Long-term acceptability, durability and bio-efficacy of ZeroVector(®) durable lining for vector control in Papua New Guinea

This study examined the acceptability, durability and bio-efficacy of pyrethroid-impregnated durable lining (DL) over a three-year period post-installation in residential homes across Papua New Guinea (PNG).; ZeroVector(®) ITPS had previously been installed in 40 homes across four study sites representing a cross section of malaria transmission risk and housing style. Structured questionnaires, DL visual inspections and group interviews (GIs) were completed with household heads at 12- and 36-months post-installation. Three DL samples were collected from all households in which it remained 36-months post-installation to evaluate the bio-efficacy of DL on Anopheles mosquitoes. Bio-efficacy testing followed WHO guidelines for the evaluation of indoor residual spraying.; The DL was still intact in 86 and 39% of study homes at the two time periods, respectively. In homes in which the DL was still intact, 92% of household heads considered the appearance at 12-months post installation to be the same as, or better than, that at installation compared to 59% at 36-months post-installation. GIs at both time points confirmed continuing high acceptance of DL, based in large part of the perceived attractiveness and functionality of the material. However, participants frequently asserted that they, or their family members, had ceased or reduced their use of mosquito nets as a result of the DL installation. A total of 16 houses were sampled for bio-efficacy testing across the 4 study sites at 36-months post-installation. Overall, combining all sites and samples, both knock-down at 30 min and mortality at 24 h were 100%.; The ZeroVector(®) DL installation remained highly acceptable at 36-months post-installation, the material and fixtures proved durable and the efficacy against malaria vectors did not decrease. However, the DL material had been removed from over 50% of the original study homes 3 years post-installation, largely due to deteriorating housing infrastructure. Furthermore, the presence of the DL installation appeared to reduce ITN use among many participating householders. The study findings suggest DL may not be an appropriate vector control method for large-scale use in the contemporary PNG malaria control programme

Infectivity of Symptomatic Malaria Patients to Anopheles farauti Colony Mosquitoes in Papua New Guinea

Plasmodium transmission from humans to mosquitoes is an understudied bottleneck in the transmission of malaria. Direct membrane feeding assays (DMFA) allow detailed malaria transmission studies from humans to mosquitoes. Especially for Plasmodium vivax, which cannot be cultured long-term under laboratory conditions, implementation of DMFAs requires proximity to P. vivax endemic areas. In this study, we investigated the infectivity of symptomatic Plasmodium infections to Anopheles farauti colony mosquitoes in Papua New Guinea (PNG). A total of 182 DMFAs were performed with venous blood collected from rapid diagnostic test (RDT) positive symptomatic malaria patients and subsequently analysed by light microscopy and quantitative real time polymerase chain reaction (qPCR). DMFAs resulted in mosquito infections in 20.9% (38/182) of cases. By light microscopy and qPCR, 10 – 11% of P. falciparum and 32 – 44% of P. vivax positive individuals infected An. farauti. Fifty-eight percent of P. vivax and 15% of P. falciparum gametocytaemic infections infected An farauti

Community end user perceptions of hessian fabric transfluthrin vapour emanators for protecting against mosquitoes under conditions of routine use in Port-au-Prince, Haiti

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

Distribution nationale de moustiquaires imprégnées d'insecticide au Niger : effets sur les anophèles vecteurs

