In the Northeast, 50% of adult ticks carry the bacteria that transmits Lyme disease

January 17, 2025 – Most of the Northeast is at risk of being bitten by black-legged ticks (also known as deer ticks) during spring, summer, and fall. A new Dartmouth study has been published. parasites and vectorsfound that 50% of adult black-legged ticks carry the bacteria that causes Lyme disease, while up to 25% of young (nymphal) black-legged ticks carry this bacterium.

A team of researchers from universities, health departments, and agricultural agencies across the Northeast looked at data from 1989 to 2021 to determine the number of black-footed ticks and the number of ticks that can transmit the pathogen that causes Lyme disease. A meta-analysis was conducted on the number of participants. Three other tick-borne diseases occur in the Northeast. The states were Connecticut, New York, New Hampshire, Vermont, and Maine.

Maine began collecting data in 1989, and most other states began collecting data in the mid-2000s. Massachusetts and Rhode Island were not included in this study due to unavailable or insufficient data.

The bacteria that causes Lyme disease has a complex transmission chain, but our results reveal the relative abundance of blacklegged ticks and how many of them carry the pathogen that causes the disease. is shown.

Lucas Price, former Dartmouth College Geography Postdoctoral Fellow

Lyme disease was first discovered in Lyme, Connecticut in 1975. Symptoms vary depending on the stage and severity of the disease but may include rash, fever, chills, fatigue, muscle or joint pain, and swollen lymph nodes. If left untreated, more severe symptoms may persist.

Lyme disease is caused by a bacterium called Borrelia burgdorferi. Some, but not all, white-footed mice, chipmunks, birds, squirrels, and other small animals carry bacteria in their blood, making them “competent” hosts.

Black widow ticks are not born infected with Lyme disease bacteria. However, when a black widow tick sucks an infected host, it can transmit the bacteria that causes Lyme disease to humans through its bite. Other animals, such as white-tailed deer, are “incompetent hosts,” meaning they are a food source for black-footed ticks but cannot transmit Lyme disease.

Black-legged ticks typically make three blood meals during their two-year life cycle. After hatching into larvae in midsummer of the first year. They emerge as nymphs the following late spring, often in May or June. For adults, falls probably occur between September and November.

Generally, a tick must be attached to a person for at least 24 hours for the Lyme disease bacteria to be transmitted. Therefore, while adult black-footed mites, which are about the size of a sesame seed, are more likely to carry bacteria, young ticks and nymphs, which are only about the size of a poppy seed, are of particular concern and are more likely to carry bacteria. It's difficult. Spot.

“The bacteria that causes Lyme disease has a complex transmission chain, but the results of this study show that blacklegged ticks are relatively common and how many of them carry the disease-causing pathogen across the Northeast. “It shows whether they're carrying something,” said lead author Lucas Price. At the time of his research, he was a postdoctoral fellow in geography at Dartmouth College and is currently a wildlife biologist with the Department of the Interior's Bureau of Land Management.

Researchers analyzed the abundance of black-footed ticks and the presence of Lyme disease bacteria and other pathogens to help determine how black-footed ticks and the pathogens they carry are changing over time and space.

“Contrary to the well-documented prevalence of black-legged ticks and Lyme disease over the past 30 years, we found very small changes in black-legged tick populations, which is likely due to the fact that we typically We think this is because we don't start sampling habitats 'until they are already established,' says the senior author. Jonathan WinterAssociate Professor and Director of Geography Applied Hydroclimatology Group At Dartmouth. “But we do find an increased proportion of black-legged ticks that carry the Lyme disease bacteria.”

These findings echo advice from the Centers for Disease Control and Prevention and health care professionals who recommend a variety of tick bite prevention measures, including performing a full-body tick check after spending time outdoors in areas where pathogen-carrying ticks are present. This confirms that. Although much of the data was already publicly available prior to the study, the researchers conducted a consistent survey across states, creating one of the most comprehensive tick abundance and pathogen prevalence datasets in the United States. We established a baseline that can be used in the study. future.

Researchers are working on another study examining the relationship between climate change and the prevalence of blacklegged ticks and Lyme disease in the Northeast.

Joseph Savage, a graduate student in the Ecology, Evolution, Environment, and Society program, also contributed to the study.