Search

In The Gambia, metal-roof houses were hotter during the day than thatched-roof houses. After 24 h, the mortality of Anopheles gambiae, the principal African malaria vector, was 38% higher in metal-roof houses than thatched ones. During the day, mosquitoes in metal-roof houses moved from the hot roof to cooler places near the floor, where the temperature was still high, reaching 35 °C. In laboratory studies, at 35 °C few mosquitoes survived 10 days, the minimum period required for malaria parasite development. Analysis of epidemiological data showed there was less malaria and lower vector survival rates in Gambian villages with a higher proportion of metal roofs. Our findings are consistent with the hypothesis that the indoor climate of metal-roof houses, with higher temperatures and lower humidity, reduces survivorship of indoor-resting mosquitoes and may have contributed to the observed reduction in malaria burden in parts of sub-Saharan Africa.

In sub-Saharan Africa, cooler houses would increase the coverage of insecticide-treated bednets, the primary malaria control tool. We examined whether improved ventilation, using windows screened with netting, cools houses at night and reduces malaria mosquito house entry in The Gambia. Identical houses were constructed, with badly fitting doors the only mosquito entry points. Two men slept in each house and mosquitoes captured using light traps. First, temperature and mosquito density were compared in four houses with 0, 1, 2 and 3 screened windows. Second, carbon dioxide (CO2), a major mosquito attractant, was measured in houses with (i) no windows, (ii) screened windows and (iii) screened windows and screened doors. Computational fluid dynamic modelling captured the spatial movement of CO2. Increasing ventilation made houses cooler, more comfortable and reduced malaria mosquito house entry; with three windows reducing mosquito densities by 95% (95%CI = 90–98%). Screened windows and doors reduced the indoor temperature by 0.6°C (95%CI = 0.5–0.7°C), indoor CO2concentrations by 31% between 21.00 and 00.00 h and malaria mosquito entry by 76% (95%CI = 69–82%). Modelling shows screening reduces CO2plumes from houses. Under our experimental conditions, cross-ventilation not only reduced indoor temperature, but reduced the density of house-entering malaria mosquitoes, by weakening CO2plumes emanating from houses.

Most malaria infections in sub-Saharan Africa are acquired indoors, thus finding effective ways of preventing mosquito house entry should reduce transmission. Since most malaria mosquitoes fly less than 1 m from the ground, we tested whether raising buildings off the ground would prevent the entry of Anopheles gambiae , the principal African malaria vector, in rural Gambia. Nightly collections of mosquitoes were made using light traps from four inhabited experimental huts, each of which could be moved up or down. Mosquito house entry declined with increasing height, with a hut at 3 m reducing An. gambiae house entry by 84% when compared with huts on the ground. A propensity for malaria vectors to fly close to the ground and reduced levels of carbon dioxide, a major mosquito attractant, in elevated huts, may explain our findings. Raised buildings may help reduce malaria transmission in Africa.

Summary Background In malaria-endemic areas, residents of modern houses have less malaria than those living in traditional houses. We aimed to assess whether children in The Gambia received an incremental benefit from improved housing, where current best practice of insecticide-treated nets, indoor residual spraying, seasonal malaria chemoprevention in children younger than 5 years, and prompt treatment against clinical malaria was in place. Methods In this randomised controlled study, 800 households with traditional thatched-roofed houses were randomly selected from 91 villages in the Upper River Region of The Gambia. Within each village, equal numbers of houses were randomly allocated to the control and intervention groups using a sampling frame. Houses in the intervention group were modified with metal roofs and screened doors and windows, whereas houses in the control group received no modifications. In each group, clinical malaria in children aged 6 months to 13 years was monitored by active case detection over 2 years (2016–17). We did monthly collections from indoor light traps to estimate vector densities. Primary endpoints were the incidence of clinical malaria in study children with more than 50% of observations each year and household vector density. The trial is registered at ISRCTN02622179. Findings In June, 2016, 785 houses had one child each recruited into the study (398 in unmodified houses and 402 in modified houses). 26 children in unmodified houses and 28 children in modified houses did not have at least 50% of visits in a year and so were excluded from analysis. 38 children in unmodified houses were recruited after study commencement, as were 21 children in modified houses, meaning 410 children in unmodified houses and 395 in modified houses were included in the parasitological analyses. At the end of the study, 659 (94%) of 702 children were reported to have slept under an insecticide-treated net; 662 (88%) of 755 children lived in houses that received indoor residual spraying; and 151 (90%) of 168 children younger than 5 years had seasonal malaria chemoprevention. Incidence of clinical malaria was 0·12 episodes per child-year in children in the unmodified houses and 0·20 episodes per child-year in the modified houses (unadjusted incidence rate ratio [RR] 1·68 [95% CI 1·11–2·55], p=0·014). Household vector density was 3·30 Anopheles gambiae per house per night in the unmodified houses compared with 3·60 in modified houses (unadjusted RR 1·28 [0·87–1·89], p=0·21). Interpretation Improved housing did not provide protection against clinical malaria in this area of low seasonal transmission with high coverage of insecticide-treated nets, indoor residual spraying, and seasonal malaria chemoprevention. Funding Global Health Trials funded by Medical Research Council, UK Department for International Development, and Wellcome Trust.

Label: BACKGROUND NlmCategory: BACKGROUND content: Recording behaviours that have the potential to impact health can be doubly challenging if the behaviour takes place in private spaces that cannot be observed directly, and where respondents answer what they think the recorder may want to hear. Sleeping under a long-lasting insecticidal net (LLIN) is an important intervention for malaria prevention, yet it is difficult to gauge the extent to which coverage (how many nets are in the community) differs from usage (how many people actually sleep under a net). List randomization, a novel method which partially obscures respondents' answers to sensitive questions, was employed to estimate LLIN usage in The Gambia. - Label: METHODS NlmCategory: METHODS content: "802 heads-of-household from 15 villages were recruited into a randomized controlled trial assessing the effect of a housing intervention on malaria. These houses were randomly assigned to a housing intervention versus control, with stratification by village so as to ensure balance between arms. From these, 125 households (63 intervention, 52 control) were randomly selected for participation in the list randomization experiment, along with 68 households from the same villages but which were not part of the housing improvement study, resulting in a total of 196 households for the list randomization experiment. Approximately half (n\xE2\x80\x89=\xE2\x80\x8997) of the 196 study participants were randomly assigned to the control group and received a four-question list about non-sensitive behaviours; the intervention group (n\xE2\x80\x89=\xE2\x80\x8999) received the same list, with the addition of one question on a sensitive behaviour: whether or not they had used a bed net the previous night. Participants were read the list of questions and then said how many of the statements were true. Bed net usage was estimated by calculating the difference in means between the number of affirmative responses between the two groups." - Label: RESULTS NlmCategory: RESULTS content: The mean number of affirmative responses in the control group was 2.60 of four statements (95% confidence interval, 95% CI 2.50-2.70), compared with 3.68 (95% CI 3.59-3.78) in the intervention group. Such difference (1.08; 95% CI 94.9-100%) suggests near universal bed net usage. - Label: CONCLUSIONS NlmCategory: CONCLUSIONS content: Bed net usage by household heads in these rural villages was found to be high. Though not entirely unexpected given other studies' estimates of high bed net usage in the area, the list randomization method should be further validated in an area with lower coverage.

