A multiphase program for malaria elimination in southern Mozambique (the Magude project): A before-after study

Antimalarial resistance risk in Mozambique detected by a novel quadruplex droplet digital PCR assay

While the Plasmodium falciparum malaria parasite continues to cause severe disease globally, Mozambique is disproportionally represented in malaria case totals. Acquisition of copy number variations (CNVs) in the parasite genome contributes to antimalarial drug resistance through overexpression of drug targets. Of interest, piperaquine resistance is associated with plasmepsin 2 and 3 CNVs (pfpmp2 and pfpmp3, respectively), while CNVs in the multidrug efflux pump, multidrug resistance-1 (pfmdr1), increase resistance to amodiaquine and lumefantrine. These antimalarials are partner drugs in artemisinin combination therapies (ACTs) and therefore, CNV detection with accurate and efficient tools is necessary to track ACT resistance risk. Here, we evaluated ~300 clinically derived samples collected from three sites in Mozambique for resistance-associated CNVs. We developed a novel, medium-throughput, quadruplex droplet digital PCR (ddPCR) assay to simultaneously quantify the copy number of pfpmp3, pfpmp2, and pfmdr1 loci in these clinical samples. By using DNA from laboratory parasite lines, we show that this nanodroplet-based method is capable of detecting picogram levels of parasite DNA, which facilitates its application for low yield and human host-contaminated clinical surveillance samples. Following ddPCR and the application of quality control standards, we detected CNVs in 13 of 229 high-quality samples (prevalence of 5.7%). Overall, our study revealed a low number of resistance CNVs present in the parasite population across all three collection sites, including various combinations of pfmdr1, pfpmp2, and pfpmp3 CNVs. The potential for future ACT resistance across Mozambique emphasizes the need for continued molecular surveillance across the region.

Sustained clinical benefit of malaria chemoprevention with sulfadoxine-pyrimethamine (SP) in pregnant women in a region with high SP resistance markers

OBJECTIVE

The effectiveness of intermittent preventive treatment of malaria in pregnancy with sulfadoxine-pyrimethamine (IPTp-SP) is threatened by increasing SP-resistance in Africa. We assessed the level of SP-resistance markers, and the clinical and parasitological effectiveness of IPTp-SP in southern Mozambique.

METHODS

P. falciparum infection, antimalarial antibodies and dhfr/dhps SP-resistance mutants were detected by quantitative polymerase chain reaction (qPCR), suspension array technology and targeted deep sequencing, respectively, among 4016 HIV-negative women in Maputo province (2016-2019). Univariate and multivariate regression models were used to assess the association between taking the recommended three or more IPTp-SP doses (IPTp3+) and parasitological and clinical outcomes.

RESULTS

84.3% (3385/4016) women received three or more IPTp-SP doses. The prevalence of quintuple mutants at first antenatal care (ANC) visit was 94.2%. IPTp3+ was associated with a higher clearance rate of qPCR-detected infections from first ANC visit to delivery (adjusted odds ratio [aOR]=5.9, 95% CI: 1.5-33.3; p = 0.012), lower seroprevalence at delivery of antibodies against the pregnancy-specific antigen VAR2CSADBL34 (aOR=0.72, 95% CI: 0.54-0.95; p = 0.022), and lower prevalence of low birth weight deliveries (aOR: 0.61, 95% CI: 0.41-0.90; p = 0.013).

CONCLUSION

A sustained parasitological effect of IPTp-SP contributes to the clinical effectiveness of IPTp3+ in areas with high prevalence of SP-resistance markers.

An evaluation of LLIN physical integrity and population attitudes towards net use, care and handling during the Magude project in southern Mozambique

BACKGROUND

The Magude Project assessed the feasibility of eliminating malaria in Magude district, a low transmission setting in southern Mozambique, using a package of interventions, including long-lasting insecticidal nets (LLINs). As the efficacy of LLINs depends in part on their physical integrity, this metric was quantified for Olyset® Nets post mass-distribution, in addition to net use, care and handling practices and other risk factors associated with net physical integrity.

METHODS

Nets were collected during a cross-sectional net evaluation, nine months after the Magude project commenced, which was 2 years after the nets were distributed by the National Malaria Control Programme (NMCP). The physical integrity of the nets was assessed by counting and sizing the holes at different positions on each net. A structured questionnaire was administered to assess how the selected net was used and treated (care, wash and repair). Net bio-efficacy was assessed following the standard World Health Organization (WHO) cone bioassay procedures.

RESULTS

Out of the 170 Olyset® Nets included in the analysis, 63.5% had been used the night before. The main reason for not using a net was the notion that there were no mosquitoes present. The average number of people using each net was 1.79. Two thirds of the nets had only been washed once or twice since distribution. Most nets (80.9%) were holed and 18% were torn, but none of the risk factors were significantly associated with net integrity, except for presence of mice in the household. Less than half of the participants noticed holes in holed nets, and of those only 38.6% attempted to repair those. None of the six nets that were tested for bio-efficacy passed the WHO threshold of 80% mosquito mortality.

CONCLUSION

Overall the majority of Olyset® Nets were in serviceable condition two years post-distribution, but their insecticidal effect may have been lost. This study-together with previous evidence on suboptimal access to and use of LLINs in Magude district-highlights that LLINs as an intervention could have been optimized during the Magude project to achieve maximum intervention impact.

Genomic malaria surveillance of antenatal care users detects reduced transmission following elimination interventions in Mozambique

Routine sampling of pregnant women at first antenatal care (ANC) visits could make Plasmodium falciparum genomic surveillance more cost-efficient and convenient in sub-Saharan Africa. We compare the genetic structure of parasite populations sampled from 289 first ANC users and 93 children from the community in Mozambique between 2015 and 2019. Samples are amplicon sequenced targeting 165 microhaplotypes and 15 drug resistance genes. Metrics of genetic diversity and relatedness, as well as the prevalence of drug resistance markers, are consistent between the two populations. In an area targeted for elimination, intra-host genetic diversity declines in both populations (p = 0.002-0.007), while for the ANC population, population genetic diversity is also lower (p = 0.0004), and genetic relatedness between infections is higher (p = 0.002) than control areas, indicating a recent reduction in the parasite population size. These results highlight the added value of genomic surveillance at ANC clinics to inform about changes in transmission beyond epidemiological data.

Multiple Anopheles species complicate downstream analysis and decision-making in a malaria pre-elimination area in southern Mozambique

BACKGROUND

Different anopheline species (even within a species group/complex) can differ in their feeding and resting behaviours, which impact both malaria transmission patterns as well as the efficacy of vector control interventions. While morphological identification of sampled specimens is an important first step towards understanding species diversity and abundance, misidentification can result in the implementation of less effective vector control measures, and consequently smaller reductions in the number of local malaria cases. Focusing on southern Mozambique, a malaria pre-elimination area where malaria remains persistent, the aims of this preliminary study were to use molecular identification (CO1 and ITS2 barcoding) to (1) validate the results from the morphological identification (with a particular focus on Anopheles pharoensis and Anopheles squamosus), and (2) have a closer look at the Anopheles coustani group (which includes Anopheles tenebrosus and Anopheles ziemanni).

METHODS

Female anopheline mosquitoes (n = 81) were identified morphologically and subsequently sequenced at the ribosomal DNA internal transcribed spacer region 2 (ITS2) and/or cytochrome oxidase subunit 1 (CO1) loci towards species determination.

RESULTS

Out of the 62 specimens that were identified morphologically to species, 4 (6.5%) were misidentified. Regarding the An. coustani group, morphological identification showed that several members are present in southern Mozambique, including An. coustani sensu lato (s.l.), An. ziemanni and An. tenebrosus. However, based on both ITS2 and CO1 sequences, the exact species remains unknown for the latter two members until voucher sequences are available for comparison.

CONCLUSION

The reason(s) for morphological misidentification of anopheline mosquitoes need to be mitigated. This is usually related to both the capacity (i.e. training) of the microscopist to identify anopheline species, and the information provided in the dichotomous identification key. As the An. coustani complex contributes to (residual) malaria transmission in sub-Saharan Africa, it may play a role in the observed persistent malaria in southern Mozambique. A better baseline characterizing of the local anophelines species diversity and behaviours will allow us to improve entomological surveillance strategies, better understand the impact of vector control on each local vector species, and identify new approaches to target those vector species.

Genomic malaria surveillance of antenatal care users detects reduced transmission following elimination interventions in Mozambique

Routine sampling of pregnant women at first antenatal care (ANC) visits could make Plasmodium falciparum genomic surveillance more cost-efficient and convenient in sub-Saharan Africa. We compared the genetic structure of parasite populations sampled from 289 first ANC attendees and 93 children from the community in Mozambique between 2015 and 2019. Samples were amplicon sequenced targeting 165 microhaplotypes and 15 drug resistance genes. Metrics of genetic diversity and relatedness, as well as the prevalence of drug resistance markers, were consistent between the two populations. In an area targeted for elimination, intra-host genetic diversity declined in both populations (p=0.002-0.007), while for the ANC population, population genetic diversity was also lower (p=0.0004), and genetic relatedness between infections were higher (p=0.002) than control areas, indicating a recent reduction in the parasite population size. These results highlight the added value of genomic surveillance at ANC clinics to inform about changes in transmission beyond epidemiological data.

