Experimental hut to study the indoor behaviour and effects of insecticide-treated bednets on phlebotomine sand flies (Diptera: Psychodidae)

Abstract

BACKGROUNDBehavioural effects of insecticides on endophagic phlebotomine sand fly vectors of Leishmania are poorly understood mainly because of the lack of an experimental hut (EH) in which to study them.OBJECTIVE To build an EH to evaluate the effects of long-lasting insecticide-treated nets (LLINs) on Lutzomyia longiflocosa.METHODS The study had two phases: (1) Laboratory experiments using tunnel tests to select the traps for the EH; and (2) EH construction and evaluation of the effects of deltamethrin and lambda-cyhalothrin LLINs on L. longiflocosa females inside the EH.FINDINGS Phase 1: The horizontal-slit trap was the best trap. This trap collected the highest percentage of sand flies, and prevented them from escaping. Therefore, this trap was used in the EH. Phase 2: The main effects of LLINs on L. longiflocosa in the EH were: landing inhibition, inhibition from entering the bednet, induced exophily, and high mortality (total and inside exit traps).CONCLUSIONS The EH was effective for evaluating the effects of LLINs on endophagic sand flies. Although both types of LLINs showed high efficacy, the lambda-cyhalothrin-treated LLIN performed better. This is the first report of induced exophily in sand flies.

Efficacy of factory-treated and dip-it-yourself long lasting insecticide-treated bednets against cutaneous leishmaniasis vectors in the sub-Andean region of Colombia: results after two years of use

“…The mortality of L. longiflocosa females at 24 h post-exposure in an experimental hut with deltamethrin LLINs or DIY lambda-cyhalothrin LLINs was very high, 82.6% and 78.8%, respectively, compared with 4.7% in the control. (24) Comparable results were found in a field study with deltamethrin CITNs (25%) in Brazil, where the mortality of L. longipalpis at 24 h outside the net was 67.7%, compared with 0.4% in the control. (25) (ii) The LLINs caused induced exophily.…”

“…In the same study with experimental huts, although not significant, there was an apparent reduction in the number of L. longiflocosa entering the huts, from 74 sand flies/night in the control to 52.6 and 43.1 sand flies/night in the deltamethrin LLIN huts and DIY lambda-cyhalothrin LLIN huts, respectively. (24) The reduction in sand fly density collected by the CDC light traps must reflect a reduction in the L. longiflocosa biting rate on humans in both LLINs, as it has been shown that there were no differences in the ratio of CDC light trap:human bait when CITNs were compared with control houses for this sand fly species in the same study area. (4) Few studies have been performed regarding the efficacy, either at the household level or in large-scale interventions at the community level, of LLINs against vectors of leishmaniases, and studies related to CL are scarce.…”

“…A previous study with experimental huts found a significant increase in the proportion, 35.8% and 19.5%, respectively, of L. longiflocosa trapped in exit traps of the huts with DIY lambda-cyhalothrin LLIN and deltamethrin LLIN compared with control (6.3%). (24) (iii) A deterrent effect cannot be discarded. In the same study with experimental huts, although not significant, there was an apparent reduction in the number of L. longiflocosa entering the huts, from 74 sand flies/night in the control to 52.6 and 43.1 sand flies/night in the deltamethrin LLIN huts and DIY lambda-cyhalothrin LLIN huts, respectively.…”

Efecto de toldillos tratados industrial o manualmente con insecticidas de larga duración, en el control vectorial de la leishmaniasis cutánea en la Región Subandina de Colombia

“…Durante los dos años que duró la evaluación pos-intervención se recolectaron en el intradomicilio un total de 5653 hembras de L. longiflocosa, en un total de 377 recolecciones. La densidad total pos-intervención en el intradomicilio se redujo de 15,5 (12,6 -19,2) h/trampa CDC/noche (Total = 3449 hembras) en el control a 5,6 (4,6 -6,7) h/trampa CDC/noche (Total = 1152 hembras) en el tratamiento con el TILD Icon Maxx y a 4,7 (3,7 -5,9) Cedral (Ne) 12,6 (9,7 -16,3) Las Juntas (Ri) 13,7 (3,8 -44,4) Las Pavas (Ca) 10, estadísticamente significativas (F (2,11) = 45,1138, p < 0,001). La reducción en la densidad de hembras tanto en el Icon Maxx como en el Permanet fue significativa comparada con el control (z = -8,80, p < 0,001 y z = -8,82, p < 0,001, respectivamente), pero no entre los dos TILD (z = 0,37, p = 0,711).…”

“…x 2 = 0,178 p = 0,915 hembras/trampa/noche, seguida por el control, 40,6 (17,3 -93,8) hembras/trampa/noche y por último el Icon Maxx,6,2 (0,8) hembras/trampa/noche, estas diferencias fueron estadísticamente significativas (F (2,14) = 27,570, p < 0,001). Por lo anterior, a continuación se comparan las densidades de L. longiflocosa pos-intervención, total y para cada momento de evaluación, con las densidades pre-intervención mediante la razón: PGW pos-intervención/PGW pre-intervención (PGW pos/pre).…”