Background Long-lasting insecticidal nets (LLINs) treated with pyrethroids are the foundation of malaria control in sub-Saharan Africa. Rising pyrethroid resistance in vectors, however, has driven the development of alternative net formulations. Here the durability of polyethylene nets with a novel combination of a pyrethroid, permethrin, and the insect juvenile hormone mimic, pyriproxyfen (PPF), compared to a standard permethrin LLIN, was assessed in rural Burkina Faso. Methods A compound-randomized controlled trial was completed in two villages. In one village 326 of the PPF-permethrin nets (Olyset Duo) and 327 standard LLINs (Olyset) were distributed to assess bioefficacy. In a second village, 170 PPF-permethrin nets and 376 LLINs were distributed to assess survivorship. Nets were followed at 6-monthly intervals for 3 years. Bioefficacy was assessed by exposing permethrin-susceptible and resistant Anopheles gambiae sensu lato mosquito strains to standard World Health Organization (WHO) cone and tunnel tests with impacts on fertility measured in the resistant strain. Insecticide content was measured using high-performance liquid chromatography. LLIN survivorship was recorded with a questionnaire and assessed by comparing the physical integrity using the proportionate hole index (pHI). Results The PPF-permethrin net met WHO bioefficacy criteria (≥ 80% mortality or ≥ 95% knockdown) for the first 18 months, compared to 6 months for the standard LLIN. Mean mosquito mortality for PPF-permethrin nets, across all time points, was 8.6% (CI 2.6–14.6%) higher than the standard LLIN. Fertility rates were reduced after PPF-permethrin net exposure at 1-month post distribution, but not later. Permethrin content of both types of nets remained within the target range of 20 g/kg ± 25% for 242/248 nets tested. The pyriproxyfen content of PPF-permethrin nets declined by 54%, from 10.4 g/kg (CI 10.2–10.6) to 4.7 g/kg (CI 3.5–6.0, p Conclusion The PPF-permethrin net, Olyset Duo, met or exceeded the performance of the WHO-recommended standard LLIN (Olyset) in the current study but both net types failed the 3-year WHO bioefficacy criteria.

Bio-Detection Dogs (BDDs) are used in some high-income countries as a diagnostic intervention, yet little is known about their potential in low/middle-income countries with limited diagnostic resources. This exploratory study investigated the opportunities and implications of deploying BDDs as a mobile diagnostic intervention to identify people with asymptomatic malaria, particularly at ports of entry, as an important step to malaria elimination in a population. A qualitative study design consisting of participant observation, five focus group discussions and informal conversations was employed in The Gambia in April–May 2017. A disciplined German Shepherd companion dog (not trained as a BDD) was introduced to research participants and their perceptions recorded. Field-notes and discussions were transcribed, translated and analysed thematically. Most research participants viewed positively the possibility of using BDDs to detect malaria, with the major advantage of being non-invasive. Some concerns, however, were raised regarding safety and efficacy, as well as cultural issues around the place of dogs within human society. The Gambia is a rabies-endemic country, and unfamiliar dogs are not usually approached, with implications for how research participants perceived BDDs. Understanding such concerns and working with local people to address such issues must be part of any successful strategy to deploy BDDs in new settings. Bio-Detection Dogs represent a potentially non-invasive diagnostic tool for the detection of asymptomatic or chronic malaria infections, particularly in areas with very low parasite rates. However, it is important to understand local concerns and work closely with communities to address those concerns. Wider deployment of BDDs will also require careful planning and sustained financial support.

Summary Introduction Unprecedented improvements in housing are occurring across much of rural sub-Saharan Africa, but the consequences of these changes on malaria transmission remain poorly explored. We examined how different typologies of rural housing affect mosquito house entry and indoor climate. Methods Five typologies of mud-block houses were constructed in rural Gambia: four were traditional designs with poorly fitted doors and one was a novel design with gable windows to improve ventilation. In each house, one male volunteer slept under a bednet and mosquitoes were collected indoors with a light trap. Typologies were rotated between houses weekly. Indoor conditions were monitored with data loggers and the perceived comfort of sleepers recorded with questionnaires. We used pyschrometric modelling to quantify the comfort of the indoor climate using the logger data. Primary measurements were mean number of Anopheles gambiae and mean temperature for each house typology. Findings In thatched-roofed houses, closing the eaves reduced A gambiae house entry by 94% (95% CI 89–97) but increased the temperature compared with thatched-roofed houses with open eaves. In houses with closed eaves, those with metal roofs had more A gambiae, were hotter (1·5°C hotter [95% CI 1·3–1·7]) between 2100h and 2300 h, and had 25% higher concentrations of carbon dioxide (211·1 ppm higher [117·8–304·6]) than those with thatched roofs. In metal-roofed houses with closed eaves, mosquito house entry was reduced by 96% (91–98) by well fitted screened doors. Improved ventilation of metal-roofed houses made them as cool as thatched houses with open eaves. Metal-roofed houses with closed eaves were considered more uncomfortable than thatched ones with closed eaves. In metal-roofed houses, ventilated houses were more comfortable than unventilated houses before midnight, when people retired to bed. Interpretation Closing the eaves reduced vector entry in thatched houses but increased entry in metal-roofed houses. Metal-roofed houses with closed eaves were, however, protected against malaria vectors by well fitted screened doors and were made comfortable by increasing ventilation. House designs that exclude mosquitoes and are comfortable to live in should be a priority in sub-Saharan Africa. Funding Sir Halley Stewart Trust, Global Clinical Trials, and Global Challenges Research Fund.

Background Insecticide resistance threatens malaria control in sub-Saharan Africa. Knockdown resistance to pyrethroids and organochlorines in Anopheles gambiae sensu lato (s.l.) is commonly caused by mutations in the gene encoding a voltage-gated sodium channel which is the target site for the insecticide. The study aimed to examine risk factors for knockdown resistance in An. gambiae s.l. and its relationship with malaria infection in children in rural Gambia. Point mutations at the Vgsc-1014 locus, were measured in An. gambiae s.l. during a 2-year trial. Cross-sectional surveys were conducted at the end of the transmission season to measure malaria infection in children aged 6 months–14 years. Results Whilst few Anopheles arabiensis and Anopheles coluzzii had Vgsc-1014 mutations, the proportion of An. gambiae sensu stricto (s.s.) mosquitoes homozygous for the Vgsc-1014F mutation increased from 64.8 to 90.9% during the study. The Vgsc-1014S or 1014F mutation was 80% higher in 2011 compared to 2010, and 27% higher in the villages with indoor residual spraying compared to those without. An increase in the proportion of An. gambiae s.l. mosquitoes with homozygous Vgsc-1014F mutations and an increase in the proportion of An. gambiae s.s. in a cluster were each associated with increased childhood malaria infection. Homozygous Vgsc-1014F mutations were, however, most common in An. gambiae s.s. and almost reached saturation during the study meaning that the two variables were colinear. Conclusions As a result of colinearity between homozygous Vgsc-1014F mutations and An. gambiae s.s., it was not possible to determine whether insecticide resistance or species composition increased the risk of childhood malaria infection. Electronic supplementary material The online version of this article (10.1186/s12936-018-2348-8) contains supplementary material, which is available to authorized users.

