Methods of active surveillance for hard ticks and associated tick-borne pathogens of public health importance in the contiguous United States: a comprehensive systematic review.

Tick-borne diseases in humans and animals have increased prevalence across the United States. To understand risk factors underlying tick-borne diseases it is useful to conduct regular surveillance and monitoring of ticks and the pathogens they carry, in a sustained and effective manner. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, this study aims to summarize the previously used methods for active surveillance of ticks and tick-borne pathogens, identify the existing knowledge gaps in ongoing surveillance, and highlight and guide the mechanisms required to inform those gaps for more effective and sustainable future surveillance efforts. After screening 2,500 unique studies between 1944 and 2018, we found 646 articles that performed active surveillance of hard ticks and/or their associated tick-borne pathogens of public health importance within the United States. An additional 103 articles were included for the 2019 to 2023 period. Active surveillance has been performed in ~42% of the counties (1944 to 2018) and ~23% of the counties (2019 to 2023) within the contiguous US, and states with the most coverage are in the Northeast, Upper Midwest, and along the West coast. The most reported tick was Ixodes scapularis (195 studies) and most commonly reported pathogen was Borrelia burgdorferi (143 studies). Overall, surveillance efforts have increased and become more diversified, and methods of tick and tick-borne pathogens testing have undergone changes, but those efforts are mainly concentrated in focal regions of a county. Future surveillance efforts should follow Centers for Disease Control and Prevention guidelines and target areas of United States with scarce reports of active surveillance and build collaborations and resources to increase surveillance.