Antimalarial mass drug administration in large populations and the evolution of drug resistance

Mass drug administration (MDA) with antimalarials has been shown to reduce prevalence and interrupt transmission in small populations, in populations with reliable access to antimalarial drugs, and in populations where sustained improvements in diagnosis and treatment are possible. In addition, when MDA is effective it eliminates both drug-resistant parasites and drug-sensitive parasites, which has the long-term benefit of extending the useful therapeutic life of first-line therapies for all populations, not just the focal population where MDA was carried out. However, in order to plan elimination measures effectively, it is necessary to characterize the conditions under which failed MDA could exacerbate resistance. We use an individual-based stochastic model of Plasmodium falciparum transmission to evaluate this risk for MDA using dihydroartemisinin-piperaquine (DHA-PPQ), in populations where access to antimalarial treatments may not be uniformly high and where re-importation of drug-resistant parasites may be common. We find that artemisinin-resistance evolution at the kelch13 locus can be accelerated by MDA when all three of the following conditions are met: (1) strong genetic bottlenecking that falls short of elimination, (2) re-importation of artemisinin-resistant genotypes, and (3) continued selection pressure during routine case management post-MDA. Accelerated resistance levels are not immediate but follow the rebound of malaria cases post-MDA, if this is allowed to occur. Crucially, resistance is driven by the selection pressure during routine case management post-MDA and not the selection pressure exerted during the MDA itself. Second, we find that increasing treatment coverage post-MDA increases the probability of local elimination in low-transmission regions (prevalence < 2%) in scenarios with both low and high levels of drug-resistance importation. This emphasizes the importance of planning for and supporting high coverage of diagnosis and treatment post-MDA.

Detecting temporal and spatial malaria patterns from first antenatal care visits

Pregnant women attending first antenatal care (ANC) visits represent a promising malaria surveillance target in Sub-Saharan Africa. We assessed the spatio-temporal relationship between malaria trends at ANC (n = 6471) and in children in the community (n = 3933) and at health facilities (n = 15,467) in southern Mozambique (2016-2019). ANC P. falciparum rates detected by quantitative polymerase chain reaction mirrored rates in children, regardless of gravidity and HIV status (Pearson correlation coefficient [PCC] > 0.8, χ²<1.1), with a 2-3 months lag. Only at rapid diagnostic test detection limits at moderate-to-high transmission, did multigravidae show lower rates than children (PCC = 0.61, 95%CI[-0.12-0.94]). Seroprevalence against the pregnancy-specific antigen VAR2CSA reflected declining malaria trends (PCC = 0.74, 95%CI[0.24-0.77]). 60% (9/15) of hotspots detected from health facility data (n = 6662) using a novel hotspot detector, EpiFRIenDs, were also identified with ANC data (n = 3616). Taken together, we show that ANC-based malaria surveillance offers contemporary information on temporal trends and geographic distribution of malaria burden in the community.

Targeted and whole-genome sequencing reveal a north-south divide in P. falciparum drug resistance markers and genetic structure in Mozambique

Mozambique is one of the four African countries which account for over half of all malaria deaths worldwide, yet little is known about the parasite genetic structure in that country. We performed P. falciparum amplicon and whole genome sequencing on 2251 malaria-infected blood samples collected in 2015 and 2018 in seven provinces of Mozambique to genotype antimalarial resistance markers and interrogate parasite population structure using genome-wide microhaplotyes. Here we show that the only resistance-associated markers observed at frequencies above 5% were pfmdr1-184F (59%), pfdhfr-51I/59 R/108 N (99%) and pfdhps-437G/540E (89%). The frequency of pfdhfr/pfdhps quintuple mutants associated with sulfadoxine-pyrimethamine resistance increased from 80% in 2015 to 89% in 2018 (p < 0.001), with a lower expected heterozygosity and higher relatedness of microhaplotypes surrounding pfdhps mutants than wild-type parasites suggestive of recent selection. pfdhfr/pfdhps quintuple mutants also increased from 72% in the north to 95% in the south (2018; p < 0.001). This resistance gradient was accompanied by a concentration of mutations at pfdhps-436 (17%) in the north, a south-to-north increase in the genetic complexity of P. falciparum infections (p = 0.001) and a microhaplotype signature of regional differentiation. The parasite population structure identified here offers insights to guide antimalarial interventions and epidemiological surveys.

Application of mathematical modelling to inform national malaria intervention planning in Nigeria

BACKGROUND

For their 2021-2025 National Malaria Strategic Plan (NMSP), Nigeria's National Malaria Elimination Programme (NMEP), in partnership with the World Health Organization (WHO), developed a targeted approach to intervention deployment at the local government area (LGA) level as part of the High Burden to High Impact response. Mathematical models of malaria transmission were used to predict the impact of proposed intervention strategies on malaria burden.

METHODS

An agent-based model of Plasmodium falciparum transmission was used to simulate malaria morbidity and mortality in Nigeria's 774 LGAs under four possible intervention strategies from 2020 to 2030. The scenarios represented the previously implemented plan (business-as-usual), the NMSP at an 80% or higher coverage level and two prioritized plans according to the resources available to Nigeria. LGAs were clustered into 22 epidemiological archetypes using monthly rainfall, temperature suitability index, vector abundance, pre-2010 parasite prevalence, and pre-2010 vector control coverage. Routine incidence data were used to parameterize seasonality in each archetype. Each LGA's baseline malaria transmission intensity was calibrated to parasite prevalence in children under the age of five years measured in the 2010 Malaria Indicator Survey (MIS). Intervention coverage in the 2010-2019 period was obtained from the Demographic and Health Survey, MIS, the NMEP, and post-campaign surveys.

RESULTS

Pursuing a business-as-usual strategy was projected to result in a 5% and 9% increase in malaria incidence in 2025 and 2030 compared with 2020, while deaths were projected to remain unchanged by 2030. The greatest intervention impact was associated with the NMSP scenario with 80% or greater coverage of standard interventions coupled with intermittent preventive treatment in infants and extension of seasonal malaria chemoprevention (SMC) to 404 LGAs, compared to 80 LGAs in 2019. The budget-prioritized scenario with SMC expansion to 310 LGAs, high bed net coverage with new formulations, and increase in effective case management rate at the same pace as historical levels was adopted as an adequate alternative for the resources available.

CONCLUSIONS

Dynamical models can be applied for relative assessment of the impact of intervention scenarios but improved subnational data collection systems are required to allow increased confidence in predictions at sub-national level.

Integrated malaria prevention in low- and middle-income countries: a systematic review

BACKGROUND

As many countries aim to eliminate malaria, use of comprehensive approaches targeting the mosquito vector and environment are needed. Integrated malaria prevention advocates the use of several malaria prevention measures holistically at households and in the community. The aim of this systematic review was to collate and summarize the impact of integrated malaria prevention in low- and middle-income countries on malaria burden.

METHODS

Literature on integrated malaria prevention, defined as the use of two or more malaria prevention methods holistically, was searched from 1st January 2001 to 31st July 2021. The primary outcome variables were malaria incidence and prevalence, while the secondary outcome measures were human biting and entomological inoculation rates, and mosquito mortality.

RESULTS

A total of 10,931 studies were identified by the search strategy. After screening, 57 articles were included in the review. Studies included cluster randomized controlled trials, longitudinal studies, programme evaluations, experimental hut/houses, and field trials. Various interventions were used, mainly combinations of two or three malaria prevention methods including insecticide-treated nets (ITNs), indoor residual spraying (IRS), topical repellents, insecticide sprays, microbial larvicides, and house improvements including screening, insecticide-treated wall hangings, and screening of eaves. The most common methods used in integrated malaria prevention were ITNs and IRS, followed by ITNs and topical repellents. There was reduced incidence and prevalence of malaria when multiple malaria prevention methods were used compared to single methods. Mosquito human biting and entomological inoculation rates were significantly reduced, and mosquito mortality increased in use of multiple methods compared to single interventions. However, a few studies showed mixed results or no benefits of using multiple methods to prevent malaria.

CONCLUSION

Use of multiple malaria prevention methods was effective in reducing malaria infection and mosquito density in comparison with single methods. Results from this systematic review can be used to inform future research, practice, policy and programming for malaria control in endemic countries.

