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Penelope A Phillipshoward - One of the best experts on this subject based on the ideXlab platform.

  • perceptions of Bed Nets and malaria prevention before and after a randomized controlled trial of permethrin treated Bed Nets in western kenya
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Jane Alaii, H W Van Den Borne, Patrick S Kachur, Halima Mwenesi, John M Vulule, William A Hawley, Martin I Meltzer, Bernard L Nahlen, Penelope A Phillipshoward
    Abstract:

    A study of mothers' perceptions regarding Bed Nets and malaria was conducted before and after a randomized controlled trial of insecticide (permethrin)-treated Bed Nets (ITNs) in western Kenya. Awareness about the trial and the rationale for Bed net use increased by the end of the trial. Knowledge that mosquitoes caused malaria also increased; however, a higher proportion of mothers from control, rather than intervention villages, cited this (44.4% versus 27.9%; P < 0.001). Mothers from intervention villages were more knowledgeable about the use and maintenance of Bed Nets and re-treatment with insecticide. Both groups specified advantages of ITNs. Mothers from intervention villages noted practical advantages such as protection against Bedbugs and falling roof debris. Few (< 1%) mothers indicated that ITNs protected children against malaria. Intervention homes used significantly fewer mosquito coils, insect spray, medicines, and burned cow dung less often compared with those in control villages. Mothers were willing to pay approximately 4.5 U.S. dollars for a regular Bed net, but only 10.5 U.S. cents (intervention) and 0.036 (control) for re-treating a Bed net. This study suggests that, despite two years of experience of use, Bed Nets and insecticides would not be purchased as a household priority in this impoverished rural community.

  • impact of permethrin treated Bed Nets on entomologic indices in an area of intense year round malaria transmission
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: John E Gimnig, Allen W. Hightower, John M Vulule, Bernard L Nahlen, Penelope A Phillipshoward, Luna Kamau, Margarette S Kolczak, Evan M Mathenge, Feiko O Ter Kuile, William A Hawley
    Abstract:

    The effect of permethrin-treated Bed Nets (ITNs) on malaria vectors was studied as part of a large-scale, randomized, controlled trial in western Kenya. Indoor resting densities of fed Anopheles gambiae s.l. and An. funestus in intervention houses were 58.5% (P 0.010) and 94.5% (P 0.001) lower, respectively, compared with control houses. The sporozoite infection rate in An. gambiae s.l. was 0.8% in intervention areas compared with 3.4% (P 0.026) in control areas, while the sporozoite infection rates in An. funestus were not significantly different between the two areas. We estimated the overall transmission of Plasmodium falciparum in intervention areas to be 90% lower than in control areas. Permethrin resistance was not detected during the study period. As measured by densities of An. gambiae s.l., the efficacy of Bed Nets decreased if one or more residents did not sleep under a net or if Bed Nets had not been re-treated within six months. These results indicate that ITNs are optimally effective if used every night and if per- methrin is reapplied at least biannually. As part of the efficacy trial, we assessed some standard entomologicparameters: the number of indoor resting mos- quitoes, house exiting behavior, the proportion of mosquitoes infected with Plasmodium falciparum sporozoites, and insec- ticide resistance. We also assessed the effect of several human factors on the number of blood fed mosquitoes found resting indoors. The most important of these is adherence, which is whether the individual owning the net actually slept under a properly deployed net during the night before resting mos- quitoes were collected. We also measured the impact of the number of Bed Nets in houses and the time since re-treatment of Nets with insecticide on numbers of fed mosquitoes.

  • reduction of malaria during pregnancy by permethrin treated Bed Nets in an area of intense perennial malaria transmission in western kenya
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Feiko O Ter Kuile, William A Hawley, Penelope A Phillipshoward, Margarette S Kolczak, Dianne J Terlouw, Jennifer F Friedman, Simon Kariuki, Ya Ping Shi, Altaf A Lal, John M Vulule
    Abstract:

