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  • 1
    Online Resource
    Online Resource
    Impacts of insecticide treated bed nets on Anopheles gambiae s.l. populations in Mbita district and Suba district, Western Kenya
    Springer Science and Business Media LLC ; 2014
    In:  Parasites & Vectors Vol. 7, No. 1 ( 2014-12)
    Details
    In: Parasites & Vectors, Springer Science and Business Media LLC, Vol. 7, No. 1 ( 2014-12)
    Type of Medium: Online Resource
    ISSN: 1756-3305
    URL: Article
    DOI: 10.1186/1756-3305-7-63
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2014
    detail.hit.zdb_id: 2409480-8
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  • 2
    Online Resource
    Online Resource
    Protective effects of Olyset® Net on Plasmodium falciparum infection after three years of distribution in western Kenya
    Springer Science and Business Media LLC ; 2020
    In:  Malaria Journal Vol. 19, No. 1 ( 2020-12)
    Details
    In: Malaria Journal, Springer Science and Business Media LLC, Vol. 19, No. 1 ( 2020-12)
    Abstract: Several types of insecticides, treating technologies and materials are available for long-lasting insecticide-treated nets (LLINs). The variations may result in different efficacies against mosquitoes and correspondingly infection risks for the Plasmodium falciparum malaria parasite. This cross-sectional study investigated whether infection risk varied among children who slept under different LLIN brands in rural villages of western Kenya. Methods Children sleeping under various types of LLINs were tested for P. falciparum infection using a diagnostic polymerase chain reaction (PCR) assay. Data were collected for other potential factors associated with infection risk: sleeping location (with bed/without bed), number of persons sharing the same net, dwelling wall material, gap of eaves (open/close), proportional hole index, socio-economic status, and density of indoor resting anophelines. Bed-net efficacy against the Anopheles gambiae susceptible strain was estimated using the WHO cone test and the tunnel test. The residual insecticide content on nets was measured. Results Seven LLIN brands were identified, and deltamethrin-based DawaPlus® 2.0 was the most popular (48%) followed by permethrin-based Olyset® Net (28%). The former LLIN was distributed in the area about six months before the present study was conducted, and the latter net was distributed at least three years before. Of 254 children analysed, P. falciparum PCR-positive prevalence was 58% for DawaPlus® 2.0 users and 38% for Olyset® users. The multiple regression analysis revealed that the difference was statistically significant (adjusted OR: 0.67, 95% credible interval: 0.45–0.97), whereas the confounders were not statistically important. Among randomly selected net samples, all DawaPlus® 2.0 (n = 20) and 95% of Olyset® (n = 19) passed either the cone test or the tunnel test. Conclusions Olyset® was more effective in reducing infection risk compared with DawaPlus® 2.0. Although the data from the present study were too limited to explain the mechanism clearly, the results suggest that the characteristics of the former brand are more suitable for the conditions, such as vector species composition, of the study area.
    Type of Medium: Online Resource
    ISSN: 1475-2875
    URL: Article
    DOI: 10.1186/s12936-020-03444-w
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2020
    detail.hit.zdb_id: 2091229-8
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  • 3
    Online Resource
    Online Resource
    Effectiveness of screened ceilings over the current best practice in reducing malaria prevalence in western Kenya: a cluster randomized-controlled trial
    Cambridge University Press (CUP) ; 2022
    In:  Parasitology Vol. 149, No. 7 ( 2022-06), p. 944-955
    Details
    In: Parasitology, Cambridge University Press (CUP), Vol. 149, No. 7 ( 2022-06), p. 944-955
    Abstract: Increases in bed net coverage and antimalarial treatment have reduced the risk of malaria in sub-Saharan Africa. However, the pace of reduction has slowed, and new tools are needed to reverse this trend. We evaluated houses screened with insecticide-treated ceiling nets using a cluster randomized-controlled trial in western Kenya. The primary endpoints were Plasmodium falciparum PCR-positive prevalence (PCR Pf PR) of children from 7 months to 10 years old and anopheline density. Ceiling nets and bed nets were provided to 1073 houses, and 1162 houses were provided with bed nets only. The treatment and control arms each had four clusters. We conducted three epidemiological and entomological post-intervention surveys over the course of a year and a half. Each epidemiological survey targeted 150 children per cluster, and entomological surveys targeted 25 houses. When the three surveys were combined, the median PCR Pf PRs were 23% (IQR 8%) in the intervention arm and 42% (IQR 12%) in the control arm. The adjusted risk ratio (RR) was 0.53 [95% confidence interval (CI) 0.41–0.71; P = 0.029]. The median anopheline densities were 0.4 (IQR 0.4) and 2.0 (IQR 1.4), respectively. The adjusted RR was 0.41 (95% CI 0.29–0.90; P = 0.029). The present study indicates additional protection from insecticide-screened ceilings over the current best practice.
