Evaluación de la actividad tóxica de los insecticidas piretroides deltametrina y lambdacihalotrina en dos poblaciones de campo de Rhodnius pallescens (Hemíptera: Reduviidae) de Panamá

Abstract

Introducción. La evaluación de la sensibilidad de las poblaciones de Rhodnius pallescens permite detectar y vigilar los grados de resistencia en el transcurso del tiempo, con el fin de evaluar los efectos de las estrategias de control y manejo de la resistencia. Objetivo. Determinar la línea base de sensibilidad de los principios activos deltametrina y lambdacihalotrina en ninfas de estadios I y V, en dos poblaciones de campo de R. pallescens. Materiales y métodos. Los bioensayos se realizaron tomando como referencia el protocolo estandarizado de aplicación tópica para R. prolixus y adaptado para R. pallescens. Resultados. Con la aplicación tópica del insecticida lambdacihalotrina en ninfas de estadio I en R. pallescens (Chilibre) y R. pallescens (Cerro Cama), los valores de la dosis letal 50 (DL 50 ) expresados en nanogramos por insecto fueron de DL 50 =0,129 y DL 50 =0,109, respectivamente. En ninfas de estadio V los valores fueron de DL 50 =1,712 y DL 50 =3,478, respectivamente. Por su parte, la aplicación tópica de deltametrina en ninfas de estadio I, registró valores de DL 50 =0,022 y DL 50 =0,021 y, en ninfas de estadio V, de DL 50 =2,110 y DL 50 =1,548. Conclusiones. En ninfas de estadios I y V de ambas poblaciones de R. pallescens, se observó mediante los valores obtenidos de factor de resistencia que no existen ninguna diferencia significativa en el efecto tóxico de los insecticidas estudiados. Esto permite establecer que las dos cepas de R. pallescens son sensibles a los insecticidas deltametrina y lambdacihalotrina.Palabras clave: Rhodnius, insecticidas/toxicidad, resistencia a los insecticidas, enfermedad de Chagas, Panamá.Evaluation of the toxic activity of the pyrethroid insecticides deltamethrin and lambdacyhalothrin in two Panamanian field populations of Rhodnius pallescens (Hemíptera: Reduviidae) Introduction. Systematic evaluation of the susceptibility of disease vectors to insecticides permits the detection of the development of insecticide resistance over time. This is necessary to evaluate the effectiveness of control methods and to plan management strategies of the resistance. Objective. The baseline susceptibility was determined for I and V instar nymphs of Rhodnius pallescens to the active ingredients of the insecticides deltamethrin and lambdacyhalothrin. Materials and methods. The bioassays were applied to two field populations of R. pallescens collected in Chilibre and Cerro Cama, Panamá. A standard protocol for topical application was adapted from that developed for Rhodnius prolixus. Bioassays were performed using topical applications on the dorsal abdominal surface, with volumes of 0.1 μl and 0.5 μl acetone solution of insecticide for nymphs of stage I and V respectively, using 5 μl and 25 μl Hamilton microsyringes with a repeating dispenser. Ten nymphs were used for each insecticide concentration. Results. With the topical application of lambdacyhalothrin on first-instar nymphs from Chilibre and Cerro Cama, the LD 50 values expressed in ng/insect were 0.13 and 0.11 respectively. In...

American trypanosomiasis, or Chagas disease, in Panama: a chronological synopsis of ecological and epidemiological research

“…Although the inattention to CHD by MINSA is likely due to the enzootic epidemiologic characteristic and chronic nature of CHD [ 2 ], some researchers attribute it to a significant degree of underreporting, and to the non-domiciliary behavior of R. pallescens in Panama [ 101 , 103 ]. For instance, Panamanian populations of R. pallescens are highly susceptible to deltamethrin and lambda-cyhalothrin, but it is impractical to implement pyrethroid residual spraying to kill a vector that does not reside indoors [ 113 ]. CHD prevention and control programs in Panama must focus on putting into action an active surveillance program for accurate case detection.…”

Insecticidal action of synthetic girgensohnine analogues and essential oils on Rhodnius prolixus (Hemiptera: Reduviidae)

“…As other authors have mentioned,differences in cuticle thickness (29) in stage I and V nymphs can affect the susceptibility to external stimuli; for instance, Reyes, et al (30), observed that the pyrethroid insecticides (beta-cypermethrin and fenitrothion) were more effective in stage I T. dimidiata and T. maculata nymphs than in stage V ones. Cáceres, et al (31), found that stage I R. pallescens nymphs were sensitive to deltamethrin and lambda-cyhalothrin in different geographical zones. In another study, Germano found similar results (23) in toxicity bioassays with deltamethrin in different stages of development in T. infestans.…”