    The impact of insecticide (permethrin)-treated Bed Nets (ITNs) on malaria in pregnancy was studied in a rural area in western Kenya with intense perennial malaria transmission. All households in 40 of 79 villages were randomized to receive ITNs by January 1997. The ITNs were distributed in control villages two years later. Complete data on birth outcome were available on 2,754 (89.6%) of 3,072 deliveries. Women (n = 780) were followed monthly throughout pregnancy in 19 of 79 villages. Among gravidae 1-4, ITNs were associated with reductions of 38% (95% confidence interval [CI] = 17-54%) in the incidence of malaria parasitemia and 47% (95% CI = 6-71%) in the incidence of severe malarial anemia (hemoglobin level < 8 g/dL with parasitemia) during pregnancy. At the time of delivery, mean hemoglobin levels were 0.6 g/dL (95% CI = 0.01-1.2 g/dL) higher, the prevalence of placental or maternal malaria was reduced by 35% (95% CI = 20-47%), and the prevalence of low birth weight was reduced by 28% (95% CI = 2-47%) in gravidae 1-4 from ITN villages. No beneficial impact was observed in gravidae five or higher. In areas of intense perennial malaria transmission, permethrin-treated Bed Nets reduce the adverse effect of malaria during the first four pregnancies.

  • the efficacy of permethrin treated Bed Nets on child mortality and morbidity in western kenya ii study design and methods
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Penelope A Phillipshoward, Jane Alaii, Bernard L Nahlen, John E Gimnig, Margarette S Kolczak, Feiko O Ter Kuile, Dianne J Terlouw, Simon Kariuki, Ya Ping Shi, Patrick S Kachur
    Abstract:

    This paper describes the study design and methods used in a large community-based, group-randomized, controlled trial of permethrin-treated Bed Nets (ITNs) in an area with intense, perennial malaria transmission in western Kenya conducted between 1996 and 1999. A multi-disciplinary framework was used to explore the efficacy of ITNs in the reduction of all-cause mortality in children less than five years old, the clinical, entomologic, immunologic, and economic impact of ITNs, the social and behavioral determinants of ITN use, and the use of a geographic information system to allow for spatial analyses of these outcomes. Methodologic difficulties encountered in such large-scale field trials are discussed.

  • the efficacy of permethrin treated Bed Nets on child mortality and morbidity in western kenya i development of infrastructure and description of study site
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Penelope A Phillipshoward, Allen W. Hightower, Jane Alaii, Patrick S Kachur, Bernard L Nahlen, John E Gimnig, Feiko O Ter Kuile, Dianne J Terlouw, Altaf A Lal, Erik Schoute
    Abstract:

    Randomized controlled trials in sub-Saharan Africa have shown that permethrin-treated Bed Nets and curtains reduce all-cause child mortality by 15-33% in areas with low or high but seasonal malaria transmission. This report describes the study site for a community-based, group-randomized, controlled trial in an area of high and year-round malaria transmission in western Kenya. We outline the development of the human and physical infrastructure required to conduct this trial and discuss some of the difficulties encountered and lessons learned in conducting it.

Feiko O Ter Kuile - One of the best experts on this subject based on the ideXlab platform.

  • impact of permethrin treated Bed Nets on entomologic indices in an area of intense year round malaria transmission
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: John E Gimnig, Allen W. Hightower, John M Vulule, Bernard L Nahlen, Penelope A Phillipshoward, Luna Kamau, Margarette S Kolczak, Evan M Mathenge, Feiko O Ter Kuile, William A Hawley
    Abstract:

    The effect of permethrin-treated Bed Nets (ITNs) on malaria vectors was studied as part of a large-scale, randomized, controlled trial in western Kenya. Indoor resting densities of fed Anopheles gambiae s.l. and An. funestus in intervention houses were 58.5% (P 0.010) and 94.5% (P 0.001) lower, respectively, compared with control houses. The sporozoite infection rate in An. gambiae s.l. was 0.8% in intervention areas compared with 3.4% (P 0.026) in control areas, while the sporozoite infection rates in An. funestus were not significantly different between the two areas. We estimated the overall transmission of Plasmodium falciparum in intervention areas to be 90% lower than in control areas. Permethrin resistance was not detected during the study period. As measured by densities of An. gambiae s.l., the efficacy of Bed Nets decreased if one or more residents did not sleep under a net or if Bed Nets had not been re-treated within six months. These results indicate that ITNs are optimally effective if used every night and if per- methrin is reapplied at least biannually. As part of the efficacy trial, we assessed some standard entomologicparameters: the number of indoor resting mos- quitoes, house exiting behavior, the proportion of mosquitoes infected with Plasmodium falciparum sporozoites, and insec- ticide resistance. We also assessed the effect of several human factors on the number of blood fed mosquitoes found resting indoors. The most important of these is adherence, which is whether the individual owning the net actually slept under a properly deployed net during the night before resting mos- quitoes were collected. We also measured the impact of the number of Bed Nets in houses and the time since re-treatment of Nets with insecticide on numbers of fed mosquitoes.

