RESUMO
BACKGROUND: A treated fabric device for emanating the volatile pyrethroid transfluthrin was recently developed in Tanzania that protected against night-biting Anopheles and Culex mosquitoes for several months. Here perceptions of community end users provided with such transfluthrin emanators, primarily intended to protect them against day-active Aedes vectors of human arboviruses that often attack people outdoors, were assessed in Port-au-Prince, Haiti. METHODS: Following the distribution of transfluthrin emanators to participating households in poor-to-middle class urban neighbourhoods, questionnaire surveys and in-depth interviews of end-user households were supplemented with conventional and Photovoice-based focus group discussions. Observations were assessed synthetically to evaluate user perceptions of protection and acceptability, and to solicit advice for improving and promoting them in the future. RESULTS: Many participants viewed emanators positively and several outlined various advantages over current alternatives, although some expressed concerns about smell, health hazards, bulkiness, unattractiveness and future cost. Most participants expressed moderate to high satisfaction with protection against mosquitoes, especially indoors. Protection against other arthropod pests was also commonly reported, although satisfaction levels were highly variable. Diverse use practices were reported, some of which probably targeted nocturnal Culex resting indoors, rather than Aedes attacking them outdoors during daylight hours. Perceived durability of protection varied: While many participants noted some slow loss over months, others noted rapid decline within days. A few participants specifically attributed efficacy loss to outdoor use and exposure to wind or moisture. Many expressed stringent expectations of satisfactory protection levels, with even a single mosquito bite considered unsatisfactory. Some participants considered emanators superior to fans, bedsheets, sprays and coils, but it is concerning that several preferred them to bed nets and consequently stopped using the latter. CONCLUSIONS: The perspectives shared by Haitian end-users are consistent with those from similar studies in Brazil and recent epidemiological evidence from Peru that other transfluthrin emanator products can protect against arbovirus infection. While these encouraging sociological observations contrast starkly with evidence of essentially negligible effects upon Aedes landing rates from parallel entomological assessments across Haiti, Tanzania, Brazil and Peru, no other reason to doubt the generally encouraging views expressed herein by Haitian end users could be identified.
Assuntos
Ciclopropanos , Fluorbenzenos , Controle de Mosquitos , Haiti , Animais , Humanos , Controle de Mosquitos/métodos , Feminino , Masculino , Inseticidas , Adulto , Mosquitos Vetores , Aedes/efeitos dos fármacos , Pessoa de Meia-Idade , Inquéritos e Questionários , Anopheles/efeitos dos fármacos , Culex/efeitos dos fármacosRESUMO
BACKGROUND: A simple treated fabric device for passively emanating the volatile pyrethroid transfluthrin was recently developed in Tanzania that protected against nocturnal Anopheles and Culex mosquitoes for several months. Here these transfluthrin emanators were assessed in Port-au-Prince, Haiti against outdoor-biting Aedes. METHODS: Transfluthrin emanators were distributed to participating households in poor-to-middle class urban neighbourhoods and evaluated once every two months in terms of their effects on human landing rates of wild Aedes populations. A series of three such entomological assessment experiments were conducted, to examine the influence of changing weather conditions, various transfluthrin formulations and emanator placement on protective efficacy measurements. Laboratory experiments assessed resistance of local Aedes aegypti to transfluthrin and deltamethrin, and the irritancy and repellency of the transfluthrin-treated fabric used in the field. RESULTS: Across all three entomological field assessments, little evidence of protection against wild Ae. aegypti was observed, regardless of weather conditions, transfluthrin formulation or emanator placement: A generalized linear mixed model fitted to the pooled data from all three assessment rounds (921 females caught over 5129 hours) estimated a relative landing rate [95% Confidence interval] of 0.87 [0.73, 1.04] for users of treated versus untreated emanators (P = 0.1241). Wild Ae. aegypti in this setting were clearly resistant to transfluthrin when compared to a fully susceptible colony. CONCLUSIONS: Transfluthrin emanators had little if any apparent effect upon Aedes landing rates by wild Ae. aegypti in urban Haiti, and similar results have been obtained by comparable studies in Tanzania, Brazil and Peru. In stark contrast, however, parallel sociological assessments of perspectives among these same end-users in urban Haitian communities indicate strong satisfaction in terms of perceived protection against mosquitoes. It remains unclear why the results obtained from these complementary entomological and sociological assessments in Haiti differ so much, as do those from a similar set of studies in Brazil. It is encouraging, however, that similar contrasts between the entomological and epidemiological results of a recent large-scale assessment of another transfluthrin emanator product in Peru, which indicate they provide useful protection against Aedes-borne arboviral infections, despite apparently providing only modest protection against Aedes mosquito bites.
