Section 69
Chapter 68,638

Efficacy of permethrin as a repellent and toxicant for personal protection against the Pacific Coast tick and the Pajaroello tick (Acari: Ixodidae and Argasidae)

Lane, R.S.; Anderson, J.R.

Journal of Medical Entomology 21(6): 692-702


ISSN/ISBN: 0022-2585
PMID: 6502628
DOI: 10.1093/jmedent/21.6.692
Accession: 068637711

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The repellency and toxicity of permethrin as a clothing impregnant was tested against adults of the Pacific Coast tick, D. occidentalis, and nymphs and adults of the pajaroello tick, O. coriaceus, under field and laboratory conditions. When offered a choice of permethrin-treated (5.7-12.8 .mu.g AI/cm2) vs. untreated cotton surfaces to crawl on, most individuals of both ticks gravitated toward the untreated surface within 1-2 min. This apparent initial repellency wore off gradually (8-15 min) in D. occidentalis and more rapidly (4-8 min) in O. coriaceus. Exposure of D. occidentalis to cotton surfaces treated with .apprx. 3.8-5.4 .mu.g AI/cm2 for 75 s caused 92% and 100% morbidity/mortality within 1 and 22 h; exposure of O. coriaceus to similar concentrations for only 45 s produced 48% and 100% morbidity/mortality within 1 and 24 h. A comparison of the number of D. occidentalis ticks collected from humans wearing treated vs. untreated overalls as they walked through tick-infested chaparral-grassland revealed that 14% fewer ticks were found on the treated clothing, but this difference was not significant. The difference in the morbidity/mortality 1 day later of ticks removed from the treated and untreated overalls (60% vs. 3%) was highly significant. When D. occidentalis adults (n = 40) were placed on the midshin region of untreated overalls (worn by standing subjects) or those containing < 3 .mu.g permethrin/cm2, 35-45% of the ticks crawled up to various points between the knee and waistline within 15 min, and all were still healthy 1 h later. In contrast, 90% of the adults (n = 20) similarly placed on overalls treated with 4 .mu.g AI/cm2 did not crawl up to the knee or beyond within 15 min, and 94% (n = 18) were morbid 1 h later. Preliminary attempts to determine the effectiveness of permethrin for personal protection against O. coriaceus ticks under field conditions were unsuccessful, apparently because of unfavorable weather conditions.

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