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BMC Medicine Sep 2014Identifying Plasmodium vivax antigen-specific antibodies associated with P. vivax infection and protective immunity is key to the development of serosurveillance tools... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Identifying Plasmodium vivax antigen-specific antibodies associated with P. vivax infection and protective immunity is key to the development of serosurveillance tools and vaccines for malaria. Antibody targets of P. vivax can be identified by seroepidemiological studies of individuals living in P. vivax-endemic areas, and is an important strategy given the limited ability to culture P. vivax in vitro. There have been numerous studies investigating the association between P. vivax antibody responses and P. vivax infection, but there has been no standardization of results to enable comparisons across populations.
METHODS
We performed a systematic review with meta-analysis of population-based, cross-sectional, case-control, and cohort studies of individuals living in P. vivax-endemic areas. We searched 6 databases and identified 18 studies that met predefined inclusion and quality criteria, and examined the association between antibody responses to P. vivax antigens and P. vivax malaria.
RESULTS
The majority of studies were published in South America (all from Brazil) and the rest from geographically diverse areas in the Asia-Pacific region. Considerable heterogeneity in estimates was observed, but IgG responses to PvCSP, PvMSP-119, PvMSP-9RIRII, and PvAMA1 were associated with increased odds of P. vivax infection in geographically diverse populations. Potential sources of heterogeneity included study design, different transmission intensities and transmigrant populations. Protective associations were observed for antibodies to PvMSP-119, PvMSP-1NT, PvMSP-3α and PvMSP-9NT antigens, but only in single geographical locations.
CONCLUSIONS
This systematic review revealed several antigen-specific antibodies that were associated with active infection and protective immunity, which may be useful biomarkers. However, more studies are needed on additional antigens, particularly cohort studies to increase the body of evidence for protective immunity. More studies representing diverse geographical regions encompassing varying P. vivax endemicities are needed to validate the generalizability of the findings and to provide a solid evidence base for the use of P. vivax antigens in vaccines and serosurveillance tools.
Topics: Antibodies, Protozoan; Antigens, Protozoan; Biomarkers; Female; Humans; Malaria, Vivax; Male; Plasmodium vivax; Protozoan Proteins; Seroepidemiologic Studies
PubMed: 25199532
DOI: 10.1186/s12916-014-0150-1 -
Tropical Medicine and Infectious Disease Sep 2023The Duffy protein, a transmembrane molecule, functions as a receptor for various chemokines and facilitates attachment between the reticulocyte and the Duffy... (Review)
Review
The Duffy protein, a transmembrane molecule, functions as a receptor for various chemokines and facilitates attachment between the reticulocyte and the Duffy antigen-binding protein. Duffy expression correlates with the Duffy receptor gene for the chemokine, located on chromosome 1, and exhibits geographical variability worldwide. Traditionally, researchers have described the Duffy negative genotype as a protective factor against infection. However, recent studies suggest that this microorganism's evolution could potentially diminish this protective effect. Nevertheless, there is currently insufficient global data to demonstrate this phenomenon. This study aimed to evaluate the relationship between the Duffy genotype/phenotype and the prevalence of infection. The protocol for the systematic review was registered in PROSPERO as CRD42022353427 and involved reviewing published studies from 2012 to 2022. The Medline/PubMed, Web of Science, Scopus, and SciELO databases were consulted. Assessments of study quality were conducted using the STROBE and GRADE tools. A total of 34 studies were included, with Africa accounting for the majority of recorded studies. The results varied significantly regarding the relationship between the Duffy genotype/phenotype and invasion. Some studies predominantly featured the negative Duffy genotype yet reported no malaria cases. Other studies identified minor percentages of infections. Conversely, certain studies observed a higher prevalence (99%) of Duffy-negative individuals infected with In conclusion, this systematic review found that the homozygous Duffy genotype positive for the A allele (FY*A/*A) is associated with a higher incidence of infection. Furthermore, the negative Duffy genotype does not confer protection against vivax malaria.
PubMed: 37888591
DOI: 10.3390/tropicalmed8100463 -
International Journal For Parasitology.... Aug 2017Recurrent P. vivax infections are associated with significant morbidity and mortality. Although radical cure can reduce recurrent infection, it is confounded by... (Review)
Review
INTRODUCTION
Recurrent P. vivax infections are associated with significant morbidity and mortality. Although radical cure can reduce recurrent infection, it is confounded by antimalarial resistance and the lack of safe and effective hypnozoitocidal treatment. This study documents the available literature of published clinical trials of P. vivax, providing an up to date, online, open access tool to view and download available information.
