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By Dr. Derick Pasternak, Ambassador, Malaria Science & Research Coordinator, MPI

“The 2023 World malaria report delves into the nexus between climate change and malaria. Changes in temperature, humidity and rainfall can influence the behaviour and survival of the malaria-carrying Anopheles mosquito. Extreme weather events, such as heatwaves and flooding, can also directly impact transmission and disease burden. Catastrophic flooding in Pakistan in 2022, for example, led to a five-fold increase in malaria cases in the country. 

“The changing climate poses a substantial risk to progress against malaria, particularly in vulnerable regions. Sustainable and resilient malaria responses are needed now more than ever, coupled with urgent actions to slow the pace of global warming and reduce its effects,’ said Dr Tedros Adhanom Ghebreyesus, WHO Director-General.  

“’Climate variability is expected to have indirect effects on malaria trends through, for example, reduced access to essential malaria services and disruptions to the supply chain of insecticide-treated nets, medicines and vaccines. Population displacement due to climate-induced factors may also lead to increased malaria as individuals without immunity migrate to endemic areas. 

“Data on the long-term impact of climate change on malaria transmission is sparse. However, the direction and magnitude of any impacts are likely to vary across social and ecological systems, both within and between countries.”

The Report is available at https://www.who.int/teams/global-malaria-programme/reports/world-malaria-report-2023.

 

According to the Johns Hopkins Malaria Minute Podcast of 6 Dec 2023, “[t]he WHO estimates that there were 249 million cases of malaria last year, resulting in 608000 deaths. These figures surpass pre-pandemic levels, with five countries bearing the brunt of this increase. This year, the report stressed the importance of climate change to malaria. Released at the start of COP, during its first-ever Health Day, it argues that extreme weather events, the frequency of which increase with global warming, could lead to unexpected outbreaks of malaria. In Pakistan, for example, there were an additional two million malaria cases as a result of flooding.  Yet, looking beyond the raw numbers reveals a more nuanced reality. Malaria incidence – that’s the number of cases for every thousand people at risk – has fallen since the year 2000. But, despite averting over 2 billion cases globally, progress has stalled. Since 2015, malaria incidence has remained largely constant. We’re currently 55% off track of the WHO’s targets.”

 

PEER REVIEWED ARTICLES

 

Prevention

 

Anabire NG, Aculley B, Pobee A & al., High Burden of Asymptomatic Malaria and Anaemia Despite High Adherence to Malaria Control Measures: A Cross-Sectional Study Among Pregnant Women Across Two Seasons in a Malaria-Endemic Setting in Ghana, Infection. 2023 Dec; 51(6):1717-1729, https://doi.org/10.1007/s15010-023-02058-z is difficult to allocate to any of the sub-headings of this section, since the study, which encompassed pregnant women in both the wet and dry seasons, showed high compliance (around 80%) with the three recommended preventive measures, namely more than 3 antenatal visits, regular use of insecticide treated nets (ITNs) and sulfadoxime-pyrimethamine (SP) prophylaxis three times.  Yet close to half of the women studied were proven to have asymptomatic Plasmodium falciparum on examination, with anemia even more frequent, but strongly correlated with the presence of parasite. {Absent the ability to read the paper itself, the abstract’s recommendation of emphasizing the same preventive measures seems less than adequate to deal with the situation.}      

 

Vaccines

 

Genton B, R21/Matrix-M™ Malaria Vaccine: A New Tool to Achieve WHO`S Goal to Eliminate Malaria int 30 Countries By 2030, J Travel Med. 2023 Nov 11: taad140, https://doi.org/10.1093/jtm/taad140 is the first of undoubtedly many articles published about the vaccine newly endorsed by the WHO.  The abstract is sparse but the article (available through the link) goes into some detail of its development and testing.  It concludes: “RTS,S/ASO1 laid the foundation for malaria vaccine development and remains a pivotal step in the battle against malaria. The R21/Matrix-M™ vaccine, with its remarkable efficacy, potential durability, and low price is a welcome additional tool to fight malaria. Its production in an endemic country is also a significant advance in ownership. To date, it has already been licensed for use in Ghana, Nigeria and Burkina Faso. Ultimately, the success of either vaccine hinges on global collaboration, investment, and a commitment to ensure equitable access. Moreover, the journey to eliminate malaria demands the thoughtful integration of these vaccines with other tools (e.g. Seasonal Malaria Chemoprevention) to achieve our shared goal of zero malaria.”

Similarly to studies conducted elsewhere, Röbl K & al. look forward to the availability of malaria vaccine in two West Africa countries. After surveying 702 and 575 households respectively in the two countries,  they report in Caregiver Acceptance of Malaria Vaccination for Children Under 5 Years of Age and Associated Factors: Cross-Sectional Household Survey, Guinea and Sierra Leone, 2022, Malaria J. 2023 Nov 20; 22(1):355, https://doi.org/10.1186/s12936-023-04783-0 that over 75% of caregivers would accept vaccination for their children. “In both countries, acceptance was lower in remote areas than in urban areas.”

