The 21st century has seen remarkable progress against malaria, particularly from 2005 to 2015. Although wide implementation of insecticide-treated mosquito nets and indoor residual spraying of insecticide, in African countries with a high burden, has resulted in an 80% reduction in malaria infection and illness,1Bhatt S Weiss DJ Cameron E et al.The effect of malaria control on Plasmodium falciparum in Africa between 2000 and 2015.Nature. 2015; 526: 207-211Crossref PubMed Scopus (1689) Google Scholar these interventions have limits due to suboptimal coverage or use, emergence of insecticide resistance, and nuances in mosquito behaviour. The WHO's 2021 World Malaria Report2WHOWorld malaria report 2021. World Health Organization, Geneva2021Google Scholar documented stagnation of progress, with malaria mortality rising from 14·8 deaths per 100 000 population in 2015 to 15·3 per 100 000 population in 2020.2WHOWorld malaria report 2021. World Health Organization, Geneva2021Google Scholar The impact of our standard vector-control interventions has plateaued: mosquitoes evolve, and so must our interventions. Each year since 2015, more than 550 000 people—mostly children—have died of malaria.2WHOWorld malaria report 2021. World Health Organization, Geneva2021Google Scholar Countries and funding agencies rely on WHO for science-based guidance on the safety, quality, and efficacy of vector-control tools. We contend that the slow adoption and roll-out of new vector-control interventions is associated with an overly stringent definition of high-quality evidence of public health value. When WHO guidance lags, so too does implementation of new or improved interventions. The pathway of nets treated with pyrethroids plus piperonyl butoxide is illustrative. While currently recommended for areas with monooxygenase-based pyrethroid resistance, these nets were introduced in 2007, but it took 10 years for an interim policy recommendation to be released, despite solid evidence of effectiveness from multiple studies with entomological outcomes.3Tungu P Magesa S Maxwell C et al.Evaluation of PermaNet 3.0 a deltamethrin-PBO combination net against Anopheles gambiae and pyrethroid resistant Culex quinquefasciatus mosquitoes: an experimental hut trial in Tanzania.Malar J. 2010; 9: 21Crossref PubMed Scopus (84) Google Scholar By that time, pyrethroid resistance had spread throughout Africa. When developing vector-control guidance, WHO places a higher value on evidence from randomised controlled trials (RCTs) with epidemiological outcomes—a method developed for assessment of medical interventions for individual patients. Over the past decade various vector-control interventions have been assessed by Cochrane Reviews, but each places the highest value on RCTs, thereby downgrading other evidence. This weighting leads to surprising conclusions in WHO's vector-control guidelines; eg, that the evidence for the effectiveness of indoor residual spraying of insecticide is of low certainty, despite this intervention having been a pillar of WHO's malaria eradication effort in the 1960s, which resulted in markedly reduced malaria in many regions.4Nájera JA González-Silva M Alonso PL Some lessons for the future from the Global Malaria Eradication Programme (1955–1969).PLoS Med. 2011; 8e1000412Crossref PubMed Scopus (254) Google Scholar The guidelines also state that for larval habitat modification, "No recommendation can be made because the evidence…was deemed to be insufficient", despite decades of experience and documentation of its impact dating back to Ronald Ross in the early 20th century.5Ross R The logical basis for the sanitary policy of mosquito reduction.Science. 1905; 22: 689-699Crossref PubMed Scopus (17) Google Scholar This minimisation of evidence from multiple continents spanning more than a century reflects a remarkably narrow view of what constitutes high-quality evidence. In areas of high transmission, a background of high coverage of insecticide-treated mosquito nets and improved case management means that RCTs are increasingly complex and costly; furthermore, the heterogeneity of malaria vector systems and environments makes generalisation across trials tenuous. In low-transmission settings, the sample size requirements for RCTs with epidemiological outcomes are prohibitive. The RCT was recognised as the gold standard for epidemiological research in 1982,6Jones DS Podolsky SH The history and fate of the gold standard.Lancet. 2015; 385: 1502-1503Summary Full Text Full Text PDF PubMed Google Scholar initiating the so-called RCT era. As varieties of methods for inference have proliferated, some have argued for a more flexible approach in assessment of evidence in support, or not, of new medicines, vaccines, and surgical procedures. Arguments for greater flexibility in evaluation of such interventions have greater force for those aimed at vectors of disease, but do not diminish the importance of well designed RCTs for evaluation of interventions, where appropriate. Hackett,7Hackett LW Malaria in Europe: an ecological study. Oxford University Press, London1937Google Scholar a pioneer of malaria elimination, noted that "perfection can be the enemy of the good" for malaria control. Making WHO guidance more inclusive of entomological outcomes8Sherrard-Smith E Ngufor C Sanou A et al.Inferring the epidemiological benefit of indoor vector control interventions against malaria from mosquito data.Nat Commun. 2022; 133862Crossref PubMed Scopus (9) Google Scholar and study designs other than RCTs—including historical evidence or implementation of novel test-negative designs—would allow countries to more easily access a range of innovative interventions, resulting in improved locally appropriate vector control, thereby accelerating malaria control and elimination globally and saving lives now. We declare no competing interests.

