DOCUMENTING RANGE EXPANSION OF TWO INVASIVE TICK (ACARI:IXODIDAE) SPECIES IN EASTERN SOUTH DAKOTA
Abstract
This project documents the expanded zoogeographic ranges of the blacklegged tick (Ixodes scapularis) and lone star tick (Amblyomma americanum) within eastern South Dakota. Ticks are important when considering a “One Health” approach, as many species are competent vectors of zoonotic pathogens causing human diseases and conditions such as Lyme disease, tularemia, rickettsia, and alpha-gal syndrome. The research involved constitutes two steps. First, tick surveillance was conducted in eastern counties of South Dakota, spanning March 2021 through August 2022. Surveillance took place along edge habitat at recreation areas, state and public parks, wildlife management areas and refuges, and other natural areas that could be identified as suitable tick habitat. All life stages and species of ticks were collected and preserved in microcentrifuge tubes filled with 95% ethanol and placed in a freezer at -20 deg C. All target species of ticks were collected using a white cloth tick drag. Second, collection data were analyzed and compared to collection data from similar tick sampling efforts from 2019 and 2020 to determine if, and to what extent, range expansion had occurred. Distribution maps were created for each year to represent areas where I. scapularis and A. americanum were reported, and changes in species establishment were displayed. This study focused primarily on the Southeastern region of the state, near where I. scapularis populations exist in bordering Minnesota, and A. americanum in Nebraska and Iowa. As of the 2022 sampling season, the only counties where I. scapularis and A. americanum appear to have overlapping ranges are Clay County and Union County. Ixodes scapularis and A. americanum both have overlapping habitat with the more widespread and common established species Dermacentor variabilis, the American dog tick. This study also yielded a state record for another human disease vector, the gulf coast tick (Amblyomma maculatum) in 2021 and 2022. A weak positive correlation was calculated between total ticks collected and the person-hours spent to collect those ticks. Target species of tick were detected in nine counties in eastern South Dakota.