Malaria in primary school children and infants in kinshasa, democratic republic of the congo: surveys from the 1980s and 2000.

Kinshasa, the capital of the Democratic Republic of the Congo, has been a perennial malarious area and has grown almost 14 times from 380,000 people in 1960 to 5,293,000 in 2003. The most complete information on malaria prevalence in Kinshasa was first acquired in 1981-1983. Blood smears were obtained from 25,135 children (ages 5-15 years) from 245 schools in 16 of 24 zones. The mean Plasmodium falciparum parasite rate was 17%; the parasite rate was similar for both sexes and was higher (P < 0.001) in older students. The parasite rate varied from 4% (urban zone) to 46% (peri-urban zone). An infant survey confirmed malaria transmission. During the Roll Back Malaria situational analysis in 2000, malaria prevalence was reassessed by the National Malaria Control Program and its partners in schools from selected health zones. A mean parasite rate of 34% was found among school children 5-9 years old. The parasite rate varied from 14% (central urban zone) to 65% (peri urban zone). Plasmodium falciparum was not the only species found, but accounted for more than 97% of the infections. Malaria incidence may have increased in Kinshasa during the last two decades due to difficulties in provision of control and prevention measures. Along with deployment of insecticide-treated bed nets and improved patient management, currently ongoing, other measures that could impact the disease are being considered, including vector control, water management, and proper urban planning.

Efficacy of permethrin-treated bed nets in the prevention of mortality in young children in an area of high perennial malaria transmission in western Kenya.

A group-randomized controlled trial of insecticide (permethrin)-treated bed nets (ITNs) was conducted in an area of high perennial malaria transmission in western Kenya to test the effect of ITNs on all-cause mortality in children 1-59 months of age. Child deaths were monitored over a two-year period by biannual household census in Asembo (1997-1998) and in Gem (1998-1999). Overall, 1,722 deaths occurred in children 1-59 months followed for 35,932 child-years. Crude mortality rates/1,000 child-years were 51.9 versus 43.9 in control and ITN villages in children 1-59 months old. The protective efficacy (PE) (95% confidence interval) adjusted for age, study year, study site, and season was 16% (6-25%). Corresponding figures in 1-11- and 12-59-month-old children in control and ITN villages were 133.3 versus 102.3, PE = 23% (11-34%) and 31.1 versus 28.7, PE = 7% (-6-19%). The numbers of lives saved/1,000 child-years were 8, 31, and 2 for the groups 1-59, 1-11, and 12-59 months old, respectively. Stratified analysis by time to insecticide re-treatment showed that the PE of ITNs re-treated per study protocol (every six months) was 20% (10-29%), overall and 26% (12-37%) and 14% (-1-26%) in 1-11- and 12-59-month-old children, respectively. ITNs prevent approximately one in four infant deaths in areas of intense perennial malaria transmission, but their efficacy is compromised if re-treatment is delayed beyond six months.

Efectos de los mosquiteros impregnados con permetrina sobre los vectores de la malaria en el norte de Guatemala / Effects of permethrin-impregnated bed nets on malaria vectors of Northern Guatemala

En un estudio con controles efectuado durante 16 meses en cuatro comunidades del norte de Guatemala, se evaluaron los efectos causados en los vectores de la malaria por mosquiteros impregnados con permetrina. Anopheles albimanus y An. vestitipennis son los vectores conocidos de la malaria en la zona. Cada casa se asignó a uno de tres grupos experimentales: las que recibieron mosquiteros impregnados con 500 mg de permetrina/m2, las que recibieron mosquiteros no tratados y aquellas en las que no se aplicaron medidas de intervención. El efecto de los mosquiteros tratados y no tratados sobre la abundancia, el comportamiento y la mortalidad de los mosquitos se determinó mediante recolecciones en el interior y el exterior de las viviendas de mosquitos que pican de noche, recoleciones matutinas con rociamientos de piretrina, inspección de la superficie de los mosquiteros para determinar la cantidad de mosquitos muertos y estudios mediante captura, liberación y recaptura. Se estimó la duración del efecto residual del insecticida en los mosquiteros tratados usando una forma modificada del ensayo biológico con conos de la OMS para empleo sobre el terreno. El contenido de piretrina en los mosquiteros se calculó mediante cromatografía de gases y líquidos. La observación más importante fue que se encontraron menos mosquitos reposando en las casas con mosquiteros tratados. Los mosquiteros tratados probablemente actuaban repeliendo y matando a los mosquitos vectores. Los estudios mediante captura, liberación y recaptura revelaron que los porcentajes de salida de las casas con mosquiteros tratados fueron más altos (94 por ciento) que los observados en las casas controles (72 por ciento), lo cual indica un efecto de repelencia. Sin embargo no se encontraron diferencias significativas entre las recolecciones de mosquitos que pican de noche en las casas con y sin mosquiteros tratados. Fue casi 20 veces más probable encontrar mosquitos anofelinos muertos en las superficies horizontales de los mosquiteros tratados que en las superficies similares de los mosquiteros no tratados. Los ennsayos biológicos indicaron que los mosquiteros impregnados con permetrina que no se lavaron retuvieron su acción onsecticida durante los 6 meses posteriores al tratamiento (AU)

Effects of Permethrin-impregnated bed nets on malaria vectors of northern Guatemala