Summary Background Substantial reductions in malaria incidence in sub-Saharan Africa have been achieved with massive deployment of long-lasting insecticidal nets (LLINs), but pyrethroid resistance threatens control. Burkina Faso is an area with intense malaria transmission and highly pyrethroid-resistant vectors. We assessed the effectiveness of bednets containing permethrin, a pyrethroid, and pyriproxyfen, an insect growth regulator, versus permethrin-only (standard) LLINs against clinical malaria in children younger than 5 years in Banfora, Burkina Faso. Methods In this two-group, step-wedge, cluster-randomised, controlled, superiority trial, standard LLINs were incrementally replaced with LLINs treated with permethrin plus pyriproxyfen (PPF) in 40 rural clusters in Burkina Faso. In each cluster, 50 children (aged 6 months to 5 years) were followed up by passive case detection for clinical malaria. Cross-sectional surveys were done at the start and the end of the transmission seasons in 2014 and 2015. We did monthly collections from indoor light traps to estimate vector densities. Primary endpoints were the incidence of clinical malaria, measured by passive case detection, and the entomological inoculation rate. Analyses were adjusted for clustering and for month and health centre. This trial is registered as ISRCTN21853394. Findings 1980 children were enrolled in the cohort in 2014 and 2157 in 2015. At the end of the study, more than 99% of children slept under a bednet. The incidence of clinical malaria was 2·0 episodes per child-year in the standard LLIN group and 1·5 episodes per child-year in the PPF-treated LLIN group (incidence rate ratio 0·88 [95% CI 0·77–0·99; p=0·04]). The entomological inoculation rate was 85 (95% CI 63–108) infective bites per transmission season in the standard LLIN group versus 42 (32–52) infective bites per transmission season in the PPF-treated LLIN group (rate ratio 0·49, 95% CI 0·32–0·66; p Interpretation PPF-treated LLINs provide greater protection against clinical malaria than do standard LLINs and could be used as an alternative to standard LLINs in areas with intense transmission of Plasmodium falciparum malaria and highly pyrethroid-resistant vectors. Funding EU Seventh Framework Programme.

Summary Background Although many malaria control programmes in sub-Saharan Africa use indoor residual spraying with long-lasting insecticidal nets (LLINs), the two studies assessing the benefit of the combination of these two interventions gave conflicting results. We aimed to assess whether the addition of indoor residual spraying to LLINs provided a significantly different level of protection against clinical malaria in children or against house entry by vector mosquitoes. Methods In this two-arm cluster, randomised, controlled efficacy trial we randomly allocated clusters of Gambian villages using a computerised algorithm to LLINs alone (n=35) or indoor residual spraying with dichlorodiphenyltrichloroethane plus LLINs (n=35). In each cluster, 65–213 children, aged 6 months to 14 years, were surveyed at the start of the 2010 transmission season and followed in 2010 and 2011 by passive case detection for clinical malaria. Exposure to parasite transmission was assessed by collection of vector mosquitoes with both light and exit traps indoors. Primary endpoints were the incidence of clinical malaria assessed by passive case detection and number of Anopheles gambiae sensu lato mosquitoes collected per light trap per night. Intervention teams had no role in data collection and the data collection teams were not informed of the spray status of villages. The trial is registered at the ISRCTN registry, number ISRCTN01738840. Findings LLIN coverage in 2011 was 3510 (93%) of 3777 children in the indoor residual spraying plus LLIN group and 3622 (95·5%) of 3791 in the LLIN group. In 2010, 7845 children were enrolled, 7829 completed passive case detection, and 7697 (98%) had complete clinical and covariate data. In 2011, 7009 children remained in the study, 648 more were enrolled, 7657 completed passive case detection, and 7545 (98·5%) had complete data. Indoor residual spraying coverage per cluster was more than 80% for both years in the indoor residual spraying plus LLIN group. Incidence of clinical malaria was 0·047 per child-month at risk in the LLIN group and 0·044 per child-month at risk in the indoor residual spraying plus LLIN group in 2010, and 0·032 per child-month at risk in the LLIN group and 0·034 per child-month at risk in the indoor residual spraying plus LLIN group in 2011. The incident rate ratio was 1·08 (95% CI 0·80–1·46) controlling for confounders and cluster by mixed-effect negative binomial regression on all malaria attacks for both years. No significant difference was recorded in the density of vector mosquitoes caught in light traps in houses over the two transmission seasons; the mean number of A gambiae sensu lato mosquitoes per trap per night was 6·7 (4·0–10·1) in the LLIN group and 4·5 (2·4–7·4) in the indoor residual spraying plus LLIN group (p=0·281 in the random-effects linear regression model). Interpretation We identified no significant difference in clinical malaria or vector density between study groups. In this area with high LLIN coverage, moderate seasonal transmission, and susceptible vectors, indoor residual spraying did not provide additional benefit. Funding UK Medical Research Council.

Many human genetic associations with resistance to malaria have been reported, but few have been reliably replicated. We collected data on 11,890 cases of severe malaria due to Plasmodium falciparum and 17,441 controls from 12 locations in Africa, Asia and Oceania. We tested 55 SNPs in 27 loci previously reported to associate with severe malaria. There was evidence of association at P < 1 × 10(-4) with the HBB, ABO, ATP2B4, G6PD and CD40LG loci, but previously reported associations at 22 other loci did not replicate in the multicenter analysis. The large sample size made it possible to identify authentic genetic effects that are heterogeneous across populations or phenotypes, with a striking example being the main African form of G6PD deficiency, which reduced the risk of cerebral malaria but increased the risk of severe malarial anemia. The finding that G6PD deficiency has opposing effects on different fatal complications of P. falciparum infection indicates that the evolutionary origins of this common human genetic disorder are more complex than previously supposed.

Interferon (IFN)-gamma is a critical mediator of immunity to malaria. This study explored the relationship between polymorphisms in the promoter region of the gene encoding IFN-gamma receptor 1 (IFNGR1) and susceptibility to malaria in African children. Four polymorphisms were found in the region between -1400 and +100 nt of the translational start site by sequencing, and analysis of 562 nuclear families revealed 6 haplotypes. Case-control analysis of 562 Gambian children with severe malaria and 569 umbilical cord blood samples (controls) showed that in Mandinka, the major Gambian ethnic group, heterozygotes for the IFNGR1-56 polymorphism were protected against cerebral malaria (odds ratio, 0.54; P=.016) and against death resulting from cerebral malaria (odds ratio, 0.22; P=.006). Analysis of a family study by transmission disequilibrium testing revealed a similar result. Further data are needed to validate this finding, but these results are reminiscent of those for other well-established heterozygote advantages, such as that associated with hemoglobin S.

