Tick Bite Illnesses Impacting Vermonters
Lyme disease is the most common tick bite illness in Vermont, followed by anaplasmosis and then babesiosis. Cases of anaplasmosis and babesiosis have increased significantly over the last ten years.
Cases of hard tick relapsing fever and Powassan virus are less common today; there have been fewer than 65 cases of hard tick relapsing fever reported to the Health Department since its emergence in 2016, and two cases of Powassan virus in Vermont residents since 1999.
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How common are disease carrying ticks in Vermont?
Several trends were revealed in the most recent Tick Pathogen Surveillance Report (2018-2022):
- 94% of the ticks collected were blacklegged ticks.
- Over half of all blacklegged ticks tested were infected with at least one pathogen; Borrelia burgdorferi (Lyme disease) was the most common.
- Borrelia burgdorferi (bacterium that causes Lyme disease) was the most common pathogen infecting blacklegged ticks with an infection prevalence of 56.7% for adult ticks and 24% for nymph ticks.
- Infection prevalence and density of infected ticks were highest in southwestern Vermont.
- Addison County had the highest density of adult ticks (per 1,000m2).
Rutland County had the highest density of nymph ticks (per 1,000m2). This is significant because ticks in the nymph life stage are tiny (less than 2 mm) and difficult to see, and they may be able to feed on human hosts longer, increasing the likelihood of tick bite illness.
In a special study to evaluate other ticks in Vermont, 1,341 American dog ticks (Dermacentor variabilis) collected during 2018-2023 were tested at the CDC for Rickettsia rickettsii, the bacterium responsible for Rocky Mountain spotted fever; all were negative.
Four lone star ticks (Amblyomma americanum) collected during the same period were tested for Ehrlichia chaffeensis and Ehrlichia ewingii, bacteria responsible for ehrlichiosis in the eastern United States; all were negative.