  • reduction of malaria during pregnancy by permethrin treated Bed Nets in an area of intense perennial malaria transmission in western kenya
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Feiko O Ter Kuile, William A Hawley, Penelope A Phillipshoward, Margarette S Kolczak, Dianne J Terlouw, Jennifer F Friedman, Simon Kariuki, Ya Ping Shi, Altaf A Lal, John M Vulule
    Abstract:

    The impact of insecticide (permethrin)-treated Bed Nets (ITNs) on malaria in pregnancy was studied in a rural area in western Kenya with intense perennial malaria transmission. All households in 40 of 79 villages were randomized to receive ITNs by January 1997. The ITNs were distributed in control villages two years later. Complete data on birth outcome were available on 2,754 (89.6%) of 3,072 deliveries. Women (n = 780) were followed monthly throughout pregnancy in 19 of 79 villages. Among gravidae 1-4, ITNs were associated with reductions of 38% (95% confidence interval [CI] = 17-54%) in the incidence of malaria parasitemia and 47% (95% CI = 6-71%) in the incidence of severe malarial anemia (hemoglobin level < 8 g/dL with parasitemia) during pregnancy. At the time of delivery, mean hemoglobin levels were 0.6 g/dL (95% CI = 0.01-1.2 g/dL) higher, the prevalence of placental or maternal malaria was reduced by 35% (95% CI = 20-47%), and the prevalence of low birth weight was reduced by 28% (95% CI = 2-47%) in gravidae 1-4 from ITN villages. No beneficial impact was observed in gravidae five or higher. In areas of intense perennial malaria transmission, permethrin-treated Bed Nets reduce the adverse effect of malaria during the first four pregnancies.

  • the efficacy of permethrin treated Bed Nets on child mortality and morbidity in western kenya ii study design and methods
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Penelope A Phillipshoward, Jane Alaii, Bernard L Nahlen, John E Gimnig, Margarette S Kolczak, Feiko O Ter Kuile, Dianne J Terlouw, Simon Kariuki, Ya Ping Shi, Patrick S Kachur
    Abstract:

    This paper describes the study design and methods used in a large community-based, group-randomized, controlled trial of permethrin-treated Bed Nets (ITNs) in an area with intense, perennial malaria transmission in western Kenya conducted between 1996 and 1999. A multi-disciplinary framework was used to explore the efficacy of ITNs in the reduction of all-cause mortality in children less than five years old, the clinical, entomologic, immunologic, and economic impact of ITNs, the social and behavioral determinants of ITN use, and the use of a geographic information system to allow for spatial analyses of these outcomes. Methodologic difficulties encountered in such large-scale field trials are discussed.

  • the efficacy of permethrin treated Bed Nets on child mortality and morbidity in western kenya i development of infrastructure and description of study site
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Penelope A Phillipshoward, Allen W. Hightower, Jane Alaii, Patrick S Kachur, Bernard L Nahlen, John E Gimnig, Feiko O Ter Kuile, Dianne J Terlouw, Altaf A Lal, Erik Schoute
    Abstract:

    Randomized controlled trials in sub-Saharan Africa have shown that permethrin-treated Bed Nets and curtains reduce all-cause child mortality by 15-33% in areas with low or high but seasonal malaria transmission. This report describes the study site for a community-based, group-randomized, controlled trial in an area of high and year-round malaria transmission in western Kenya. We outline the development of the human and physical infrastructure required to conduct this trial and discuss some of the difficulties encountered and lessons learned in conducting it.

  • community wide effects of permethrin treated Bed Nets on child mortality and malaria morbidity in western kenya
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: William A Hawley, John M Vulule, Bernard L Nahlen, Penelope A Phillipshoward, John E Gimnig, Feiko O Ter Kuile, Dianne J Terlouw, Simon Kariuki, Maurice Ombok, Margarette S Kolczak
    Abstract:

    Spatial analyses of the effect of insecticide (permethrin)-treated Bed Nets (ITNs) on nearby households both with and without ITNs was performed in the context of a large-scale, group-randomized, controlled mortality trial in Asembo, western Kenya. Results illustrate a protective effect of ITNs on compounds lacking ITNs located within 300 meters of compounds with ITNs for child mortality, moderate anemia, high-density parasitemia, and hemoglobin levels. This community effect on nearby compounds without Nets is approximately as strong as the effect observed within villages with ITNs. This implies that in areas with intense malaria transmission with high ITN coverage, the primary effect of insecticide-treated Nets is via area-wide effects on the mosquito population and not, as commonly supposed, by simple imposition of a physical barrier protecting individuals from biting. The strength of the community effect depended upon the proportion of nearby compounds with treated Nets. To maximize their public health impact, high coverage with treated Nets is essential.