The leading blood-stage malaria vaccine candidate antigen, Plasmodium falciparum merozoite surface protein-1 (MSP-1) occurs in two major allelic types worldwide. The molecular basis promoting this stable dimorphism is unknown. In this study, we have shown that allelic altered peptide ligand (APL) T cell epitopes of MSP-1 mutually inhibited IFN-gamma secretion as well as proliferation of CD4+ T cells in 27/34 malaria exposed Gambian volunteers. Besides this inhibition of malaria-specific immunity, the same variant epitopes were also able to impair the priming of human T cells in malaria naive individuals. Epitope variants capable of interfering with T cell priming as well as inhibiting memory T cell effector functions offer a uniquely potent combination for immune evasion. Indeed, enhanced co-habitation of parasites bearing such antagonistic allelic epitope regions was observed in a study of 321 West African children, indicating a survival advantage for parasites able to engage this inhibitory immune interference mechanism.

Several lines of evidence link glucose-6-phosphate dehydrogenase (G6PD) deficiency to protection from severe malaria. Early reports suggested most G6PD deficiency in sub-Saharan Africa was because of the 202A/376G G6PD A− allele, and recent association studies of G6PD deficiency have employed genotyping as a convenient way to determine enzyme status. However, further work has suggested that other G6PD deficiency alleles are relatively common in some regions of West Africa. To investigate the consequences of unrecognized allelic heterogeneity on association studies, in particular studies of G6PD deficiency and malaria, we carried out a case–control analysis of 2488 Gambian children with severe malaria and 3875 controls. No significant association was found between severe malaria and the 202A/376G G6PD A− allele when analyzed alone, but pooling 202A/376G with other deficiency alleles revealed the signal of protection (male odds ratio (OR) 0.77, 95% CI 0.62–0.95, P=0.016; female OR 0.71, 95% CI 0.56–0.89, P=0.004). We have identified the 968C mutation as the most common G6PD A− allele in The Gambia. Our results highlight some of the consequences of allelic heterogeneity, particularly the increased type I error. They also suggest that G6PD-deficient male hemizygotes and female heterozygotes are protected from severe malaria.

Functional studies have demonstrated an interaction between the stimulatory G protein alpha subunit (G-alpha-s) and the malaria parasite at a cellular level. Obstruction of signal transduction via the erythrocyte G-alpha-s subunit reduced invasion by Plasmodium falciparum parasites. We sought to determine whether this signal pathway had an impact at the disease level by testing polymorphisms in the gene encoding G-alpha-s (GNAS) for association with severe malaria in a large multi-centre study encompassing family and case-control studies from The Gambia, Kenya and Malawi, and a case-control study from Ghana. We gained power to detect association using meta-analysis across the seven studies, with an overall sample size approximating 4,000 cases and 4,000 controls. Out of 12 SNPs investigated in the 19 kb GNAS region, four presented signals of association (P < 0.05) with severe malaria. The strongest single-locus association demonstrated an odds ratio of 1.13 (1.05-1.21), P = 0.001. Three of the loci presenting significant associations were clustered at the 5-prime end of the GNAS gene. Accordingly, haplotypes constructed from these loci demonstrated significant associations with severe malaria [OR = 0.88 (0.81-0.96), P = 0.005 and OR = 1.12 (1.03-1.20), P = 0.005]. The evidence presented here indicates that the influence of G-alpha-s on erythrocyte invasion efficacy may, indeed, alter individual susceptibility to disease.

Interferon-gamma, encoded by IFNG, is a key immunological mediator that is believed to play both a protective and a pathological role in malaria. Here, we investigate the relationship between IFNG variation and susceptibility to malaria. We began by analysing West African and European haplotype structure and patterns of linkage disequilibrium across a 100 kb genomic region encompassing IFNG and its immediate neighbours IL22 and IL26. A large case-control study of severe malaria in a West Africa population identified several weak associations with individual single-nucleotide polymorphisms in the IFNG and IL22 genes, and defined two IL22 haplotypes that are, respectively, associated with resistance and susceptibility. These data provide a starting point for functional and genetic analysis of the IFNG genomic region in malaria and other infectious and inflammatory conditions affecting African populations.

Background In malaria-endemic areas, residents of modern houses have less malaria than those living in traditional houses. This study will determine if modern housing provides incremental protection against clinical malaria over the current best practice of long-lasting insecticidal nets (LLINs) and prompt treatment in The Gambia, determine the incremental cost-effectiveness of the interventions, and analyze the housing market in The Gambia. Methods/design A two-armed, household, cluster-randomized, controlled study will be conducted to assess whether improved housing and LLINs combine to provide better protection against clinical malaria in children than LLINs alone in The Gambia. The unit of randomization will be the household, defined as a house and its occupants. A total of 800 households will be enrolled and will receive LLINs, and 400 will receive improved housing before clinical follow-up. One child aged 6 months to 13 years will be enrolled from each household and followed for clinical malaria using active case detection to estimate malaria incidence for two malaria transmission seasons. Episodes of clinical malaria will be the primary endpoint. Study children will be surveyed at the end of each transmission season to estimate the prevalence of Plasmodium falciparum infection, parasite density, and the prevalence of anemia. Exposure to malaria parasites will be assessed using light traps, followed by detection of Anopheles gambiae species and sporozoite infection. Ancillary economic and social science studies will undertake a cost-effectiveness analysis and use qualitative and participatory methods to explore the acceptability of the housing modifications and to design strategies for scaling-up housing interventions. Discussion The study is the first of its kind to measure the efficacy of housing on reducing clinical malaria, assess the incremental cost-effectiveness of improved housing, and identify mechanisms for scaling up housing interventions. Trial findings will help inform policy makers on improved housing for malaria control in sub-Saharan Africa. Trial registration ISRCTN Registry, ISRCTN02622179. Registered on 23 September 2014. Electronic supplementary material The online version of this article (doi:10.1186/s13063-016-1400-7) contains supplementary material, which is available to authorized users.