METHODS
A systematic review was conducted according to PRISMA guidelines to identify prospective P. vivax therapeutic clinical trials with at least 28 days follow-up published between 1st January 1960 and 12th October 2016. Treatment arms and evidence of chloroquine resistance were mapped to trial sites.
RESULTS
Since 1960, a total of 1152 antimalarial clinical trials with a minimum 28 days follow-up have been published, of which 230 (20.0%) enrolled patients with P. vivax and were included. Trials were conducted in 38 countries: 168 (73.0%) in the Asia-Pacific, 13 (5.7%) in Africa and 43 (18.7%) in the Americas. The proportion of antimalarial trials assessing P. vivax rose from 10.7% (12/112) in 1991-1995, to 24.9% (56/225) in 2011-2015. Overall, 188 (81.7%) P. vivax trials included a chloroquine treatment arm, either alone or in combination with primaquine, and 107 (46.5%) trials included a chloroquine treatment arm with early primaquine to assess radical cure. There has been a recent increase in treatment arms with artemisinin derivatives. Of the 131 sites in which chloroquine resistance could be quantified, resistance was present in 59 (45.0%) sites in 15 endemic countries.
CONCLUSIONS
Over the last 20 years there has been a substantial increase in clinical research on the treatment of P. vivax, which has generated a greater awareness of the global extent of chloroquine resistance. The WWARN open access, online interactive map provides up to date information of areas where drug resistant P. vivax is emerging.
Topics: Africa; Americas; Antimalarials; Asia; Chloroquine; Clinical Trials as Topic; Databases, Factual; Drug Resistance; Humans; Malaria, Vivax; Online Systems
PubMed: 28384505
DOI: 10.1016/j.ijpddr.2017.03.003 -
PLoS Medicine Jan 2022Plasmodium vivax infects an estimated 7 million people every year. Previously, vivax malaria was perceived as a benign condition, particularly when compared to... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Plasmodium vivax infects an estimated 7 million people every year. Previously, vivax malaria was perceived as a benign condition, particularly when compared to falciparum malaria. Reports of the severe clinical impacts of vivax malaria have been increasing over the last decade.
METHODS AND FINDINGS
We describe the main clinical impacts of vivax malaria, incorporating a rapid systematic review of severe disease with meta-analysis of data from studies with clearly defined denominators, stratified by hospitalization status. Severe anemia is a serious consequence of relapsing infections in children in endemic areas, in whom vivax malaria causes increased morbidity and mortality and impaired school performance. P. vivax infection in pregnancy is associated with maternal anemia, prematurity, fetal loss, and low birth weight. More than 11,658 patients with severe vivax malaria have been reported since 1929, with 15,954 manifestations of severe malaria, of which only 7,157 (45%) conformed to the World Health Organization (WHO) diagnostic criteria. Out of 423 articles, 311 (74%) were published since 2010. In a random-effects meta-analysis of 85 studies, 68 of which were in hospitalized patients with vivax malaria, we estimated the proportion of patients with WHO-defined severe disease as 0.7% [95% confidence interval (CI) 0.19% to 2.57%] in all patients with vivax malaria and 7.11% [95% CI 4.30% to 11.55%] in hospitalized patients. We estimated the mortality from vivax malaria as 0.01% [95% CI 0.00% to 0.07%] in all patients and 0.56% [95% CI 0.35% to 0.92%] in hospital settings. WHO-defined cerebral, respiratory, and renal severe complications were generally estimated to occur in fewer than 0.5% patients in all included studies. Limitations of this review include the observational nature and small size of most of the studies of severe vivax malaria, high heterogeneity of included studies which were predominantly in hospitalized patients (who were therefore more likely to be severely unwell), and high risk of bias including small study effects.
CONCLUSIONS
Young children and pregnant women are particularly vulnerable to adverse clinical impacts of vivax malaria, and preventing infections and relapse in this groups is a priority. Substantial evidence of severe presentations of vivax malaria has accrued over the last 10 years, but reporting is inconsistent. There are major knowledge gaps, for example, limited understanding of the underlying pathophysiology and the reason for the heterogenous geographical distribution of reported complications. An adapted case definition of severe vivax malaria would facilitate surveillance and future research to better understand this condition.
