Livestock Inspections Facilitate Monitoring of the Geographic Spread of Native and Invasive Tick Species

Abstract Various tick species of human health concern are undergoing range expansions across the United States (US), a consequence of land use or climate change. Concurrently, the US is also experiencing the spread of a true invasive tick specie, the Asian Longhorned Tick (Haemaphysalis longicornis), throughout much of the eastern and midwestern United States following its detection in 2017 in New Jersey. Passive surveillance, relying on routine observations of pests or disease vectors, can supplement active field surveys potentially aiding in early detection of invasive species and range expansions. The objective of this study was to determine the utility of an underused host-based sampling strategy, namely sale barn, cattle buying station, and research center cattle, as a passive surveillance strategy for tick range expansions and detection of H. longicornis in Illinois (IL). Weekly sampling was conducted at two locations - a livestock auction barn in Fruitland, Missouri (n = 7) and cattle buying station in Salem, IL (n = 8). The same subset of cattle at Dixon Springs Agricultural Center (DSAC; Simpson, IL) were evaluated for ticks 2 times at a one-month interval. Ticks per animal were recorded and preserved in 85% ethanol in labeled vials. Samples were processed and identified at the Illinois Natural History Survey Medical Entomology Lab (INHS-MEL) at the University of Illinois. Ticks were identified to species using standard taxonomic keys, enumerated by life stage, and archived in the biorepository at INHS-MEL. Two specimens of H. longicornis were submitted to the USDA National Veterinary Services Laboratory (NVSL) in Ames, IA for taxonomic confirmation and documentation. At Fruitland, 9 ticks were collected from 7 cattle sourced from 4 counties. Ticks were detected on 3 out of 7 collection days. At Salem, 53 ticks from 24 cows were sourced from 7 counties and ticks were detected on 5 out of 7 collection days. The first collection at DSAC resulted in 282 ticks removed from 100 of the 298 cows. In total, 344 ticks were collected from 10 counties in southern Illinois (Table 1). These included detections of the Gulf Coast tick, Amblyomma maculatum, in 6 counties, of which Clay County is a first report. Additionally, 6 adult female H. longicornis originating from a farm in Clay County were detected, a new report for this county and the third county in which this invasive species has now been detected in Illinois. Mitochondrial genome sequencing of two H. longicornis specimens will be performed to aid in understanding possible introduction pathways into Illinois. Jointly, this work highlights the utility of livestock-based passive tick collections to help track the spread of ticks. The detection of H. longicornis suggests continued establishment of this species in IL, with ramifications for livestock producers, warranting further monitoring, research, and prevention measures.