Objective To explore ways of controlling Chrysomya putoria, the African latrine fly, in pit latrines. As pit latrines are a major source of these flies, eliminating these important breeding sites is likely to reduce village fly populations, and may reduce the spread of diarrhoeal pathogens. Methods We treated 24 latrines in a Gambian village: six each with (i) pyriproxyfen, an insect juvenile hormone mimic formulated as Sumilarv® 0.5G, a 0.5% pyriproxyfen granule, (ii) expanded polystyrene beads (EPB), (iii) local soap or (iv) no treatment as controls. Flies were collected using exit traps placed over the drop holes, weekly for five weeks. In a separate study, we tested whether latrines also function as efficient flytraps using the faecal odours as attractants. We constructed six pit latrines each with a built-in flytrap and tested their catching efficiency compared to six fish-baited box traps positioned 10 m from the latrine. Focus group discussions conducted afterwards assessed the acceptability of the flytrap latrines. Results Numbers of emerging C. putoria were reduced by 96.0% (95% CIs: 94.5–97.2%) 4–5 weeks after treatment with pyriproxyfen; by 64.2% (95% CIs: 51.8–73.5%) after treatment with local soap; by 41.3% (95% CIs = 24.0–54.7%) after treatment with EPB 3–5 weeks after treatment. Flytraps placed on latrines collected C. putoria and were deemed acceptable to local communities. Conclusions Sumilarv 0.5G shows promise as a chemical control agent, whilst odour-baited latrine traps may prove a useful method of non-chemical fly control. Both methods warrant further development to reduce fly production from pit latrines. A combination of interventions may prove effective for the control of latrine flies and the diseases they transmit. Objectif Explorer les moyens de lutter contre Chrysomya putoria, la mouche africaine des latrines, dans les latrines a fosse. Comme les latrines sont une source importante de production pour ces mouches, l’elimination de ces sites de reproduction importants est susceptible de reduire les populations de mouches du village et peut reduire la propagation des agents pathogenes diarrheiques. Methodes Nous avons traite 24 latrines dans un village gambien: six avec soit (1) du pyriproxyfene, une formulation imitant une hormone juvenile des insectes appelee Sumilarv® 0.5G, a granules de 0,5% de pyriproxyfene, (2) des billes de polystyrene gonflees (EPB), (3) du savon local ou (4) aucun traitement i.e. temoins. Les mouches ont ete recueillies a l'aide de pieges de sortie places au dessus des orifices des fosses, chaque semaine pendant cinq semaines. Dans une autre etude, nous avons teste si les latrines pouvaient servir egalement comme pieges a mouches efficaces en utilisant les odeurs fecales comme attractifs. Nous avons construit six latrines a fosse chacune avec un piege a mouche integre et avons teste leur efficacite de capture par rapport a six pieges appâtes sous forme de boites de poisson placees a 10 m de la latrine. Des discussions de groupe focalisees ont ete menees par la suite pour evaluer l'acceptabilite des latrines attrape-mouche. Resultats Le nombre de C. putoria emergents a ete reduit de 96,0% (IC95%: 94,5 a 97,2%) 4 a 5 semaines apres le traitement avec le pyriproxyfene, de 64,2% (IC95%: 51,8 a 73,5%) apres traitement avec du savon local, de 41,3% (IC95%: 24,0 a 54,7%) 3 a 5 semaines apres traitement avec des EPB. Les pieges a mouches places sur latrines ont collecte C. putoria et etaient juges acceptables par les collectivites locales. Conclusions Sumilarv 0,5 G est prometteur comme agent de lutte chimique, tandis que les pieges appâtes aux odeurs de latrines peuvent s'averer une methode utile non chimique pour lutter contre les mouches. Les deux methodes justifient un developpement supplementaire afin de pouvoir reduire la production de mouches a partir des latrines a fosse. Une combinaison des interventions peut s'averer efficace pour le controle des mouches des latrines et des maladies qu'elles transmettent. Objetivo Explorar las formas de controlar Chrysomya putoria, la mosca Africana de letrinas, en letrinas de hoyo seco. Puesto que las letrinas de hoyo seco son una fuente importante de estas moscas, eliminar estos lugares de reproduccion puede reducir las poblaciones de la mosca y por lo tanto reducir la diseminacion de patogenos diarreicos. Metodos Hemos tratado 24 letrinas en un poblado de Gambia: cada grupo de seis se trato con una de las siguientes (1) piriproxifen, que mimetiza una hormona juvenil del insecto formulada como Sumilarv® 0.5G, y piriproxifen granulado al 0.5%, (2) pastillas de poliestireno expandido (PPE), (3) jabon local (4) sin tratamiento como controles. Las moscas se recolectaron utilizando trampas de salida localizadas sobre los orificios de entrada, semanalmente, durante cinco semanas. En un estudio separado evaluamos si las letrinas tambien funcionaban como trampas eficientes utilizando los olores fecales como atrayentes. Construimos seis letrinas de fosa, cada una con una trampa para moscas incluida, y evaluamos su eficiencia para atrapar las moscas en comparacion con seis cajas-trampa con pescado como cebo, localizadas a 10 m de la letrina. Se llevaron a cabo grupos de discusion focalizada despues para evaluar la aceptacion de las letrinas con trampas para moscas. Resultados El numero de C. putoria emergentes se redujo en un 96.0% (IC95%: 94.5–97.2%) 4–5 semanas despues del tratamiento con piriproxifen; en un 64.2% (IC 95%: 51.8–73.5%) despues del tratamiento con jabon local; en un 41.3% (IC 95% = 24.0–54.7%) tras el tratamiento con PPE, 3–5 semanas despues del tratamiento. Las trampas de moscas localizadas en las letrinas recolectaron C. putoria y fueron consideradas como aceptables por las comunidades locales. Conclusiones El Sumilarv 0.5G parece ser prometedor como agente de control quimico, mientras que las letrinas con trampas de olor podrian ser utiles como metodo no quimico para el control de las moscas. Ambos metodos garantizan un mayor desarrollo para reducir la produccion de moscas de las letrinas de fosas. Una combinacion de intervenciones podria ser efectiva para el control de las moscas de letrinas y la enfermedad que transmiten.

Research and development into whole organism malaria vaccines is progressing rapidly thanks to the major investments over recent years from several funders, and the commitment and interest of many leading researchers. Progress includes the discovery of potential new candidate vaccines and the start of the first phase 1/2a clinical trial of the radiation attenuated sporozoite approach for Plasmodium falciparum, under US Food and Drug Administration regulatory oversight. A group of leading scientists, clinical trialists and stakeholders, together with representatives of regulatory authorities including some from African countries, met recently to document the issues that will require detailed consideration to assess this promising approach. Questions related to scale-up, quality, purity and consistency of a manufacturing process using mosquitoes to generate a commercial product, and demonstration of the stability of attenuated sporozoites will need further work. Should a high level of efficacy be demonstrated in clinical challenge studies, it will become a priority to agree in which populations and age groups questions about strain-transcendence and duration of efficacy should be answered, and how clinical development can progress with an approach based on cryopreservation in liquid nitrogen.

SUMMARY Longitudinal cohort studies are important to describe the dynamics of naturally acquired antibody response profiles to defined Plasmodium falciparum malaria antigens relative to clinical malaria episodes. In children under 7 years of age in The Gambia, serum IgG responses were measured to P. falciparum merozoite antigens AMA1, EBA175, MSP119, MSP2 and crude schizont extract, over a 10-month period. Persistence of antibody responses was measured in 152 children during the dry season when there was virtually no malaria transmission, and 103 children were monitored for new episodes of clinical malaria during the subsequent wet season when transmission occurred. Children who experienced clinical malaria had lower antibody levels at the start of the study than those who remained free from malaria. Associations between dry season antibody persistence and subsequent wet season antibody levels suggested robust immunological memory responses. Mean antibody levels to all antigens were elevated by the end of the wet season in children who experienced clinical malaria; each of these children had a boosted antibody response to at least one antigen. In all children, antibody avidities were lower against MSP2 than other antigens, a difference that did not change throughout the study period or in relation to clinical malaria episodes.