Topics: Anemia; Humans; Malaria, Vivax; Prevalence
PubMed: 35041650
DOI: 10.1371/journal.pmed.1003890 -
The Lancet. Global Health Jul 2023Malaria infections during pregnancy can cause adverse birth outcomes, yet many infections are undetected by microscopy. We aimed to describe the epidemiology of... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Malaria infections during pregnancy can cause adverse birth outcomes, yet many infections are undetected by microscopy. We aimed to describe the epidemiology of submicroscopic malaria infections in pregnant women in Asia, the Americas, and Africa using aggregated and individual participant data (IPD).
METHODS
For this systematic review and meta-analysis, studies (published Jan 1, 1997 to Nov 10, 2021) with information on both microscopic and submicroscopic infections during pregnancy from Asia, the Americas, or Africa, identified in the Malaria-in-Pregnancy Library, were eligible. Studies (or subgroups or study groups) that selected participants on the basis of the presence of fever or a positive blood smear were excluded to avoid selection bias. We obtained IPD (when available) and aggregated data. Estimates of malaria transmission intensity and sulfadoxine-pyrimethamine resistance, matched by study location and year, were obtained using publicly available data. One-stage multivariable logit and multinomial models with random intercepts for study site were used in meta-analysis to assess prevalence of and risk factors for submicroscopic infections during pregnancy and at delivery. This study is registered with PROSPERO, number CRD42015027342.
FINDINGS
The search identified 87 eligible studies, 68 (78%) of which contributed to the analyses. Of these 68 studies, 45 (66%) studies contributed IPD (48 869 participants) and 23 (34%) studies contributed aggregated data (11 863 participants). During pregnancy, median prevalence estimates were 13·5% (range 0·0-55·9, 66 substudies) for submicroscopic and 8·0% (0·0-50·6, 66 substudies) for microscopic malaria. Among women with positive Plasmodium nucleic acid amplification tests (NAATs), the median proportion of submicroscopic infections was 58·7% (range 0·0-100); this proportion was highest in the Americas (73·3%, 0·0-100), followed by Asia (67·2%, 36·4-100) and Africa (56·5%, 20·5-97·7). In individual patient data analysis, compared with women with no malaria infections, those with submicroscopic infections were more likely to present with fever in Africa (adjusted odds ratio 1·32, 95% CI 1·02-1·72; p=0·038) but not in other regions. Among women with NAAT-positive infections in Asia and the Americas, Plasmodium vivax infections were more likely to be submicroscopic than Plasmodium falciparum infections (3·69, 2·45-5·54; p<0·0001). Risk factors for submicroscopic infections among women with NAAT-positive infections in Africa included older age (age ≥30 years), multigravidity, and no HIV infection.
INTERPRETATION
During pregnancy, submicroscopic infections are more common than microscopic infections and are associated with fever in Africa. Malaria control in pregnancy should target both microscopic and submicroscopic infections.
FUNDING
Bill & Melinda Gates Foundation through the Worldwide Antimalarial Resistance Network.
Topics: Female; Humans; Pregnancy; Adult; Prevalence; Malaria; Antimalarials; Malaria, Falciparum; Risk Factors
PubMed: 37276878
DOI: 10.1016/S2214-109X(23)00194-8 -
PLoS Neglected Tropical Diseases Jan 2015Sub-microscopic (SM) Plasmodium infections represent transmission reservoirs that could jeopardise malaria elimination goals. A better understanding of the epidemiology... (Review)
Review
BACKGROUND
Sub-microscopic (SM) Plasmodium infections represent transmission reservoirs that could jeopardise malaria elimination goals. A better understanding of the epidemiology of these infections and factors contributing to their occurrence will inform effective elimination strategies. While the epidemiology of SM P. falciparum infections has been documented, that of SM P. vivax infections has not been summarised. The objective of this study is to address this deficiency.
