Effects of infection by Arsenophonus and Rickettsia bacteria on the locomotive ability of the ticks Amblyomma americanum, Dermacentor variabilis, and Ixodes scapularis.

The goal of this study was to determine the effect of vertically transmitted Arsenophonus and Rickettsia bacteria on locomotive ability of larvae of three eastern North American tick species: Amblyomma americanum, Dermacentor variabilis, and Ixodes scapularis. We conducted two different experiments on flat or inclined surfaces to measure tick motility. In each experiment, a moderately heated surface was used and placed at a selected incline. The individual's path across the surface was traced for a period of 2 min, or until the larval tick had moved off the surface. Following the microbial identification of Arsenophonus and Rickettsia, a mixed model analysis of variance (ANOVA) indicated that clutch microbial infection status had a significant effect on tick motility with Rickettsia increasing and Arsenophonus decreasing motility averaged over tick species and inclines. There was also a significant difference in motility among tick species and a highly significant effect of the Species*Incline interaction where Dermacentor had higher motility than Ixodes on the flat surface.