John E Gimnig

Centers for Disease Control and Prevention, Атланта, Michigan, United States

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Publications (68)259.28 Total impact

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    ABSTRACT: Although it is well known that drug pressure selects for drug-resistant parasites, the role of transmission reduction by insecticide-treated bed nets (ITNs) on drug resistance remains unclear. In this study, the drug resistance profile of current and previous first-line anti-malarials in Kenya was assessed within the context of drug policy change and scale-up of ITNs. National first-line treatment changed from chloroquine (CQ) to sulphadoxine-pyrimethamine (SP) in 1998 and to artemether-lumefantrine (AL) in 2004. ITN use was scaled-up in the Asembo, Gem and Karemo areas of western Kenya in 1997, 1999 and 2006, respectively. Smear-positive samples (N = 253) collected from a 2007 cross-sectional survey among children in Asembo, Gem and Karemo were genotyped for mutations in pfcrt and pfmdr1 (CQ), dhfr and dhps (SP), and at pfmdr-N86 and the gene copy number in pfmdr1 (lumefantrine). Results were compared among the three geographic areas in 2007 and to retrospective molecular data from children in Asembo in 2001. In 2007, 69 and 85% of samples harboured the pfmdr1-86Y mutation and dhfr/dhps quintuple mutant, respectively, with no significant differences by study area. However, the prevalence of the pfcrt-76T mutation differed significantly among areas (p <0.02), between 76 and 94%, with the highest prevalence in Asembo. Several 2007 samples carried mutations at dhfr-164L, dhps-436A, or dhps-613T. From 2001 to 2007, there were significant increases in the pfcrt-76T mutation from 82 to 94% (p <0.03), dhfr/dhps quintuple mutant from 62 to 82% (p <0.03), and an increase in the septuple CQ and SP combined mutant haplotype, K 76 Y 86 I 51 R 59 N 108 G 437 E 540 , from 28 to 39%. The prevalence of the pfmdr1-86Y mutation remained unchanged. All samples were single copy for pfmdr1. Molecular markers associated with lumefantrine resistance were not detected in 2007. More recent samples will be needed to detect any selective effects by AL. The prevalence of CQ and SP resistance markers increased from 2001 to 2007 in the absence of changes in transmission intensity. In 2007, only the prevalence of pfcrt-76T mutation differed among study areas of varying transmission intensity. Resistant parasites were most likely selected by sustained drug pressure from the continued use of CQ, SP, and mechanistically similar drugs, such as amodiaquine and cotrimoxazole. There was no clear evidence that differences in transmission intensity, as a result of ITN scale-up, influenced the prevalence of drug resistance molecular markers.
    Malaria Journal 12/2015; 14(1). DOI:10.1186/s12936-015-0588-4 · 3.49 Impact Factor
  • PLoS ONE 06/2015; 10(6):e0128499. DOI:10.1371/journal.pone.0128499 · 3.53 Impact Factor
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    ABSTRACT: A malaria cohort study was conducted among young children in Machinga District, Malawi, following distribution of insecticide-treated bednets (ITN) in May 2012. To assess ITN use, two independently sampled subsets of children (211 during survey 1 [December 2012-January 2013] and 325 during survey 2 [September-October 2013]) were randomly selected to compare the proportions of positive and negative agreement between caregiver verbal reports at monthly interviews with visual observation of the ITN at home visits. Caregiver-reported ITN use was consistently high during both surveys (96.0% and 98.1%, respectively; P = 0.17). Home visit-based ITN use fell significantly (P < 0.001) from survey 1 (98.6%) to survey 2 (88.6%). The proportions of positive agreement between caregiver report and home visit in the first and second surveys were 98.8% (95% confidence interval [CI] 97.6-99.8%) and 93.3% (95% CI 91.2-95.3%), respectively. The proportions of negative agreement in the first and second surveys were 28.6% (95% CI 0-75.0%) and 20.0% (95% CI 0.1-35.0%), respectively. ITN use by children was high in Machinga District, and caregiver reports and home visits with visual confirmation of the net demonstrated a high level of agreement for use of ITNs, but a low level of agreement when ITNs were not used. © The American Society of Tropical Medicine and Hygiene.
