Ovicidal effect of monoterpenoids against permethrin-resistant human head louse (Phthiraptera: Pediculidae)

TOLOZA AC, VASSENA C AND PICOLLO MI

Durban, Sudáfrica

Congreso; XXIII International Congress of Entomology; 2008

Introduction. The human head louse Pediculus humanus capitis De Geer is an important cosmopolitan pest affecting school-aged children. Previous works of our laboratory have detected populations in Buenos Aires with high resistance levels to pyrethroids in both adult and egg stages (RR>80). In the search of new insecticides, monoterpenoids seem to be good control alternative candidates because they are environmental friendly and not acutely toxic to mammals. The purposes of this work were to describe a methodology employed to detect the ovicidal effect of 23 monoterpenoids against P.h.capitis from Buenos Aires, and to compare it with the activity previously reported on adults. Methods. Eggs were collected from heads of children 5-12 yr old, using an antilouse comb. Groups of 15-20 late development eggs were exposed to the vapours of the evaluated monoterpenoids in an enclosed chamber. The number of emerged nymphs was counted, and those with incomplete emergence were considered as dead. Results. There were highly significant differences among the evaluated monoterpenoids (p<0.0001). Ten of the monoterpenoids gave mortality above 80%. The most effective monoterpenoids were hydrocarbons and ethers, followed by ketones, alcohols, phenols and esters. Regression analysis revealed a statistically significant relationship between ovicidal mortality and adulticidal knockdown of the same evaluated monoterpenoids at the 99% confidence level. Conclusion. This study indicates that those components that were lethal to eggs were also effective against adults. The potential use of new pediculicide formulations based on monoterpenoids is discussed.