    Type of Medium: Online Resource
    ISSN: 0031-1820 , 1469-8161
    URL: Article
    DOI: 10.1017/S0031182022000415
    RVK:
    WA 15000
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2022
    detail.hit.zdb_id: 1491287-9
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    Sleeping on the floor decreases insecticide treated bed net use and increases risk of malaria in children under 5 years of age in Mbita District, Kenya
    Cambridge University Press (CUP) ; 2015
    In:  Parasitology Vol. 142, No. 12 ( 2015-10), p. 1516-1522
    Details
    In: Parasitology, Cambridge University Press (CUP), Vol. 142, No. 12 ( 2015-10), p. 1516-1522
    Abstract: Children who sleep on the floor are less likely to use long-lasting insecticidal nets (LLINs); however, the relationship between sleeping location and Plasmodium falciparum infection has not been investigated sufficiently. This study revealed whether sleeping location (bed vs floor) is associated with P. falciparum infection among children 7–59 months old. More than 60% of children slept on the floor. Younger children were significantly more likely to sleep in beds [odds ratio, OR 2·31 (95% confidence interval (CI) 2·02–2·67)]. Nearly 70% of children slept under LLINs the previous night. LLIN use among children who slept on the floor was significantly less than ones sleeping in beds [OR 0·49 (95% CI 0·35–0·68)] . The polymerase chain reaction (PCR) based P. falciparum infection rate and slide based infection rate were 65·2 and 29·7%, respectively. Both infections were significantly higher among children slept on the floor [OR1·51 (95% CI 1·08–2·10) for PCR base, OR 1·62 (95% CI 1·14–2·30) for slide base] while net availability was not significant. Sleeping location was also significant for slide based infection with fever (⩾37·5 °C) [2·03 (95% CI 1·14–3·84)] and high parasitemia cases (parasite ⩾2500 µ L −1 ) [2·07 (95% CI 1·03–4·50)]. The results suggest that sleeping location has a direct bearing on the effectiveness of LLINs.
    Type of Medium: Online Resource
    ISSN: 0031-1820 , 1469-8161
    URL: Article
    DOI: 10.1017/S0031182015000955
    RVK:
    WA 15000
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2015
    detail.hit.zdb_id: 1491287-9
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  • 5
    Online Resource
    Online Resource
    Antimalarial bednet protection of children disappears when shared by three or more people in a high transmission setting of western Kenya
    Cambridge University Press (CUP) ; 2019
    In:  Parasitology Vol. 146, No. 3 ( 2019-03), p. 363-371
    Details
    In: Parasitology, Cambridge University Press (CUP), Vol. 146, No. 3 ( 2019-03), p. 363-371
    Abstract: A sizeable proportion of households is forced to share single long-lasting insecticide treated net (LLIN). However, the relationship between increasing numbers of people sharing a net and the risk for Plasmodium infection is unclear. This study revealed whether risk for Plasmodium falciparum infection is associated with the number of people sharing a LLIN in a holoendemic area of Kenya. Children ⩽5 years of age were tested for P. falciparum infection using polymerase chain reaction. Of 558 children surveyed, 293 (52.5%) tested positive for parasitaemia. Four hundred and fifty-eight (82.1%) reported sleeping under a LLIN. Of those, the number of people sharing a net with the sampled child ranged from 1 to 5 (median = 2). Children using a net alone or with one other person were at lower risk than non-users (OR = 0.29, 95% CI 0.10–0.82 and OR = 0.47, 95% CI 0.22–0.97, respectively). On the other hand, there was no significant difference between non-users and children sharing a net with two (OR = 0.88, 95% CI 0.44–1.77) or more other persons (OR = 0.75, 95% CI 0.32–1.72). LLINs are effective in protecting against Plasmodium infection in children when used alone or with one other person compared with not using them. Public health professionals should inform caretakers of the risks of too many people sharing a net.