Plasmodium vivax is much more common elsewhere, but it does cause infections in Africa, especially in Ethiopia. Thus the work of Kunkeaw N & al., A Pvs25 mRNA Vaccine Induces Complete and Durable Transmission-Blocking Immunity to Plasmodium vivax, NPJ Vaccines, 2023 Dec 14; 8(1):187, https://doi.org/10.1038/S41541-023-00786-9.  reporting a vaccine against the parasite is of import in Africa as well. Their article is focused on work in mice and concludes that the beneficial results justify “further testing in non-human primates.”

 

Vector control and protection from vectors

 

“Irrigation has been associated with increased malaria risk, but risk prediction remains difficult due to the heterogeneity of irrigation and the environment… By coupling a hydrologic model with an agent-based malaria model for a sugarcane plantation site in Arjo, Ethiopia,” Jiang A-L & al., Investigating the Impact of Irrigation on Malaria Vector Larval Habitats and Transmission Using a Hydrology-Based Model, Geohealth, 2023 Dec 10; 7(12):E2023gh000868, https://doi.org/10.1029/2023GH000868  demonstrated “how incorporating hydrologic processes to estimate larval habitats can affect malaria transmission. …. The inclusion of hydrologic processes increased the variability of larval habitat area by around two-fold and resulted in reduction in malaria transmission by 60%.” However, “irrigation increased all habitat types in the dry season by up to 7.4 times. It converted temporary and semi-permanent habitats to permanent habitats during the rainy season, which grew by about 24%. Consequently, malaria transmission was sustained all-year round and intensified during the main transmission season…”

 

On the same issue of irrigation, Djègbè I & al., “Farmer Field School”, a Participatory Educational Approach for Improving the Fight Against Malaria Vectors in Irrigated Rice-Growing Areas in Benin, Med Trop Sante Int, 2023 Sep 24; 3(3):Mtsi.V3i3.2023.281, https://doi.org/10.48327/Mtsi.V3i3.2023.281 reports on a project to educate rice farmers on how to reduce flooding of the rice fields from constant to intermittent timing.  This method is demonstrated by the authors to reduce the density of Anopheles mosquitoes in the fields, with the inference that this will result in fewer cases of malaria in the area.  The abstract is in English, the article in French.  

 

Sadoine ML & al. “explored how vector control interventions may modify associations between environmental factors and malaria.” They constructed regression models and report in Differential Influence of Environmental Factors on Malaria Due to Vector Control Interventions in Uganda, Int J Environ Res Public Health. 2023 Nov 9; 20(22):7042, https://doi.org/10.3390/ijerph20227042 that “malaria risk related to environmental variables was reduced by about 35% with LLINs and 63% with IRS. Significant interactions were observed between some environmental variables and vector control interventions. There was site-specific variability in the shape of the environment-malaria risk relationship and in the influence of interventions (6 to 72% reduction in cases with LLINs and 43 to 74% with IRS).”

According to Omondi S & al., the mosquito responsible for transmitting malaria in western Kenya has lately shifted its biting timing to late in the morning. In their paper, Late Morning Biting Behaviour of Anopheles funestus Is a Risk Factor for Transmission in Schools in Siaya, Western Kenya, Malaria J, 2023 Nov 30, 22:366, https://doi.org/10.1186/s12936-023-04806-w, they describe a process of collecting mosquitoes in four schools. “Anopheles funestus was the predominant species collected, forming 93.2% … of the entire collection, with peak landing between 06:00 and 07:00 h and continuing until 11:00 h. More than half of the collected An. funestus were either fed or gravid, potentially indicative of multiple bloodmeals within each gonotrophic cycle, and had a sporozoite rate of 2.05%…  School children spend up to 10 h of their daytime in schools, reporting between 06:00 and 07:00 h and staying in school until as late as 17:00 h, meaning that they receive potentially infectious mosquito bites during the morning hours in these settings.”

Agbevo A & al., Community Evaluation of the Physical and Insecticidal Durability of DuraNet® Plus, an Alpha-Cypermethrin and Piperonyl Butoxide Incorporated Mosquito Net: Protocol for a Multi-Country Study in West, Central and East Africa, Arch Public Health. 2023 Nov 20; 81(1):202, https://doi.org/ 10.1186/s13690-023-01217-w is a description of the study to be conducted in the future in 3 different regions in sub-Saharan Africa.

“The standard operating procedure for testing the susceptibility of adult mosquitoes to … insecticides recommends using a vegetable oil ester … as surfactant. However, there is growing evidence that this adjuvant … can enhance insecticide activity, mask resistance and bias the bioassay.” Ashu FA & al. set out to test this hypothesis and report in Vegetable Oil-Based Surfactants are Adjuvants That Enhance the Efficacy of Neonicotinoid Insecticides and Can Bias Susceptibility Testing in Adult Mosquitoes, PLOS Negl Trop Dis, 2023 Nov 17, https://doi.org/10.1371/journal.pntd.0011737 that indeed “three different brands of linseed oil soap used as cleaning products drastically enhanced neonicotinoid activity in Anopheles mosquitoes. At 1% (v/v), the surfactant reduced the median lethal concentration, LC50, of clothianidin more than 10-fold both in susceptible and in resistant populations of Anopheles gambiae.” While this finding indicates “that surfactants are not inert ingredients, and their use in susceptibility testing may jeopardize the ability to detect resistance,” it also implies that adding this kind of soap to insecticides may overcome insect resistance to them. The authors recommend pursuing this avenue.