8The authors evaluated the effects on malaria vectors of bed nets impregnated with permethrin over the course of a 16-month controlled study in four communities of Northern Guatemala. Anopheles albimanus and An. vestitipennis were the known malaria vectors in the area. Households were allocated to one of three experimental groups: those receiving bed nets impregnated with 500 mg/m2 of permethrim, those receiving untreated bed nets, and those where no intervention measures were taken. The impact of the treated and untreated bed nets on mosquito abundance, behavior, and mortality was determined by indoor/outdoor night-bite mosquito collections, morning pyrethrum spray collections, inspection of bed net surfaces for dead mosquitoes, and capture-release-recapture studies. The duration of the treated nets' residual insecticide effect was assessed by modified WHO cone fiel bioassays, and their pyrethrin content was estimated by gas-liquid chromatography analysis. The most important observation was that fewer mosquitoes were found to be resting in the households with treated bed nets. The treated nets probably functioned by both repelling and killing vector mosquitoes. Capture-release-recapture studies showed exit rated from houses with treated nets were higher (94 percent) than those from control houses (72 percent), a finding that suggests repellency. However, no significant differences were noted between the indoor night-bite mosquito collections at houses with and without treated nets. The horizontal surfaces of treated bed nets were nearly 20 times more likely to contain dead anopheline mosquitoes than were the comparable surfaces of untreated nets. The bioassays indicated that unwashed permethrin-impregnated bed nets retained their insecticidal activity for 6 months after treatment

Effects of Permethrin-impregnated bed nets on malaria vectors of northern Guatemala

8The authors evaluated the effects on malaria vectors of bed nets impregnated with permethrin over the course of a 16-month controlled study in four communities of Northern Guatemala. Anopheles albimanus and An. vestitipennis were the known malaria vectors in the area. Households were allocated to one of three experimental groups: those receiving bed nets impregnated with 500 mg/m2 of permethrim, those receiving untreated bed nets, and those where no intervention measures were taken. The impact of the treated and untreated bed nets on mosquito abundance, behavior, and mortality was determined by indoor/outdoor night-bite mosquito collections, morning pyrethrum spray collections, inspection of bed net surfaces for dead mosquitoes, and capture-release-recapture studies. The duration of the treated nets' residual insecticide effect was assessed by modified WHO cone fiel bioassays, and their pyrethrin content was estimated by gas-liquid chromatography analysis. The most important observation was that fewer mosquitoes were found to be resting in the households with treated bed nets. The treated nets probably functioned by both repelling and killing vector mosquitoes. Capture-release-recapture studies showed exit rated from houses with treated nets were higher (94 percent) than those from control houses (72 percent), a finding that suggests repellency. However, no significant differences were noted between the indoor night-bite mosquito collections at houses with and without treated nets. The horizontal surfaces of treated bed nets were nearly 20 times more likely to contain dead anopheline mosquitoes than were the comparable surfaces of untreated nets. The bioassays indicated that unwashed permethrin-impregnated bed nets retained their insecticidal activity for 6 months after treatment

This article will also be published in Spanish in the BOSP. Vol. 117, 1994

Efectos de los mosquiteros impregnados con permetrina sobre los vectores de la malaria en el norte de Guatemala / Effects of permethrin-impregnated bed nets on malaria vectors of Northern Guatemala

En un estudio con controles efectuado durante 16 meses en cuatro comunidades del norte de Guatemala, se evaluaron los efectos causados en los vectores de la malaria por mosquiteros impregnados con permetrina. Anopheles albimanus y An. vestitipennis son los vectores conocidos de la malaria en la zona. Cada casa se asignó a uno de tres grupos experimentales: las que recibieron mosquiteros impregnados con 500 mg de permetrina/m2, las que recibieron mosquiteros no tratados y aquellas en las que no se aplicaron medidas de intervención. El efecto de los mosquiteros tratados y no tratados sobre la abundancia, el comportamiento y la mortalidad de los mosquitos se determinó mediante recolecciones en el interior y el exterior de las viviendas de mosquitos que pican de noche, recoleciones matutinas con rociamientos de piretrina, inspección de la superficie de los mosquiteros para determinar la cantidad de mosquitos muertos y estudios mediante captura, liberación y recaptura. Se estimó la duración del efecto residual del insecticida en los mosquiteros tratados usando una forma modificada del ensayo biológico con conos de la OMS para empleo sobre el terreno. El contenido de piretrina en los mosquiteros se calculó mediante cromatografía de gases y líquidos. La observación más importante fue que se encontraron menos mosquitos reposando en las casas con mosquiteros tratados. Los mosquiteros tratados probablemente actuaban repeliendo y matando a los mosquitos vectores. Los estudios mediante captura, liberación y recaptura revelaron que los porcentajes de salida de las casas con mosquiteros tratados fueron más altos (94 por ciento) que los observados en las casas controles (72 por ciento), lo cual indica un efecto de repelencia. Sin embargo no se encontraron diferencias significativas entre las recolecciones de mosquitos que pican de noche en las casas con y sin mosquiteros tratados. Fue casi 20 veces más probable encontrar mosquitos anofelinos muertos en las superficies horizontales de los mosquiteros tratados que en las superficies similares de los mosquiteros no tratados. Los ennsayos biológicos indicaron que los mosquiteros impregnados con permetrina que no se lavaron retuvieron su acción onsecticida durante los 6 meses posteriores al tratamiento (AU)

Se publica en inglés en el Bull. PAHO. Vol. 28(2), 1994