In areas of moderate to intense Plasmodium falciparum transmission, malaria in pregnancy remains a significant cause of low birth weight, stillbirth, and severe anaemia. Previously, fetal sex has been identified to modify the risks of maternal asthma, pre-eclampsia, and gestational diabetes. One study demonstrated increased risk of placental malaria in women carrying a female fetus. We investigated the association between fetal sex and malaria in pregnancy in 11 pregnancy studies conducted in sub-Saharan African countries and Papua New Guinea through meta-analysis using log binomial regression fitted to a random-effects model. Malaria infection during pregnancy and delivery was assessed using light microscopy, polymerase chain reaction, and histology. Five studies were observational studies and six were randomised controlled trials. Studies varied in terms of gravidity, gestational age at antenatal enrolment and bed net use. Presence of a female fetus was associated with malaria infection at enrolment by light microscopy (risk ratio 1.14 [95% confidence interval 1.04, 1.24]; P = 0.003; n = 11,729). Fetal sex did not associate with malaria infection when other time points or diagnostic methods were used. There is limited evidence that fetal sex influences the risk of malaria infection in pregnancy.

BackgroundJoint efforts by government and non-government organizations have helped to reduce malaria in Bangladesh and set the country on a clear path to eventual malaria elimination. However, achieving that goal would be challenging without a comprehensive understanding of vector bionomics.MethodsTargeted capturing of Anopheles mosquitoes over a rainy season, utilizing specific sampling methods, including human landing catches (HLCs), CDC-light traps (CDC-LTs), and pyrethrum spray catches (PSCs) were aimed to characterize entomological drivers of transmission in four sites of Bandarban, Bangladesh.ResultsMolecular characterization of a subset of 4637 mosquitoes has demonstrated the presence of at least 17 species whose capture rates were representative of the rainy season. Species compositions and bionomic traits did not vary between sites with Anopheles maculatus having the highest landing rate by HLCs and Anopheles vagus having the highest capture rate with CDC-LTs. Interestingly, Anopheles species compositions and capture rates varied significantly (p < 0.05) for An. vagus, between HLCs and its often-used proxy-CDC-LTs- suggesting impacts on downstream analysis. CDC-LTs capture rates demonstrated differing compositions with indoor and outdoor biting rates. For example, Anopheles nigerrimus and Anopheles nivipes were more endophagic by HLCs and more exophagic by CDC-LTs. The use of a cow-baited CDC-LT also demonstrated significantly different results when compared to a human-baited CDC-LT considering the high degree of anthropophily in these species. The exception to both zoophily and indoor resting was An. vagus, which demonstrated both anthropophily and high resting rates indoors-pointing to this species being a possible primary vector at this site.ConclusionA diverse Anopheles fauna in Bandarban has been confirmed through molecular methods, highlighting the potential impact of sampling techniques. Given the complexity of the local ecosystem, a better understanding of mosquito behaviour and ecology is required to achieve the goal of malaria elimination in Bangladesh.

