Tick activity is running high across much of the South Shore, with Norwell, Hanover and Hingham among the Plymouth County communities facing conditions favorable for tick bites, according to a new report.
TickZone, a free forecasting service that calculates daily tick risk for Massachusetts communities, rated all three towns at high risk Tuesday, July 21. Hanover recorded a score of 82 out of 100, followed by Norwell at 77 and Hingham at 73. The scores are updated each morning and can rise or fall as weather conditions change.
The daily numbers are different from TickZone’s peak-season ranking, which measures the underlying risk associated with habitat, seasonal activity and disease prevalence. On that measure, Norwell and Hanover lead Plymouth County with scores of 72, while Hingham and Pembroke each score 71. All four are classified as high risk.
The service places Plymouth County seventh among Massachusetts’ 14 counties for overall modeled tick risk. Its separate disease baseline, which is built from federal Lyme disease surveillance, is listed as the sixth-highest in the state.
Plymouth County has an estimated annual Lyme disease rate of 189 cases per 100,000 residents, according to TickZone’s analysis of U.S. Centers for Disease Control and Prevention data. That is nearly 19 times the threshold of 10 confirmed cases per 100,000 that the CDC has used when identifying high-incidence areas.
The county’s rate is also the 108th highest among 1,268 counties in the Northeast, according to TickZone. CDC surveillance shows that the deer tick, also known as the blacklegged tick, and the American dog tick are established in Plymouth County.
Norwell’s elevated underlying risk is partly tied to its wooded landscape. TickZone estimates that 89% of the town is forested and 97% consists of natural land cover, including wooded, grassy and brushy areas where ticks may wait for people or animals to pass.
Hanover is estimated to be 85% forested, while Hingham is 84% forested. Weather conditions pushed Hanover’s daily score above Norwell’s on Tuesday, demonstrating how rainfall and humidity can temporarily change the relative risk between neighboring communities.
TickZone calculates a score from zero to 100 by combining temperature, atmospheric dryness, recent rainfall and soil moisture with seasonal tick activity. It also analyzes satellite land-cover information, local tick species and county-level disease rates. Scores of 67 or higher are classified as high risk.
The service cautions that its forecast is a general hazard estimate rather than a validated epidemiological model. A high score means the weather, season and local environment favor tick activity, but it cannot determine whether an individual tick is carrying a disease.
July falls within the primary risk period for deer tick nymphs in Massachusetts. The tiny nymphs peak from late May through July and are responsible for most human Lyme disease infections, according to TickZone’s seasonal calendar. American dog ticks are also active during the summer.
Across Massachusetts, 345 of the state’s 351 communities were classified as having moderate or high tick risk Tuesday. Residents can use TickZone’s Plymouth County page to see the current score and seven-day outlook for each town.
The CDC recommends using an EPA-registered insect repellent, wearing permethrin-treated clothing and conducting tick checks after spending time outdoors. Attached ticks should be removed promptly, and anyone who develops a rash or fever after a possible bite should seek medical care.
