CONTACT TOXICITY OF PERMETHRIN-IMPREGNATED FABRIC TO HYALOMMA-ANATOLICUM-EXCAVATUM (ACARI, IXODIDAE) - EFFECTS OF LAUNDERING AND EXPOSURE AND RECOVERY TIMES

A previous study that documented enhanced host attachment by the camel ticks Hyalomma dromedarii Koch after permethrin exposure prompted a s imilar investigation of permethrin effects in H. anatolicum excavatum Koch, an Old World hardbacked tick suspected of vectoring human pathog ens. Contact toxicity tests were conducted with laboratory-colonized m ale and female H. a. excavatum of the same age exposed for periods of 5, 10, 30, and GO min to each of 5 fabric treatments: unwashed/untreat ed; unwashed and treated; and treated fabric given 1, 2, or 3 laundry cycles of warm-water detergent machine washing, followed by hot-air dr ying. Fabric was tropical weight 100% cotton military uniform. Treated fabric was impregnated with permethrin at 0.125 mg (Al)/cm(2). Contac t toxicity was measured immediately after and 24 h after fabric contac t as proportion of ticks that attached mouthparts to the skin of a hos t (rabbit) within a 60-min quest period and time lapse (minutes) betwe en contact with the host and attachment. Attachment response immediate ly after. permethrin contact was exposure time-and wash-dependent in b oth sexes. Proportion of attaching ticks and times to attachment were comparable in controls and in groups exposed to all permethrin-treated fabrics for 5 or 10 min. Contact periods of 30 and GO min with 0-wash /treated or 1-wash and treated fabric significantly reduced the freque ncy of attachment and significantly prolonged mean times to attachment . Compared with low levels of attachment response observed immediately after fabric contact, recovery of attachment response was observed 24 h after exposure in these wash/treatment groups, but inhibition was s till evident. Permethrin-induced intoxication was more pronounced in m ales than females. Mortality 24 h after exposure was only significant among females exposed to 0-wash/treated fabric for 60 min. There was n o evidence of permethrin-mediated stimulation of the attachment respon se in H. a. excavatum.