Detecting temporal and spatial malaria patterns from first antenatal care visits

Pregnant women attending first antenatal care (ANC) visits represent a promising malaria surveillance target in Sub-Saharan Africa. Here we assessed the spatio-temporal relationship between malaria at ANC (n=6,471), in children at the community(n=9,362) and at health facilities (n=15,467) in southern Mozambique (2016-2019). ANC P. falciparum rates detected by quantitative polymerase chain reaction mirrored rates in children, regardless of gravidity and HIV status (Pearson correlation coefficient [PCC]>0.8, χ²<1.1), with a 2-3 months lag. Only at rapid diagnostic test detection limits at moderate-to-high transmission, multigravidae showed lower rates than children (PCC=0.61, 95%CI[-0.12-0.94]). Seroprevalence against the pregnancy-specific antigen VAR2CSA reflected declining malaria trends (PCC=0.74, 95%CI[0.24-0.77]). 80% (12/15) of hotspots detected from health facility data using a novel hotspot detector, EpiFRIenDs, were also identified with ANC data. The results show that ANC-based malaria surveillance offers contemporary information on temporal trends and the geographic distribution of malaria burden in the community.

Gaps in protection: the actual challenge in malaria elimination

Progress in reducing both malaria cases and deaths has stalled with regression seen in many geographies. While significant attention is given to the contributing challenges of drug and insecticide resistance, 'residual' malaria is often diminished to transmission resulting from outdoor-biting or zoophagic/opportunistic mosquito vectors. These specific vector bionomic traits are only part of the problem, as residual transmission may be driven by (a combination of) (1) sub-optimal intervention coverage, quality, acceptance, and/or usage, (2) drug resistance, (3) insecticide resistance, (4) refractory, resistant and adaptive vector and human behaviours that lower intervention effectiveness, (5) lack of, limited access to, and/or willingness to use healthcare systems, (6) diagnostic sensitivity along with the parallel issue of hrp2/3 mutations, (7) (inter)national policy, (8) the research and development pipeline, and (9) external factors such as natural disasters and conflict zones. Towards combating the minimization of this extensive and multipronged issue among the scientific community, funding agencies, and public health officials responsible for guiding or developing malaria programmes, an alternative way of describing this transmission is proposed by focusing in on the causative 'gaps in protection'. Defining and wording it as such zeros in on the drivers that result in the observed remaining (or increasing) transmission, allowing the malaria community to focus on solutions by identifying the actual causes. Outlining, defining and quantifying the gaps in protection for a given system is of utmost importance to understand what needs to be done, differentiating what can be done versus what cannot be tackled at that moment, along with delineating the technical and financial capacity required.

Acceptability and perceived barriers to reactive focal mass drug administration in the context of a malaria elimination program in Magude district, Southern Mozambique: A qualitative study

This study analysed acceptability and perceived barriers to reactive focal mass drug administration (rfMDA) among community members exposed to community engagement campaigns and malaria elimination interventions in Magude district, following mass drug administration (MDA) in the same district. The study used a formative qualitative study design, consisting of 56 semi-structured interviews with community members, including community leaders, household heads, women of reproductive age, members of the community and adolescents, 4 semi-structured interviews with community health workers, 9 semi-structured interviews with healthcare professionals; and 16 focus group discussions with the general adult population. Data were collected between June and September 2017. A content thematic analysis approach was used to analyse the data. The results of this study showed that rfMDA was accepted due to awareness about the intervention, experience of a previous similar programme, the MDA campaign, and due to favourable perceptions built on the believe that rfMDA would help to prevent, treat and eliminate malaria in the community. Perceived barriers to rfMDA include lack of access to accurate information, reluctance to take a pregnancy test, concern on drug adverse reactions, and reluctance to take antimalarial drugs without any symptom. In conclusion, the community found rfMDA acceptable for malaria intervention. But more community engagement is needed to foster community involvement and self-appropriation of the malaria programme elimination.

An evaluation of LLIN ownership, access, and use during the Magude project in southern Mozambique

The Magude Project assessed the feasibly of eliminating malaria in a low transmission setting in southern Mozambique using a package of interventions. This study measured the ownership, access and use of long-lasting insecticide treated nets (LLINs) and inequalities in these indicators across household wealth, size and population subgroups, to understand the protection that LLINs provided during the project. Data were obtained from various household surveys. At least 31% of the nets distributed during the 2014 and 2017 campaigns were lost during the first year post-distribution. Most nets (77.1%) present in the district were Olyset Nets. LLIN access never exceeded 76.3% and use varied seasonally between 40% and 76.4%. LLIN access limited LLIN use during the project, especially during the high transmission season. LLIN ownership, access and use were lower in harder-to-reach localities, in poorer and larger households. Children and women below 30 had poorer access to LLINs than the overall population. Net use was lowest among school-aged children and young adults, especially among young males, and highest in children under 5, pregnant women, in older adults and in households that received indoor residual spraying (IRS). This study revealed that LLIN mass-distribution campaigns alone are not sufficient to achieve the high level of net protection needed during elimination programs and that reviewing the LLIN allocation scheme, top-up distributions and/or community engagement campaigns is needed, also to reduce inequalities in populations' access to LLINs.

Gravidity and malaria trends interact to modify P. falciparum densities and detectability in pregnancy: a 3-year prospective multi-site observational study

BACKGROUND

Low-density Plasmodium falciparum infections prevail in low transmission settings, where immunity is expected to be minimal, suggesting an immune-independent effect on parasite densities. We aimed to describe parasite densities in pregnancy, and determine how gravidity and antibody-mediated immunity affect these, during a period of declining malaria transmission in southern Mozambique.

METHODS

We documented P. falciparum infections at first antenatal care visits (n = 6471) between November 2016 and October 2019 in Ilha Josina (high-to-moderate transmission area), Manhiça (low transmission area), and Magude (pre-elimination area). Two-way interactions in mixed-effects regression models were used to assess gravidity-dependent differences in quantitative PCR-determined P. falciparum positivity rates (PfPR_qPCR) and densities, in the relative proportion of detectable infections (pDi) with current diagnostic tests (≥ 100 parasites/μL) and in antimalarial antibodies.

RESULTS

PfPR_qPCR declined from 28 to 13% in Ilha Josina and from 5-7 to 2% in Magude and Manhiça. In primigravidae, pDi was highest in Ilha Josina at the first study year (p = 0.048), which declined with falling PfPR_qPCR (relative change/year: 0.41, 95% CI [0.08; 0.73], p = 0.029), with no differences in antibody levels. Higher parasite densities in primigravidae from Ilha Josina during the first year were accompanied by a larger reduction of maternal hemoglobin levels (- 1.60, 95% CI [- 2.49; - 0.72; p < 0.001), than in Magude (- 0.76, 95% CI [- 1.51; - 0.01]; p = 0.047) and Manhiça (- 0.44, 95% CI [- 0.99; 0.10; p = 0.112). In contrast, multigravidae during the transmission peak in Ilha Josina carried the lowest pDi (p = 0.049). As PfPR_qPCR declined, geometric mean of parasite densities increased (4.63, 95% CI [1.28; 16.82], p = 0.020), and antibody levels declined among secundigravidae from Ilha Josina.

CONCLUSIONS

The proportion of detectable and clinically relevant infections is the highest in primigravid women from high-to-moderate transmission settings and decreases with declining malaria. In contrast, the falling malaria trends are accompanied by increased parasite densities and reduced humoral immunity among secundigravidae. Factors other than acquired immunity thus emerge as potentially important for producing less detectable infections among primigravidae during marked declines in malaria transmission.

The realized efficacy of indoor residual spraying campaigns falls quickly below the recommended WHO threshold when coverage, pace of spraying and residual efficacy on different wall types are considered

Indoor residual spraying (IRS) has been and remains an important malaria control intervention in southern Mozambique, South Africa and Eswatini. A better understanding of the effectiveness of IRS campaigns is critical to guide future elimination efforts. We analyze the three IRS campaigns conducted during a malaria elimination demonstration project in southern Mozambique, the "Magude project", and propose a new method to calculate the efficacy of IRS campaigns adjusting for IRS coverage, pace of house spraying and IRS residual efficacy on different wall types. Anopheles funestus sensu lato (s.l.) and An. gambiae s.l. were susceptible to pirimiphos-methyl and DDT. Anopheles funestus s.l. was resistant to pyrethroids, with 24h post-exposure mortality being lower for An. funestus sensu stricto (s.s.) than for An. parensis (collected indoors). The percentage of structures sprayed was above 90% and percentage of people covered above 86% in all three IRS campaigns. The percentage of households sprayed was above 83% in 2015 and 2016, but not assessed in 2017. Mosquito mortality 24h post-exposure stayed above 80% for 196 days after the 2016 IRS campaign and 222 days after the 2017 campaign and was 1.5 months longer on mud walls than on cement walls. This was extended by up to two months when 120h post-exposure mortality was considered. The district-level realized IRS efficacy was 113 days after the 2016 campaign. While the coverage of IRS campaigns in Magude were high, IRS protection did not remain optimal for the entire high malaria transmissions season. The use of a longer-lasting IRS product could have further supported the interruption of malaria transmission in the district. To better estimate the protection afforded by IRS campaigns, National Malaria Control Programs and partners are encouraged to adjust the calculation of IRS efficacy for IRS coverage, pace of house spraying during the campaign and IRS efficacy on different wall types combined with wall type distribution in the sprayed area.