Assuntos
Aedes , Ciclopropanos , Fluorbenzenos , Inseticidas , Controle de Mosquitos , Animais , Aedes/efeitos dos fármacos , Ciclopropanos/farmacologia , Haiti , Controle de Mosquitos/métodos , Humanos , Inseticidas/farmacologia , Feminino , Piretrinas/farmacologia , Mosquitos Vetores/efeitos dos fármacos , Resistência a Inseticidas , Mordeduras e Picadas de Insetos/prevenção & controle , Nitrilas/farmacologia , Características da Família , Repelentes de Insetos/farmacologiaRESUMO
Vector control is a key means of combating mosquito-borne diseases and the only tool available for tackling the transmission of dengue, a disease for which no vaccine, prophylaxis, or therapeutant currently exists. The most effective mosquito control methods include a variety of insecticidal tools that target adults or juveniles. Their successful implementation depends on impacting the largest proportion of the vector population possible. We demonstrate a control strategy that dramatically improves the efficiency with which high coverage of aquatic mosquito habitats can be achieved. The method exploits adult mosquitoes as vehicles of insecticide transfer by harnessing their fundamental behaviors to disseminate a juvenile hormone analogue (JHA) between resting and oviposition sites. A series of field trials undertaken in an Amazon city (Iquitos, Peru) showed that the placement of JHA dissemination stations in just 3-5% of the available resting area resulted in almost complete coverage of sentinel aquatic habitats. More than control mortality occurred in 95-100% of the larval cohorts of Aedes aegypti developing at those sites. Overall reductions in adult emergence of 42-98% were achieved during the trials. A deterministic simulation model predicts amplifications in coverage consistent with our observations and highlights the importance of the residual activity of the insecticide for this technique.
Assuntos
Aedes/efeitos dos fármacos , Dengue/prevenção & controle , Ecossistema , Insetos Vetores/efeitos dos fármacos , Hormônios Juvenis/toxicidade , Metamorfose Biológica/efeitos dos fármacos , Controle de Mosquitos/métodos , Aedes/ultraestrutura , Animais , Simulação por Computador , Inseticidas , Microscopia Eletrônica de Varredura , Modelos Biológicos , PeruRESUMO
Sub-Saharan Africa has long suffered under the yoke of the Anopheles gambiae mosquito, but for northeast Brazil (figure 1) its arrival over 60 years ago was a new and horrifying experience. This African mosquito is an exceptionally effective malaria vector because it is well adapted to feeding upon people and to exploiting aquatic habitats associated with our daily activities. Anopheles gambiae sensu lato probably accounts for most of the world's malaria deaths and socioeconomic burden. Fortunately, the Brazilian experience had a happy ending. The prospect of A gambiae spreading across much of the Americas motivated a ruthlessly effective response that deserves a special and heroic place in the annals of public health. Building on the successes and infrastructure of the Yellow Fever Service for Aedes aegypti elimination, the Rockefeller Foundation and Brazilian government collaborated to form a new Malaria Service of the Northeast. This new entity rolled the invader back into oblivion with an aggressive eradication campaign, focusing primarily upon larviciding of all potential habitats. The driving force of this endeavour was an enigmatic man called Fred Soper whose sheer will and determination was a key element in this success, and a source of inspiration today (see Killeen GF, et al. Eradication of Anopheles gambiae from Brazil: lessons for malaria control in Africa? Lancet Infect Dis 2002; 2: 618-27). I recently took an opportunity to fulfil a long-held dream and follow in some of Soper's footsteps. Tired of gazing at yellowing maps like figure 1, I went to see the northeast of Brazil for myself.
Assuntos
Surtos de Doenças/história , Malária/história , Controle de Mosquitos/história , Animais , Anopheles , Brasil/epidemiologia , Surtos de Doenças/prevenção & controle , História do Século XX , Humanos , Insetos Vetores , Malária/epidemiologia , Malária/transmissãoRESUMO
Current malaria-control strategies emphasise domestic protection against adult mosquitoes with insecticides, and improved access to medical services. Malaria prevention by killing adult mosquitoes is generally favoured because moderately reducing their longevity can radically suppress community-level transmission. By comparison, controlling larvae has a less dramatic effect at any given level of coverage and is often more difficult to implement. Nevertheless, the historically most effective campaign against African vectors is the eradication of accidentally introduced Anopheles gambiae from 54000 km(2) of largely ideal habitat in northeast Brazil in the 1930s and early 1940s. This outstanding success was achieved through an integrated programme but relied overwhelmingly upon larval control. This experience was soon repeated in Egypt and another larval control programme successfully suppressed malaria for over 20 years around a Zambian copper mine. These affordable approaches were neglected after the advent of dichlorodiphenyl trichloroethane (DDT) and global malaria-control policy shifted toward domestic adulticide methods. Larval-control methods should now be re-prioritised for research, development, and implementation as an additional way to roll back malaria.