Expanding Distribution into the Midwest by the Lone Star Tick is Facilitated by Recognizing Excreta of Previously Established Ticks

Indianapolis, IN

The southeastern lone star tick, Amblyomma americanum, has recently appeared in our field sweeps. This new tick in our area brings the potential for diseases, such as ehrlichiosis, tularemia, and Southern rash illness borreliosis. Favorable habitats are indicated by excreta of ticks that are already established, with the excreta acting as an assembly pheromone that retains ticks in areas with proper temperature, moisture, and suitable hosts. Our hypothesis is that excreta from different tick species may function as an assembly pheromone for lone star ticks, which may have contributed toward lone star ticks establishing here. Clustering responses by lone star ticks on excreta of ticks from different tick species was tested using six-sector Petri dish attraction bioassays with an added relative humidity component. Dry 33% RH conditions elicited greater clustering (higher speed, more ticks involved) than under humid 93% RH, mostly by female adults and nymphs and only a few larvae. Greatest response was to excreta of black-legged tick Ixodes scapularis. Other excreta that was attractive and resulted in clustering, but less intense, was Gulf Coast tick A. maculatum, American dog tick Dermacentor variabilis, and brown dog tick Rhipicephalus sanguineus. The conclusion is that lone star ticks can recognize assembly pheromone of other ticks, migration probably occurs by adults during dry weather, and arrival of the Lyme disease vector I. scapularis seems likely.