    The American journal of tropical medicine and hygiene 02/2015; 92(4). DOI:10.4269/ajtmh.14-0768 · 2.74 Impact Factor
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    ABSTRACT: Background Insecticide-treated bed nets (ITNs) are the cornerstone of malaria control in sub-Saharan Africa but their effectiveness may be compromised by the spread of pyrethroid resistance among malaria vectors. The objective of this investigation was to assess the effectiveness of ITNs to prevent malaria in an area of Malawi with moderate pyrethroid resistance.Methods One deltamethrin ITN was distributed in the study area for every two individuals in each household plus one extra ITN for households with an odd number of residents. A fixed cohort of 1,199 children aged six to 59 months was seen monthly for one year and at sick visits to measure malaria infection and use of ITNs. Insecticide resistance among malaria vectors was measured. The effect of ITN use on malaria incidence was assessed, adjusting for potential confounders using generalized estimating equations accounting for repeated measures.ResultsThere were 1,909 infections with Plasmodium falciparum over 905 person-years at risk (PYAR), resulting in an observed incidence of 2.1 infections per person-year (iPPY). ITNs were used during 97% of the PYAR. The main vector was Anopheles funestus: mortality in WHO tube assays after exposure to 0.05% deltamethrin was 38% (95% confidence interval (CI) 29¿47), and resistance was due to elevated oxidase enzymes. After adjusting for potential confounders, the incidence of malaria infection among ITN users was 1.7 iPPY (95% CI 1.5-2.1) and among non-bed net users was 2.6 iPPY (95% CI 2.0-3.3). Use of ITNs reduced the incidence of malaria infection by 30% (rate ratio 0.7; 95% CI, 0.5-0.8) compared to no bed nets.ConclusionITNs significantly reduced the incidence of malaria infection in children in an area with moderate levels of pyrethroid resistance and considerable malaria transmission. This is the first study to show that ITNs provide protection in areas where pyrethroid-resistant An. funestus is the major malaria vector. Malaria control programmes should continue to distribute and promote ITNs in areas with low to moderate pyrethroid resistance; however, insecticide resistance may intensify further and it is not known whether ITNs will remain effective at higher levels of resistance. There is an urgent need to identify or develop new insecticides and technologies to limit the vulnerability of ITNs to insecticide resistance.
    Malaria Journal 01/2015; 14(1):31. DOI:10.1186/s12936-015-0554-1 · 3.49 Impact Factor
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    ABSTRACT: Measurement of densities of host-seeking malaria vectors is important for estimating levels of disease transmission, for appropriately allocating interventions, and for quantifying their impact. The gold standard for estimating mosquito-human contact rates is the human landing catch (HLC), where human volunteers catch mosquitoes that land on their exposed body parts. This approach necessitates exposure to potentially infectious mosquitoes, and is very labour intensive. There are several safer and less labour-intensive methods, with Centers for Disease Control light traps (LT) placed indoors near occupied bed nets being the most widely used. This paper presents analyses of 13 studies with paired mosquito collections of LT and HLC to evaluate these methods for their consistency in sampling indoor-feeding mosquitoes belonging to the two major taxa of malaria vectors across Africa, the Anopheles gambiae sensu lato complex and the Anopheles funestus s.l. group. Both overall and study-specific sampling efficiencies of LT compared with HLC were computed, and regression methods that allow for the substantial variations in mosquito counts made by either method were used to test whether the sampling efficacy varies with mosquito density. Generally, LT were able to collect similar numbers of mosquitoes to the HLC indoors, although the relative sampling efficacy, measured by the ratio of LT:HLC varied considerably between studies. The overall best estimate for An. gambiae s.l. was 1.06 (95% credible interval: 0.68-1.64) and for An. funestus s.l. was 1.37 (0.70-2.68). Local calibration exercises are not reproducible, since only in a few studies did LT sample proportionally to HLC, and there was no geographical pattern or consistent trend with average density in the tendency for LT to either under- or over-sample. LT are a crude tool at best, but are relatively easy to deploy on a large scale. Spatial and temporal variation in mosquito densities and human malaria transmission exposure span several orders of magnitude, compared to which the inconsistencies of LT are relatively small. LT, therefore, remain an invaluable and safe alternative to HLC for measuring indoor malaria transmission exposure in Africa.