Larviciding to control malaria was assessed in rural areas with extensive seasonal flooding. Larval and adult mosquitoes and malaria incidence were surveyed routinely in four 100-km(2) areas either side of the Gambia River. Baseline data were collected in 2005. Microbial larvicide was applied to all water bodies by hand application with water-dispersible granular formulations and corn granules weekly from May to November in two areas in 2006 and in the other two areas in 2007 in a cross-over design. The intervention was associated with a reduction in habitats with late stage anopheline larvae and an 88% reduction in larval densities (P < 0.001). The effect of the intervention on mosquito densities was not pronounced and was confounded by the distance of villages to the major breeding sites and year (P = 0.002). There was no reduction in clinical malaria or anemia. Ground applications of non-residual larvicides with simple equipment are not effective in riverine areas with extensive flooding, where many habitats are poorly demarcated, highly mobile, and inaccessible on foot.

Summary Placental malaria infection affects the T helper type 1 (Th1)/Th2 balance in neonatal children. We investigated a potential role of regulatory T cells in this balance by comparing T cell responses of cord blood mononuclear cells (CBMC) from parasitized and non-parasitized placenta of Gambian women. CBMC were depleted of CD4+CD25+ forkhead box P3 (FoxP3)+ regulatory T cells and analysed in vitro for their ability to produce interferon (IFN)-γ, sCD30 and interleukin (IL)-10 in response to phytohaemagglutinin (PHA), live Plasmodium falciparum, schizont extracts and the recombinant P. falciparum blood stage antigen merozoite surface protein 1 (MSP119). As expected, lower IFN-γ and higher sCD30 responses were observed for the cells from the parasitized group. In addition, higher IL-10 levels were produced by CBMC from the parasitized group. Depletion of regulatory T cells decreased IL-10 production, which resulted in a restoration of IFN-γ expression in response to all stimuli. The Th2 marker sCD30 remained significantly higher in the parasitized group in response to malaria protein antigens while similar levels were recovered between both groups in response to live P. falciparum. Similar effects were observed by adding an antibody that blocks IL-10 function. These results suggest that the impact of P. falciparum infection on Th1 differentiation of neonatal T cells can be ascribed to regulatory T cells through production of IL-10.

RTS,S is a pre-erythrocytic malaria vaccine candidate antigen based on the circumsporozoite surface protein of Plasmodium falciparum fused to HBsAg, incorporating a novel Adjuvant System (AS02). The first field efficacy of RTS,S/AS02 against infection was demonstrated in a trial initiated in The Gambia in 1998. This paper presents the five-year safety and immunogenicity follow up of the 306 men who were enrolled in the original trial. In the primary study men aged 18 to 45 years were randomized to receive either RTS, S/AS02 or rabies vaccine at 0, 1, 5 months followed by a booster dose at month 19. The subjects were observed for long term safety and immunogenicity continuously until month 58. Of the 153 subjects in each group at enrollment, 80 (52%) subjects in the RTS,S/AS02 group and 83 (54%) subjects in the rabies group returned for the final long-term follow-up visit at month 58. The main reason for non-attendance at month 58 was migration (76% of all drop-outs). Nine subjects in the RTS, S/AS02 group and seven in the rabies group experienced serious adverse events (SAEs) over the 58 month surveillance period, of which seven had a fatal outcome (five RTS, S/AS02 and two rabies group). None of the SAEs with fatal outcome were attributed to the study vaccine. Anti-CS antibody persistence compared to control was observed for five years, although titres had waned from post-booster levels; similar responses in anti-HBs antibody persistence were observed in initially HBsAg seronegative subjects. This study provides the first indication of the long-term safety and persistence of anti-CS and anti-HBs antibodies of the RTS, S vaccine candidate in combination with the novel AS02 Adjuvant System.

The tumor necrosis factor gene (TNF) and lymphotoxin-alpha gene (LTA) have long attracted attention as candidate genes for susceptibility traits for malaria, and several of their polymorphisms have been found to be associated with severe malaria (SM) phenotypes. In a large study involving >10,000 individuals and encompassing 3 African populations, we found evidence to support the reported associations between the TNF -238 polymorphism and SM in The Gambia. However, no TNF/LTA polymorphisms were found to be associated with SM in cohorts in Kenya and Malawi. It has been suggested that the causal polymorphisms regulating the TNF and LTA responses may be located some distance from the genes. Therefore, more-detailed mapping of variants across TNF/LTA genes and their flanking regions in the Gambian and allied populations may need to be undertaken to find any causal polymorphisms.

Background Glucose-6-phosphate dehydrogenase (G6PD) deficiency exhibits considerable allelic heterogeneity which manifests with variable biochemical and clinical penetrance. It has long been thought that G6PD deficiency confers partial protection against severe malaria, however prior genetic association studies have disagreed with regard to the strength and specificity of a protective effect, which might reflect differences in the host genetic background, environmental influences, or in the specific clinical phenotypes considered. Methods A case-control association study of severe malaria was conducted in The Gambia, a region in West Africa where there is considerable allelic heterogeneity underlying expression of G6PD deficiency trait, evaluating the three major nonsynonymous polymorphisms known to be associated with enzyme deficiency (A968G, T542A, and C202T) in a cohort of 3836 controls and 2379 severe malaria cases. Results Each deficiency allele exhibited a similar trend toward protection against severe malaria overall (15–26 % reduced risk); however, in stratifying severe malaria to two of its constituent clinical subphenotypes, severe malarial anaemia (SMA) and cerebral malaria (CM), the three deficiency alleles exhibited trends of opposing effect, with risk conferred to SMA and protection with respect to CM. To assess the overall effect of G6PD deficiency trait, deficiency alleles found across all three loci were pooled. G6PD deficiency trait was found to be significantly associated with protection from severe malaria overall (OR 0.83 [0.75–0.92], \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P = 0.0006$$\end{document}P=0.0006), but this was limited to CM (OR 0.73 [0.61–0.87], \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P = 0.0005$$\end{document}P=0.0005), with a trend toward increased risk for SMA, especially in fully-deficient individuals (OR 1.43 [0.99–2.08], \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P = 0.056$$\end{document}P=0.056). Sex-stratified testing largely comported with these results, with evidence suggesting that protection by G6PD deficiency trait is conferred to both males and females, though susceptibility to SMA may be restricted to fully-deficient male hemizygotes. Conclusions In a part of Africa where multiple alleles contribute to expression of G6PD deficiency trait, these findings clarify and extend previous work done in populations where a single variant predominates, and taken together suggest a causal role for G6PD deficiency trait itself with respect to severe malaria, with opposing effects seen on two major clinical subphenotypes.