Six decades of malaria vector control in southern Africa: a review of the entomological evidence-base

BACKGROUND

Countries in the southern Africa region have set targets for malaria elimination between 2020 and 2030. Malaria vector control is among the key strategies being implemented to achieve this goal. This paper critically reviews published entomological research over the past six decades in three frontline malaria elimination countries namely, Botswana Eswatini and Namibia, and three second-line malaria elimination countries including Mozambique, Zambia, and Zimbabwe. The objective of the review is to assess the current knowledge and highlight gaps that need further research attention to strengthen evidence-based decision-making toward malaria elimination.

METHODS

Publications were searched on the PubMed engine using search terms: "(malaria vector control OR vector control OR malaria vector*) AND (Botswana OR Swaziland OR Eswatini OR Zambia OR Zimbabwe OR Mozambique)". Opinions, perspectives, reports, commentaries, retrospective analysis on secondary data protocols, policy briefs, and reviews were excluded.

RESULTS

The search resulted in 718 publications with 145 eligible and included in this review for the six countries generated over six decades. The majority (139) were from three countries, namely Zambia (59) and Mozambique (48), and Zimbabwe (32) whilst scientific publications were relatively scanty from front-line malaria elimination countries, such as Namibia (2), Botswana (10) and Eswatini (4). Most of the research reported in the publications focused on vector bionomics generated mostly from Mozambique and Zambia, while information on insecticide resistance was mostly available from Mozambique. Extreme gaps were identified in reporting the impact of vector control interventions, both on vectors and disease outcomes. The literature is particularly scanty on important issues such as change of vector ecology over time and space, intervention costs, and uptake of control interventions as well as insecticide resistance.

CONCLUSIONS

The review reveals a dearth of information about malaria vectors and their control, most noticeable among the frontline elimination countries: Namibia, Eswatini and Botswana. It is of paramount importance that malaria vector research capacity and routine entomological monitoring and evaluation are strengthened to enhance decision-making, considering changing vector bionomics and insecticide resistance, among other determinants of malaria vector control.

Overlaying human and mosquito behavioral data to estimate residual exposure to host-seeking mosquitoes and the protection of bednets in a malaria elimination setting where indoor residual spraying and nets were deployed together

Characterizing persistent malaria transmission that occurs after the combined deployment of indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) is critical to guide malaria control and elimination efforts. This requires a detailed understanding of both human and vector behaviors at the same temporal and spatial scale. Cross-sectional human behavior evaluations and mosquito collections were performed in parallel in Magude district, Mozambique. Net use and the exact time when participant moved into each of five environments (outdoor, indoor before bed, indoor in bed, indoor after getting up, and outdoor after getting up) were recorded for individuals from three different age groups and both sexes during a dry and a rainy season. Malaria mosquitoes were collected with CDC light traps in combination with collection bottle rotators. The percentage of residual exposure to host-seeking vectors that occurred in each environment was calculated for five local malaria vectors with different biting behaviors, and the actual (at observed levels of LLIN use) and potential (i.e. if all residents had used an LLIN) personal protection conferred by LLINs was estimated. Anopheles arabiensis was responsible for more than 74% of residents' residual exposure to host-seeking vectors during the Magude project. The other four vector species (An. funestus s.s., An. parensis, An. squamosus and An. merus) were responsible for less than 10% each. The personal protection conferred by LLINs prevented only 39.2% of the exposure to host-seeking vectors that survived the implementation of both IRS and LLINs, and it differed significantly across seasons, vector species and age groups. At the observed levels of bednet use, 12.5% of all residual exposure to host-seeking vectors occurred outdoor during the evening, 21.9% indoor before going to bed, almost two thirds (64%) while people were in bed, 1.4% indoors after getting up and 0.2% outdoor after leaving the house. Almost a third of the residual exposure to host-seeking vectors (32.4%) occurred during the low transmission season. The residual bites of An. funestus s.s. and An. parensis outdoors and indoor before bedtime, of An. arabiensis indoors when people are in bed, and of An. squamosus both indoors and outdoors, are likely to have sustained malaria transmission throughout the Magude project. By increasing LLIN use, an additional 24.1% of exposure to the remaining hosts-seeking vectors could have been prevented. Since An. arabiensis, the most abundant vector, feeds primarily while people are in bed, increasing net use and net feeding inhibition (through e.g. community awareness activities and the selection of more effective LLINs) could significantly reduce the exposure to remaining host-seeking mosquitoes. Nonetheless, supplementary interventions aiming to reduce human-vector contact outdoors and/or indoors before people go to bed (e.g. through larval source management, window and eave screening, eave tubes, and spatial repellents) will be needed to reduce residual exposure to the outdoor and early biting An. funestus s.s. and An. parensis.

The mosquito vectors that sustained malaria transmission during the Magude project despite the combined deployment of indoor residual spraying, insecticide-treated nets and mass-drug administration

The "Magude project" aimed but failed to interrupt local malaria transmission in Magude district, southern Mozambique, by using a comprehensive package of interventions, including indoor residual spraying (IRS), pyrethroid-only long-lasting insecticide treated nets (LLINs) and mass-drug administration (MDA). Here we present detailed information on the vector species that sustained malaria transmission, their association with malaria incidence and behaviors, and their amenability to the implemented control interventions. Mosquitoes were collected monthly between May 2015 and October 2017 in six sentinel sites in Magude district, using CDC light traps both indoors and outdoors. Anopheles arabiensis was the main vector during the project, while An. funestus s.s., An. merus, An. parensis and An. squamosus likely played a secondary role. The latter two species have never previously been found positive for Plasmodium falciparum in southern Mozambique. The intervention package successfully reduced vector sporozoite rates in all species throughout the project. IRS was effective in controlling An. funestus s.s. and An. parensis, which virtually disappeared after its first implementation, but less effective at controlling An. arabiensis. Despite suboptimal use, LLINs likely provided significant protection against An. arabiensis and An. merus that sought their host largely indoors when people where in bed. Adding IRS on top of LLINs and MDA likely added value to the control of malaria vectors during the Magude project. Future malaria elimination attempts in the area could benefit from i) increasing the use of LLINs, ii) using longer-lasting IRS products to counteract the increase in vector densities observed towards the end of the high transmission season, and iii) a higher coverage with MDA to reduce the likelihood of human infection. However, additional interventions targeting vectors that survive IRS and LLINs by biting outdoors or indoors before people go to bed, will be likely needed to achieve local malaria elimination.

Piperaquine Pharmacokinetic and Pharmacodynamic Profiles in Healthy Volunteers of Papua New Guinea after Administration of Three-Monthly Doses of Dihydroartemisinin–Piperaquine

Mass drug administration (MDA) with monthly dihydroartemisinin-piperaquine (DHA-PQP) appears useful in malaria control and elimination strategies. Determining the relationship between consecutive piperaquine phosphate (PQP) exposure and its impact on QT interval prolongation is a key safety consideration for MDA campaigns.

Temporal trends and adverse perinatal outcomes of twin pregnancies at differing gestational ages: an observational study from China between 2012–2020

Background

With the development of assisted reproductive technology, the twinning rate in China has been increasing. However, little is known about twinning from 2014 onwards. In addition, previous studies analysing optimal gestational times have rarely considered maternal health conditions. Therefore, whether maternal health conditions affect the optimal gestational time remains unclear.

Methods

Data of women delivered between January 2012 and December 2020 were collected through China’s National Maternal Near Miss Surveillance System. Interrupted time series analysis was used to determine the rates of twinning, stillbirth, smaller than gestational age (SGA), and low Apgar scores (< 4) among twins in China. To estimate the risk of each adverse perinatal outcome for separate gestational weeks, a multivariate generalised linear model was used. Infants born at 37 weeks of gestational age or foetuses staying in utero were used as reference separately. The analyses were adjusted for the sampling distribution of the population and the cluster effect at the hospital and individual levels were considered.

Results

There were 442,268 infants enrolled in this study, and the adjusted rates for twinning, stillbirth, SGA, and low Apgar scores were 3.10%, 1.75%, 7.70%, and 0.79%, respectively. From 2012 to 2020, the twinning rate showed an increasing trend. Adverse perinatal outcomes, including stillbirth, SGA, and low Apgar scores showed a decreasing trend. A gestational age between 34 and 36 weeks decreased most for rate of stillbirth (average changing rate -9.72%, 95% confidence interval [CI] -11.41% to -8.00%); and a gestational age of between 37 and 38 weeks decreased most for rates of SGA (average changing rate -4.64%, 95% CI -5.42% to -3.85%) and low Apgar scores (average changing rate -17.61%, 95% CI -21.73% to -13.26%). No significant difference in changes in twinning rate or changes of each perinatal outcome was observed during periods of different fertility policies. Infants born at 37 weeks of gestation had a decreased risk of stillbirth, SGA, and low Apgar scores. Maternal antepartum or medical complications increased the risk of SGA and low Apgar scores in different gestational weeks.

Conclusion

China’s twinning rate showed an increasing trend, while adverse perinatal outcomes decreased from 2012 to 2020. Fertility policy changes have had little effect on the twinning rate or the rate of adverse perinatal outcomes such as stillbirth, SGA, or low Apgar scores. The optimal gestational age for twins was 37 weeks. Women pregnant with twins and with antepartum or medical complications should be cautious due to an increased risk of SGA and low Apgar scores.