    Malaria Journal 01/2015; 14:247. DOI:10.1186/s12936-015-0761-9 · 3.49 Impact Factor
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    ABSTRACT: In the past decade, there has been rapid scale-up of insecticide-based malaria vector control in the context of integrated vector management (IVM) according to World Health Organization recommendations. Endemic countries have deployed indoor residual spraying (IRS) and long-lasting insecticidal nets as hallmark vector control interventions. This paper discusses the successes and continued challenges and the way forward for the IRS programme in Malawi. The National Malaria Control Programme in Malawi, with its efforts to implement an integrated approach to malaria vector control, was the 'case' for this study. Information sources included all available data and accessible archived documentary records on IRS in Malawi. A methodical assessment of published and unpublished documents was conducted via a literature search of online electronic databases. Malawi has implemented IRS as the main malaria transmission-reducing intervention. However, pyrethroid and carbamate resistance in malaria vectors has been detected extensively across the country and has adversely affected the IRS programme. Additionally, IRS activities have been characterized by substantial inherent logistical and technical challenges culminating into missed targets. As a consequence, programmatic IRS operations have been scaled down from seven districts in 2010 to only one district in 2014. The future of the IRS programme in Malawi is uncertain due to limited funding, high cost of alternative insecticides and technical resource challenges being experienced in the country. The availability of a long-lasting formulation of the organophosphate pirimiphos-methyl makes the re-introduction of IRS a possibility and may be a useful approach for the management of pyrethroid resistance. Implementing the IVM strategy, advocating for sustainable domestic funding, including developing an insecticide resistance monitoring and management plan and vector surveillance guidelines will be pivotal in steering entomologic monitoring and future vector control activities in Malawi.
    Malaria Journal 01/2015; 14(1):254. DOI:10.1186/s12936-015-0759-3 · 3.49 Impact Factor
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    ABSTRACT: Monitoring local malaria transmission intensity is essential for planning evidence-based control strategies and evaluating their impact over time. Anti-malarial antibodies provide information on cumulative exposure and have proven useful, in areas where transmission has dropped to low sustained levels, for retrospectively reconstructing the timing and magnitude of transmission reduction. It is unclear whether serological markers are also informative in high transmission settings, where interventions may reduce transmission, but to a level where considerable exposure continues. This study was conducted through ongoing KEMRI and CDC collaboration. Asembo, in Western Kenya, is an area where intense malaria transmission was drastically reduced during a 1997-1999 community-randomized, controlled insecticide-treated net (ITN) trial. Two approaches were taken to reconstruct malaria transmission history during the period from 1994 to 2009. First, point measurements were calculated for seroprevalence, mean antibody titre, and seroconversion rate (SCR) against three Plasmodium falciparum antigens (AMA-1, MSP-119, and CSP) at five time points for comparison against traditional malaria indices (parasite prevalence and entomological inoculation rate). Second, within individual post-ITN years, age-stratified seroprevalence data were analysed retrospectively for an abrupt drop in SCR by fitting alternative reversible catalytic conversion models that allowed for change in SCR. Generally, point measurements of seroprevalence, antibody titres and SCR produced consistent patterns indicating that a gradual but substantial drop in malaria transmission (46-70%) occurred from 1994 to 2007, followed by a marginal increase beginning in 2008 or 2009. In particular, proportionate changes in seroprevalence and SCR point estimates (relative to 1994 baseline values) for AMA-1 and CSP, but not MSP-119, correlated closely with trends in parasite prevalence throughout the entire 15-year study period. However, retrospective analyses using datasets from 2007, 2008 and 2009 failed to detect any abrupt drop in transmission coinciding with the timing of the 1997-1999 ITN trial. In this highly endemic area, serological markers were useful for generating accurate point estimates of malaria transmission intensity, but not for retrospective analysis of historical changes. Further investigation, including exploration of different malaria antigens and/or alternative models of population seroconversion, may yield serological tools that are more informative in high transmission settings.
