Rising Threat: Blacklegged Ticks and Lyme Disease in the Northeastern US

In the Northeast United States, the arrival of spring, summer, and fall brings with it a significant risk of blacklegged tick bites, commonly known as deer ticks.

A recent study from Dartmouth, published in Parasites and Vectors, has found that about half of adult blacklegged ticks carry the bacteria that cause Lyme disease.

Interestingly, younger nymph ticks have a transmission rate of around 20% to 25%.

Study Overview

This research project was a collective effort among scientists from various universities, health departments, and agricultural agencies in the Northeast.

Their investigation spanned over three decades, from 1989 to 2021, examining the prevalence of blacklegged ticks and their tendency to harbor pathogens associated not only with Lyme disease but also with three other tick-borne illnesses.

The states included in the study were Connecticut, New York, New Hampshire, Vermont, and Maine.

Data collection began in Maine in 1989, while other states initiated their tracking efforts in the mid-2000s.

Unfortunately, Massachusetts and Rhode Island were excluded from the analysis due to insufficient data.

Lyme Disease Transmission

Lyme disease first emerged in Lyme, Connecticut, in 1975.

This illness manifests through various symptoms, which can differ significantly depending on the stage and severity of the disease.

Common signs of Lyme disease include fever, chills, fatigue, joint and muscle pain, swollen lymph nodes, and a distinctive rash.

If not treated, Lyme disease can lead to serious complications.

The bacterium responsible for Lyme disease, Borrelia burgdorferi, resides in the blood of certain small mammals, including white-footed mice, chipmunks, birds, and squirrels, which serve as hosts.

It’s important to note that blacklegged ticks are not born with this bacteria; they acquire it by feeding on infected mammals.

In contrast, while white-tailed deer provide a blood meal for ticks, they do not facilitate the bacteria’s transmission.

Over the course of their two-year life cycle, blacklegged ticks will consume blood three times: as larvae in the summer of their first year, as nymphs in late spring of the following year, and as adults in the fall, usually from September to November.

To transmit Lyme disease bacteria, a tick needs to be attached for at least 24 hours.

This risk is heightened with nymphs, which are significantly smaller than adults—about the size of a poppy seed compared to the sesame seed-like size of adult ticks.

Research Findings and Implications

The lead researcher emphasized that, although Lyme disease transmission is intricate, the study highlights the notable presence of blacklegged ticks and their associated pathogens throughout the Northeast.

The research team assessed how tick populations and the pathogens they host have shifted over time and across different locations.

Interestingly, despite the well-documented expansion of both blacklegged ticks and Lyme disease in recent decades, researchers found only minor variations in tick populations.

This may be due to the timing of their sampling, which typically starts after tick populations have already increased.

However, the proportion of blacklegged ticks carrying Lyme disease bacteria has seen a significant rise.

These findings reinforce the preventive measures recommended by the Centers for Disease Control and Prevention (CDC) and health professionals.

They urge individuals to perform thorough tick checks after spending time outdoors in areas known for these pathogens.

Although many underlying data were publicly available before this study, the research team’s efforts to standardize survey methods across states have created one of the most comprehensive datasets on tick populations and pathogen prevalence in the country.

Additionally, the research team is delving into how climate change could influence the interactions between blacklegged ticks and the spread of Lyme disease in the Northeast, thereby enhancing our understanding of this pressing public health issue.

Source: ScienceDaily