Relationship between viscosity and pediculicide potency of mono-terpenoids in human lice

GALLARDO A., G. MOUGABURE CUETO & M.I. PICOLLO

Urgup, Cappadocia

Congreso; 9. Fourth International Conference on Phthiraptera (ICP4); 2010

International Society of Phthirapterists

Insect cuticle is the first barrier that insecticides should penetrate in order to produce toxic effects. The penetration rate of these compounds mainly depends on its physico-chemical properties such as molecular size, polarity, vapor pressure and viscosity. The goal of this work was to determine weather there is a relationship between viscosity and pediculicide potency of some monoterpenoids in human lice. The study was carried out on Pediculus humanus humanus males and P. humanus capitis males and females. The Lethal Dose 50% (LD50) of the monoterpenoids was determined by the topical application of 0.1 µl acetone solutions of tested compounds on each insect’s abdomen. Mortality was measured 18 hs after treatment. The viscosity of the compounds was established using a modified Ostwald viscosimeter. The relationship between viscosity and potency was evaluated by means of regression analysis. The results of these analyses showed a clear correlation between the viscosity and toxic effect of the evaluated monoterpenoids. It was a non-linear relationship which demonstrated low potency at the lowest and highest viscosity values, and the highest pediculicide potency at medium range of viscosities.