William A Hawley - One of the best experts on this subject based on the ideXlab platform.

  • reemergence of anopheles funestus as a vector of plasmodium falciparum in western kenya after long term implementation of insecticide treated Bed Nets
    American Journal of Tropical Medicine and Hygiene, 2014
    Co-Authors: Robert S Mccann, John M Vulule, William A Hawley, Mary J Hamel, John E Gimnig, Nabie M Bayoh, Eric Ochomo, Edward D Walker
    Abstract:

    Historically, the malaria vectors in western Kenya have been Anopheles funestus, Anopheles gambiae s.s., and Anopheles arabiensis. Of these species, An. funestus populations declined the most after the introduction of insecticide-treated Bed Nets (ITNs) in the 1990s in Asembo, and collections of An. funestus in the region remained low until at least 2008. Contrary to findings during the early years of ITN use in Asembo, the majority of the Anopheles collected here in 2010 and 2011 were An. funestus. Female An. funestus had characteristically high Plasmodium falciparum sporozoite rates and showed nearly 100% anthropophily. Female An. funestus were found more often indoors than outdoors and had relatively low mortality rates during insecticide bioassays. Together, these results are of serious concern for public health in the region, indicating that An. funestus may once again be contributing significantly to the transmission of malaria in this region despite the widespread use of ITNs/long-lasting insecticidal Nets (LLINs).

  • perceptions of Bed Nets and malaria prevention before and after a randomized controlled trial of permethrin treated Bed Nets in western kenya
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Jane Alaii, H W Van Den Borne, Patrick S Kachur, Halima Mwenesi, John M Vulule, William A Hawley, Martin I Meltzer, Bernard L Nahlen, Penelope A Phillipshoward
    Abstract:

    A study of mothers' perceptions regarding Bed Nets and malaria was conducted before and after a randomized controlled trial of insecticide (permethrin)-treated Bed Nets (ITNs) in western Kenya. Awareness about the trial and the rationale for Bed net use increased by the end of the trial. Knowledge that mosquitoes caused malaria also increased; however, a higher proportion of mothers from control, rather than intervention villages, cited this (44.4% versus 27.9%; P < 0.001). Mothers from intervention villages were more knowledgeable about the use and maintenance of Bed Nets and re-treatment with insecticide. Both groups specified advantages of ITNs. Mothers from intervention villages noted practical advantages such as protection against Bedbugs and falling roof debris. Few (< 1%) mothers indicated that ITNs protected children against malaria. Intervention homes used significantly fewer mosquito coils, insect spray, medicines, and burned cow dung less often compared with those in control villages. Mothers were willing to pay approximately 4.5 U.S. dollars for a regular Bed net, but only 10.5 U.S. cents (intervention) and 0.036 (control) for re-treating a Bed net. This study suggests that, despite two years of experience of use, Bed Nets and insecticides would not be purchased as a household priority in this impoverished rural community.

  • impact of permethrin treated Bed Nets on entomologic indices in an area of intense year round malaria transmission
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: John E Gimnig, Allen W. Hightower, John M Vulule, Bernard L Nahlen, Penelope A Phillipshoward, Luna Kamau, Margarette S Kolczak, Evan M Mathenge, Feiko O Ter Kuile, William A Hawley
    Abstract:

    The effect of permethrin-treated Bed Nets (ITNs) on malaria vectors was studied as part of a large-scale, randomized, controlled trial in western Kenya. Indoor resting densities of fed Anopheles gambiae s.l. and An. funestus in intervention houses were 58.5% (P 0.010) and 94.5% (P 0.001) lower, respectively, compared with control houses. The sporozoite infection rate in An. gambiae s.l. was 0.8% in intervention areas compared with 3.4% (P 0.026) in control areas, while the sporozoite infection rates in An. funestus were not significantly different between the two areas. We estimated the overall transmission of Plasmodium falciparum in intervention areas to be 90% lower than in control areas. Permethrin resistance was not detected during the study period. As measured by densities of An. gambiae s.l., the efficacy of Bed Nets decreased if one or more residents did not sleep under a net or if Bed Nets had not been re-treated within six months. These results indicate that ITNs are optimally effective if used every night and if per- methrin is reapplied at least biannually. As part of the efficacy trial, we assessed some standard entomologicparameters: the number of indoor resting mos- quitoes, house exiting behavior, the proportion of mosquitoes infected with Plasmodium falciparum sporozoites, and insec- ticide resistance. We also assessed the effect of several human factors on the number of blood fed mosquitoes found resting indoors. The most important of these is adherence, which is whether the individual owning the net actually slept under a properly deployed net during the night before resting mos- quitoes were collected. We also measured the impact of the number of Bed Nets in houses and the time since re-treatment of Nets with insecticide on numbers of fed mosquitoes.