    Type of Medium: Online Resource
    ISSN: 0031-1820 , 1469-8161
    URL: Article
    DOI: 10.1017/S003118201800149X
    RVK:
    WA 15000
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2019
    detail.hit.zdb_id: 1491287-9
    SSG: 12
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  • 6
    Online Resource
    Online Resource
    A preliminary study on designing a cluster randomized control trial of two new mosquito nets to prevent malaria parasite infection
    Springer Science and Business Media LLC ; 2020
    In:  Tropical Medicine and Health Vol. 48, No. 1 ( 2020-12)
    Details
    In: Tropical Medicine and Health, Springer Science and Business Media LLC, Vol. 48, No. 1 ( 2020-12)
    Abstract: Although long-lasting insecticidal nets (LLINs) are the most effective tool for preventing malaria parasite transmission, the nets have some limitations. For example, the increase of LLIN use has induced the rapid expansion of mosquito insecticide resistance. More than two persons often share one net, which increases the infection risk. To overcome these problems, two new mosquito nets were developed, one incorporating piperonyl butoxide and another covering ceilings and open eaves. We designed a cluster randomized controlled trial (cRCT) to evaluate these nets based on the information provided in the present preliminary study. Results Nearly 75% of the anopheline population in the study area in western Kenya was Anopheles gambiae s. l. , and the remaining was Anopheles funestus s. l . More female anophelines were recorded in the western part of the study area. The number of anophelines increased with rainfall. We planned to have 80% power to detect a 50% reduction in female anophelines between the control group and each intervention group. The between-cluster coefficient of variance was 0.192. As the number of clusters was limited to 4 due to the size of the study area, the estimated cluster size was 7 spray catches with an alpha of 0.05. Of 1619 children tested, 626 (48%) were Plasmodium falciparum positive using a rapid diagnostic test (RDT). The prevalence was higher in the northwestern part of the study area. The number of children who slept under bed nets was 929 (71%). The P. falciparum RDT-positive prevalence (RDTpfPR) of net users was 45%, and that of non-users was 55% (OR 0.73; 95% CI 0.56, 0.95). Using 45% RDTpfPR of net users, we expected each intervention to reduce prevalence by 50%. The intracluster correlation coefficient was 0.053. With 80% power and an alpha of 0.05, the estimated cluster size was 116 children. Based on the distribution of children, we modified the boundaries of the clusters and established 300-m buffer zones along the boundaries to minimize a spillover effect. Conclusions The cRCT study design is feasible. As the number of clusters is limited, we will apply a two-stage procedure with the baseline data to evaluate each intervention.
    Type of Medium: Online Resource
    ISSN: 1349-4147
    URL: Article
    DOI: 10.1186/s41182-020-00276-x
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2020
    detail.hit.zdb_id: 2209835-5
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  • 7
    Online Resource
    Online Resource
    Long-Lasting Insecticidal Nets Incorporating Piperonyl Butoxide Reduce the Risk of Malaria in Children in Western Kenya: A Cluster Randomized Controlled Trial
    American Society of Tropical Medicine and Hygiene ; 2021
    In:  The American Journal of Tropical Medicine and Hygiene Vol. 105, No. 2 ( 2021-08-11), p. 461-471
    Details
    In: The American Journal of Tropical Medicine and Hygiene, American Society of Tropical Medicine and Hygiene, Vol. 105, No. 2 ( 2021-08-11), p. 461-471
    Abstract: Malaria vectors have acquired an enzyme that metabolizes pyrethroids. To tackle this problem, we evaluated long-lasting insecticidal nets incorporating piperonyl butoxide (PBO-LLINs) with a community-based cluster randomized control trial in western Kenya. The primary endpoints were anopheline density and Plasmodium falciparum polymerase chain reaction (PCR)-positive prevalence (PCRpfPR) of children aged 7 months to 10 years. Four clusters were randomly selected for each of the treatment and control arms (eight clusters in total) from 12 clusters, and PBO-LLINs and standard LLINs were distributed in February 2011 to 982 and 1,028 houses for treatment and control arms, respectively. Entomological surveys targeted 20 houses in each cluster, and epidemiological surveys targeted 150 children. Cluster-level permutation tests evaluated the effectiveness using the fitted values from individual level regression models adjusted for baseline. Bootstrapping estimated 95% confidence intervals (CIs). The medians of anophelines per house were 1.4 (interquartile range [IQR]: 2.3) and 3.4 (IQR: 3.7) in the intervention and control arms after 3 months, and 0.4 (IQR: 0.2) and 1.6 (IQR: 0.5) after 10 months, respectively. The differences were –2.5 (95% CI: –6.4 to –0.6) and –1.3 (95% CI: –2.0 to –0.7), respectively. The datasets of 861 and 775 children were analyzed in two epidemiological surveys. The median PCRpfPRs were 25% (IQR: 11%) in the intervention arm and 52% (IQR: 11%) in the control arm after 5 months and 33% (IQR: 11%) and 45% (IQR: 5%) after 12 months. The PCRpfPR ratios were 0.67 (95% CI: 0.38, 0.91) and 0.74 (95% CI: 0.53, 0.90), respectively. We confirmed the superiority of PBO-LLINs.
