Cross-continental hitchhiking of exotic ticks on human travelers and ensuing public health challenges in the USA

Abstract

Facilitated by the increased frequency of travel and a rise in legal and illegal animal trades, invasive ticks have been inadvertently introduced into the US in recent years. We received ticks removed from human travelers returning to Connecticut, US, identified them to species, and screened for evidence of infection. We report seven nonnative ticks introduced to Connecticut from 2019 to 2023, including two Amblyomma mixtum nymphs from Guatemala and Costa Rica, one Amblyomma coelebs nymph from Belize, one Rhipicephalus pulchellus female from Tanzania, two Ixodes ricinus nymphs from Germany and Poland, and one I. ricinus larva from Scotland. Of these, the two A. mixtum nymphs tested positive for Rickettsia amblyommatis. The importation of exotic tick species and their likelihood to establish populations is a global challenge, and thus the establishment of tick surveillance programs, which include tick species identification and pathogen screening, is important for protecting human and veterinary health.