  • reduction of malaria during pregnancy by permethrin treated Bed Nets in an area of intense perennial malaria transmission in western kenya
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Feiko O Ter Kuile, William A Hawley, Penelope A Phillipshoward, Margarette S Kolczak, Dianne J Terlouw, Jennifer F Friedman, Simon Kariuki, Ya Ping Shi, Altaf A Lal, John M Vulule
    Abstract:

    The impact of insecticide (permethrin)-treated Bed Nets (ITNs) on malaria in pregnancy was studied in a rural area in western Kenya with intense perennial malaria transmission. All households in 40 of 79 villages were randomized to receive ITNs by January 1997. The ITNs were distributed in control villages two years later. Complete data on birth outcome were available on 2,754 (89.6%) of 3,072 deliveries. Women (n = 780) were followed monthly throughout pregnancy in 19 of 79 villages. Among gravidae 1-4, ITNs were associated with reductions of 38% (95% confidence interval [CI] = 17-54%) in the incidence of malaria parasitemia and 47% (95% CI = 6-71%) in the incidence of severe malarial anemia (hemoglobin level < 8 g/dL with parasitemia) during pregnancy. At the time of delivery, mean hemoglobin levels were 0.6 g/dL (95% CI = 0.01-1.2 g/dL) higher, the prevalence of placental or maternal malaria was reduced by 35% (95% CI = 20-47%), and the prevalence of low birth weight was reduced by 28% (95% CI = 2-47%) in gravidae 1-4 from ITN villages. No beneficial impact was observed in gravidae five or higher. In areas of intense perennial malaria transmission, permethrin-treated Bed Nets reduce the adverse effect of malaria during the first four pregnancies.

  • community wide effects of permethrin treated Bed Nets on child mortality and malaria morbidity in western kenya
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: William A Hawley, John M Vulule, Bernard L Nahlen, Penelope A Phillipshoward, John E Gimnig, Feiko O Ter Kuile, Dianne J Terlouw, Simon Kariuki, Maurice Ombok, Margarette S Kolczak
    Abstract:

    Spatial analyses of the effect of insecticide (permethrin)-treated Bed Nets (ITNs) on nearby households both with and without ITNs was performed in the context of a large-scale, group-randomized, controlled mortality trial in Asembo, western Kenya. Results illustrate a protective effect of ITNs on compounds lacking ITNs located within 300 meters of compounds with ITNs for child mortality, moderate anemia, high-density parasitemia, and hemoglobin levels. This community effect on nearby compounds without Nets is approximately as strong as the effect observed within villages with ITNs. This implies that in areas with intense malaria transmission with high ITN coverage, the primary effect of insecticide-treated Nets is via area-wide effects on the mosquito population and not, as commonly supposed, by simple imposition of a physical barrier protecting individuals from biting. The strength of the community effect depended upon the proportion of nearby compounds with treated Nets. To maximize their public health impact, high coverage with treated Nets is essential.

John M Vulule - One of the best experts on this subject based on the ideXlab platform.

  • reemergence of anopheles funestus as a vector of plasmodium falciparum in western kenya after long term implementation of insecticide treated Bed Nets
    American Journal of Tropical Medicine and Hygiene, 2014
    Co-Authors: Robert S Mccann, John M Vulule, William A Hawley, Mary J Hamel, John E Gimnig, Nabie M Bayoh, Eric Ochomo, Edward D Walker
    Abstract:

    Historically, the malaria vectors in western Kenya have been Anopheles funestus, Anopheles gambiae s.s., and Anopheles arabiensis. Of these species, An. funestus populations declined the most after the introduction of insecticide-treated Bed Nets (ITNs) in the 1990s in Asembo, and collections of An. funestus in the region remained low until at least 2008. Contrary to findings during the early years of ITN use in Asembo, the majority of the Anopheles collected here in 2010 and 2011 were An. funestus. Female An. funestus had characteristically high Plasmodium falciparum sporozoite rates and showed nearly 100% anthropophily. Female An. funestus were found more often indoors than outdoors and had relatively low mortality rates during insecticide bioassays. Together, these results are of serious concern for public health in the region, indicating that An. funestus may once again be contributing significantly to the transmission of malaria in this region despite the widespread use of ITNs/long-lasting insecticidal Nets (LLINs).