Modelling sociodemographic factors that affect malaria prevalence in Sussundenga, Mozambique: a cross-sectional study

Background: Malaria is still one of the leading causes of mortality and morbidity in Mozambique with little progress in malaria control over the past 20 years. Sussundenga is one of most affected areas. Malaria transmission has a strong association with environmental and sociodemographic factors. The knowledge of sociodemographic factors that affects malaria, may be used to improve the strategic planning for its control. Currently such studies have not been performed in Sussundenga. Thus, the objective of this study is to model the relationship between malaria and sociodemographic factors in Sussundenga, Mozambique.

Methods: Houses in the study area were digitalized and enumerated using Google Earth Pro version 7.3. In this study 100 houses were randomly selected to conduct a community survey of Plasmodiumfalciparum parasite prevalence using rapid diagnostic test (RDT). During the survey, a questionnaire was conducted to assess the sociodemographic factors of the participants. Descriptive statistics were analyzed and backward stepwise logistic regression was performed establishing a relationship between positive cases and the factors. The analysis was carried out using SPSS version 20 package.

Results: The overall P. falciparum prevalence was 31.6%. Half of the malaria positive cases occurred in age group 5 to 14 years. Previous malaria treatment, population density and age group were significant predictors for the model. The model explained 13.5% of the variance in malaria positive cases and sensitivity of the final model was 73.3%.

Conclusion: In this area the highest burden of P. falciparum infection was among those aged 5–14 years old. Malaria infection was related to sociodemographic factors. Targeting malaria control at community level can combat the disease more effectively than waiting for cases at health centers. These finding can be used to guide more effective interventions in this region.

Impact of the malaria comprehensive case management programme in Odisha, India

Background

The Comprehensive Case Management Project (CCMP), was a collaborative implementation research initiative to strengthen malaria early detection and complete treatment in Odisha State, India.

Methods

A two-arm quasi-experimental design was deployed across four districts in Odisha, representing a range of malaria endemicity: Bolangir (low), Dhenkanal (moderate), Angul (high), and Kandhamal (hyper). In each district, a control block received routine malaria control measures, whereas a CCMP block received a range of interventions to intensify surveillance, diagnosis, and case management. Impact was evaluated by difference-in-difference (DID) analysis and interrupted time-series (ITS) analysis of monthly blood examination rate (MBER) and monthly parasite index (MPI) over three phases: phase 1 pre-CCMP (2009–2012) phase 2 CCMP intervention (2013–2015), and phase 3 post-CCMP (2016–2017).

Results

During CCMP implementation, adjusting for control blocks, DID and ITS analysis indicated a 25% increase in MBER and a 96% increase in MPI, followed by a –47% decline in MPI post-CCMP, though MBER was maintained. Level changes in MPI between phases 1 and 2 were most marked in Dhenkanal and Angul with increases of 976% and 287%, respectively, but declines in Bolangir (−57%) and Kandhamal (−22%). Between phase 2 and phase 3, despite the MBER remaining relatively constant, substantial decreases in MPI were observed in Dhenkanal (−78%), and Angul (−59%), with a more modest decline in Bolangir (−13%), and an increase in Kandhamal (14%).

Conclusions

Overall, CCMP improved malaria early detection and treatment through the enhancement of the existing network of malaria services which positively impacted case incidence in three districts. In Kandhamal, which is hyperendemic, the impact was not evident. However, in Dhenkanal and Angul, areas of moderate-to-high malaria endemicity, CCMP interventions precipitated a dramatic increase in case detection and a subsequent decline in malaria incidence, particularly in previously difficult-to-reach communities.

Indoor residual spraying for preventing malaria in communities using insecticide-treated nets

BACKGROUND

Insecticide-treated nets (ITNs) and indoor residual spraying (IRS) are used to prevent malaria transmission. Both interventions use insecticides to kill mosquitoes that bite and rest indoors. Adding IRS to ITNs may improve malaria control simply because two interventions can be better than one. Furthermore, IRS may improve malaria control where ITNs are failing due to insecticide resistance. Pyrethroid insecticides are the predominant class of insecticide used for ITNs, as they are more safe than other insecticide classes when in prolonged contact with human skin. While many mosquito populations have developed some resistance to pyrethroid insecticides, a wider range of insecticides can be used for IRS. This review is an update of the previous Cochrane 2019 edition.

OBJECTIVES

To summarize the effect on malaria of additionally implementing IRS, using non-pyrethroid-like or pyrethroid-like insecticides, in communities currently using ITNs.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; CENTRAL; MEDLINE; and five other databases for records from 1 January 2000 to 8 November 2021, on the basis that ITN programmes did not begin to be implemented as policy before the year 2000.

SELECTION CRITERIA

We included cluster-randomized controlled trials (cRCTs), interrupted time series (ITS), or controlled before-after studies (CBAs) comparing IRS plus ITNs with ITNs alone. We included studies with at least 50% ITN ownership (defined as the proportion of households owning one or more ITN) in both study arms.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for eligibility, analyzed risk of bias, and extracted data. We used risk ratio (RR) and 95% confidence intervals (CI). We stratified by type of insecticide, 'pyrethroid-like' and 'non-pyrethroid-like'; the latter could improve malaria control better than adding IRS insecticides that have the same way of working as the insecticide on ITNs ('pyrethroid-like'). We used subgroup analysis of ITN usage in the studies to explore heterogeneity. We assessed the certainty of evidence using the GRADE approach.

MAIN RESULTS

Eight cRCTs (10 comparisons), one CBA, and one ITS study, all conducted since 2008 in sub-Saharan Africa, met our inclusion criteria. The primary vectors in all sites were mosquitoes belonging to the Anopheles gambiae s.l. complex species; five studies in Benin, Mozambique, Ghana, Sudan, and Tanzania also reported the vector Anopheles funestus. Five cRCTs and both quasi-experimental design studies used insecticides with targets different to pyrethroids (two used bendiocarb, three used pirimiphos-methyl, and one used propoxur. Each of these studies were conducted in areas where the vectors were described as resistant or highly resistant to pyrethroids. Two cRCTs used dichloro-diphenyl-trichlorethane (DDT), an insecticide with the same target as pyrethroids. The remaining cRCT used both types of insecticide (pyrethroid deltamethrin in the first year, switching to bendiocarb for the second year). Indoor residual spraying using 'non-pyrethroid-like' insecticides Six studies were included (four cRCTs, one CBA, and one ITS). Our main analysis for prevalence excluded a study at high risk of bias due to repeated sampling of the same population. This risk did not apply to other outcomes. Overall, the addition of IRS reduced malaria parasite prevalence (RR 0.61, 95% CI 0.42 to 0.88; 4 cRCTs, 16,394 participants; high-certainty evidence). IRS may also reduce malaria incidence on average (rate ratio 0.86, 95% CI 0.61 to 1.23; 4 cRCTs, 323,631 child-years; low-certainty evidence) but the effect was absent in two studies. Subgroup analyses did not explain the qualitative heterogeneity between studies. One cRCT reported no effect on malaria incidence or parasite prevalence in the first year, when a pyrethroid-like insecticide was used for IRS, but showed an effect on both outcomes in the second year, when a non-pyrethroid-like IRS was used. The addition of IRS may also reduce anaemia prevalence (RR 0.71, 95% CI 0.38 to 1.31; 3 cRCTs, 4288 participants; low-certainty evidence). Four cRCTs reported the impact of IRS on entomological inoculation rate (EIR), with variable results; overall, we do not know if IRS had any effect on the EIR in communities using ITNs (very low-certainty evidence). Studies also reported the adult mosquito density and the sporozoite rate, but we could not summarize or pool these entomological outcomes due to differences in the reported data. Three studies measured the prevalence of pyrethroid resistance before and after IRS being introduced: there was no difference detected, but these data are limited. Indoor residual spraying using 'pyrethroid-like' insecticides Adding IRS using a pyrethroid-like insecticide did not appear to markedly alter malaria incidence (rate ratio 1.07, 95% CI 0.80 to 1.43; 2 cRCTs, 15,717 child-years; moderate-certainty evidence), parasite prevalence (RR 1.11, 95% CI 0.86 to 1.44; 3 cRCTs, 10,820 participants; moderate-certainty evidence), or anaemia prevalence (RR 1.12, 95% CI 0.89 to 1.40; 1 cRCT, 4186 participants; low-certainty evidence). Data on EIR were limited so no conclusion was made (very low-certainty evidence).

AUTHORS' CONCLUSIONS

in communities using ITNs, the addition of IRS with 'non-pyrethroid-like' insecticides was associated with reduced malaria prevalence. Malaria incidence may also be reduced on average, but there was unexplained qualitative heterogeneity, and the effect may therefore not be observed in all settings. When using 'pyrethroid-like' insecticides, there was no detectable additional benefit of IRS in communities using ITNs.