There is growing epidemiological and molecular evidence that ABO blood group affects host susceptibility to severe Plasmodium falciparum infection. The high frequency of common ABO alleles means that even modest differences in susceptibility could have a significant impact on the health of people living in malaria endemic regions. We performed an association study, the first to utilize key molecular genetic variation underlying the ABO system, genotyping >9000 individuals across three African populations. Using population- and family-based tests, we demonstrated that alleles producing functional ABO enzymes are associated with greater risk of severe malaria phenotypes (particularly malarial anemia) in comparison with the frameshift deletion underlying blood group O: case-control allelic odds ratio (OR), 1.2; 95% confidence interval (CI), 1.09-1.32; P = 0.0003; family-studies allelic OR, 1.19; 95% CI, 1.08-1.32; P = 0.001; pooled across all studies allelic OR, 1.18; 95% CI, 1.11-1.26; P = 2 x 10(-7). We found suggestive evidence of a parent-of-origin effect at the ABO locus by analyzing the family trios. Non-O haplotypes inherited from mothers, but not fathers, are significantly associated with severe malaria (likelihood ratio test of Weinberg, P = 0.046). Finally, we used HapMap data to demonstrate a region of low F(ST) (-0.001) between the three main HapMap population groups across the ABO locus, an outlier in the empirical distribution of F(ST) across chromosome 9 (approximately 99.5-99.9th centile). This low F(ST) region may be a signal of long-standing balancing selection at the ABO locus, caused by multiple infectious pathogens including P. falciparum.

Background The effectiveness of pyrethroid-treated bednets for malaria control in sub-Saharan Africa is under threat because of high levels of resistance to pyrethroid insecticides in the vectors. Here we assess the durability of polyethylene nets with a novel combination of permethrin, a pyrethroid, with pyriproxyfen, an insect juvenile mimic (PPF-LLIN), in comparison with a typical permethrin-treated long-lasting insecticidal net (LLIN). Methods This is a cluster randomised controlled trial of net durability in Burkina Faso, with clustering at the level of the compound and includes entomological outcome measurements. Half the compounds in each village will be randomly allocated PPF-LLIN and half the LLIN. All sleeping places in a compound will be provided with one type of net. We will distribute the nets at the start of the first transmission season and follow net use at the start and end of each transmission season for 3 years. In one village, bio-efficacy and chemical content will be recorded immediately after net distribution and then at 6, 12, 18, 24, 30 and 36 months. In the other village net survivorship and fabric integrity will be recorded immediately after distribution, and then at 6, 12, 18, 24, 30 and 36 months. Routine measurements of indoor temperature and relative humidity will be made in both villages during the study. Residents will be followed for possible side effects of the PPF-LLIN by surveillance of known asthmatic subjects during the first month post-distribution and pregnancy outcomes will be monitored from antenatal clinic records. Discussion The protocol is novel on two accounts. Firstly, it is the first to describe the procedure for measuring net durability following recent World Health Organisation (WHO) guidelines. Meeting the minimum requirements set in the guidelines is essential before a new type of net can be recommended by WHO’s Pesticide Evaluation Scheme (WHOPES). Secondly, it describes methods to monitor the persistence of an active ingredient that reduces vector fertility and fecundity. If the PPF-LLIN is both effective and persistent it will provide an alternative vector control strategy where pyrethroid-resistant vectors are present. Trial registration ISRCTN30634670 assigned 13 August 2014. Electronic supplementary material The online version of this article (doi:10.1186/s13063-015-0700-7) contains supplementary material, which is available to authorized users.

Background Recent reductions in malaria in sub-Saharan Africa have been associated with increased coverage with long-lasting insecticidal nets (LLINs). Pyrethroids are currently the only insecticide class used for treating nets, and the rapid increase in resistance to pyrethroids in vector mosquitoes may jeopardise future vector control. Nets containing a novel combination of permethrin, a pyrethroid, and pyriproxyfen, an insect juvenile hormone mimic, (PPF-LLIN) may enhance malaria control, as well as reducing the spread of pyrethroid-resistant mosquitoes. This trial will determine whether PPF-LLINs provide incremental protection against malaria over current best practice of LLINs and prompt treatment in an area with pyrethroid-resistant vectors. Methods A 2 armed cluster-randomised controlled trial will be conducted in Burkina Faso to assess whether PPF-LLIN (containing 2% permethrin and 1% pyriproxyfen w/w) provide better protection against clinical malaria in children than 2% permethrin-treated LLINs. Study subjects will be recruited and provided with LLINs at the start of the study. The LLINs will be exchanged for PPF-LLIN by cluster in a step-wedge fashion so 3 months before the end of the 2 year trial all participants will have a PPF-LLIN. The primary endpoint will be clinical malaria incidence measured by passive case detection in a cohort of children, aged 6 months to 5 years. Anaemia and parasite prevalence will also be measured in children during cross-sectional surveys. Exposure to malaria parasites will be assessed using light traps followed by identification of common vector species and their sporozoite infection rates. Safety evaluation will include recording of adverse events and pregnancy outcomes. The main endpoint analysis will include adjusting for distance between village clusters with different types of nets, as the impact of PPF-LLIN is likely to increase as larger areas are dominated by PPF-LLIN, reducing the spill over of mosquitoes from villages with LLINs. Discussion The step-wedge design is to measure the impact of an incrementally delivered environmental intervention where we expect the degree of control to be improved as more people use PPF-LLIN over a larger area. Trial findings will help inform policy makers on the effectiveness of PPF-LLIN nets for malaria control in areas of pyrethroid resistance. Trial registration ISRCTN21853394 – AvecNet, registered on 3 April 2013. Electronic supplementary material The online version of this article (doi:10.1186/s13063-015-0606-4) contains supplementary material, which is available to authorized users.

Contains fulltext : 48037.pdf (Publisher’s version ) (Closed access) Two hundred thirty-four Gambian children with severe falciparum malaria who were admitted to the pediatric ward of a rural district hospital each were matched for age with a same-sex control subject presenting as an outpatient with uncomplicated falciparum malaria. Severe malarial anemia (SMA) was the most common presentation (152 cases), followed by cerebral malaria (38 cases) and hyperparasitemia (26 cases). Children presenting with SMA were significantly younger and more likely to carry gametocytes than were children with other severe presentations. Alleles of the genes pfcrt and pfmdr1 associated with chloroquine-resistant parasites occurred together among cases presenting with SMA alone more often than among their matched controls (odds ratio, 2.08 [95% confidence interval, 1.04-4.38]; P=.039). Costs of travel to the hospital of more than US $0.20, use of mosquito repellents, and carriage of resistant parasites were identified as independent risk factors for severe malaria in the case-control analysis. We conclude that, in this setting, poor access to the hospital and a high prevalence of chloroquine-resistant parasites lead to a delay of adequate treatment for young children with malaria, who may then develop SMA.