A targeted entomological survey, both larvae and adult, was conducted [by Hawaria & al.] in Hawassa City, southern Ethiopia between November 2022 and February 2023. Their First Report of Anopheles stephensi from Southern Ethiopia, Malaria J, 2023 Dec 8, 22:373, https://doi.org/10.1186/s12936-023-04813-x state that both larvae and adult forms of An. stephensi were found as a significant percentage of all Anopheles species. “The presence of both larval and adult stages of this mosquito attests that this species established sympatric colonization with native vector species such as An. gambiae (s.l.) in southern Ethiopia.”

Gonzalez-Olvera G & al. report on an apparently highly efficacious (100% mortality under laboratory conditions) agent to kill larvae of An. stephensi in Laboratory Evaluation of Efficacy of the Larvicide Spinosad Against Anopheles stephensi in Jigjiga, Ethiopia, J Am Mosq Control Assoc, 2023 Dec 1; 39(4):284-287, https://doi.org/10.2987/23-7141. Spinosad is a natural substance made by a soil bacterium that can be toxic to insects. It is a mixture of two chemicals called spinosyn A and spinosyn D. It is used to control a wide variety of pests. (Ref: National Pesticide Information Center)

 

In view of the problems inherent in the expansion of Anopheles stephensi into urban environments of both East and West Africa, Sanei-Dehkordi A & al., Promising Larvicidal Effects of Nanoliposomes Containing Carvone and Mentha spicata and Tanacetum balsamita Essential Oils Against Anopheles stephensi, Acta Parasitol. 2023 Nov 18, https://doi.org/10.1007/s11686-023-00735-5 is of great interest. The preparations used by the authors were found to have potent larvicidal effects against the vector.  However, the abstract is unclear the method used in testing.

As a result of literature search, Aschale Y & al. report results of examining over 148,000 mosquito specimens in Systematic Review of Sporozoite Infection Rate of Anopheles Mosquitoes in Ethiopia, 2001-2021, Parasit Vectors. 2023 Nov 27; 16(1):437, https://doi.org/10.1186/s13071-023-06054-y. Twenty-one mosquitoes of Anopheles species were tested for sporozoites. “Anopheles arabiensis was the dominant species followed by An. pharoensis and An. coustani complex. The overall proportion infected with sporozoites over 21 years was 0.87%. Individual proportions included Anopheles arabiensis (1.09), An. pharoensis (0.79), An. coustani complex (0.13), An. funestus (2.71), An. demeilloni (0.31), An. stephensi (0.70), and An. cinereus (0.73). Plasmodium falciparum sporozoites accounted 79.2% of Plasmodium species.”

Chemoprophylaxis

 

Gatiba P & al. reviewed 65 articles that deal with administration of various chemoprevention regimens recommended by the WHO. They report in Contextual Factors to Improve Implementation of Malaria Chemoprevention in Children: A Systematic Review, Am J Trop Med Hyg, 2023 Dec 11: Tpmd23047 https://doi.org/10.4269/Ajtmh.23-0478 that the “most frequently evaluated strategy was SMC [seasonal malaria chemoprevention] (n = 40), followed by IPTi [intermittent preventive treatment in infants] (n = 18) and then IPTsc [intermittent preventive gtreatment in schoolchildren] (n = 6). Overall, these strategies were highly acceptable, although with IPTsc, there were community concerns with providing drugs to girls of reproductive age and the use of nonmedical staff for drug distribution. For SMC, door-to-door delivery resulted in higher coverage, improved caregiver acceptance, and reduced cost. Lower adherence was noted when caregivers were charged with giving doses 2 and 3 unsupervised.”

 

Closely related to the above article and appearing on the same day, Thwing J & al., Systematic Review and Meta-Analysis of Seasonal Malaria Chemoprevention, Am J Trop Med Hyg, 2023 Dec 11: Tpmd230481, https://doi.org/10.4269/Ajtmh.23-0481 analyzed 12 articles on the subject to SMC in children. “Seasonal malaria chemoprevention resulted in substantial reductions in uncomplicated malaria incidence measured during that transmission season [in both children below and above the age of five] and in the prevalence of malaria parasitemia measured within 4-6 weeks from the final SMC cycle [again in both age groups]. In high-transmission zones, SMC resulted in a moderately reduced risk of any anemia … [in one study]. Children < 10 years of age had a moderate reduction in severe malaria, but not mortality.”

 

These reviews do not usually include articles that report malaria in travelers to endemic regions.  However, Kotepui M & al.’s article, Evidence of Malarial Chemoprophylaxis Among Travellers who Died from Malaria: A Systematic Review and Meta-Analysis, Malaria J, 2023 Nov 25, 22:359, https://doi.org/10.1186/s12936-023-04794-x, is highly relevant to readers who may travel to those areas in the course of their occupation or volunteer work. In their literature search, the authors identified 602 pooled death cases, of whom 187 (30%) had taken chemoprophylaxis.  When these latter were subjected to analysis, however, only 24 (5%) among the deceased had used the chemoprophylactic agent fully in accordance with WHO’s recommendations.  There was an indication in the article, but not in its conclusion nor in the abstract, that advanced age and pregnancy may have been risk factors among those who took appropriate chemoprophylaxis.

