STIMULATION OF ATTACHMENT IN A CAMEL TICK, HYALOMMA-DROMEDARII (ACARI, IXODIDAE) - THE UNINTENDED RESULT OF SUBLETHAL EXPOSURE TO PERMETHRIN-IMPREGNATED FABRIC

The susceptibility of a camel tick, Hyalomma dromedarii (Koch), to per methrin-impregnated military uniform fabric was studied to determine t he effects of laundering and contact time. Separate contact toxicity t ests were conducted with laboratory-colonized male and female ticks of uniform age. Unfed, unmated ticks were exposed for periods of 5, 10, 30, and 60 min to each of five fabrics: unwashed-untreated, unwashed-t reated, and 1, 2, or 3 times washed after treatment (1-, 2-, 3-wash-tr eated). Treated fabric was impregnated with permethrin at 0.125 mg (AI )/cm2. Laundering was by machine washing with detergent followed by ho t air machine drying. Intoxication immediately after exposure was asse ssed by activity response: the proportion of ticks attaching to a host (rabbit) within 60 min and the average time elapsed between contact a nd insertion of mouthparts. Unexpectedly, permethrin exposure activate d an attachment response in both sexes. At all contact times, and in e ach wash-treated group, a greater proportion of ticks attached, and di d so more rapidly, than in controls. Mortality assessment 24 h after e xposure showed that females were more tolerant than males and experien ced light mortality even after 60 min of contact. Both natural and acq uired factors may account for permethrin tolerance in this species. Co nsistent with pyrethroid mode of action and pheromone function in tick s, it is hypothesized that sublethal levels of permethrin may act on H . dromedarii to induce premature or excess release of a neurosecretory substance that elicits attachment.