Differential application of lambda‐cyhalothrin to control the sandfly Lutzomyia longipalpis

Abstract

To study the impact of residual pyrethroid insecticide on the abundance and distribution of peridomestic Lutzomyia longipalpis, the sandfly vector of visceral leishmaniasis in Brazil, lambda-cyhalothrin was applied at 20 mg a.i.m-2 in the following interventions: (i) spraying of all animal pens in a village (blanket coverage); (ii) treatment of a subset of animal pens, either by spraying, or by installation of insecticide-impregnated 1 m2 cotton sheets as 'targets' (focal coverage). By sampling with CDC light traps, and using a novel analytical approach, we detected a 90% reduction in Lu.longipalpis abundance in sprayed sheds of the focal intervention. However, there was no discernible effect on the abundance of other phlebotomines trapped in sheds, or on the abundance of Lu.longipalpis in untreated dining-huts and houses. This differential impact on Lu.longipalpis abundance is explained in terms of the disruption of male pheromone production. Treated targets were approximately half as effective as residual spraying in reducing the abundance of Lu.longipalpis in sheds. Following blanket intervention, the abundance of Lu.longipalpis in traps fell by only 45% (not significant): catches at untreated dining-huts actually increased, possibly because the blanket coverage diverted Lu.longipalpis away from major aggregation sites at animal pens. It is recommended that care be taken during vector control programmes to ensure that all potential aggregation sites are treated. The possible consequences of leaving some sites untreated include poor control of peridomestic sandfly abundance and an increase in the biting rate on dogs and humans.

Progress in the Mathematical Modelling of Visceral Leishmaniasis

“…On the ISC, numbers are lowest in December and January, when temperatures are lowest, and typically highest in summer and the post-Monsoon period; numbers correlate positively with temperature, but correlations with rainfall are more variable (Ghosh et al, 1999;Picado et al, 2010a). In Amazon Brazil, sandfly numbers peak at the end of the dry season, and this variation in population size is reflected in a marked variation in the incidence of canine infection across the year Kelly et al, 1997). The seasonal pattern in other areas of Brazil is different, with highest numbers in the more arid NE Brazil typically occurring during or after the rainy season (Sherlock, 1996;Deane and Deane, 1962), though some areas show no clear seasonal pattern (Costa et al, 2013b).…”

Avaliação de medidas de controle de flebotomíneos no norte do Estado do Paraná, Brasil

“…In 2001 average captures in 1996-1997and 1997-1998Numerosos trabalhos de controle de flebotomíneos têm dado um enfoque para o uso de inseticidas químicos em paredes de casas e anexos (abrigos de animais, silos) 3,4,5,6,7,8,9 , em ambientes silvestres 10,11,12 e impregnados em mosquiteiros 13,14,15,16,17 . Essas medidas apesar de atrativas não são permanentes 18 , além do que, a precariedade das habitações, a descontinuidade e/ou o uso em épocas inapropriadas e os riscos ambientais advindos da aplicação de inseticidas em ambientes silvestres, constituem fatores limitantes para o controle de flebotomíneos 15,19,20,21 .…”

Lutzomyia longipalpis behavior and control at an urban visceral leishmaniasis focus in Argentina

“…Although some studies reported deltamethrin residual effects up to 9-12 months inside houses 13,19 , strong anti-feeding effects when applied to dogs as collars or topically, and repellent effects in impregnated bednets 7,8,9 , and pyrethroids as lambdacyalothrin reducing impact on Lu. longipalpis sand fly captures after focal or indoor applications 14,18 , there are many reports about the short or transient effects of fenitrothion 14 , cypermethrin 12 and deltamethrin as peridomestic sprayed insecticide 1,13,22,36 . Unfortunately the effects of insecticides for longer periods than 14 days could not be assessed in this study due to an abrupt change in the weather conditions that reduced the population; both in the intervention and the control group, but the results obtained were consistent with the literature.…”