Evaluation de la protection personnelle contre les Anophelinae par utilisation de moustiquaires détériorées imprégnées de répulsifs

L’efficacité de moustiquaires détériorées imprégnées avec des répulsifs (DEET et KBR 3023) ou avec la perméthrine a été évaluée dans la protection contre Anopheles gambiae s.l. L’étude a été conduite dans le village de Goden près de Ouagadougou. Les moustiquaires ont été installées dans des cases sélectionnées dans le village et les moustiques ont été échantillonnés à l’aide de pièges lumineux CDC, de captures manuelles et de pièges à sortie. Les résultats montrent que le nombre de moustiques capturé ainsi que leur état physiologique varie selon le traitement et le degré de détérioration de la moustiquaire. La réduction de l’agressivité exprimée par les moustiques gorgés est plus importante avec le DEET et le KBR 3023 qu’avec la perméthrine (57%, 76% et 43% respectivement). Ce résultat est observé pour une surface de détérioration égale à 0,1% et une tendance similaire est observée à 1% de surface de détérioration. L’efficacité des moustiquaires varie en fonction de la case, de la surface de détérioration et du temps après imprégnation de la moustiquaire. Le KBR 3023 procure la meilleure protection par rapport aux autres traitements et même par rapport à la moustiquaire intacte lorsque la surface de détérioration est faible (0,1%). L’utilisation des répulsifs en imprégnation pourrait accroître l’efficacité des moustiquaires usagées.Mots clés: DEET, KBR 3023, Perméthrine, fraction agressive, rémanence, moustiquaires endommagées &#160

Child mortality in a West African population protected with insecticide-treated curtains for a period of up to 6 years

Objectives To determine the impact of insecticide-treated curtains (ITC) on all-cause child mortality (6–59 months) over a period of six years. To determine whether initial reductions in child mortality following the implementation of ITC are sustained over the longer term or whether “delayed” mortality occurs. Methods A rural population of ca 100 000 living in an area with high, seasonal Plasmodium falciparum transmission was studied in Burkina Faso. Annual censuses were conducted from 1993 to 2000 to measure child mortality. ITC to cover doors, windows, and eaves were provided to half the population in 1994 with the remainder receiving ITC in 1996. Curtains were re-treated or, if necessary, replaced annually. Findings Over six years of implementation of ITC, no evidence of the shift in child mortality from younger to older children was observed. Estimates of the reduction in child mortality associated with ITC ranged from 19% to 24%. Conclusions In our population there was no evidence to suggest that initial reduction in child mortality associated with the introduction of insecticide-treated materials was subsequently compromised by a shift in child mortality to older-aged children. Estimates of the impact of ITC on child mortality in this population range from 19% to 24%. Keywords Malaria/epidemiology/mortality; Bedding and linens/utilization/statistics; Child, Preschool; Infant mortality; Plasmodium falciparum/immunology; Malaria, Falciparum/prevention and control/transmission; Anopheles; Mosquito control; Permethrin; Remission induction; Age factors; Regression analysis; Incidence; Survival rate; Randomized controlled trials; Burkina Faso/epidemiology (source: MeSH, NLM). Mots clés Paludisme/épidémiologie/mortalité; Literie et linge/utilisation/statistique; Enfant âge pré-scolaire; Mortalité nourrisson; Plasmodium falciparum/immunologie; Paludisme plasmodium falciparum/prévention et contrôle/transmission; Anophèles; Lutte contre moustique; Perméthrine; Traitement induction rémission; Facteur âge; Analyse régression; Incidence; Taux survie; Essai clinique randomisé; Burkina Faso/épidémiologie (source: MeSH, INSERM). Palabras clave Paludismo/epidemiología/mortalidad; Ropa de cama y ropa blanca/utilización/estadística; Infante; Mortalidad infantil; Plasmodium falciparum/inmunología; Paludismo falciparum/prevención y control/ transmisión; Anopheles; Control de mosquitos; Permetrina; Inducción de remisión; Factores de edad; Análisis de regresión; Incidencia; Tasa de supervivencia; Ensayos controlados aleatorios; Burkina Faso/epidemiología (fuente: DeCS, BIREME). Bulletin of the World Health Organization 2004;82:85-91

How is childhood development of immunity to Plasmodium falciparum enhanced by certain antimalarial interventions?

The development of acquired protective immunity to Plasmodium falciparum infection in young African children is considered in the context of three current strategies for malaria prevention: insecticide-impregnated bed nets or curtains, anti-sporozoite vaccines and intermittent preventive therapy. Evidence is presented that each of these measures may permit attenuated P. falciparum blood-stage infections, which do not cause clinical malaria but can act as an effective blood-stage "vaccine". It is proposed that the extended serum half-life, and rarely considered liver-stage prophylaxis provided by the anti-folate combination sulphadoxine-pyrimethamine frequently lead to such attenuated infections in high transmission areas, and thus contribute to the sustained protection from malaria observed among children receiving the combination as intermittent preventative therapy or for parasite clearance in vaccine trials

Distribution Systems of Insecticide-Treated Bed Nets for Malaria Control in Rural Burkina Faso: Cluster-Randomized Controlled Trial