  • perceptions of Bed Nets and malaria prevention before and after a randomized controlled trial of permethrin treated Bed Nets in western kenya
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Jane Alaii, H W Van Den Borne, Patrick S Kachur, Halima Mwenesi, John M Vulule, William A Hawley, Martin I Meltzer, Bernard L Nahlen, Penelope A Phillipshoward
    Abstract:

    A study of mothers' perceptions regarding Bed Nets and malaria was conducted before and after a randomized controlled trial of insecticide (permethrin)-treated Bed Nets (ITNs) in western Kenya. Awareness about the trial and the rationale for Bed net use increased by the end of the trial. Knowledge that mosquitoes caused malaria also increased; however, a higher proportion of mothers from control, rather than intervention villages, cited this (44.4% versus 27.9%; P < 0.001). Mothers from intervention villages were more knowledgeable about the use and maintenance of Bed Nets and re-treatment with insecticide. Both groups specified advantages of ITNs. Mothers from intervention villages noted practical advantages such as protection against Bedbugs and falling roof debris. Few (< 1%) mothers indicated that ITNs protected children against malaria. Intervention homes used significantly fewer mosquito coils, insect spray, medicines, and burned cow dung less often compared with those in control villages. Mothers were willing to pay approximately 4.5 U.S. dollars for a regular Bed net, but only 10.5 U.S. cents (intervention) and 0.036 (control) for re-treating a Bed net. This study suggests that, despite two years of experience of use, Bed Nets and insecticides would not be purchased as a household priority in this impoverished rural community.

  • impact of permethrin treated Bed Nets on entomologic indices in an area of intense year round malaria transmission
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: John E Gimnig, Allen W. Hightower, John M Vulule, Bernard L Nahlen, Penelope A Phillipshoward, Luna Kamau, Margarette S Kolczak, Evan M Mathenge, Feiko O Ter Kuile, William A Hawley
    Abstract:

    The effect of permethrin-treated Bed Nets (ITNs) on malaria vectors was studied as part of a large-scale, randomized, controlled trial in western Kenya. Indoor resting densities of fed Anopheles gambiae s.l. and An. funestus in intervention houses were 58.5% (P 0.010) and 94.5% (P 0.001) lower, respectively, compared with control houses. The sporozoite infection rate in An. gambiae s.l. was 0.8% in intervention areas compared with 3.4% (P 0.026) in control areas, while the sporozoite infection rates in An. funestus were not significantly different between the two areas. We estimated the overall transmission of Plasmodium falciparum in intervention areas to be 90% lower than in control areas. Permethrin resistance was not detected during the study period. As measured by densities of An. gambiae s.l., the efficacy of Bed Nets decreased if one or more residents did not sleep under a net or if Bed Nets had not been re-treated within six months. These results indicate that ITNs are optimally effective if used every night and if per- methrin is reapplied at least biannually. As part of the efficacy trial, we assessed some standard entomologicparameters: the number of indoor resting mos- quitoes, house exiting behavior, the proportion of mosquitoes infected with Plasmodium falciparum sporozoites, and insec- ticide resistance. We also assessed the effect of several human factors on the number of blood fed mosquitoes found resting indoors. The most important of these is adherence, which is whether the individual owning the net actually slept under a properly deployed net during the night before resting mos- quitoes were collected. We also measured the impact of the number of Bed Nets in houses and the time since re-treatment of Nets with insecticide on numbers of fed mosquitoes.