A nationwide long-lasting insecticide-treated bed nets distribution targeting most vulnerable people was implemented throughout Niger in 2005. This malaria control tool is known for its efficiency in small scale pilot studies, however it is important to evaluate the effects of large operational programmes that are implemented in Africa. Noteworthy, few data are published on anopheline vector populations modification following such programmes. We performed entomological studies that included mosquito collections in sentinel sites accross the Sahelian zone of Niger during three transmission seasons, one control period before intervention and two after. Entomological parameters of malaria transmission were evaluated and the distribution of the two major vectors, An. gambiae and An. arabiensis, was determined. The temporal follow-up has shown a global decrease of malaria transmission level that may have resulted from the increase of pyrethroid treated nets use. The study of the kdr mutation however showed a rise of pyrethroid resistance in An. gambiae populations. This increase could lead in the near future to lower the efficiency of such nets as a major tool in malaria control strategies. The genetic structure of An. gambiae and An. arabiensis populations, studied with microsatellites markers, was highly homogenous in space between villages, and time, bewteen 2005 and 2006 transmission seasons. These results suggest that the net distribution did not impact significantly the genetic diversity and structure of vector populations in a single year. The low genetic differentiation among samples, within both species, indicated high gene flow across the area. This hypothesis is sustained by the fast expansion of the kdr mutation where An. gambiae is present, probably due to dispersion of adults. The evaluation of such control programmes will allow to identify potential improvements that could keep the efficiency of pyrethroids, the only insecticide class currently available for nets treatment.Une distribution nationale de moustiquaires imprégnées d'insecticide à longue durée d'action à destination des populations vulnérables du Niger a été effectuée fin 2005. Déjà montrée lors d'études pilotes à l'échelle du village, l'efficacité de cet outil dans le contrôle du paludisme restait à évaluer à l'occasion de vastes programmes opérationnels qui se multiplient en Afrique. Peu d'études des populations de vecteurs ont été publiées dans ce cadre. Nous avons mis en place un suivi entomologique au niveau de sites sentinelles répartis dans la zone Sahélienne du Niger, ayant couvert trois saisons de transmission, dont une avant intervention considérée comme période contrôle. Les paramètres entomologiques de la transmission ont été déterminés pour An. gambiae s.l., et la distribution spatiale des deux principaux vecteurs, An. gambiae et An. arabiensis, a été précisée. Le suivi temporel a mis en évidence une baisse globale du niveau de transmission de P. falciparum, probablement entrainée par la forte hausse d'utilisation de moustiquaires imprégnées. Cependant la hausse de la résistance des populations aux pyréthrinoïdes semble avoir été rapidement amorcée faisant craindre à moyen terme une perte d'efficacité de cet outil central des stratégies de lutte contre le paludisme. L'étude de la structure génétique des populations d'An. gambiae et d'An. arabiensis à l'aide de marqueurs microsatellites a montré une homogénéité génétique dans l'espace, entre les villages, même séparés par plusieurs centaines de kilomètres, ainsi que dans le temps, entre la saison de transmission 2005 contrôle et la saison 2006 après distribution. Ces résultats ont suggéré qu'au cours de la première année d'intervention, la couverture en moustiquaires imprégnées atteinte n'a pas eu d'effet de masse suffisant pour entrainer une baisse de la diversité génétique ou une modification des fréquences alléliques des populations. La faible différenciation spatiale observée pourrait être expliquée par des échanges de gènes importants à l'intérieur de la zone d'étude, hypothèse appuyée par l'expansion rapide de la mutation kdr dans l'ensemble des sites où An. gambiae est présent. L'évaluation rigoureuse de tels programmes de contrôle permettra d'améliorer les outils de contrôle et par exemple de préserver l'efficacité des pyréthrinoïdes, seule classe d'insecticides actuellement disponible pour l'imprégnation des moustiquaires

Distribution nationale de moustiquaires imprégnées d'insecticide au Niger (effets sur les anophèles vecteurs)