Phiri KS & al. conducted a review of three “double-blind, placebo-controlled trials, including 3663 children with severe anaemia,” which were culled from 91 potential articles after exclusion. The studies took place in four countries and three different post-discharge chemoprevention regimens were applied.During the intervention period, post-discharge malaria chemoprevention was associated with a 77% reduction in mortality … and a 55% reduction in all-cause readmissions … compared with placebo.” The article is Post-Discharge Malaria Chemoprevention in Children Admitted with Severe Anaemia in Malaria-Endemic Settings in Africa: A Systematic Review and Individual Patient Data Meta-Analysis of Randomised Controlled Trials, Lancet Glob Health, 2024 Jan; 12(1):E33-E44, https://doi.org/10.1016/S2214-109x(23)00492-8. Tahita MC & Bassat Q, Post-Discharge Malaria Chemoprevention in Children with Severe Anaemia: A Robust Strategy to Save Lives, Lancet Glob Health, 2024 Jan;12(1): e2-e3, https:/doi.org/10.1016/S2214-109X(23)00524-7 is an editorial, commenting on the above article.

Other

 

The arrival of Anopheles stephensi in Africa has raised major concerns about its presence in urban environments. Yared S & al. add to those concerns by reporting in Building the Vector In: Construction Practices and the Invasion and Persistence of Anopheles stephensi in Jigjiga, Ethiopia, Lancet Planet Health. 2023 Dec; 7(12):e999-e1005, https://doi.org/10.1016/s2542-5196(23)00250-4 that “the knowledge about An stephensi ecology in Africa has been generated from studies conducted during the rainy season, when vectors are most abundant.” The authors “provide evidence from the peak of the dry season in the city of Jigjiga in Ethiopia, and report An stephensi immature stages infesting predominantly in water reservoirs made to support construction operations (ie, in construction sites or associated with brick-manufacturing businesses). Political and economic changes in Ethiopia (particularly the Somali Region) have fuelled an unprecedented construction boom since 2018 that, in our opinion, has been instrumental in the establishment, persistence, and propagation of An stephensi via the year-round availability of perennial larval habitats associated with construction.”

Mulebeke R & al. report on the additional benefit of mass drug administration (MDA) in addition to IRS in a high transmission setting in Uganda.  In comparison to another area where IRS alone was being used, MDA showed significantly greater drop in malaria incidence, especially in children under the age of 5, while the impact was much less for those over 5 years of age, as reported in Impact of Population Based Indoor Residual Spraying in Combination with Mass Drug Administration on Malaria Incidence and Test Positivity in a High Transmission Setting in North Eastern Uganda, Malaria J, 2023 Dec 13, 22:378, https://doi.org/10.1186/s12936-023-04799-6.  The study took place between 2016 and 2018 and the authors concede that the “duration of this impact needs to be further investigated.” This paper is in direct  relationship with the Katakwi project in which former MPI Board member Dorothy Echodu was heavily involved, and which had results previously published in Echodu DC & al., Impact of Population Based Indoor Residual Spraying with And Without Mass Drug Administration with Dihydroartemisinin-Piperaquine on Malaria Prevalence in a High Transmission Setting: A Quasi-Experimental Controlled Before-And-After Trial in Northeastern Uganda, BMC Infect Dis, 2023 Feb 6; 23(1):72, https://doi.org/10.1186/s12879-023-07991-w. {There are more recent data that demonstrate that the beneficial effect of these interventions was not long lasting.}

 

Construction of homes that restrict the entry of mosquitoes is one way of reducing exposure to the parasite. Meta J & al. encountered barriers to the acceptance of these homes by prospective recipients. As they recount in Understanding Reticence to Occupy Free, Novel-Design Homes: A Qualitative Study in Mtwara, Southeast Tanzania, PLOS Glob Public Health. 2023 Nov 22; 3(11):e0002307, https://doi.org/10.1371/journal.pgph.0002307, “[a]fter constructing 110 of such homes across 60 villages, project staff encountered a certain reticence of the target population to occupy the homes and were faced with accusations of having nefarious intentions.” Based on community interviews, they uncovered accusations that the Freemasons were involved in the project and traced these to other members of the community who were not projected recipients. The authors conclude that there is a “need for long-term and proactive community engagement, which focuses on building relationships and providing information through recognizable voices and formats. Given the stakes at play in housing interventions, research teams should be prepared for the social upheaval the provision of free new housing can cause.”