  • reduction of malaria during pregnancy by permethrin treated Bed Nets in an area of intense perennial malaria transmission in western kenya
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Feiko O Ter Kuile, William A Hawley, Penelope A Phillipshoward, Margarette S Kolczak, Dianne J Terlouw, Jennifer F Friedman, Simon Kariuki, Ya Ping Shi, Altaf A Lal, John M Vulule
    Abstract:

    The impact of insecticide (permethrin)-treated Bed Nets (ITNs) on malaria in pregnancy was studied in a rural area in western Kenya with intense perennial malaria transmission. All households in 40 of 79 villages were randomized to receive ITNs by January 1997. The ITNs were distributed in control villages two years later. Complete data on birth outcome were available on 2,754 (89.6%) of 3,072 deliveries. Women (n = 780) were followed monthly throughout pregnancy in 19 of 79 villages. Among gravidae 1-4, ITNs were associated with reductions of 38% (95% confidence interval [CI] = 17-54%) in the incidence of malaria parasitemia and 47% (95% CI = 6-71%) in the incidence of severe malarial anemia (hemoglobin level < 8 g/dL with parasitemia) during pregnancy. At the time of delivery, mean hemoglobin levels were 0.6 g/dL (95% CI = 0.01-1.2 g/dL) higher, the prevalence of placental or maternal malaria was reduced by 35% (95% CI = 20-47%), and the prevalence of low birth weight was reduced by 28% (95% CI = 2-47%) in gravidae 1-4 from ITN villages. No beneficial impact was observed in gravidae five or higher. In areas of intense perennial malaria transmission, permethrin-treated Bed Nets reduce the adverse effect of malaria during the first four pregnancies.

  • community wide effects of permethrin treated Bed Nets on child mortality and malaria morbidity in western kenya
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: William A Hawley, John M Vulule, Bernard L Nahlen, Penelope A Phillipshoward, John E Gimnig, Feiko O Ter Kuile, Dianne J Terlouw, Simon Kariuki, Maurice Ombok, Margarette S Kolczak
    Abstract:

    Spatial analyses of the effect of insecticide (permethrin)-treated Bed Nets (ITNs) on nearby households both with and without ITNs was performed in the context of a large-scale, group-randomized, controlled mortality trial in Asembo, western Kenya. Results illustrate a protective effect of ITNs on compounds lacking ITNs located within 300 meters of compounds with ITNs for child mortality, moderate anemia, high-density parasitemia, and hemoglobin levels. This community effect on nearby compounds without Nets is approximately as strong as the effect observed within villages with ITNs. This implies that in areas with intense malaria transmission with high ITN coverage, the primary effect of insecticide-treated Nets is via area-wide effects on the mosquito population and not, as commonly supposed, by simple imposition of a physical barrier protecting individuals from biting. The strength of the community effect depended upon the proportion of nearby compounds with treated Nets. To maximize their public health impact, high coverage with treated Nets is essential.

Bernard L Nahlen - One of the best experts on this subject based on the ideXlab platform.

  • perceptions of Bed Nets and malaria prevention before and after a randomized controlled trial of permethrin treated Bed Nets in western kenya
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Jane Alaii, H W Van Den Borne, Patrick S Kachur, Halima Mwenesi, John M Vulule, William A Hawley, Martin I Meltzer, Bernard L Nahlen, Penelope A Phillipshoward
    Abstract:

    A study of mothers' perceptions regarding Bed Nets and malaria was conducted before and after a randomized controlled trial of insecticide (permethrin)-treated Bed Nets (ITNs) in western Kenya. Awareness about the trial and the rationale for Bed net use increased by the end of the trial. Knowledge that mosquitoes caused malaria also increased; however, a higher proportion of mothers from control, rather than intervention villages, cited this (44.4% versus 27.9%; P < 0.001). Mothers from intervention villages were more knowledgeable about the use and maintenance of Bed Nets and re-treatment with insecticide. Both groups specified advantages of ITNs. Mothers from intervention villages noted practical advantages such as protection against Bedbugs and falling roof debris. Few (< 1%) mothers indicated that ITNs protected children against malaria. Intervention homes used significantly fewer mosquito coils, insect spray, medicines, and burned cow dung less often compared with those in control villages. Mothers were willing to pay approximately 4.5 U.S. dollars for a regular Bed net, but only 10.5 U.S. cents (intervention) and 0.036 (control) for re-treating a Bed net. This study suggests that, despite two years of experience of use, Bed Nets and insecticides would not be purchased as a household priority in this impoverished rural community.