    Malaria Journal 11/2014; 13(1):451. DOI:10.1186/1475-2875-13-451 · 3.49 Impact Factor
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    ABSTRACT: Eliminating malaria requires vector control interventions that dramatically reduce adult mosquito population densities and survival rates. Indoor applications of insecticidal nets and sprays are effective against an important minority of mosquito species that rely heavily upon human blood and habitations for survival. However, complementary approaches are needed to tackle a broader diversity of less human-specialized vectors by killing them at other resource targets.
    Malaria Journal 08/2014; 13(1):338. DOI:10.1186/1475-2875-13-338 · 3.49 Impact Factor
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    ABSTRACT: It has been speculated that widespread and sustained use of insecticide treated bed nets (ITNs) for over 10 years in Asembo, western Kenya, may have selected for changes in the location (indoor versus outdoor) and time (from late night to earlier in the evening) of biting of the predominant species of human malaria vectors (Anopheles funestus, Anopheles gambiae sensu stricto, and Anopheles arabiensis).
    Parasites & Vectors 08/2014; 7(1):380. DOI:10.1186/1756-3305-7-380 · 3.25 Impact Factor
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    ABSTRACT: Using mobile devices, such as personal digital assistants (PDAs), smartphones, tablet computers, etc., to electronically collect malaria-related field data is the way for the field questionnaires in the future. This case study seeks to design a generic survey framework PDA-based geo-tagged malaria-related data collection tool (PGMS) that can be used not only for large-scale community-level geo-tagged electronic malaria-related surveys, but also for a wide variety of electronic data collections of other infectious diseases. The framework includes two parts: the database designed for subsequent cross-sectional data analysis and the customized programs for the six study sites (two in Kenya, three in Indonesia, and one in Tanzania). In addition to the framework development, we also present our methods used when configuring and deploying the PDAs to 1) reduce data entry errors, 2) conserve battery power, 3) field install the programs onto dozens of handheld devices, 4) translate electronic questionnaires into local languages, 5) prevent data loss, and 6) transfer data from PDAs to computers for future analysis and storage. Since 2008, PGMS has successfully accomplished quite a few surveys that recorded 10,871 compounds and households, 52,126 persons, and 17,100 bed nets from the six sites. These numbers are still growing.
    The American journal of tropical medicine and hygiene 07/2014; 91(3). DOI:10.4269/ajtmh.13-0652 · 2.74 Impact Factor
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    ABSTRACT: BackgroundPredictive models of malaria vector larval habitat locations may provide a basis for understanding the spatial determinants of malaria transmission.MethodsWe used four landscape variables (topographic wetness index [TWI], soil type, land use-land cover, and distance to stream) and accumulated precipitation to model larval habitat locations in a region of western Kenya through two methods: logistic regression and random forest. Additionally, we used two separate data sets to account for variation in habitat locations across space and over time.ResultsLarval habitats were more likely to be present in locations with a lower slope to contributing area ratio (i.e. TWI), closer to streams, with agricultural land use relative to nonagricultural land use, and in friable clay/sandy clay loam soil and firm, silty clay/clay soil relative to friable clay soil. The probability of larval habitat presence increased with increasing accumulated precipitation. The random forest models were more accurate than the logistic regression models, especially when accumulated precipitation was included to account for seasonal differences in precipitation. The most accurate models for the two data sets had area under the curve (AUC) values of 0.864 and 0.871, respectively. TWI, distance to the nearest stream, and precipitation had the greatest mean decrease in Gini impurity criteria in these models.ConclusionsThis study demonstrates the usefulness of random forest models for larval malaria vector habitat modeling. TWI and distance to the nearest stream were the two most important landscape variables in these models. Including accumulated precipitation in our models improved the accuracy of larval habitat location predictions by accounting for seasonal variation in the precipitation. Finally, the sampling strategy employed here for model parameterization could serve as a framework for creating predictive larval habitat models to assist in larval control efforts.