“…mosquitoes are strongly affected by temperature, which causes unimodal responses in mosquito life history traits (e.g., biting rate, adult mortality rate, mosquito development rate, and probability of egg-to-adult survival) that exhibit upper and lower thermal limits and intermediate thermal optima in laboratory studies. However, it remains unknown how mosquito thermal responses measured in laboratory experiments relate to the realized thermal responses of mosquitoes in the field. To address this gap, Athni TS & al. “leverage[d] thousands of global mosquito occurrences and geospatial satellite data at high spatial resolution to construct machine-learning based species distribution models, from which vector thermal responses are estimated” report in Temperature Dependence of Mosquitoes: Comparing Mechanistic and Machine Learning Approaches, Biorxiv, 2023 Dec 12: 2023.12.04.569955, https://doi.org/10.1101/2023.12.04.569955 “that thermal minima estimated from laboratory studies were highly correlated with those from the species distributions (r = 0.90). The thermal optima were less strongly correlated (r = 0.69). For most species, [the authors] did not detect thermal maxima from their observed distributions so were unable to compare to laboratory-based estimates. The results suggest that laboratory studies have the potential to be highly transportable to predicting lower thermal limits and thermal optima of mosquitoes in the field.”  {This article, as well as one in the Epidemiology section below, is cited in PubMed as a “Preprint” that has not been peer reviewed, the inclusion being on a pilot basis, because the work was funded by a branch of the US Government.  This fact raised the question whether other articles cited from bioRxiv in the past have been peer reviewed, the answer being that none of the bioRxiv or medxiv articles undergo peer review prior to publication. This will be noted in citations in the future.} 

 

Diagnosis

 

General diagnostics

 

Koepfli C, Is qPCR Always the Most Sensitive Method for Malaria Diagnostic Quality Surveillance? Malaria J, 2023 Dec 15, 22:380, https://doi.org/10.1186/s12936-023-04822-w is an opinion piece following a recent article (Abebe A & al., Significant Number of Plasmodium vivax Mono-Infections by PCR Misidentified as Mixed Infections [P. vivax/P. falciparum] by Microscopy and Rapid Diagnostic Tests: Malaria Diagnostic Challenges in Ethiopia, Malaria J, 2023 Jul 1, 22:201, https://doi.org/10.1186/s12936-023-04635-x). The author of this paper argues that in fact the limit of detection of qPCR [quantitative polymerase chain reaction] in case of low parasite counts may make it actually less sensitive than the most sensitive repaid diagnostic tests (RDTs) available.   

 

“Light microscopy and rapid diagnostic tests (RDT) have long been the recommended diagnostic methods for malaria. However, in recent years, loop-mediated isothermal amplification (LAMP) techniques have been shown to offer superior performance, in particular concerning low-grade parasitaemia, by delivering higher sensitivity and specificity with low laboratory capacity requirements in little more than an hour.” Ivarsson A-C & al., Head-to-Head Comparison of Two Loop-Mediated Isothermal Amplification (LAMP) Kits for Diagnosis of Malaria in a Non-Endemic Setting, Malaria J, 2023 Dec 13, 22:377, https://doi.org/10.1186/s12936-023-04809-7 reports on the comparison of two “LAMP kits; Alethia® Illumigene Malaria kit and HumaTurb Loopamp™ Malaria Pan Detection (PDT) kit.” According to the authors, the first of the two had results 100% congruent with PCR results in a small sample of 41, whereas the second one missed 10% of the same samples tested.

Field diagnostics

 

Lupaka M & al., Diagnostic Performance of Ultrasensitive Rapid Diagnostic Test for the Detection of Plasmodium falciparum Infections in Asymptomatic Individuals in Kisangani, Northeast Democratic Republic Of Congo, Malaria J. 2023 Nov 19; 22:354, https://doi.org/10.1186/s12936-023-04790-1 is  a report of comparison of the utility of ultrasensitive rapid diagnostic test (usRDT) for P. falciparum versus that of conventional RDT (cRDT) in the area studied.  Reference points were PCR and microscopy. The prevalence of asymptomatic P. falciparum malaria was between 40% and 54% using the four diagnostic tests. “By using PCR as a reference, usRDT had sensitivity and specificity of 87.0% … and 100.0% …, respectively, whereas the cRDT had sensitivity and specificity of 74.6% … and 100% …, respectively.” The authors conclude that “usRDT showed better diagnostic performance with higher sensitivity than the cRDT which is currently in use as point-of-care test. Further research is necessary to assess the access and cost-effectiveness of the usRDTs to use for malaria surveillance.”

In Togo, Teou DC & al. conducted a “cross-sectional analytical study … on malaria-suspected cases received in three sentinel sites … from whom capillary blood was collected to perform … two [different] RDTs according to the manufacturer’s instructions. Sensitivity and specificity were estimated by comparing to thick/thin blood smear, the gold standard, and to PCR, which is a more sensitive. .. A total of 390 participants … were included in the study. The sensitivity of both Advantage P.f. Malaria Card® and Advantage Malaria Pan + Pf Card® compared to thick/thin blood smear was 91.8% and 91.3%, respectively, and for both the specificity was 94.7%. Compared to PCR, the sensitivity was 84.2% and 83.8%, respectively, and the specificity 96.5%. The paper is Evaluation of the Performance of Advantage P.F. Malaria Card® and Advantage Malaria Pan + Pf Card®, Two Rapid Diagnostic Tests for Parasitological Confirmation of Malaria Cases in Field Situation in Togo, Parasit Vectors. 2023 Nov 30; 16(1):444, https://doi.org/10.1186/s13071-023-06062-y.