Using nationally representative data, we estimate intergenerational persistence in health in India. Results from the instrumental variable method show that children of anemic mothers are more likely to be anemic, with an intergenerational health correlation of 0.26. Results are robust to the inclusion of confounding factors including the mother's height. We find that the correlation between mothers' anemic status and children's anemic status differs by wealth quintile, indicating that economic status may play a role in the persistence of poor health across generations in developing countries.

Malaria and malnutrition remain primary causes of morbidity and mortality among children younger than 5 years in Africa. Studies investigating the association between malnutrition and subsequent malaria outcomes are inconsistent. We studied the effects of malnutrition on incidence and prevalence of malaria parasitemia in data from a cohort studied in the 1990s. Data came from the Asembo Bay cohort study, which collected malaria and health information on children from 1992 to 1996 in western Kenya. Infants were enrolled at birth and followed up until loss to follow-up, death, end of study, or 5 years old. Anthropometric measures and blood specimens were obtained monthly. Nutritional exposures included categorized Z-scores for height-for-age, weight-for-age, and weight-for-height. Febrile parasitemia and afebrile parasitemia were assessed with thick and thin blood films. Multiply imputed and weighted multinomial generalized estimating equation models estimated odds ratios (OR) for the association between exposures and outcomes. The sample included 1,182 children aged 0-30 months who contributed 18,028 follow-up visits. There was no significant association between malnutrition and either incident febrile parasitemia or prevalent febrile parasitemia. Prevalence ORs for afebrile parasitemia increased from 1.07 (95% CI: 0.89, 1.29) to 1.35 (1.03, 1.76) as stunting severity increased from mild to severe, and from 1.16 (1.02, 1.33) to 1.35 (1.09, 1.66) as underweight increased from mild to moderate. Stunting and underweight did not show a significant association with subsequent febrile parasitemia infections, but they did show a modest association with subsequent afebrile parasitemia. Consideration should be given to testing malnourished children for malaria, even if they present without fever.

According to the WHO, unmanaged insecticide resistance may lead to increases in malaria-related mortality and morbidity. Bangladesh, having made significant progress in malaria control efforts, has recently seen an upswing in malaria cases-58% of which occurred in Bandarban district. Toward identifying entomological drivers of increased malaria, an entomological survey including Anopheles susceptibility to the insecticides in use was conducted in Bandarban. Anopheles vagus, the primary vector of malaria, was found to be resistant to both permethrin and deltamethrin-with only 29% and 55% mortality at 30 minutes, respectively. Intervention strategies in this area-all based on pyrethroids, may need to be reevaluated toward closing this gap in protection and increasing intervention efficacy.