    International Journal of Health Geographics 06/2014; 13(1):17. DOI:10.1186/1476-072X-13-17 · 2.62 Impact Factor
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    ABSTRACT: Eliminating malaria from highly endemic settings will require unprecedented levels of vector control. To suppress mosquito populations, vector control products targeting their blood hosts must attain high biological coverage of all available sources, rather than merely high demographic coverage of a targeted resource subset, such as humans while asleep indoors. Beyond defining biological coverage in a measurable way, the proportion of blood meals obtained from humans and the proportion of bites upon unprotected humans occurring indoors also suggest optimal target product profiles for delivering insecticides to humans or livestock. For vectors that feed only occasionally upon humans, preferred animal hosts may be optimal targets for mosquito-toxic insecticides, and vapour-phase insecticides optimized to maximize repellency, rather than toxicity, may be ideal for directly protecting people against indoor and outdoor exposure. However, for vectors that primarily feed upon people, repellent vapour-phase insecticides may be inferior to toxic ones and may undermine the impact of contact insecticides applied to human sleeping spaces, houses or clothing if combined in the same time and place. These concepts are also applicable to other mosquito-borne anthroponoses so that diverse target species could be simultaneously controlled with integrated vector management programmes. Measurements of these two crucial mosquito behavioural parameters should now be integrated into programmatically funded, longitudinal, national-scale entomological monitoring systems to inform selection of available technologies and investment in developing new ones.
    Malaria Journal 04/2014; 13(1):146. DOI:10.1186/1475-2875-13-146 · 3.49 Impact Factor
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    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).
    The American journal of tropical medicine and hygiene 01/2014; 90(4). DOI:10.4269/ajtmh.13-0614 · 2.74 Impact Factor
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    ABSTRACT: The spatial distribution of malaria prevalence is often heterogeneous across a landscape, differing among households within a community. This is especially true in areas where community-wide malaria interventions are implemented and reduce malaria prevalence in most households. Understanding the spatial heterogeneity of malaria prevalence is especially important in this context of public health interventions in order to identify the factors that limit an intervention’s effectiveness. In the case of insecticide-treated bed nets (ITNs) and long lasting impregnated nets (LLINs), it is vital to understand the factors that influence the spatial distribution of the vectors. Using data from indoor resting mosquito collections and larval habitat surveys, we quantified the relative contributions of larval habitat spatial distribution and ITN/LLIN use on the spatial distributions of the malaria vector populations in a holoendemic region of western Kenya. We sampled 526 houses and collected 227 An. gambiae s.l. and 125 An. funestus females. Ownership and use of LLINs was high, but at least one person did not sleep under a bed net in 21% of the houses sampled. Larval Anopheles habitats were more likely to be found in areas of agricultural land use, closer to streams, and where topography favored the pooling of runoff water. Houses where at least one person did not sleep under an LLIN had more Anopheles females than houses where everyone slept under a bed net. Additionally, the number of An. gambiae s.l. females increased with the number of larval habitats within 50m of a house. While ITNs and LLINs have been shown to be effective at reducing malaria vector populations across broad scales, our results highlight fine scale factors influencing where vectors persist.
    Entomological Society of America Annual Meeting 2013; 11/2013
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    ABSTRACT: While insecticide treated nets (ITNs) and other strategies have reduced the burden of malaria, the disease remains a major cause of morbidity and mortality across sub-Saharan Africa. We assessed the cost-effectiveness of a promising new malaria prevention tool, the insecticide treated wall liner (ITWL). Its manufacturer projects a useful life of 3-4 years. The efficacy of ITWL is based on a 6-month cluster randomized trial by Gimnig et al of 1,592 children (aged 6 months-11 years) in 12 rural villages in Nyanza Province, Kenya during 2010. Control villages had only ITNs; experimental villages had both ITNs and ITWLs. The cost-effectiveness analysis considered unit costs and quantities of each input, demographic records, and published literature. The adjusted protective efficacy for ITWL was 38% (95% CI: 23%-50%), or 1.1 infection averted per child per year. The added cost of ITWL was US$64.23 per person covered, consisting of ITWL's projected factory price (44.9%), shipping and offloading (5.1%), management and supervisory personnel (24.5%), installation materials (0.4%), local transportation (13.9%), and installation labor (11.1%). Under the least favorable assumption (ITWL protection ends at 3 months, the average follow up in the previous trial), the cost per discounted life-year gained (DLYG) is US$4,837. Under the most favorable assumption (ITWL remains effective for 4 years), the cost per DLYG is US$482. Kenya's per capita GDP in 2010 was US$795. WHO considers interventions with cost-effectiveness ratios below a country's GDP highly cost-effective. As long as ITWL remains effective for at least 2.2 years, it will be highly cost-effective.
