbit ticks were not exactly R. rickettsii but rather a closely related strain that had not previously been described, which researchers labeled ME2023.
Although this research provides important new information about the distribution of bacteria related to R. rickettsii, questions about public health implications remain. The similarity of ME2023 to R. rickettsii suggests that it could cause disease in people, but its pathogenicity is unknown. Moreover, RMSF is typically transmitted to people by dog ticks, but the researchers did not find R. rickettsii or ME2023 in Maine dog ticks. The researchers emphasize that more work is needed to evaluate the clinical importance of ME2023 and the role of rabbit ticks in its possible transmission to humans.