Une distribution nationale de moustiquaires imprégnées d'insecticide à longue durée d'action à destination des populations vulnérables du Niger a été effectuée fin 2005. L'efficacité de cet outil dans le contrôle du paludisme a été montrée lors d'études pilotes à l'échelle du village, mais il est important d'évaluer les modifications causées par les vastes programmes opérationnels se mutlipliant en Afrique. Peu d'études des populations de vecteurs ont en particulier été publiées dans ce cadre. Nous avons mis en place un suivi entomologique au niveau de sites sentinels répartis dans la zone Sahélienne du Niger, ayant couvert trois saisons de transmission, dont une avant intervention considérée comme période contrôle. Les paramètres entomologiques de la transmission ont été déterminés pour An. gambiae s.l., et la distribution spatiale des deux principaux vecteurs, An. gambiae et An. arabiensis, a été précisée. Le suivi temporel a mis en évidence une baisse globale du niveau de transmission de P. falciparum, probablement entrainée par la forte hausse d'utilisation de moustiquaires imprégnées. Cependant la hausse de la résistance des populations aux pyréthrinoïdes semble avoir été rapidement amorcée faisant craindre à moyen terme une perte d'efficacité de cet outil central des stratégies de lutte contre le paludisme. L'étude de la structure génétique des populations d'An. gambiae et d'An. arabiensis à l'aide de marqueurs microsatellites a montré une homogénéïté génétique dans l'espace, entre les villages, même séparés par plusieurs centaines de kilomètres, ainsi que dans le temps, entre la saison de transmission 2005 contrôle et la saison 2006 après distribution. Ces résultats ont suggéré qu'au cours de la première année d'intervention, la couverture en moustiquaires imprégnées atteinte n'a pas eu d'effet de masse suffisant pour entrainer une baisse de la diversité génétique ou une modification des fréquences allèliques des populations. La faible différenciation spatiale observée pourrait être expliquée par des échanges de gènes importants à l'intérieur de la zone d'étude, hypothèse appuyée par l'expansion rapide de la mutation kdr dans l'ensemble des sites où An. gambiae est présent. L'évaluation de tels programmes de contrôle permettra d'identifier des améliorations possibles et d'optimiser la durée de vie des pyréthrinoïdes, seule classe d'insecticides actuellement disponible pour l'imprégnation des moustiquaires.A nationwide long-lasting insecticide-treated bed nets distribution targeting most vulnerable people was implemented throughout Niger in 2005. This malaria control tool is known for its efficiency in small scale pilot studies, however it is important to evaluate the effects of large operational programmes that are organized in Africa. Noteworthy, few data are published on anopheline vector populations modification following such programmes. We performed entomological studies that included mosquito collections in sentinel sites accross the Sahelian zone of Niger during three transmission seasons, one control period before intervention and two after. Entomological parameters of malaria transmission were evaluated and the distribution of the two major vectors, An. gambiae and An. arabiensis, was determined. The temporal follow-up has shown a global decrease of malaria transmission level that may have resulted from the increase of pyrethroid treated nets use. The study of the kdr mutation however showed a rise of pyrethroid resistance in An. gambiae populations, that could in the near future decrease the efficiency of such nets, that are a major tool in malaria control strategies. The genetic structure of An. gambiae and An. arabiensis populations, studied with microsatellites markers, was highly homogenous in space between villages, and time, bewteen 2005 and 2006 transmission seasons. These results suggest that the net distribution did not impact significantly the genetic diversity and structure of vector populations in a single year. The low genetic differentiation among samples, within both species, indicated high gene flow across the area. This hypothesis is sustained by the fast expansion of the kdr mutation where An. gambiae is present, probably due to dispersion of adults. The evaluation of such control programmes will allow to identify potential improvements that could keep the efficiency of pyrethroids, the only insecticide class available for nets treatment.VERSAILLES-BU Sciences et IUT (786462101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Population Genetic Structure of <I>Anopheles gambiae</I> and <I>Anopheles arabiensis</I> in Niger

International audienceThe increasing usage of long-lasting insecticide-treated nets allows protection of millions of people from malaria infection. Monitoring studies should be planned during any wide-scale malaria control program integrating insecticide-treated materials, to evaluate their effects and effectiveness on epidemiologically relevant parameters. Such operational control interventions may be challenged by insecticide resistance spread within vector populations, as a result of wide insecticide pressure. A nationwide distribution of long-lasting insecticidal nets was implemented throughout Niger in 2005. We studied the population genetic structure of major malaria vectors across Nigerien Sahel, and investigated potential effects of this large malaria control intervention. Wild-caught Anopheles gambiae sensu lato females from seven villages and two wet seasons were genotyped at 12 microsatellite loci. The genetic diversity within both species appeared homogenous between villages and years. The estimated genetic differentiation among samples was very low within both species, indicating high gene flow across the area. An absence of differentiation was also found between 2005 and 2006 wet seasons, for all samples but one, showing that the net distribution did not impact significantly the genetic diversity and structure of vector populations in a single year. We provide valuable results participating to document effects of large malaria control programs, to maximize the efficiency of available tools in future interventions