At the 1998 outset of the Roll Back Malaria (RBM) Partnership, malaria was a known major cause of deaths globally, particularly among children in sub-Saharan Africa. RBM was built on the premise that the available package of proven malaria interventions, if taken to high coverage in countries, would lead tomarked reductions in childmortality inAfrica and overall improvement in health and well-being. The premise also highlighted the need to document progress and impact to demonstrate to external donors and national governments that financing malaria burden reduction would provide a great return on investment. The impact evaluation methods described in these reports evolved from a consensus process that engaged key RBM partners: endemic countries in Africa; the World Health Organization (WHO); The United Nations Children’s Fund (UNICEF); the President’s Malaria Initiative (PMI); the Global Fund to Fight AIDS, Tuberculosis, and Malaria (GF); and partners involved in the implementation and measurement of inputs, outcomes, and impact. This collaboration was a crucial step in directing efforts to improve systems for data collection and use. The continued ability to track progress on malaria intervention scale-up and report on impact will remain central to sustaining and increasing the funding required to meet the Sustainable Development Goal targets for malaria andmove us closer to amalaria-free world. The reports presented here provide further evidence of the impact that has occurred in many African countries— supported in particular by the countries, PMI, the GF, and many other donors and implementing partners. This remarkable success story highlights the benefit for thosemost at risk, African children. It convincingly shows that the core malaria interventions, when deployed at increasing coverage rates, save lives—and not just a few; there has been an estimated 60% overall reduction of deaths since 2000 in children under 5 years of age. Many children are alive today because of this work. The initial RBM focus was on Africa, where transmission was the most intense and where the vast majority of malaria infections and deaths occurred. The core measure was allcause child mortality (ACCM), the metric already used and regularly measured in essentially all countries by the broader child survival community. Alternative measures of “malariaspecific” or “malaria-associated”† deaths were considered; however, the diverse definitions, challenging diagnostic requirements, and lack of standard collection methods made them far from ideal for tracking impact. In Africa, there was ample evidence that malaria-specific and malaria-associated deaths were major contributors to ACCM, so the impact of malaria interventions on ACCM would be highly visible and more readily measureable. The agreed approach to monitoring changes in malaria-associated mortality using ACCM requires a plausibility argument (i.e., an assumption that mortality reductions can be attributed to programmatic efforts if improvements are found in steps along the causal pathway between intervention scale-up and mortality trends, while accounting for other contextual factors known to influence child survival). ACCM was not the only measure needed. Data were required on the coverage of malaria interventions and the changes in other measures that were either malaria specific (e.g., parasite prevalence or case rates) or malaria associated (e.g., anemia in young children). Data to track changes in other diseases, risks, or intervention coverage were needed for the many other contributors to child death. Quality methods and data from population-representative surveys were available (e.g., demographic and health surveys and UNICEF multiple indicator cluster surveys) and were supplemented through the development of the RBM malaria indicator survey that could be deployed at alternate intervals and at the peak of malaria transmission season. More recently, national health information systems have improved in quality and timeliness in some countries and, if quality can be maintained, these systemscould permit reliable tracking ofmalaria casedata. As noted in the manuscripts, additional data—including climate and geopositioning—have added value to the impact assessments, improving the robustness of the evaluations. The success of a decade and a half of this major collaborative effort is summarized in recent UNICEF, WHO, and academic reports. However, the country reports in this supplement along with other recent reports using similar methods provide a more thorough evaluation of saving child lives amidst the broader efforts of improved immunization coverage, nutrition and micronutrient supplementation, diarrheal and respiratory disease control, education, socioeconomic status, and other factors. The work presented here focuses on the decade from 2000 to 2010. By 2015, as per WHO and the United Nations Interagency Group for Child Mortality Estimation, the underfive mortality rate in low-income countries had decreased by 53% overall, but remains approximately 11 times the average rate found in high-income countries (seven deaths per 1,000 live births). The population coverage for vector control, effective case management, and prevention in pregnancy certainly increased in the first decade of RBM (2000 and 2010) and has continued to increase between 2010 and 2015. However, the most recent estimates for Africa show an unacceptably high number ofmalaria deaths associatedwith the *Address correspondence toRichardW. Steketee,Malaria Control and Elimination Partnership in Africa (MACEPA), PATH, 2201 Westlake Avenue, Suite 200, Seattle, WA 98121. E-mail: rsteketee@path.org † “Malaria-associated” deathsmay have another primary or concurrent cause,butmalaria likelycontributedsubstantially to the riskofdeath: for example, severe malaria-associated anemia contributing to death in a child with lower respiratory infection.