The impact of a malaria elimination initiative on school outcomes: Evidence from Southern Mozambique

Despite the significant improvements achieved over the last ten years, primary education attainment in Mozambique is still low. Potential reasons acting from the demand perspective include ill health, among other factors. In Mozambique, ill health is still largely linked to malaria, which is a leading cause of outpatient contacts, hospital admissions and death, particularly among under-five and school-aged children. Despite this, in Mozambique and more generally, in malaria endemic countries, the identification and measurement of how improved malaria indicators may contribute to better school outcomes remains largely unknown. In particular, there is a low understanding of the extent to which better health translates immediately into school indicators, such as absenteeism and grades. In this study, we exploit the first year of a malaria elimination initiative implemented in Magude district (Southern Mozambique) that started in 2015, as a quasi-experiment to estimate the impact of malaria on selected primary school outcomes. While malaria was not eliminated, its incidence drastically dropped. We use as control a neighbouring district (Manhiça) with similar socio-economic and epidemiological characteristics. By employing a difference-in-differences (DiD) approach, we examine whether the positive health shock translated into improved school outcomes. Using information from school registers, we generated a dataset on school attendance and grades for 9,848 primary-school students from 9 schools (4 in the treated district and 5 in the control district). In our main specification, a repeated cross-section analysis, we find that the elimination initiative led to a 28% decrease in school absenteeism and a 2% increase in students' grades. Our results are robust across different specifications, including a panel DiD individual fixed effects estimate on a sub-sample of students. These findings provide evidence on the negative impact of malaria on primary education attainment and suggest remarkable economic benefits consequent to its elimination.

Towards global control of parasitic diseases in the Covid-19 era: One Health and the future of multisectoral global health governance

Human parasitic infections—including malaria, and many neglected tropical diseases (NTDs)—have long represented a Gordian knot in global public health: ancient, persistent, and exceedingly difficult to control. With the coronavirus disease (Covid-19) pandemic substantially interrupting control programmes worldwide, there are now mounting fears that decades of progress in controlling global parasitic infections will be undone. With Covid-19 moreover exposing deep vulnerabilities in the global health system, the current moment presents a watershed opportunity to plan future efforts to reduce the global morbidity and mortality associated with human parasitic infections. In this chapter, we first provide a brief epidemiologic overview of the progress that has been made towards the control of parasitic diseases between 1990 and 2019, contrasting these fragile gains with the anticipated losses as a result of Covid-19. We then argue that the complementary aspirations of the United Nations Sustainable Development Goals (SDGs) and the World Health Organization (WHO)’s 2030 targets for parasitic disease control may be achieved by aligning programme objectives within the One Health paradigm, recognizing the interdependence between humans, animals, and the environment. In so doing, we note that while the WHO remains the preeminent international institution to address some of these transdisciplinary concerns, its underlying challenges with funding, authority, and capacity are likely to reverberate if left unaddressed. To this end, we conclude by reimagining how models of multisectoral global health governance—combining the WHO's normative and technical leadership with greater support in allied policy-making areas—can help sustain future malaria and NTD elimination efforts.

Wild populations of malaria vectors can mate both inside and outside human dwellings

BACKGROUND

Wild populations of Anopheles mosquitoes are generally thought to mate outdoors in swarms, although once colonized, they also mate readily inside laboratory cages. This study investigated whether the malaria vectors Anopheles funestus and Anopheles arabiensis can also naturally mate inside human dwellings.

METHOD

Mosquitoes were sampled from three volunteer-occupied experimental huts in a rural Tanzanian village at 6:00 p.m. each evening, after which the huts were completely sealed and sampling was repeated at 11:00 p.m and 6 a.m. the next morning to compare the proportions of inseminated females. Similarly timed collections were done inside local unsealed village houses. Lastly, wild-caught larvae and pupae were introduced inside or outside experimental huts constructed inside two semi-field screened chambers. The huts were then sealed and fitted with exit traps, allowing mosquito egress but not entry. Mating was assessed in subsequent days by sampling and dissecting emergent adults caught indoors, outdoors and in exit traps.

RESULTS

Proportions of inseminated females inside the experimental huts in the village increased from approximately  60% at 6 p.m. to approximately 90% the following morning despite no new mosquitoes entering the huts after 6 p.m. Insemination in the local homes increased from approximately 78% to approximately 93% over the same time points. In the semi-field observations of wild-caught captive mosquitoes, the proportions of inseminated An. funestus were 20.9% (95% confidence interval [CI]: ± 2.8) outdoors, 25.2% (95% CI: ± 3.4) indoors and 16.8% (± 8.3) in exit traps, while the proportions of inseminated An. arabiensis were 42.3% (95% CI: ± 5.5) outdoors, 47.4% (95% CI: ± 4.7) indoors and 37.1% (CI: ± 6.8) in exit traps.

CONCLUSION

Wild populations of An. funestus and An. arabiensis in these study villages can mate both inside and outside human dwellings. Most of the mating clearly happens before the mosquitoes enter houses, but additional mating happens indoors. The ecological significance of such indoor mating remains to be determined. The observed insemination inside the experimental huts fitted with exit traps and in the unsealed village houses suggests that the indoor mating happens voluntarily even under unrestricted egress. These findings may inspire improved vector control, such as by targeting males indoors, and potentially inform alternative methods for colonizing strongly eurygamic Anopheles species (e.g. An. funestus) inside laboratories or semi-field chambers.

Mass drug administration for malaria

BACKGROUND

Studies evaluating mass drug administration (MDA) in malarious areas have shown reductions in malaria immediately following the intervention. However, these effects vary by endemicity and are not sustained. Since the 2013 version of this Cochrane Review on this topic, additional studies have been published.

OBJECTIVES

Primary objectives To assess the sustained effect of MDA with antimalarial drugs on: - the reduction in malaria transmission in moderate- to high-transmission settings; - the interruption of transmission in very low- to low-transmission settings. Secondary objective To summarize the risk of drug-associated adverse effects following MDA.

SEARCH METHODS

We searched several trial registries, citation databases, conference proceedings, and reference lists for relevant articles up to 11 February 2021. We also communicated with researchers to identify additional published and unpublished studies.

SELECTION CRITERIA

Randomized controlled trials (RCTs) and non-randomized studies comparing MDA to no MDA with balanced co-interventions across study arms and at least two geographically distinct sites per study arm.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for eligibility and extracted data. We calculated relative risk (RR) and rate ratios with corresponding 95% confidence intervals (CIs) to compare prevalence and incidence, respectively, in MDA compared to no-MDA groups. We stratified analyses by malaria transmission and by malaria species. For cluster-randomized controlled trials (cRCTs), we adjusted standard errors using the intracluster correlation coefficient. We assessed the certainty of the evidence using the GRADE approach. For non-randomized controlled before-and-after (CBA) studies, we summarized the data using difference-in-differences (DiD) analyses.

