A Review of Trends and Contributing Factors in Tick-borne Disease Surveillance in Maine, 2001–2024

Importance: Tick-borne diseases have a major health impact in Maine. There are 5 endemic diseases: anaplasmosis, babesiosis, hard tick relapsing fever, Lyme disease, and Powassan virus disease. Cases of these 5 diseases have increased dramatically over the past 15 years. Objective: The objective of this review is to summarize tick-borne disease data in Maine. This summary includes showing trends and identifying factors that may be contributing to the trends. Review: There is a long history of publications about tick-borne diseases in Maine, with articles first appearing in the 1980s. We analyzed tick-borne disease surveillance data collected by Maine Center for Disease Control and Prevention from 2001 to 2024. Findings: Anaplasmosis, babesiosis, hard tick relapsing fever, Lyme disease, and Powassan virus disease are all being diagnosed more often in Maine. Increasing case counts led to historical highs for most of these conditions in 2024. Coastal counties are most affected. Providers report most cases during the summer months, but they identify cases year-round. Many factors can influence the trends, including climate, diagnostic capabilities, education, and surveillance approaches. Conclusions: Providers should be aware of tick-borne diseases, consider them in differential diagnoses, and educate patients on how to protect themselves. Without effective measures to combat ticks or immunize humans, community members should be aware of the risks and take precautions to prevent tick bites.