    141st APHA Annual Meeting and Exposition 2013; 11/2013
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    ABSTRACT: Long-lasting insecticide-treated mosquito nets (LLINs) are a primary malaria prevention strategy in sub-Saharan Africa. However, emergence of insecticide resistance threatens the effectiveness of LLINs. Cross-sectional surveys of LLINs were conducted in houses of seven and four villages in Gem and Bungoma Districts in western Kenya, respectively. Condition (number and area of holes in the nets), number and species of mosquitoes resting inside them, and insecticidal activity of nets were quantified. Mosquitoes collected inside nets were allowed to lay eggs and progeny tested for susceptibility to deltamethrin and permethrin, pyrethoids commonly deployed in LLINs in western Kenya. In Gem, 83.3% of nets were less than three years old and 32.4% had at least one hole of any size; while in Bungoma, 92% were less than three years old and 48% had at least one hole. No anopheline and five Culex spp. mosquitoes were found resting inside nets in Gem regardless of the number and size of holes, while 552 Anopheles gambiae s.l., five Anopheles funestus s.l. and 137 Culex spp. were in nets in Bungoma. The number of mosquitoes resting inside nets increased with hole areas >50 cm in Bungoma. In WHO resistance assays, f1 offspring of samples collected in nets in Bungoma were 94 and 65% resistant to deltamethrin and permethrin, respectively. Nets from Bungoma retained strong activity against a susceptible laboratory strain, but not against f1 offspring of field-collected An. gambiae s.s. All An. gambiae s.s. samples collected in nets were homozygous for the kdr genotype L1014S. In areas with pyrethroid resistant vectors, LLINs with modest hole areas permit mosquito entry and feeding, providing little protection against the vectors. LLIN formulations develop large holes within three years of use, diminishing their presupposed lifetime effectiveness.
    Malaria Journal 10/2013; 12(1):368. DOI:10.1186/1475-2875-12-368 · 3.49 Impact Factor
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    ABSTRACT: Malaria is an important cause of illness and death in people living in many parts of the world, especially sub-Saharan Africa. Long-lasting insecticide treated bed nets (LLINs) and indoor residual spraying (IRS) reduce malaria transmission by targeting the adult mosquito vector and are key components of malaria control programmes. However, mosquito numbers may also be reduced by larval source management (LSM), which targets mosquito larvae as they mature in aquatic habitats. This is conducted by permanently or temporarily reducing the availability of larval habitats (habitat modification and habitat manipulation), or by adding substances to standing water that either kill or inhibit the development of larvae (larviciding). To evaluate the effectiveness of mosquito LSM for preventing malaria. We searched the Cochrane Infectious Diseases Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE; EMBASE; CABS Abstracts; and LILACS up to 24 October 2012. We handsearched the Tropical Diseases Bulletin from 1900 to 2010, the archives of the World Health Organization (up to 11 February 2011), and the literature database of the Armed Forces Pest Management Board (up to 2 March 2011). We also contacted colleagues in the field for relevant articles. We included cluster randomized controlled trials (cluster-RCTs), controlled before-and-after trials with at least one year of baseline data, and randomized cross-over trials that compared LSM with no LSM for malaria control. We excluded trials that evaluated biological control of anopheline mosquitoes with larvivorous fish. At least two authors assessed each trial for eligibility. We extracted data and at least two authors independently determined the risk of bias in the included studies. We resolved all disagreements through discussion with a third author. We analyzed the data using Review Manager 5 software. We included 13 studies; four cluster-RCTs, eight controlled before-and-after trials, and one randomized cross-over trial. The included studies evaluated habitat modification (one study), habitat modification with larviciding (two studies), habitat manipulation (one study), habitat manipulation plus larviciding (two studies), or larviciding alone (seven studies) in a wide variety of habitats and countries. Malaria incidenceIn two cluster-RCTs undertaken in Sri Lanka, larviciding of abandoned mines, streams, irrigation ditches, and rice paddies reduced malaria incidence by around three-quarters compared to the control (RR 0.26, 95% CI 0.22 to 0.31, 20,124 