Purpose The Maternal Malaria and Malnutrition (M3) initiative has pooled together 13 studies with the hope of improving understanding of malaria–nutrition interactions during pregnancy and to foster collaboration between nutritionists and malariologists. Participants Data were pooled on 14 635 singleton, live birth pregnancies from women who had participated in 1 of 13 pregnancy studies. The 13 studies cover 8 countries in Africa and Papua New Guinea in the Western Pacific conducted from 1996 to 2015. Findings to date Data are available at the time of antenatal enrolment of women into their respective parent study and at delivery. The data set comprises essential data such as malaria infection status, anthropometric assessments of maternal nutritional status, presence of anaemia and birth weight, as well as additional variables such gestational age at delivery for a subset of women. Participating studies are described in detail with regard to setting and primary outcome measures, and summarised data are available from each contributing cohort. Future plans This pooled birth cohort is the largest pregnancy data set to date to permit a more definite evaluation of the impact of plausible interactions between poor nutritional status and malaria infection in pregnant women on fetal growth and gestational length. Given the current comparative lack of large pregnancy cohorts in malaria-endemic settings, compilation of suitable pregnancy cohorts is likely to provide adequate statistical power to assess malaria–nutrition interactions, and could point towards settings where such interactions are most relevant. The M3 cohort may thus help to identify pregnant women at high risk of adverse outcomes who may benefit from tailored intensive antenatal care including nutritional supplements and alternative or intensified malaria prevention regimens, and the settings in which these interventions would be most effective.

Background 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. Methods 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. Results In 2007, 69 and 85% of samples harboured the pfmdr1 -86 Y mutation and dhfr/dhps quintuple mutant, respectively, with no significant differences by study area. However, the prevalence of the pfcrt -76 T 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 -164 L , dhps -436 A , or dhps -613 T . From 2001 to 2007, there were significant increases in the pfcrt -76 T 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 -86 Y mutation remained unchanged. All samples were single copy for pfmdr1 . Conclusions 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 -76 T 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.

An initial study of genetic diversity of Plasmodium falciparum in Asembo, western Kenya showed that the parasite maintained overall genetic stability 5 years after insecticide-treated bed net (ITN) introduction in 1997. This study investigates further the genetic diversity of P. falciparum 10 years after initial ITN introduction in the same study area and compares this with two other neighbouring areas, where ITNs were introduced in 1998 (Gem) and 2004 (Karemo).

BACKGROUND: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.METHODS: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.RESULTS: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.CONCLUSIONS: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.

BACKGROUND:Although several studies have investigated the impact of reduced malaria transmission due to insecticide-treated bed nets (ITNs) on the patterns of morbidity and mortality, there is limited information on their effect on parasite diversity. METHODS:Sequencing was used to investigate the effect of ITNs on polymorphisms in two genes encoding leading Plasmodium falciparum vaccine candidate antigens, the 19 kilodalton blood stage merozoite surface protein-1 (MSP-1(19kDa)) and the Th2R and Th3R T-cell epitopes of the pre-erythrocytic stage circumsporozoite protein (CSP) in a large community-based ITN trial site in western Kenya. The number and frequency of haplotypes as well as nucleotide and haplotype diversity were compared among parasites obtained from children <5 years old prior to the introduction of ITNs (1996) and after 5 years of high coverage ITN use (2001). RESULTS:A total of 12 MSP-1(19kDa) haplotypes were detected in 1996 and 2001. The Q-KSNG-L and E-KSNG-L haplotypes corresponding to the FVO and FUP strains of P. falciparum were the most prevalent (range 32-37%), with an overall haplotype diversity of > 0.7. No MSP-1(19kDa) 3D7 sequence-types were detected in 1996 and the frequency was less than 4% in 2001. The CSP Th2R and Th3R domains were highly polymorphic with a total of 26 and 14 haplotypes, respectively detected in 1996 and 34 and 13 haplotypes in 2001, with an overall haplotype diversity of > 0.9 and 0.75 respectively. The frequency of the most predominant Th2R and Th3R haplotypes was 14 and 36%, respectively. The frequency of Th2R and Th3R haplotypes corresponding to the 3D7 parasite strain was less than 4% at both time points. There was no significant difference in nucleotide and haplotype diversity in parasite isolates collected at both time points. CONCLUSION:High diversity in these two genes has been maintained overtime despite marked reductions in malaria transmission due to ITNs use. The frequency of 3D7 sequence-types was very low in this area. These findings provide information that could be useful in the design of future malaria vaccines for deployment in endemic areas with high ITN coverage and in interpretation of efficacy data for malaria vaccines based on 3D7 parasite strains.