“Dual hrp2/hrp3 genes deletions in P. falciparum isolates are increasingly reported in malaria-endemic countries and can produce false negative RDT results leading to inadequate case management” Tarama CW & al., Assessing the Histidine-Rich Protein 2/3 Gene Deletion in Plasmodium falciparum Isolates from Burkina Faso, Malaria J, 2023 Nov 29, 22:363, https://doi.org/10.1186/s12936-023-04796-9 reports “that P. falciparum isolates lacking hrp2 genes are present in 4.4% of samples obtained from the asymptomatic children population in three sites in Burkina Faso. These parasites are circulating and causing malaria, but they are also still detectable by HRP2-based RTDs due to the presence of the intact pfhrp3 gene.” Still, they also report that the “proportion of RDTs negative cases among microscopy positive slides was 12.7% (32/251).” {There must have been other reasons for the false negative RTDs.} 

New diagnostic methods

 

“P. ovale spp. infections are endemic across multiple African countries and are caused by two distinct non-recombining species, P. ovale curtisi ( Poc ) and P. ovale wallikeri ( Pow ). These species are thought to differ in clinical symptomatology and latency, but existing diagnostic assays have limited ability to detect and distinguish them.” He W & al. “developed a new duplex assay for the detection and differentiation of Poc and Pow that can be used to improve our understanding of these parasites.” Their “duplex assay had 100% specificity and 95% confidence lower limits of detection of 4.2 and 41.2 parasite genome equivalents/µl for Poc and Pow , respectively. Species was determined in 80% of all P. ovale spp.-positive field samples and 100% of those with >10 parasites/µl. Most P. ovale spp. field samples from the DRC were found to be Poc infections.” The paper is A Novel Duplex Qualitative Real-Time PCR Assay for the Detection and Differentiation of Plasmodium ovale curtisi and Plasmodium ovale wallikeri Malaria, medRxiv. 2023 Oct 31: 2023.10.31.23297819, https://doi.org/10.1101/ 2023.10.31.23297819.

Potlapalli VR & al. also report on diagnosing the two species mentioned above and how they were able to distinguish them with PCR assys in Real-Time PCR Detection of Mixed Plasmodium ovale curtisi and wallikeri Infections in Human and Mosquito Hosts, PLoS Negl Trop Dis. 2023 Dec 8; 17(12):e0011274, https://doi.org/10.1371/journal.pntd.0011274.

 

Other

 

“Plasmodium ovale was the last of the exclusively human malaria parasites to be described, in 1922, and has remained the least well studied. Beginning in 1995, two divergent forms of the parasite, later termed ‘classic’ and ‘variant’, were described. By 2010, it was realised that these forms are two closely related, but genetically distinct and non-recombining species; they were given the names Plasmodium ovale curtisi and Plasmodium ovale wallikeri. Since then, substantial additional data have confirmed that the two parasites are indeed separate species, but the trinomial nomenclature has often led to confusion about their status, with many authors describing them as subspecies. Snounou G & al. formally name them Plasmodium ovalecurtisi and Plasmodium ovalewallikeri in The Two Parasite Species Formerly Known as Plasmodium ovale, Trends Parasitol. 2023 Nov 30: S1471-4922(23)00284-2, https://doi.org/10.1016/j.pt.2023.11.004

Treatment

 

Treatment results

 

Thriemer K & al. studied communities in Ethiopia and two SE Asian countries where coinfections of P. falciparum (Pf) and P. vivax (Pv) are common. In Primaquine Radical Cure in Patients with Plasmodium falciparum Malaria in Areas Co-Endemic for P falciparum and Plasmodium vivax (PRIMA): A Multicentre, Open-Label, Superiority Randomised Controlled Trial, Lancet. 2023 Nov 15: S0140-6736(23)01553-2, https://doi.org/10.1016/s0140-6736(23)01553-2 they report that a short course of relatively high dose of primaquine resulted in superior results in terms of eradicating P. vivax than using “standard” dosage of the drug. {This study, although it is registered with ClinicalTrials.gov, and therefore presumably vetted for appropriateness, is problematic on several levels: (1) the inclusion criteria for subjects in the three countries were not uniform, (2) the authors lumped together results of patients who had demonstrated Pf  monoinfections and mixed Pf Pv infections, (3) they defined “severe anemia” as a complication at less than 40% of normal levels of hemoglobin, thereby enabling the authors to classify 10% of patients in the study arm as having “mild” primaquine related complications.}

Negative research results are often very important in learning how best to treat diseases. It is unclear whether Varo R & al., Adjunctive Rosiglitazone Treatment for Severe Paediatric Malaria: A Randomized Placebo-Controlled Trial in Mozambican Children, Int J Infect Dis. 2023 Nov 25: S1201-9712(23)00792-0, https://doi.org/10.1016/j.ijid.2023.11.031 falls into this category. They investigated the adjunctive use of the antidiabetic medication rosiglitazone, which also has anti-inflammatory properties, in the treatment of severe malaria in children.  The drug is not an antimalarial, it was hypothesized that it would show significant improvement by reducing the body’s reaction to the infection.  Accordingly, the authors did not use recovery from malaria as an endpoint, but the concentration of a chemical (angiopoietin-2) which is said to reflect inflammation in the body.  The study results did not show significant drop in this chemical, when compared to placebo.  Nonetheless the authors recommend further research into the use of rosiglitazone. 

