Tick Densities and Infection Prevalence on Coastal Islands in Massachusetts, USA: Establishing a Baseline

Simple Summary: People who use hiking trails may be exposed to blacklegged ticks (Ixodes scapularis, also known as deer ticks), some of which are infected with the pathogens that cause Lyme disease, anaplasmosis, and babesiosis. In areas that also have lone star ticks (Amblyomma americanum), an added concern is acquiring the alpha-gal red meat allergy. Here, we describe an example of how such tick-related risks can be assessed at the scale of a local community, while providing a baseline for further monitoring. We used drag sampling along public trails to quantify tick abundance in June 2020-2022 at 12 study sites in the town of Nantucket, Massachusetts, USA. One of these sites was located on nearby Tuckernuck Island. Blacklegged nymphs were common at sites with moist deciduous woodlands and rare in open grasslands. For several sites, we carried out pathogen testing and found that similar to 10-20% of blacklegged nymphs on Nantucket were infected with the bacterium that causes Lyme disease. Lone star ticks were extremely common on Tuckernuck Island and rare on Nantucket Island, where they are expected to become more widespread in the future. Both tick species represent a significant threat to public health and mitigating their impact is an ongoing challenge. Tick-borne diseases and a tick-induced red meat allergy have become increasingly common in the northeastern USA and elsewhere. At the scale of local communities, few studies have documented tick densities or infection levels to characterize current conditions and provide a baseline for further monitoring. Using the town of Nantucket, MA, as a case study, we recorded tick densities by drag sampling along hiking trails in nature preserves on two islands. Nymphal blacklegged ticks (Ixodes scapularis Say) were most abundant at shadier sites and least common in grasslands and scrub oak thickets (Quercus ilicifolia). Lone star ticks (Amblyomma americanum L.) were common on Tuckernuck Island and rare on Nantucket Island, while both tick species were more numerous in 2021 compared to 2020 and 2022. We tested for pathogens in blacklegged nymphs at five sites over two years. In 2020 and 2021, infection levels among the four Nantucket Island sites averaged 10% vs. 19% for Borrelia burgdorferi, 11% vs. 15% for Babesia microti, and 17% (both years) for Anaplasma phagocytophilum, while corresponding levels were significantly greater on Tuckernuck in 2021. Our site-specific, quantitative approach represents a practical example of how potential exposure to tick-borne diseases can be monitored on a local scale.