Immunoglobulin (Ig) GM and KM allotypes, genetic markers of γ and κ chains, are associated with humoral immune responsiveness. Previous studies have shown the relationships between GM6-carrying haplotypes and susceptibility to malaria infection in children and adults; however, the role of the genetic markers in placental malaria (PM) infection and PM with HIV co-infection during pregnancy has not been investigated. We examined the relationship between the gene polymorphisms of Ig GM6 and KM allotypes and the risk of PM infection in pregnant women with known HIV status. DNA samples from 728 pregnant women were genotyped for GM6 and KM alleles using polymerase chain reaction-restriction fragment length polymorphism method. Individual GM6 and KM genotypes and the combined GM6 and KM genotypes were assessed in relation to PM in HIV-1 negative and positive women, respectively. There was no significant effect of individual GM6 and KM genotypes on the risk of PM infection in HIV-1 negative and positive women. However, the combination of homozygosity for GM6(+) and KM3 was associated with decreased risk of PM (adjusted OR, 0.25; 95% CI, 0.08-0.8; P = 0.019) in HIV-1 negative women while in HIV-1 positive women the combination of GM6(+/-) with either KM1-3 or KM1 was associated with increased risk of PM infection (adjusted OR, 2.10; 95% CI, 1.18-3.73; P = 0.011). Hardy-Weinberg Equilibrium (HWE) tests further showed an overall significant positive F(is) (indication of deficit in heterozygotes) for GM6 while there was no deviation for KM genotype frequency from HWE in the same population. These findings suggest that the combination of homozygous GM6(+) and KM3 may protect against PM in HIV-1 negative women while the HIV-1 positive women with heterozygous GM6(+/-) combined with KM1-3 or KM1 may be more susceptible to PM infection. The deficit in heterozygotes for GM6 further suggests that GM6 could be under selection likely by malaria infection.

The KEMRI/Centers for Disease Control and Prevention (CDC) Health and Demographic Surveillance System (HDSS) is located in Rarieda, Siaya and Gem Districts (Siaya County), lying northeast of Lake Victoria in Nyanza Province, western Kenya. The KEMRI/CDC HDSS, with approximately 220 000 inhabitants, has been the foundation for a variety of studies, including evaluations of insecticide-treated bed nets, burden of diarrhoeal disease and tuberculosis, malaria parasitaemia and anaemia, treatment strategies and immunological correlates of malaria infection, and numerous HIV, tuberculosis, malaria and diarrhoeal disease treatment and vaccine efficacy and effectiveness trials for more than a decade. Current studies include operations research to measure the uptake and effectiveness of the programmatic implementation of integrated malaria control strategies, HIV services, newly introduced vaccines and clinical trials. The HDSS provides general demographic and health information (such as population age structure and density, fertility rates, birth and death rates, in- and out-migrations, patterns of health care access and utilization and the local economics of health care) as well as disease- or intervention-specific information. The HDSS also collects verbal autopsy information on all deaths. Studies take advantage of the sampling frame inherent in the HDSS, whether at individual, household/compound or neighbourhood level.