Adherence to guidelines

 

“[T]he World Health Organization (WHO) Test, Treat and Track (T3) strategy … has been implemented in Uganda since 2010. Mumali RK & al. hypothesized that during the COVID-19 epidemic there may have been barriers to its implementation. Indeed, as a result of interviews with 103 health workers (HWs) and 333 patients, they report in Health Workers’ Adherence to the Malaria Test, Treat and Track Strategy During the COVID-19 Pandemic in Malaria High Transmission Area in Eastern Uganda, Malaria J. 2023 Nov 27, 22:360, https://doi.org/10.1186/s12936-023-04786-x that “[a]mong the patients … a majority 257/333 (77%) were tested, of whom 139/333 (42%) tested positive. Out of the positive cases, 115/333 (35%) were treated and tracked. About 75/333 (23%) were not tested but treated for malaria.” The authors judge “low level of [i]n-service training, overwhelming number of patients and stock-out of supplies as a key factor [sic] for poor HW adherence to T3 strategy.”

Based on “openly accessible data sources” Takyi A & al. estimated that “an estimated nearly 1 in 4 people with uncomplicated confirmed P. falciparum malaria in Africa are at risk of receiving a sub-optimal antimalarial drug dosing. This increases the risk of antimalarial drug resistance and poses a serious threat to malaria control and elimination efforts.” As documented in Characterisation of Populations at Risk of Sub-Optimal Dosing of Artemisinin-Based Combination Therapy in Africa, PLoS Glob Pub Health, 2023 Dec 1, 3:e0002059, https://doi.org/10.1371/journal.pgph.0002059, they identify high risk populations as “wasted children <5 years of age, patients with hyperparasitaemia, pregnant women, people living with HIV, and overweight adults.”

Hossain MS & al. go into a great deal of detail in reporting data from the Malaria Indicator Survey (apparently from 2005[!] according to the citation), their paper, Examining the Disparities of Anti-Malarial Drug Consumption Among Children Under the Age of Five: A Study of [Five] Malaria-Endemic Countries, Malaria J, 2023 Dec 5, 22:370, https://doi.org/10.1186/s12936-023-04805-x quotes wide disparities in antimalarial drug use among and within the five countries studied. {However, even though they repeatedly use the term “antimalarial drugs taken for malaria,” this reviewer failed to find credible data in the article linking the prevalence of malaria in children in the areas studied to the drug consumption reports.}

Side effects and complications

 

The drug of choice for radical cure of P. vivax and other non-falciparum malaria remains primarily primaquine. Manjurano A & al. state in Prevalence of G6PD Deficiency and Submicroscopic Malaria Parasites Carriage in Malaria Hotspot Area in Northwest Tanzania, Malaria J, 2023 Dec 7, 22:372, https://doi.org/ 10.1186/s12936-023-04801-1 that primaquine is also effective against P. falciparum gametocytes and “is the sole potent drug against mature/infectious P. falciparum gametocytes.” Also, according to the authors, the “use of primaquine for mass drug administration (MDA) is being considered as a key strategy for malaria elimination.” However, it may cause severe anemia through the mechanism of hemolysis among patients with G6PD deficiency.  The authors carried out a “retrospective cross-sectional study …, using archived samples to establish the prevalence of G6PD deficiency in a malaria hotspot area” in Northwest Tanzania. Their results showed that “16.4% of the population in this part of Northwestern Tanzania carry the G6PD A− mutation…,” thereby presenting a risk to these individuals if they are treated with primaquine. 

Drug resistance

 

“Emergence of artemisinin partial resistance (ArtR) in Plasmodium falciparum in East Africa is a growing threat to the efficacy of artemisinin combination therapies (ACT) and the global efforts for malaria elimination. The emergence of Pfkelch13 R561H in Rwanda raised concern about the impact in neighboring Tanzania, …. In addition, regional concern over resistance affecting sulfadoxine-pyrimethamine (SP) which is used for chemoprevention strategies is high.” Juliano JJ, Giesbrecht DJ, Simkin A & al. report in Country Wide Surveillance Reveals Prevalent Artemisinin Partial Resistance Mutations with Evidence for Multiple Origins and Expansion of Sulfadoxine-Pyrimethamine Resistance Mutations in Northwest Tanzania, medRxiv. 2023 Nov 8: 2023.11.07.23298207, https://doi.org/10.1101/2023.11.07.23298207 that as a result of a large scale study that the resistant mutation identified in Rwanda “is entrenched in the region and that multiple origins of ArtR, similar as to what was seen in Southeast Asia, are likely to occur. Mutations associated with high levels of SP resistance are increasing.”

“The risk of widespread resistance to artemisinin-based combination therapy (ACT) remains high in Uganda following detection of Plasmodium falciparum parasites with delayed artemisinin clearance genotype and phenotype. Establishment of context specific interventions to mitigate emergence and spread of artemisinin resistance is thus key in the fight against malaria in the country.” Nonetheless, Ocan M & al.’s report, Experiences of Healthcare Personnel on the Efficacy of Artemisinin-Based Combination Therapy and Malaria Diagnosis in Hospitals in Uganda, Malaria J, 2023 Nov 29, 22:362, https://doi.org/10.1186/s12936-023-04800-2 recounts interviews with a small number (22) of healthcare providers and the abstract is silent on their experience with artemisinin resistance.