METHODOLOGY/PRINCIPAL FINDINGS
A systematic search of PubMed was conducted, and results of both light microscopy (LM) and polymerase chain reaction (PCR)-based diagnostic tests for P. vivax from 44 cross-sectional surveys or screening studies of clinical malaria suspects were analysed. Analysis revealed that SM P. vivax is prevalent across different geographic areas with varying transmission intensities. On average, the prevalence of SM P. vivax in cross-sectional surveys was 10.9%, constituting 67.0% of all P. vivax infections detected by PCR. The relative proportion of SM P. vivax is significantly higher than that of the sympatric P. falciparum in these settings. A positive relationship exists between PCR and LM P. vivax prevalence, while there is a negative relationship between the proportion of SM P. vivax and the LM prevalence for P. vivax. Amongst clinical malaria suspects, however, SM P. vivax was not identified.
CONCLUSIONS/SIGNIFICANCE
SM P. vivax is prevalent across different geographic areas, particularly areas with relatively low transmission intensity. Diagnostic tools with sensitivity greater than that of LM are required for detecting these infection reservoirs. In contrast, SM P. vivax is not prevalent in clinical malaria suspects, supporting the recommended use of quality LM and rapid diagnostic tests in clinical case management. These findings enable malaria control and elimination programs to estimate the prevalence and proportion of SM P. vivax infections in their settings, and develop appropriate elimination strategies to tackle SM P. vivax to interrupt transmission.
Topics: Global Health; Humans; Malaria, Vivax; Plasmodium vivax; Polymerase Chain Reaction
PubMed: 25569135
DOI: 10.1371/journal.pntd.0003413 -
Malaria Journal Dec 2014Malaria caused by Plasmodium vivax was long considered to have a low mortality, but recent reports from some geographical areas suggest that severe and complicated vivax... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Malaria caused by Plasmodium vivax was long considered to have a low mortality, but recent reports from some geographical areas suggest that severe and complicated vivax malaria may be more common than previously thought.
METHODS
The primary objective of this systematic review and meta-analysis was to describe the reported clinical characteristics and the geographical variation in prevalence of reported severe vivax malaria and its change over time derived from English-language articles published since 1900. Medline and Scopus databases were searched for original papers on severe vivax malaria, using as inclusion criteria modified 2010 WHO criteria for the diagnosis of severe falciparum malaria. Articles before 1949 were identified through reference lists in journals, textbooks, and personal collections of colleagues.
RESULTS
A total of 77 studies with reported severe vivax malaria and 63 studies with no reported severe vivax malaria (totaling 46,411 and 6,753 vivax malaria patients, respectively) were included. The 77 studies with reported severe vivax malaria were mainly from India (n = 33), USA (n = 8), Indonesia (n = 6), and Pakistan (n = 6). Vivax endemic countries not reporting severe vivax malaria beyond individual case reports included: the Greater Mekong Sub-region, China, North Korea, Bangladesh, Afghanistan, Middle East (except Qatar), the horn of Africa, and Madagascar. Only 17/77 reports were from before 2000. Vivax mono-infection was confirmed by PCR in 14 studies and co-morbidities were ruled out in 23 studies. Among the 77 studies reporting severe vivax malaria, severe thrombocytopenia (<50,000/mm3) was the most common "severe" manifestation (888/45,775 with pooled prevalence of 8.6%). The case fatality was 0.3% (353/46,411). Severity syndromes varied widely between different geographical areas, with severe anaemia being most prominent in areas of high transmission and chloroquine resistance.
CONCLUSION
Plasmodium vivax can cause severe and even fatal disease, but there is a recent increase in reports over the past 15 years with larger series restricted to a limited number of geographical areas. The biological basis of these variations is currently not known. More detailed epidemiological studies are needed which dissociate causation from association to refine the definition and estimate the prevalence of severe vivax malaria.
Topics: Adult; Child; Child, Preschool; Female; Global Health; Humans; Malaria, Vivax; Male; Prevalence; Survival Analysis; Topography, Medical
PubMed: 25486908
DOI: 10.1186/1475-2875-13-481 -
Parasites & Vectors Dec 2022The production of Plasmodium gametocytes in vitro is a real challenge. Many protocols have been described, but few have resulted in the production of viable and... (Review)
Review
BACKGROUND
The production of Plasmodium gametocytes in vitro is a real challenge. Many protocols have been described, but few have resulted in the production of viable and infectious gametocytes in sufficient quantities to conduct research on-but not limited to-transmission-blocking drug and vaccine development. The aim of this review was to identify and discuss gametocyte production protocols that have been developed over the last two decades.
METHODS
We analyzed the original gametocyte production protocols published from 2000 onwards based on a literature search and a thorough review. A systematic review was performed of relevant articles identified in the PubMed, Web of Sciences and ScienceDirect databases.