A characteristic retinopathy associated with a poor prognosis has previously been described in African children with established cerebral malaria. However, relatively little is known about retinal abnormalities in children with severe non-cerebral malaria, the group most at risk of developing the cerebral complications of this disease. In this study the prevalence, pattern, clinical significance and accessibility to clinical examination of this characteristic retinopathy are described in 106 Gambian children admitted consecutively to hospital with severe malaria, including six with established cerebral malaria.

SUMMARYThe effects of exposure to placental malaria infection on newborn immunological responses, in particular Th1/Th2 cytokines and antigen-presenting cell (APC) function, were compared between cord blood mononuclear cells (CBMC) from parasitized and non-parasitized placentas of Gambian women. Cells were analysed in vitro for their ability to respond to mitogens [phorbol myristate acetate (PMA)/ionomycin, phytohaemagglutinin (PHA)], a malaria-unrelated test antigen [purified protein derivative of Mycobacterium tuberculin[purified protein derivative (PPD)] and Plasmodium falciparum schizont extracts. Mitogens induced strong proliferation and secretion of high concentrations of both IL-13 and sCD30 in CBMC from both groups. Conversely, significantly lower amounts of IFN-γ were induced in the parasitized group in response to low doses of PHA. Protein antigens induced very low amounts of all tested cytokines, in particular IFN-γ. However, a significantly higher release of sCD30 was observed in response to schizont extracts in the parasitized group. Addition of LPS to activate APC to low doses of PHA or schizont extracts increased the IFN-γ production in both groups but levels remained lower in CBMC from the parasitized group. This result correlates with the lower production of IL-12 found following lipopolysaccharide (LPS) stimulation in this group. Taken together, these data show that placental infection with P. falciparum affects Th1 differentiation and sCD30 priming of neonatal lymphocytes and that the probable mode of action is via APC.

In a randomized controlled trial, chloroquine monotherapy was compared with the combination of artesunate and chloroquine for treating uncomplicated Plasmodium falciparum malaria in 536 Gambian children. Chloroquine-treated children exhibited a 28-day clinical failure rate of 15% (95% confidence interval [CI] = 9.2-22%) compared with 11% (7.8-15%) among children receiving the combination (P = 0.08, by Wilcoxon test). Seventy-three percent of chloroquine-treated children exhibited parasitemia during follow-up compared with 49% of children receiving the combination (relative risk = 1.5, 95% CI = 1.3-1.7; chi2 = 21.18, P < 0.001). A significant reduction in clinical and parasitologic treatment failure in the combination group occurred in the first two weeks following treatment, but this was eroded over weeks three and four of follow-up. The impact of combination therapy on the transmission of chloroquine-resistant parasites is discussed. Chloroquine plus artesunate is not sufficiently efficacious to justify its introduction as a replacement for chloroquine monotherapy in The Gambia.

Polymorphisms in two genes of Plasmodium falciparum (P. falciparum multidrug resistance 1 [pfmdr1] and P. falciparum chloroquine [CQ] resistance transporter [pfcrt]) are associated with CQ treatment failure. We found significant linkage disequilibrium between these loci among isolates from symptomatic Gambian children (P = 0.026) and strong selection for the resistance-associated alleles pfmdr1-86Tyr and pfcrt-76Thr in children with persistent or re-emerging P. falciparum trophozoites during post-treatment follow-up (P = 1.9 x 10(-7)). Therefore, this genotype is characteristic of resistant infections among our study population. Since the long-term public health impact of parasites carrying such resistant genotypes depends upon their transmissibility, we examined the prevalence of pfmdr1-86Tyr and pfcrt-76Thr among Gambian children harboring sexual stage parasites during post-treatment follow-up. Gametocytes that emerged after successful treatment with CQ were significantly more likely to be of this genotype than were those emerging after other treatments (P = 4.83 x 10(-4)), and were infective to Anopheles mosquitoes. Therapeutic success may thus be accompanied by public health failure as cured children pass resistance genes on to mosquitoes at an enhanced rate.

Malaria is a major cause of illness and an indirect cause of mortality in pregnant women. It can also cause stillbirths and low-birthweight babies. We have shown previously that pregnant women attracted twice as many Anopheles gambiae mosquitoes, the principal African malaria vector, as their non-pregnant counterparts over distances of about 15 m. In the current study (in 1998/99) we compared the short-range attractiveness of both pregnant and non-pregnant women sleeping under untreated bednets in Gambian villages. First, we measured the rate of mosquito entry under bednets and, second, we calculated the proportion of mosquitoes biting mothers under each bednet compared to their children. The feeding preference of An. gambiae collected under nets was determined by DNA fingerprinting blood samples from human subjects sleeping under each bednet and comparing these to fingerprints obtained from mosquito bloodmeals. Pregnant women were more attractive to An. gambiae mosquitoes than non-pregnant women under an untreated bednet. The number of mosquitoes entering bednets each night was 1.7-4.5 times higher in the pregnant group (P = 0.02) and pregnant women also received a higher proportion of bites under the bednets than did non-pregnant women (70% vs 52%, P = 0.001). This study clearly demonstrates that pregnant women are more exposed to malaria parasites than other women, which contributes to the greater vulnerability of pregnant women to malaria.

Summary Background RTS,S/AS02 is a pre-erythrocytic malaria vaccine based on the circumsporozoite surface protein of Plasmodium falciparum fused to HBsAg, incorporating a new adjuvant (AS02). We did a randomised trial of the efficacy of RTS,S/AS02 against natural P falciparum infection in semi-immune adult men in The Gambia. Methods 306 men aged 18–45 years were randomly assigned three doses of either RTS,S/AS02 or rabies vaccine (control). Volunteers were given sulfadoxine/pyrimethamine 2 weeks before dose 3, and kept under surveillance throughout the malaria transmission season. Blood smears were collected once a week and whenever a volunteer developed symptoms compatible with malaria. The primary endpoint was time to first infection with P falciparum. Analysis was per protocol. Findings 250 men (131 in the RTS,S/AS02 group and 119 in the control group) received three doses of vaccine and were followed up for 15 weeks. RTS,S/AS02 was safe and well tolerated. P falciparum infections occurred significantly earlier in the control group than the RTS,S/AS02 group (Wilcoxon's test p=0–018). Vaccine efficacy, adjusted for confounders, was 34% (95% CI 8–0–53, p=0–014). Protection seemed to wane: estimated efficacy during the first 9 weeks of follow-up was 71% (46–85), but decreased to 0% (−52 to 34) in the last 6 weeks. Vaccination induced strong antibody responses to circumsporozoite protein and strong T-cell responses. Protection was not limited to the NF54 parasite genotype from which the vaccine was derived. 158 men received a fourth dose the next year and were followed up for 9 weeks; during this time, vaccine efficacy was 47% (4–71, p=0–037). Interpretation RTS,S/AS02 is safe, immunogenic, and is the first pre-erythrocytic vaccine to show significant protection against natural P falciparum infection.