Community-engaged passive tick surveillance highlights the diversity of ticks and tick-borne pathogens in Illinois.

The continuing increase in incidence of tick-borne illnesses in the United States necessitates expanded surveillance, especially in areas like Illinois experiencing range expansion of key vectors such as Ixodes scapularis and Amblyomma americanum. We report on the initial years (2018-2023) of a community-engaged passive tick surveillance program in Illinois designed to complement active collections by casting a wide net for tick species, tick-host encounters, and emerging pathogens. Participants submitted eight tick species, dominated by A. americanum, I. scapularis, and D. variabilis. Submissions, primarily adults, occurred almost year-round (except February), and were most often associated with humans, dogs, and deer. We used a microfluidic system and sequencing to test a subset of the submitted ticks. Six tick-borne pathogens were detected, including Borrelia burgdorferi s.s. (14% prevalence in adult I. scapularis), B. miyamotoi (4.7% in adult I. scapularis), and Anaplasma phagocytophilum (1.2% in I. scapularis as well as 1 out of 7 tested Dermacentor albipictus). We also documented spotted fever group Rickettsia species, such as R. amblyommatis (53% prevalence in nymphal A. americanum), R. montanensis (2.1% in D. variabilis), and Candidatus R. andeanae (in 2 out of 3 A. maculatum). These efforts helped document the year-round risk of tick exposure and expanded our knowledge of the diversity of ticks and circulating pathogens in Illinois. We believe the combination of a sustainable, low-cost passive surveillance program coupled with multi-pathogen assays can serve a useful function as complementary surveillance for emerging pathogens and changing tick distributions.