EVALUATION OF DELTAMETHRIN-IMPREGNATED BEDNETS AND CURTAINS AGAINST PHLEBOTOMINE SANDFLIES IN VALLE DEL CAUCA, COLOMBIA

The effectiveness of bednets and curtains (nylon mesh 64 per cm(2)) im pregnated with deltamethrin at 26 mg a.i./m(2) in reducing the biting nuisance caused by three phlebotomine sandfly species: Lutzomyia colum biana, Lu.lichyi and the predominant Lu.youngi (Diptera: Psychodidae), was evaluated at La Guaira, a rural settlement in Valle de Cauca near Call, Colombia. Pairs of volunteers collected sandflies under impregn ated bednets, in rooms protected by impregnated curtains or in unprote cted rooms in a randomized matched design. Collections were made in th ree houses per night on three consecutive nights, so that each house w as sampled under each of the three treatments. This routine was repeat ed at 2-week intervals for 6 months. There was no significant differen ce between the overall numbers of sandflies collected in rooms with or without impregnated curtains. Only 0.14 sandflies/man-hour were caugh t on human bait under impregnated bednets, significantly fewer than th e numbers collected on human bait outside the nets in the same room (1 .91) or in unprotected rooms (3.29). In a second set of experiments ca rried out in La Guaira and the neighbouring community of Jiguales, the effect of deltamethrin impregnation was evaluated by comparing number s of sandflies collected on human bait under treated and untreated net s. Significantly fewer were collected under the impregnated nets (0.25 v. 0.69/man-hour). Wild-caught female Lu.youngi exposed to treated ne tting for 2 min in. the laboratory all died with 24 h. The impact of d eltamethrin-impregnated bednets was considered to be useful against Lu .youngi and other potential vectors of leishmaniasis in such communiti es.