Effectiveness of residual spraying of peridomestic ecotopes with deltamethrin and permethrin on Triatoma infestans in rural western Argentina: a district-wide randomized trial

Fil: Gürtler, Ricardo E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Laboratorio de Ecología General; Argentina. ; Fil: Canale, Delmi M. Coordinación Nacional de Control de Vectores; Argentina. ; Fil: Spillmann, Cynthia. Coordinación Nacional de Control de Vectores; Argentina. ; Fil: Stariolo, Raúl. Coordinación Nacional de Control de Vectores; Argentina. ; Fil: Salomón, Oscar D. ANLIS Dr.C.G.Malbrán. Centro Nacional de Diagnóstico e Investigación de Endemo-Epidemias; Argentina. ; Fil: Blanco, Sonia. Coordinación Nacional de Control de Vectores; Argentina. ; Fil: Segura, Elsa L. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Parasitología; Argentina. ; Objective: To compare the effectiveness of a single residual spraying of pyrethroids on the occurrence and abundance of Triatoma infestans in peridomestic ecotopes in rural La Rioja. Methods: A total of 667 (32.8%) peridomestic sites positive for T. infestans in May 1999 were randomly assigned to treatment within each village, sprayed in December 1999, and reinspected in December 2000. Treatments included 2.5% suspension concentrate (SC) deltamethrin in water at 25 mg active ingredient (a.i.)/m(2) applied with: (a) manual compression sprayers (standard treatment) or (b) power sprayers; (c) 1.5% emulsifiable concentrate (EC) deltamethrin at 25 mg a.i./m(2); and (d) 10% EC cis-permethrin at 170 mg a.i./m(2). EC pyrethroids were diluted in soybean oil and applied with power sprayers. All habitations were sprayed with the standard treatment. Findings: The prevalence of T. infestans 1-year post-spraying was significantly lower in sites treated with SC deltamethrin applied with manual (24%) or power sprayers (31%) than in sites treated with EC deltamethrin (40%) or EC permethrin (53%). The relative odds of infestation and catch of T. infestans 1-year post-spraying significantly increased with the use of EC pyrethroids, the abundance of bugs per site before spraying, total surface, and host numbers. All insecticides had poor residual effects on ...