MAIN RESULTS

Thirteen studies met our criteria for inclusion. Ten were cRCTs and three were CBAs. Cluster-randomized controlled trials Moderate- to high-endemicity areas (prevalence ≥ 10%) We included data from two studies conducted in The Gambia and Zambia.  At one to three months after MDA, the Plasmodium falciparum (hereafter, P falciparum) parasitaemia prevalence estimates may be higher compared to control but the CIs included no effect (RR 1.76, 95% CI 0.58 to 5.36; Zambia study; low-certainty evidence); parasitaemia incidence was probably lower (RR 0.61, 95% CI 0.40 to 0.92; The Gambia study; moderate-certainty evidence); and confirmed malaria illness incidence may be substantially lower,  but the CIs included no effect (rate ratio 0.41, 95% CI 0.04 to 4.42; Zambia study; low-certainty evidence).  At four to six months after MDA, MDA showed little or no effect on P falciparum parasitaemia prevalence (RR 1.18, 95% CI 0.89 to 1.56; The Gambia study; moderate-certainty evidence) and, no persisting effect was demonstrated with parasitaemia incidence (rate ratio 0.91, 95% CI 0.55 to 1.50; The Gambia study). Very low- to low-endemicity areas (prevalence < 10%) Seven studies from Cambodia, Laos, Myanmar (two studies), Vietnam, Zambia, and Zanzibar evaluated the effects of multiple rounds of MDA on P falciparum. Immediately following MDA (less than one month after MDA), parasitaemia prevalence was reduced (RR 0.12, 95% CI 0.03 to 0.52; one study; low-certainty evidence). At one to three months after MDA, there was a reduction in both parasitaemia incidence (rate ratio 0.37, 95% CI 0.21 to 0.55; 1 study; moderate-certainty evidence) and prevalence (RR 0.25, 95% CI 0.15 to 0.41; 7 studies; low-certainty evidence). For confirmed malaria incidence, absolute rates were low, and it is uncertain whether MDA had an effect on this outcome (rate ratio 0.58, 95% CI 0.12 to 2.73; 2 studies; very low-certainty evidence).  For P falciparum prevalence, the relative differences declined over time, from RR 0.63 (95% CI 0.36 to 1.12; 4 studies) at four to six months after MDA, to RR 0.86 (95% CI 0.55 to 1.36; 5 studies) at 7 to 12 months after MDA. Longer-term prevalence estimates showed overall low absolute risks, and relative effect estimates of the effect of MDA on prevalence varied from RR 0.82 (95% CI 0.20 to 3.34) at 13 to 18 months after MDA, to RR 1.25 (95% CI 0.25 to 6.31) at 31 to 36 months after MDA in one study. Five studies from Cambodia, Laos, Myanmar (2 studies), and Vietnam evaluated the effect of MDA on Plasmodium vivax (hereafter, P vivax). One month following MDA, P vivax prevalence was lower (RR 0.18, 95% CI 0.08 to 0.40; 1 study; low-certainty evidence). At one to three months after MDA, there was a reduction in P vivax prevalence (RR 0.15, 95% CI 0.10 to 0.24; 5 studies; low-certainty evidence). The immediate reduction on P vivax prevalence was not sustained over time, from RR 0.78 (95% CI 0.63 to 0.95; 4 studies) at four to six months after MDA, to RR 1.12 (95% CI 0.94 to 1.32; 5 studies) at 7 to 12 months after MDA. One of the studies in Myanmar provided estimates of longer-term effects, where overall absolute risks were low, ranging from RR 0.81 (95% CI 0.44 to 1.48) at 13 to 18 months after MDA, to RR 1.20 (95% CI 0.44 to 3.29) at 31 to 36 months after MDA. Non-randomized studies Three CBA studies were conducted in moderate- to high-transmission areas in Burkina Faso, Kenya, and Nigeria. There was a reduction in P falciparum parasitaemia prevalence in MDA groups compared to control groups during MDA (DiD range: -15.8 to -61.4 percentage points), but the effect varied at one to three months after MDA (DiD range: 14.9 to -41.1 percentage points).  AUTHORS' CONCLUSIONS: In moderate- to high-transmission settings, no studies reported important effects on P falciparum parasitaemia prevalence within six months after MDA. In very low- to low-transmission settings, parasitaemia prevalence and incidence were reduced initially for up to three months for both P falciparum and P vivax; longer-term data did not demonstrate an effect after four months, but absolute risks in both intervention and control groups were low. No studies provided evidence of interruption of malaria transmission.

Self-diagnosis and self-treatment of malaria in hard-to-reach and mobile populations of the Amazon: results of Malakit, an international multicentric intervention research project

Background

Illegal gold miners are currently key hosts for malaria in French Guiana (FG), with a risk of emergence of resistance linked to improper use of artemisinin-based combination therapy (ACT). The remoteness of the mines and regulatory issues hinder their access to health care.

Methods

A quasi-experimental researched project (Malakit) implemented in FG borders with Brazil and Suriname aimed at determining the effectiveness of distributed kits for self-diagnosis and self-treatment to illegal gold miners, after training, at strategic border staging areas. Evaluation relied on questionnaires at inclusion and follow-up visits, and pre/post intervention surveys. The primary outcome was the proportion of persons reporting a use of certified ACT after a positive malaria diagnosis. The secondary outcomes assessed antimalarial adherence, kit use and impact on malaria epidemiology.

Findings

The proportion of patients reporting a use of certified ACT after a positive diagnosis increased after the intervention (OR 1.8, 95%CI [1.1-3.0]). From April 2018 to March 2020, 3,733 persons participated in the intervention. The kit was used correctly by 71.7% [65.8-77.7] of the 223 persons reporting having used a malakit during the follow-up visits. No serious adverse events related to the misuse of malakit have been reported. The intervention appears to have accelerated the decline in malaria incidence in the region by 42.9%.

Interpretation

This innovative international project showed that people with low education can correctly self-manage their malaria symptoms. This strategy could be integrated in the malaria control programs of the countries involved and considered in other regions with residual malaria in remote areas.

Funding

This project was funded by the European Union, the Global Fund, Brazil MoH, Cayenne Hospital and FG Health Regional Agency.

Editor's note

This translation in French was submitted by the authors and we reproduce it as supplied. It has not been peer reviewed. Our editorial processes have only been applied to the original abstract in English, which should serve as reference for this manuscript. The Lancet Group takes a neutral position with respect to territorial claims in published maps and institutional affiliations.

Contexte

Les chercheurs d'or illégaux sont actuellement un réservoir clé du paludisme en Guyane, avec un risque d'émergence de résistance lié à une mauvaise utilisation des combinaisons thérapeutiques à base d'artémisinine (ACT). L'isolement de ces sites miniers clandestins et des contraintes règlementaires entravent leur accès aux soins.

Méthodes

Un projet de recherche opérationnelle quasi-expérimental (Malakit) a été mis en œuvre aux frontières de la Guyane avec le Brésil et le Suriname. Il visait à déterminer l'efficacité de la distribution de kits d'autodiagnostic et d'autotraitement à des orpailleurs illégaux, après une formation adaptée, dans des zones stratégiques transfrontalières. L'évaluation s'est appuyée sur des questionnaires lors des visites d'inclusion et de suivi, et sur des enquêtes pré/post intervention. L'indicateur principal était la proportion de personnes déclarant avoir utilisé une ACT certifiée après un diagnostic positif de paludisme. Les indicateurs secondaires reposaient sur l'adhérence aux traitements antipaludiques, l'utilisation des kits et l'impact sur l'épidémiologie du paludisme.

Résultats

La proportion de patients déclarant une utilisation d'ACT certifiée après un diagnostic positif a augmenté après l'intervention (OR 1,8, 95%CI [1,1-3,0]). D'avril 2018 à mars 2020, 3 733 personnes ont participé à l'intervention. Le kit a été utilisé correctement par 71,7% [65,8-77,7] des 223 personnes revues en visites de suivi ayant déclaré avoir utilisé un malakit. Aucun événement indésirable grave lié à une mauvaise utilisation du malakit n'a été signalé. L'intervention semble avoir accéléré la diminution de l'incidence du paludisme dans la région de 42,9%.

Interprétation

Ce projet international innovant a montré que les personnes ayant un faible niveau d'éducation peuvent se prendre en charge par eux-mêmes pour des symptômes de paludisme. Cette stratégie pourrait être intégrée dans les programmes de lutte contre le paludisme des pays impliqués et envisagée dans d'autres régions où du paludisme résiduel persiste dans des zones isolées.

Financement

Ce projet a été financé par l'Union Européenne, le Fonds Mondial, le Ministère de la santé du Brésil, le Centre Hospitalier de Cayenne et l'Agence Régionale de Santé de Guyane.

The short-term impact of a malaria elimination initiative in Southern Mozambique: Application of the synthetic control method to routine surveillance data

In public health epidemiology, quasi-experimental methods are widely used to estimate the causal impacts of interventions. In this paper, we demonstrate the contribution the synthetic control method (SCM) can make in evaluating public health interventions, when routine surveillance data are available and the validity of other quasi-experimental approaches may be in question. In our application, we evaluate the short-term effects of a large-scale Mass Drug Administration (MDA) based malaria elimination initiative in Southern Mozambique. We apply the SCM to district level weekly malaria incidence data and compare the observed reduction in age group specific malaria incidence. Between August 2015 and April 2017, a total of 13,322 (78%) cases of malaria were averted relative to the synthetic control. During the peak malaria seasons, the elimination initiative resulted in an 87% reduction in Year 1 (December 2015-April 2016), and 79% reduction in Year 2 (December 2016-April 2017). Comparison with an interrupted time series approach shows the SCM accounts for pre-intervention trends in the data and post-intervention weather events influencing malaria cases. We conclude MDA brought about a drastic reduction in malaria burden and can be a useful addition to existing (or new) vector control strategies and tools in accelerating towards elimination.

Malaria infection and severe disease risks in Africa

The relationship between community prevalence of Plasmodium falciparum and the burden of severe, life-threatening disease remains poorly defined. To examine the three most common severe malaria phenotypes from catchment populations across East Africa, we assembled a dataset of 6506 hospital admissions for malaria in children aged 3 months to 9 years from 2006 to 2020. Admissions were paired with data from community parasite infection surveys. A Bayesian procedure was used to calibrate uncertainties in exposure (parasite prevalence) and outcomes (severe malaria phenotypes). Each 25% increase in prevalence conferred a doubling of severe malaria admission rates. Severe malaria remains a burden predominantly among young children (3 to 59 months) across a wide range of community prevalence typical of East Africa. This study offers a quantitative framework for linking malaria parasite prevalence and severe disease outcomes in children.

Community acceptability to antimalarial mass drug administrations in Magude district, Southern Mozambique: A mixed methods study

Background

This study aimed to capture the acceptability prior to, during and after the implementation of the first year of MDA rounds conducted under the Magude project, a malaria elimination project in southern Mozambique.

