Medical and veterinary pathogens detected in invading Asian longhorned ticks (Haemaphysalis longicornis) from Ohio and Pennsylvania.

OBJECTIVE

To estimate the prevalence of medical and veterinary pathogens in invading Asian longhorned tick (ALT; Haemaphysalis longicornis) populations in 2 adjoining states, Ohio and Pennsylvania.

METHODS

We conducted a cross-sectional study to test ALTs collected through active (probability-based) surveillance in Pennsylvania and active or passive (opportunistic) surveillance in Ohio for medical and veterinary pathogens using PCR.

RESULTS

We collected 563 nymphs and adult females from 2021 through 2025 from the environment and domestic cows. We detected DNA of Anaplasma phagocytophilum (3 of 563 [0.53%]; 95% CI, 0.11 to 1.55). A subsample of ticks from both states was tested for Babesia spp. The DNA of Babesia spp was detected in Ohio (20 of 61 [32.79%]; 95% CI, 21.31 to 46.00;), and sequence data (from 8 samples) identified 4 detections of Babesia odocoilei and 4 detections of Theileria orientalis Ikeda. The DNA of Babesia spp was also detected in Pennsylvania (6 of 41 [14.63%]; 95% CI, 5.57 to 29.17); however, we were unable to retrieve any sequence data.

CONCLUSIONS

Our findings, albeit partially based on opportunistic sampling, suggest that the epidemiology of ALT-associated pathogens is evolving as we detected medical and veterinary pathogens of concern, primarily in Ohio. Surveillance can help guide veterinary and public health professionals to inform management.

CLINICAL RELEVANCE: To the best of our knowledge, this is the first reported detection of B odocoilei from host-seeking ALTs anywhere in the US and the first reported detection of T orientalis Ikeda from host-seeking ALTs in Ohio.