participants, two trials, moderate quality evidence). In three controlled before-and-after trials in urban and rural India and rural Kenya, results were inconsistent (98,233 participants, three trials, very low quality evidence). In one trial in urban India, the removal of domestic water containers together with weekly larviciding of canals and stagnant pools reduced malaria incidence by three quarters. In one trial in rural India and one trial in rural Kenya, malaria incidence was higher at baseline in intervention areas than in controls. However dam construction in India, and larviciding of streams and swamps in Kenya, reduced malaria incidence to levels similar to the control areas. In one additional randomized cross-over trial in the flood plains of the Gambia River, where larval habitats were extensive and ill-defined, larviciding by ground teams did not result in a statistically significant reduction in malaria incidence (2039 participants, one trial). Parasite prevalenceIn one cluster-RCT from Sri Lanka, larviciding reduced parasite prevalence by almost 90% (RR 0.11, 95% CI 0.05 to 0.22, 2963 participants, one trial, moderate quality evidence). In five controlled before-and-after trials in Greece, India, the Philippines, and Tanzania, LSM resulted in an average reduction in parasite prevalence of around two-thirds (RR 0.32, 95% CI 0.19 to 0.55, 8041 participants, five trials, moderate quality evidence). The interventions in these five trials included dam construction to reduce larval habitats, flushing of streams, removal of domestic water containers, and larviciding. In the randomized cross-over trial in the flood plains of the Gambia River, larviciding by ground teams did not significantly reduce parasite prevalence (2039 participants, one trial). In Africa and Asia, LSM is another policy option, alongside LLINs and IRS, for reducing malaria morbidity in both urban and rural areas where a sufficient proportion of larval habitats can be targeted. Further research is needed to evaluate whether LSM is appropriate or feasible in parts of rural Africa where larval habitats are more extensive.
    Cochrane database of systematic reviews (Online) 08/2013; 8(8):CD008923. DOI:10.1002/14651858.CD008923.pub2 · 5.94 Impact Factor
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    ABSTRACT: Anti-malarial regimens containing sulphonamide or artemisinin ingredients are widely used in malaria-endemic countries. However, evidence of the incidence of adverse drug reactions (ADR) to these drugs is limited, especially in Africa, and there is a complete absence of information on the economic burden such ADR place on patients. This study aimed to document ADR incidence and associated household costs in three high malaria transmission districts in rural Tanzania covered by demographic surveillance systems. Active and passive surveillance methods were used to identify ADR from sulphadoxine-pyrimethamine (SP) and artemisinin (AS) use. ADR were identified by trained clinicians at health facilities (passive surveillance) and through cross-sectional household surveys (active surveillance). Potential cases were followed up at home, where a complete history and physical examination was undertaken, and household cost data collected. Patients were classified as having 'possible' or 'probable' ADR by a physician. A total of 95 95 suspected ADR were identified during a two-year period, of which 79 were traced, and 67 reported use of SP and/or AS prior to ADR onset. Thirty-four cases were classified as 'probable' and 33 as 'possible' ADRs. Most (53) cases were associated with SP monotherapy, 13 with the AS/SP combination (available in one of the two areas only), and one with AS monotherapy. Annual ADR incidence per 100,000 exposures was estimated based on 'probable' ADR only at 5.6 for AS/SP in combination, and 25.0 and 11.6 for SP monotherapy. Median ADR treatment costs per episode ranged from US$2.23 for those making a single provider visit to US$146.93 for patients with four visits. Seventy-three per cent of patients used out-of-pocket funds or sold part of their farm harvests to pay for treatment, and 19% borrowed money. Both passive and active surveillance methods proved feasible methods for anti-malarial ADR surveillance, with active surveillance being an important complement to facility-based surveillance, given the widespread practice of self-medication. Household costs associated with ADR treatment were high and potentially catastrophic. Efforts should be made to both improve pharmacovigilance across Africa and to identify strategies to reduce the economic burden endured by households suffering from ADR.
