Effects of permethrin-treated screens on phlebotomine sand flies, with reference to Phlebotomus martini (Diptera: Psychodidae)

Effects of permethrin-treated screens on the sand fly, Phlebotomus martini Parrot, a vector of visceral leishmaniasis in Kenya, were evaluated after the eighth treatment. Screens treated with 0.50 g/m2 of permethrin 20% emulsifiable concentrate were fitted inside houses and re-treated every 6 mo from August 1989 to December 1993. Before application of the treated screens, a geometric mean of 0.83 P. martini were collected per trap night inside houses, whereas after the eighth treatment only 0.05 sand flies were caught. P. martini abundance was reduced by 88.8%. Analysis of the effects of treated screens on the total sand fly population (all species) indicated that 1.79 sand flies were collected per night per house before deployment of treated screens, whereas 0.16 flies were caught after the eighth treatment. The percentage of sand fly reduction inside treated houses increased with successive treatment of the screens, and a reduction of 81.4% was observed after the eighth treatment. Permethrin-treated screens did not reduce the sand fly engorgement rate inside houses.