    Type of Medium: Online Resource
    ISSN: 0002-9637 , 1476-1645
    URL: Article
    DOI: 10.4269/ajtmh.20-1069
    Language: Unknown
    Publisher: American Society of Tropical Medicine and Hygiene
    Publication Date: 2021
    detail.hit.zdb_id: 1491674-5
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  • 8
    Online Resource
    Online Resource
    Effects of Bacillus thuringiensis israelensis on Anopheles arabiensis
    American Mosquito Control Association ; 2011
    In:  Journal of the American Mosquito Control Association Vol. 27, No. 1 ( 2011-03), p. 81-83
    Details
    In: Journal of the American Mosquito Control Association, American Mosquito Control Association, Vol. 27, No. 1 ( 2011-03), p. 81-83
    Type of Medium: Online Resource
    ISSN: 8756-971X
    URL: Article
    DOI: 10.2987/10-5998.1
    Language: English
    Publisher: American Mosquito Control Association
    Publication Date: 2011
    detail.hit.zdb_id: 2322636-5
    SSG: 12
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  • 9
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    Online Resource
    Limited genetic variations of the Rh5-CyRPA-Ripr invasion complex in Plasmodium falciparum parasite population in selected malaria-endemic regions, Kenya
    Frontiers Media SA ; 2023
    In:  Frontiers in Tropical Diseases Vol. 4 ( 2023-3-1)
    Details
    In: Frontiers in Tropical Diseases, Frontiers Media SA, Vol. 4 ( 2023-3-1)
    Abstract: The invasion of human erythrocytes by Plasmodium falciparum merozoites requires interaction between parasite ligands and host receptors. Interaction of Pf Rh5-CyRPA-Ripr protein complex with basigin, an erythrocyte surface receptor, via PfRh5 is essential for erythrocyte invasion. Antibodies raised against each antigen component of the complex have demonstrated erythrocyte invasion inhibition, making these proteins potential blood-stage vaccine candidates. Genetic polymorphisms present a significant challenge in developing efficacious vaccines, leading to variant-specific immune responses. This study investigated the genetic variations of the Pf Rh5 complex proteins in P. falciparum isolates from Lake Victoria islands, Western Kenya. Here, twenty-nine microscopically confirmed P. falciparum field samples collected from islands in Lake Victoria between July 2014 and July 2016 were genotyped by whole genome sequencing, and results compared to sequences mined from the GenBank database, from a study conducted in Kilifi, as well as other sequences from the MalariaGEN repository. We analyzed the frequency of polymorphisms in the Pf Rh5 protein complex proteins, Pf Rh5, Pf CyRPA, Pf Ripr, and Pf P113, and their location mapped on the 3D protein complex structure. We identified a total of 58 variants in the Pf Rh5 protein complex. Pf Rh5 protein was the most polymorphic with 30 SNPs, while Pf CyRPA was relatively conserved with 3 SNPs. The minor allele frequency of the SNPs ranged between 1.9% and 21.2%. Ten high-frequency alleles ( & gt;5%) were observed in Pf Rh5 at codons 147, 148, 277, 410, and 429 and in Pf Ripr at codons 190, 255, 259, and 1003. A SNP was located in protein-protein interaction region C203Y and F292V of Pf Rh5 and Pf CyRPA, respectively. Put together, this study revealed low polymorphisms in the Pf Rh5 invasion complex in the Lake Victoria parasite population. However, the two mutations identified on the protein interaction regions prompts for investigation on their impacts on parasite invasion process to support the consideration of Pf Rh5 components as potential malaria vaccine candidates.
    Type of Medium: Online Resource
    ISSN: 2673-7515
    URL: Article
    DOI: 10.3389/fitd.2023.1102265
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2023
    detail.hit.zdb_id: 3097199-8
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