  • impact of permethrin treated Bed Nets on entomologic indices in an area of intense year round malaria transmission
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: John E Gimnig, Allen W. Hightower, John M Vulule, Bernard L Nahlen, Penelope A Phillipshoward, Luna Kamau, Margarette S Kolczak, Evan M Mathenge, Feiko O Ter Kuile, William A Hawley
    Abstract:

    The effect of permethrin-treated Bed Nets (ITNs) on malaria vectors was studied as part of a large-scale, randomized, controlled trial in western Kenya. Indoor resting densities of fed Anopheles gambiae s.l. and An. funestus in intervention houses were 58.5% (P 0.010) and 94.5% (P 0.001) lower, respectively, compared with control houses. The sporozoite infection rate in An. gambiae s.l. was 0.8% in intervention areas compared with 3.4% (P 0.026) in control areas, while the sporozoite infection rates in An. funestus were not significantly different between the two areas. We estimated the overall transmission of Plasmodium falciparum in intervention areas to be 90% lower than in control areas. Permethrin resistance was not detected during the study period. As measured by densities of An. gambiae s.l., the efficacy of Bed Nets decreased if one or more residents did not sleep under a net or if Bed Nets had not been re-treated within six months. These results indicate that ITNs are optimally effective if used every night and if per- methrin is reapplied at least biannually. As part of the efficacy trial, we assessed some standard entomologicparameters: the number of indoor resting mos- quitoes, house exiting behavior, the proportion of mosquitoes infected with Plasmodium falciparum sporozoites, and insec- ticide resistance. We also assessed the effect of several human factors on the number of blood fed mosquitoes found resting indoors. The most important of these is adherence, which is whether the individual owning the net actually slept under a properly deployed net during the night before resting mos- quitoes were collected. We also measured the impact of the number of Bed Nets in houses and the time since re-treatment of Nets with insecticide on numbers of fed mosquitoes.

  • the efficacy of permethrin treated Bed Nets on child mortality and morbidity in western kenya ii study design and methods
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Penelope A Phillipshoward, Jane Alaii, Bernard L Nahlen, John E Gimnig, Margarette S Kolczak, Feiko O Ter Kuile, Dianne J Terlouw, Simon Kariuki, Ya Ping Shi, Patrick S Kachur
    Abstract:

    This paper describes the study design and methods used in a large community-based, group-randomized, controlled trial of permethrin-treated Bed Nets (ITNs) in an area with intense, perennial malaria transmission in western Kenya conducted between 1996 and 1999. A multi-disciplinary framework was used to explore the efficacy of ITNs in the reduction of all-cause mortality in children less than five years old, the clinical, entomologic, immunologic, and economic impact of ITNs, the social and behavioral determinants of ITN use, and the use of a geographic information system to allow for spatial analyses of these outcomes. Methodologic difficulties encountered in such large-scale field trials are discussed.

  • the efficacy of permethrin treated Bed Nets on child mortality and morbidity in western kenya i development of infrastructure and description of study site
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: Penelope A Phillipshoward, Allen W. Hightower, Jane Alaii, Patrick S Kachur, Bernard L Nahlen, John E Gimnig, Feiko O Ter Kuile, Dianne J Terlouw, Altaf A Lal, Erik Schoute
    Abstract:

    Randomized controlled trials in sub-Saharan Africa have shown that permethrin-treated Bed Nets and curtains reduce all-cause child mortality by 15-33% in areas with low or high but seasonal malaria transmission. This report describes the study site for a community-based, group-randomized, controlled trial in an area of high and year-round malaria transmission in western Kenya. We outline the development of the human and physical infrastructure required to conduct this trial and discuss some of the difficulties encountered and lessons learned in conducting it.

  • community wide effects of permethrin treated Bed Nets on child mortality and malaria morbidity in western kenya
    American Journal of Tropical Medicine and Hygiene, 2003
    Co-Authors: William A Hawley, John M Vulule, Bernard L Nahlen, Penelope A Phillipshoward, John E Gimnig, Feiko O Ter Kuile, Dianne J Terlouw, Simon Kariuki, Maurice Ombok, Margarette S Kolczak
    Abstract:

    Spatial analyses of the effect of insecticide (permethrin)-treated Bed Nets (ITNs) on nearby households both with and without ITNs was performed in the context of a large-scale, group-randomized, controlled mortality trial in Asembo, western Kenya. Results illustrate a protective effect of ITNs on compounds lacking ITNs located within 300 meters of compounds with ITNs for child mortality, moderate anemia, high-density parasitemia, and hemoglobin levels. This community effect on nearby compounds without Nets is approximately as strong as the effect observed within villages with ITNs. This implies that in areas with intense malaria transmission with high ITN coverage, the primary effect of insecticide-treated Nets is via area-wide effects on the mosquito population and not, as commonly supposed, by simple imposition of a physical barrier protecting individuals from biting. The strength of the community effect depended upon the proportion of nearby compounds with treated Nets. To maximize their public health impact, high coverage with treated Nets is essential.