RESULTS
A total 23 studies on the production of Plasmodium gametocytes were identified, 19 involving in vitro Plasmodium falciparum, one involving Plasmodium knowlesi and three involving ex vivo Plasmodium vivax. Of the in vitro studies, 90% used environmental stressors to trigger gametocytogenesis. Mature gametocytemia of up to 4% was reported.
CONCLUSIONS
Several biological parameters contribute to an optimal production in vitro of viable and infectious mature gametocytes. The knowledge gained from this systematic review on the molecular mechanisms involved in gametocytogenesis enables reproducible gametocyte protocols with transgenic parasite lines to be set up. This review highlights the need for additional gametocyte production protocols for Plasmodium species other than P. falciparum.
Topics: Humans; Malaria, Falciparum; Plasmodium falciparum; Plasmodium knowlesi; Plasmodium vivax; Systematic Reviews as Topic
PubMed: 36471426
DOI: 10.1186/s13071-022-05566-3 -
Scientific Reports Mar 2022A better understanding of the occurrence and risk of Plasmodium vivax infection among Duffy-negative individuals is required to guide further research on these... (Meta-Analysis)
Meta-Analysis
A better understanding of the occurrence and risk of Plasmodium vivax infection among Duffy-negative individuals is required to guide further research on these infections across Africa. To address this, we used a meta-analysis approach to investigate the prevalence of P. vivax infection among Duffy-negative individuals and assessed the risk of infection in these individuals when compared with Duffy-positive individuals. This study was registered with The International Prospective Register of Systematic Reviews website (ID: CRD42021240202) and followed Preferred Reporting Items for Systematic review and Meta-Analyses guidelines. Literature searches were conducted using medical subject headings to retrieve relevant studies in Medline, Web of Science, and Scopus, from February 22, 2021 to January 31, 2022. Selected studies were methodologically evaluated using the Joanna Briggs Institute (JBI) Critical Appraisal Tools to assess the quality of cross-sectional, case-control, and cohort studies. The pooled prevalence of P. vivax infection among Duffy-negative individuals and the odds ratio (OR) of infection among these individuals when compared with Duffy-positive individuals was estimated using a random-effects model. Results from individual studies were represented in forest plots. Heterogeneity among studies was assessed using Cochrane Q and I statistics. We also performed subgroup analysis of patient demographics and other relevant variables. Publication bias among studies was assessed using funnel plot asymmetry and the Egger's test. Of 1593 retrieved articles, 27 met eligibility criteria and were included for analysis. Of these, 24 (88.9%) reported P. vivax infection among Duffy-negative individuals in Africa, including Cameroon, Ethiopia, Sudan, Botswana, Nigeria, Madagascar, Angola, Benin, Kenya, Mali, Mauritania, Democratic Republic of the Congo, and Senegal; while three reported occurrences in South America (Brazil) and Asia (Iran). Among studies, 11 reported that all P. vivax infection cases occurred in Duffy-negative individuals (100%). Also, a meta-analysis on 14 studies showed that the pooled prevalence of P. vivax infection among Duffy-negative individuals was 25% (95% confidence interval (CI) - 3%-53%, I = 99.96%). A meta-analysis of 11 studies demonstrated a decreased odds of P. vivax infection among Duffy-negative individuals (p = 0.009, pooled OR 0.46, 95% CI 0.26-0.82, I = 80.8%). We confirmed that P. vivax infected Duffy-negative individuals over a wide prevalence range from 0 to 100% depending on geographical area. Future investigations on P. vivax infection in these individuals must determine if Duffy-negativity remains a protective factor for P. vivax infection.
Topics: Brazil; Cross-Sectional Studies; Humans; Kenya; Malaria, Vivax; Plasmodium vivax; Prevalence
PubMed: 35256675
DOI: 10.1038/s41598-022-07711-5 -
The Cochrane Database of Systematic... Sep 2021Studies evaluating mass drug administration (MDA) in malarious areas have shown reductions in malaria immediately following the intervention. However, these effects vary... (Meta-Analysis)
Meta-Analysis Review
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.
Topics: Antimalarials; Humans; Malaria; Malaria, Falciparum; Mass Drug Administration; Parasitemia
PubMed: 34585740
DOI: 10.1002/14651858.CD008846.pub3