Background Resistance to sulphadoxine-pyrimethamine (SP) in Plasmodium falciparum parasites is associated with mutations in the dihydrofolate reductase ( dhfr ) and dihydropteroate synthase ( dhps ) genes and has spread worldwide. SP remains the recommended drug for intermittent preventive treatment for malaria in pregnancy (IPTp) and information on population prevalence of the SP resistance molecular markers in pregnant women is limited. Methods Temporal trends of SP resistance molecular markers were investigated in 489 parasite samples collected from pregnant women at delivery from three different observational studies between 1996 and 2009 in Kenya, where SP was adopted for both IPTp and case treatment policies in 1998. Using real-time polymerase chain reaction, pyrosequencing and direct sequencing, 10 single-nucleotide polymorphisms (SNPs) of SP resistance molecular markers were assayed. Results The prevalence of quintuple mutant ( dhfr N51 I /C59 R /S108 N and dhps A437 G /K540 E combined genotype) increased from 7 % in the first study (1996–2000) to 88 % in the third study (2008–2009). When further stratified by sample collection year and adoption of IPTp policy, the prevalence of the quintuple mutant increased from 2.4 % in 1998 to 44.4 % three years after IPTp policy adoption, seemingly in parallel with the increase in percentage of SP use in pregnancy. However, in the 1996–2000 study, more mutations in the combined dhfr / dhps genotype were associated with SP use during pregnancy only in univariable analysis and no associations were detected in the 2002–2008 and 2008–2009 studies. In addition, in the 2008–2009 study, 5.3 % of the parasite samples carried the dhps triple mutant (A437 G /K540 E /A581 G ). There were no differences in the prevalence of SP mutant genotypes between the parasite samples from HIV + and HIV- women over time and between paired peripheral and placental samples. Conclusions There was a significant increase in dhfr/dhps quintuple mutant and the emergence of new genotype containing dhps 581 in the parasites from pregnant women in western Kenya over 13 years. IPTp adoption and SP use in pregnancy only played a minor role in the increased drug-resistant parasites in the pregnant women over time. Most likely, other major factors, such as the high prevalence of resistant parasites selected by the use of SP for case management in large non-pregnant population, might have contributed to the temporally increased prevalence of SP resistant parasites in pregnant women. Further investigations are needed to determine the linkage between SP drug resistance markers and efficacy of IPTp-SP.

Pregnant women have abundant natural killer (NK) cells in their placenta, and NK cell function is regulated by polymorphisms of killer cell immunoglobulin-like receptors (KIRs). Previous studies report different roles of NK cells in the immune responses to placental malaria (PM) and human immunodeficiency virus (HIV-1) infections. Given these references, the aim of this study was to determine the association between KIR gene content polymorphism and PM infection in pregnant women of known HIV-1 status. Sixteen genes in the KIR family were analyzed in 688 pregnant Kenyan women. Gene content polymorphisms were assessed in relation to PM in HIV-1 negative and HIV-1 positive women, respectively. Results showed that in HIV-1 negative women, the presence of the individual genes KIR2DL1 and KIR2DL3 increased the odds of having PM, and the KIR2DL2/KIR2DL2 homozygotes were associated with protection from PM. However, the reverse relationship was observed in HIV-1 positive women, where the presence of individual KIR2DL3 was associated with protection from PM, and KIR2DL2/KIR2DL2 homozygotes increased the odds for susceptibility to PM. Further analysis of the HIV-1 positive women stratified by CD4 counts showed that this reverse association between KIR genes and PM remained only in the individuals with high CD4 cell counts but not in those with low CD4 cell counts. Collectively, these results suggest that inhibitory KIR2DL2 and KIR2DL3, which are alleles of the same locus, play a role in the inverse effects on PM and PM/HIV co-infection and the effect of KIR genes on PM in HIV positive women is dependent on high CD4 cell counts. In addition, analysis of linkage disequilibrium (LD) of the PM relevant KIR genes showed strong LD in women without PM regardless of their HIV status while LD was broken in those with PM, indicating possible selection pressure by malaria infection on the KIR genes.