    Malaria Journal 07/2013; 12(1):236. DOI:10.1186/1475-2875-12-236 · 3.49 Impact Factor
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    ABSTRACT: Malaria vectors which predominantly feed indoors upon humans have been locally eliminated from several settings with insecticide treated nets (ITNs), indoor residual spraying or larval source management. Recent dramatic declines of An. gambiae in east Africa with imperfect ITN coverage suggest mosquito populations can rapidly collapse when forced below realistically achievable, non-zero thresholds of density and supporting resource availability. Here we explain why insecticide-based mosquito elimination strategies are feasible, desirable and can be extended to a wider variety of species by expanding the vector control arsenal to cover a broader spectrum of the resources they need to survive. The greatest advantage of eliminating mosquitoes, rather than merely controlling them, is that this precludes local selection for behavioural or physiological resistance traits. The greatest challenges are therefore to achieve high biological coverage of targeted resources rapidly enough to prevent local emergence of resistance and to then continually exclude, monitor for and respond to re-invasion from external populations.
    Parasites & Vectors 06/2013; 6(1):172. DOI:10.1186/1756-3305-6-172 · 3.25 Impact Factor
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    ABSTRACT: Background Operational vector sampling methods lack standardization, making quantitative comparisons of malaria transmission across different settings difficult. Human landing catch (HLC) is considered the research gold standard for measuring human-mosquito contact, but is unsuitable for large-scale sampling. This study assessed mosquito catch rates of CDC light trap (CDC-LT), Ifakara tent trap (ITT), window exit trap (WET), pot resting trap (PRT), and box resting trap (BRT) relative to HLC in western Kenya to 1) identify appropriate methods for operational sampling in this region, and 2) contribute to a larger, overarching project comparing standardized evaluations of vector trapping methods across multiple countries. Methods Mosquitoes were collected from June to July 2009 in four districts: Rarieda, Kisumu West, Nyando, and Rachuonyo. In each district, all trapping methods were rotated 10 times through three houses in a 3 × 3 Latin Square design. Anophelines were identified by morphology and females classified as fed or non-fed. Anopheles gambiae s.l. were further identified as Anopheles gambiae s.s. or Anopheles arabiensis by PCR. Relative catch rates were estimated by negative binomial regression. Results When data were pooled across all four districts, catch rates (relative to HLC indoor) for An. gambiae s.l (95.6% An. arabiensis, 4.4% An. gambiae s.s) were high for HLC outdoor (RR = 1.01), CDC-LT (RR = 1.18), and ITT (RR = 1.39); moderate for WET (RR = 0.52) and PRT outdoor (RR = 0.32); and low for all remaining types of resting traps (PRT indoor, BRT indoor, and BRT outdoor; RR < 0.08 for all). For Anopheles funestus, relative catch rates were high for ITT (RR = 1.21); moderate for HLC outdoor (RR = 0.47), CDC-LT (RR = 0.69), and WET (RR = 0.49); and low for all resting traps (RR < 0.02 for all). At finer geographic scales, however, efficacy of each trap type varied from district to district. Conclusions ITT, CDC-LT, and WET appear to be effective methods for large-scale vector sampling in western Kenya. Ultimately, choice of collection method for operational surveillance should be driven by trap efficacy and scalability, rather than fine-scale precision with respect to HLC. When compared with recent, similar trap evaluations in Tanzania and Zambia, these data suggest that traps which actively lure host-seeking females will be most useful for surveillance in the face of declining vector densities.
    Malaria Journal 04/2013; 12(1):143. DOI:10.1186/1475-2875-12-143 · 3.49 Impact Factor

Publication Stats

2k Citations
259.28 Total Impact Points

Institutions

  • 2003–2015
    • Centers for Disease Control and Prevention
      • Division of Parasitic Diseases and Malaria
      Атланта, Michigan, United States
    • Kenya Centers for Disease Control and Prevention
      Winam, Kisumu, Kenya
  • 2012
    • University of Notre Dame
      • Department of Biological Sciences
      South Bend, Indiana, United States
  • 2006
    • Kenyatta University
      Nairoba, Nairobi Area, Kenya
  • 2005
    • Tulane University
      New Orleans, Louisiana, United States
  • 2001–2003
    • Kenya Medical Research Institute
      • Centre for Global Health Research
      Nairoba, Nairobi Area, Kenya
    • University of Nairobi
      Nairoba, Nairobi Area, Kenya