Methods

This was a mixed-methods study, consisting of focus group discussions (FGDs) prior to the implementation of MDA rounds (September 2015), non-participant observations (NPOs) conducted during the MDA rounds (November 2015 –beginning of February 2016), and semi-structured interviews (SSIs) after the second round (end of February 2016). Community leaders, women in reproductive age, general members of the community, traditional healers and health professionals were recruited to capture the opinions of all representing key members of the community. A generic outline of nodes and codes was designed to analyze FGDs and SSI separately. Qualitative and quantitative NPO information was analyzed following a content analysis approach.

Findings

222 participants took part in the FGDs (n = 154), and SSIs (n = 68); and 318 household visits during the MDA underwent NPOs. The community engagement campaign emerged throughout the study stages as a crucial factor for the acceptability of MDAs. Acceptability was also fostered by the community’s general will to cooperate in any government-led activity that would reduce malaria burden, the appropriate behavior and knowledge of field workers, or the fact that the intervention was available free of charge to all. Absenteeism of heads of households was identified as the main barrier for the success of the campaign. The most commonly reported factors that negatively affected acceptability were the fear of adverse events, rumors of deaths, being unable to drink alcohol while taking DHAp, or the fear to take DHAp while in anti-retroviral treatment. Pregnancy testing and malaria testing were generally well accepted by the community.

Conclusion

Magude’s community generally accepted the first and second antimalarial MDA rounds, and the procedures associated to the intervention. Future implementation of antimalarial MDAs in southern Mozambique should focus on locally adapted strategies that engage the community to minimize absenteeism and refusals to the intervention.

Transmission-Blocking Vaccines: Harnessing Herd Immunity for Malaria Elimination

INTRODUCTION

Transmission-blocking vaccines (TBV) prevent community spread of malaria by targeting mosquito sexual stage parasites, a life-cycle bottleneck, and will be used in elimination programs. TBV rely on herd immunity to reduce mosquito infections and thereby new infections in both vaccine recipients and non-recipients, but do not provide protection once an individual receives an infectious mosquito bite which complicates clinical development.

AREAS COVERED

Here, we describe the concept and biology behind TBV, and we provide an update on clinical development of the leading vaccine candidate antigens. Search terms 'malaria vaccine,' 'sexual stages,' 'transmission blocking vaccine,' 'VIMT' and 'SSM-VIMT' were used for PubMed queries to identify relevant literature.

EXPERT OPINION

Candidates targeting P. falciparum zygote surface antigen Pfs25, and its P. vivax orthologue Pvs25, induced functional activity in humans that reduced mosquito infection in surrogate assays, but require increased durability to be useful in the field. Candidates targeting gamete surface antigens Pfs230 and Pfs48/45, respectively, are in or nearing clinical trials. Nanoparticle platforms and adjuvants are being explored to enhance immunogenicity. Efficacy trials require special considerations, such as cluster-randomized designs to measure herd immunity that reduces human and mosquito infection rates, while addressing human and mosquito movements as confounding factors.

Field performance of ultrasensitive and conventional malaria rapid diagnostic tests in southern Mozambique

Background

An ultrasensitive malaria rapid diagnostic test (RDT) was recently developed for the improved detection of low-density Plasmodium falciparum infections. This study aimed to compare the diagnostic performance of the PfHRP2-based Abbott Malaria Ag P. falciparum ultrasensitive RDT (uRDT) to that of the conventional SD-Bioline Malaria Ag P. falciparum RDT (cRDT) when performed under field conditions.

Methods

Finger-prick blood samples were collected from adults and children in two cross-sectional surveys in May of 2017 in southern Mozambique. Using real-time quantitative PCR (RT-qPCR) as the reference method, the age-specific diagnostic performance indicators of the cRDT and uRDT were compared. The presence of histidine-rich protein 2 (HRP2) and Plasmodium lactate dehydrogenase (pLDH) antigens was evaluated in a subset from dried blood spots by a quantitative antigen assay. pfhrp2 and pfhrp3 gene deletions were assessed in samples positive by RT-qPCR and negative by both RDTs.

Results

Among the 4,396 participants with complete test results, the sensitivity of uRDTs (68.2; 95% CI 60.8 to 74.9) was marginally better than that of cRDTs (61.5; 95% CI 53.9 to 68.6) (p-value = 0.004), while the specificities were similar (uRDT: 99.0 [95% CI 98.6 to 99.2], cRDT: 99.2 [95% CI 98.9 to 99.4], p-value = 0.02). While the performance of both RDTs was lowest in ≥ 15-year-olds, driven by the higher prevalence of low parasite density infections in this group, the sensitivity of uRDTs was significantly higher in this age group (54.9, 95% CI 40.3 to 68.9) compared to the sensitivity of cRDTs (39.2, 95% CI 25.8 to 53.9) (p-value = 0.008). Both RDTs detected P. falciparum infections at similar geometric mean parasite densities (112.9  parasites/μL for uRDTs and 145.5 parasites/μL for cRDTs). The presence of HRP2 antigen was similar among false positive (FP) samples of both tests (80.5% among uRDT-FPs and 84.4% among cRDT-FPs). Only one false negative sample was detected with a partial pfhrp2 deletion.

Conclusion

This study showed that the uRDTs developed by Abbott do not substantially outperform SD-Bioline Pf malaria RDTs in the community and are still not comparable to molecular methods to detect P. falciparum infections in this study setting.

Changing malaria fever test positivity among paediatric admissions to Tororo district hospital, Uganda 2012-2019

BACKGROUND

The World Health Organization (WHO) promotes long-lasting insecticidal nets (LLIN) and indoor residual house-spraying (IRS) for malaria control in endemic countries. However, long-term impact data of vector control interventions is rarely measured empirically.

METHODS

Surveillance data was collected from paediatric admissions at Tororo district hospital for the period January 2012 to December 2019, during which LLIN and IRS campaigns were implemented in the district. Malaria test positivity rate (TPR) among febrile admissions aged 1 month to 14 years was aggregated at baseline and three intervention periods (first LLIN campaign; Bendiocarb IRS; and Actellic IRS + second LLIN campaign) and compared using before-and-after analysis. Interrupted time-series analysis (ITSA) was used to determine the effect of IRS (Bendiocarb + Actellic) with the second LLIN campaign on monthly TPR compared to the combined baseline and first LLIN campaign periods controlling for age, rainfall, type of malaria test performed. The mean and median ages were examined between intervention intervals and as trend since January 2012.

RESULTS

Among 28,049 febrile admissions between January 2012 and December 2019, TPR decreased from 60% at baseline (January 2012-October 2013) to 31% during the final period of Actellic IRS and LLIN (June 2016-December 2019). Comparing intervention intervals to the baseline TPR (60.3%), TPR was higher during the first LLIN period (67.3%, difference 7.0%; 95% CI 5.2%, 8.8%, p < 0.001), and lower during the Bendiocarb IRS (43.5%, difference - 16.8%; 95% CI - 18.7%, - 14.9%) and Actellic IRS (31.3%, difference - 29.0%; 95% CI - 30.3%, - 27.6%, p < 0.001) periods. ITSA confirmed a significant decrease in the level and trend of TPR during the IRS (Bendicarb + Actellic) with the second LLIN period compared to the pre-IRS (baseline + first LLIN) period. The age of children with positive test results significantly increased with time from a mean of 24 months at baseline to 39 months during the final IRS and LLIN period.

CONCLUSION

IRS can have a dramatic impact on hospital paediatric admissions harbouring malaria infection. The sustained expansion of effective vector control leads to an increase in the age of malaria positive febrile paediatric admissions. However, despite large reductions, malaria test-positive admissions continued to be concentrated in children aged under five years. Despite high coverage of IRS and LLIN, these vector control measures failed to interrupt transmission in Tororo district. Using simple, cost-effective hospital surveillance, it is possible to monitor the public health impacts of IRS in combination with LLIN.

Effect of mass dihydroartemisinin-piperaquine administration in southern Mozambique on the carriage of molecular markers of antimalarial resistance

BACKGROUND

Mass drug administration (MDA) can rapidly reduce the burden of Plasmodium falciparum (Pf). However, concerns remain about its contribution to select for antimalarial drug resistance.

METHODS

We used Sanger sequencing and real-time PCR to determine the proportion of molecular markers associated with antimalarial resistance (k13, pfpm2, pfmdr1 and pfcrt) in Pf isolates collected before (n = 99) and after (n = 112) the implementation of two monthly MDA rounds with dihydroartemisinin-piperaquine (DHAp) for two consecutive years in Magude district of Southern Mozambique.

RESULTS

None of the k13 polymorphisms associated with artemisinin resistance were observed in the Pf isolates analyzed. The proportion of Pf isolates with multiple copies of pfpm2, an amplification associated with piperaquine resistance, was similar in pre- (4.9%) and post-MDA groups (3.4%; p = 1.000). No statistically significant differences were observed between pre- and post-MDA groups in the proportion of Pf isolates neither with mutations in pfcrt and pfmdr1 genes, nor with the carriage of pfmdr1 multiple copies (p>0.05).

CONCLUSIONS

This study does not show any evidence of increased frequency of molecular makers of antimalarial resistance after MDA with DHAp in southern Mozambique where markers of antimalarial resistance were absent or low at the beginning of the intervention.