Pathogen Surveillance of Haemaphysalis longicornis Ticks in Southern Pennsylvania, USA Using Targeted and Metatranscriptomic Screening

Haemaphysalis longicornis (Asian longhorned tick) is an invasive species recently established in the United States and a potential vector for pathogens. This study included 620 H. longicornis collected in southern Pennsylvania from 2022 to 2023 with the aim of investigating the microbial community and host preferences of these ticks along with any association with newly emerging pathogens. To assess specific emerging pathogen carriage, all collected ticks were screened for Theileria orientalis and Anaplasma marginale by targeted PCR. To evaluate host use and broader pathogen diversity, a subset of 56 partially engorged ticks was analyzed by cytochrome b PCR and tested with a multiplex Luminex xMAP® panel for 16 tick-borne pathogens. A subset of these partially engorged (44) H. longicornis were further examined by Oxford Nanopore metatranscriptomic sequencing. Sequencing identified a bacterial community dominated by Coxiella-like endosymbionts, with additional genera including Acinetobacter, Sphingomonas, Pseudomonas, Staphylococcus, Escherichia, Klebsiella, and Wolinella. Neither targeted screening nor sequencing detected recognized human or veterinary pathogens. Blood meal analysis of partially engorged ticks indicated deer (Odocoileus spp.) as primary hosts. The feeding behavior of H. longicornis and its known role as an established vector for pathogens highlight the need for continued surveillance.