BACKGROUND: Insecticide-impregnated bed nets (ITNs) have been shown to be a highly effective tool against malaria in the endemic regions of sub-Saharan Africa (SSA). There are however different opinions about the role of ITN social marketing and ITN free distribution in the roll-out of ITN programmes. The objective of this study was to evaluate the effects of free ITN distribution through antenatal care services in addition to an ITN social marketing programme in an area typical for rural SSA. METHODS: A cluster-randomised controlled ITN trial took place in the whole Kossi Province in north-western Burkina Faso, an area highly endemic for malaria. Twelve clusters were assigned to long-term ITN (Serena brand) social marketing plus free ITN (Serena brand) distribution to all pregnant women attending governmental antenatal care services (group A), and 13 clusters to ITN social marketing only (group B). The intervention took place during the rainy season of 2006 and thereafter. The trial was evaluated through a representative household survey at baseline and after one year. Serena ITN household ownership was the primary outcome measure. FINDINGS: A total of 1052 households were visited at baseline in February 2006 and 1050 at follow-up in February 2007. Overall Serena ITN household ownership increased from 16% to 28% over the study period, with a significantly higher increase in group A (13% to 35%) than in group B (18% to 23%) (p<0.001). INTERPRETATION: The free distribution of ITNs to pregnant women through governmental antenatal care services in addition to ITN social marketing substantially improved ITN household ownership in rural Burkina Faso. TRIAL REGISTRATION: Controlled-Trials.com ISRCTN07985309

Malaria transmission pattern resilience to climatic variability is mediated by insecticide-treated nets

<p>Abstract</p> <p>Background</p> <p>Malaria is an important public-health problem in the archipelago of Vanuatu and climate has been hypothesized as important influence on transmission risk. Beginning in 1988, a major intervention using insecticide-treated bed nets (ITNs) was implemented in the country in an attempt to reduce <it>Plasmodium </it>transmission. To date, no study has addressed the impact of ITN intervention in Vanuatu, how it may have modified the burden of disease, and whether there were any changes in malaria incidence that might be related to climatic drivers.</p> <p>Methods and findings</p> <p>Monthly time series (January 1983 through December 1999) of confirmed <it>Plasmodium falciparum </it>and <it>Plasmodium vivax </it>infections in the archipelago were analysed. During this 17 year period, malaria dynamics underwent a major regime shift around May 1991, following the introduction of bed nets as a control strategy in the country. By February of 1994 disease incidence from both parasites was reduced by at least 50%, when at most 20% of the population at risk was covered by ITNs. Seasonal cycles, as expected, were strongly correlated with temperature patterns, while inter-annual cycles were associated with changes in precipitation. Following the bed net intervention, the influence of environmental drivers of malaria dynamics was reduced by 30–80% for climatic forces, and 33–54% for other factors. A time lag of about five months was observed for the qualitative change ("regime shift") between the two parasites, the change occurring first for <it>P. falciparum</it>. The latter might be explained by interspecific interactions between the two parasites within the human hosts and their distinct biology, since <it>P. vivax </it>can relapse after a primary infection.</p> <p>Conclusion</p> <p>The Vanuatu ITN programme represents an excellent example of implementing an infectious disease control programme. The distribution was undertaken to cover a large, local proportion (~80%) of people in villages where malaria was present. The successful coverage was possible because of the strategy for distribution of ITNs by prioritizing the free distribution to groups with restricted means for their acquisition, making the access to this resource equitable across the population. These results emphasize the need to implement infectious disease control programmes focusing on the most vulnerable populations.</p

Comparative evaluation of carbosulfan- and permethrin-impregnated curtains for preventing house-entry by the malaria vector Anopheles gambiae in Burkina Faso.

Pyrethroid-impregnated bednets and curtains are widely employed to reduce the risk of malaria transmission, but pyrethroid-resistance is becoming more prevalent among malaria vector Anopheles mosquitoes (Diptera: Culicidae). As an alternative treatment for curtains, we assessed carbosulfan (a carbamate insecticide) in comparison with permethrin as the standard pyrethroid, against endophilic female mosquitoes of the Anopheles gambiae Giles complex in a village near Ouagadougou, Burkina Faso. The main criterion evaluated was the impact of curtains (hung inside windows, eaves and doorways) on the number of An. gambiae s.l. females active indoors at night. Light-traps were operated overnight (21.00-06.00 hours beside occupied untreated bednets) to sample mosquitoes in houses fitted with net curtains treated with carbosulfan 0.2 g ai/m2 or permethrin 1 g ai/m2 or untreated, compared with houses without curtains. The treated and untreated curtains significantly reduced the numbers of mosquitoes collected indoors, compared with houses without curtains. Carbosulfan-treated curtains had a highly significantly greater effect than permethrin-treated or untreated curtains, the scale of the difference being estimated as three-fold. However, there was no significant difference between the impact of untreated and permethrin-treated curtains on densities of An. gambiae s.l. trapped indoors. Samples of the An. gambiae complex comprised An. arabiensis Patton and both the S- and M-forms of An. gambiae Giles s.s. Susceptibility tests revealed some resistance to DDT and low frequencies of permethrin-resistance, insufficient to explain the poor performance of permethrin on curtains. Among survivors from the diagnostic dosage of permethrin were some specimens of all three members of the An. gambiae complex, but the kdr resistance mechanism was detected only in the S-form of An. gambiae s.s. Questions arising for further investigation include clarification of resistance mechanisms in, and foraging behaviour of, each member of the An. gambiae complex in this situation and the need to decide whether carbosulfan-treated curtains are acceptably safe for use to reduce risks of malaria transmission