The Eastern provinces of the DRC lie immediately to the West of Rwanda and Uganda. Mesia Kahunu G & al. raise the cross-border migration of parasites that contain genetic markers of antimalarial resistance. In Identification of the PfK13 Mutations R561H and P441L in Democratic Republic Of Congo (DRC), Int J Infect Dis. 2023 Nov 26: S1201-9712(23)00787-7, https://doi.org/10.1016/j.ijid.2023.11.026 they report that these markers are indeed present in these regions; to a very slight extent when it comes to artemisinin resistance, but up to 42.2% in one Eastern province regarding resistance to chemoprevention.  This conclusion is consistent with that of Kayiba NK & al., The Landscape of Drug Resistance in Plasmodium falciparum Malaria in The Democratic Republic Of Congo: A Mapping Systematic Review, Trop Med Health. 2023 Nov 15; 51(1):64, https://doi.org/10.1186/s41182-023-00551-7, which is a literature review of “1541 primary studies of which 29 fulfilled inclusion criteria and provided information related to 6385 Plasmodium falciparum clinical isolates (collected from 2000 to 2020).” These showed significant resistance to chloroquine and to sulfadoxine-pyrimethamine, but only a single instance of artemisinin resistance.  The authors conclude that this resistance pattern poses a significant barrier to successful chemoprevention in the DRC.

Atul & al., Artemisinin Resistance in P. falciparum: Probing the Interacting Partners of Kelch13 Protein in Parasite, J Glob Antimicrob Resist, 2023 Dec; 35:67-75, https://doi.org/10.1016/j.jgar.2023.08.012 is a biomolecular study of the mechanisms of artemisinin resistance induced by the K13 mutation in the P. falciparum genome.

Girgis ST & al. report on a genetic analysis of parasites collected on dried blood spots for drug resistance in Drug Resistance and Vaccine Target Surveillance of Plasmodium falciparum Using Nanopore Sequencing in Ghana, Nat Microbiol. 2023 Nov 23, https://doi.org/10.1038/s41564-023-01516-6. They “analysed 196 clinical samples and showed that [their] method is rapid, robust, accurate and straightforward to implement. Importantly, [the] method could be applied to dried blood spot samples, which are readily collected in endemic settings. [They] report that P. falciparum parasites in Ghana are mostly susceptible to chloroquine, with persistent sulfadoxine-pyrimethamine resistance and no evidence of artemisinin resistance.”

Based on data they have been collecting since 2010, van Loon W & al., Escalating Plasmodium falciparum K13 Marker Prevalence Indicative of Artemisinin Resistance in Southern Rwanda, Antimicrob Agents Chemother, 2023 Dec 11: E0129923, https://doi.org/10.1128/Aac.01299-23 reports that in “southern Rwanda, markers signaling resistance to artemisinin and lumefantrine are increasing, albeit at a relatively slow rate.”

“Antimalarial drug resistance has been a threat to malaria control and elimination for many decades and is still of concern today. Despite the continued effectiveness of current first-line treatments, namely artemisinin-based combination therapies, … the occurrence of resistance mutations in Africa is of great concern and requires immediate attention.” Schäfer TM & al., The Problem of Antimalarial Resistance and Its Implications for Drug Discovery, Expert Opin Drug Discov, 2023 Dec 18: 1-16, https://doi/10.1080/17460441.2023.2284820 contains a “comprehensive overview of the mechanisms underlying the acquisition of drug resistance in Plasmodium falciparum …. Understanding these processes provides valuable insights that can be harnessed for the development and selection of novel antimalarials with reduced resistance potential. Additionally, strategies to mitigate resistance to antimalarial compounds on the short term by using approved drugs are discussed.”

New drug research

Triazoles are chemicals with formulae that include five-member ring structures that contain three nitrogen atoms. Ravindar L & al., Triazole Hybrid Compounds: A New Frontier in Malaria Treatment, Eur J Med Chem. 2023 Nov 5; 259:115694, https://doi.org/10.1016/j.ejmech.2023.115694 states that their “potential as effective antimalarial agents has captured the attention of researchers and holds promise for overcoming the challenges posed by drug-resistant malaria strains.” In this apparently literature review-focused article, the authors refer to a “versatility [that] makes them highly effective against both drug-sensitive and drug-resistant strains of P. falciparum, making them invaluable tools in regions where resistance is prevalent. The synergistic effects of combining the triazole moiety with other pharmacophores have resulted in even greater antimalarial potency. This approach has the potential to circumvent existing resistance mechanisms and provide a more sustainable solution to malaria treatment. While triazole hybrid compounds show great promise, further research and clinical trials are warranted to fully evaluate their safety, efficacy and long-term effects.”

Looking for a way to overcome drug resistance, Askarani HK & al. investigated the feasibility of creating an artemisinin with a substance called eosin B. In their paper, In vitro and in vivo Antiplasmodial Activity of a Synthetic Dihydroartemisinin-Eosin B Hybrid, Naunyn Schmiedebergs Arch Pharmacol. 2023 Nov 24, https://doi.org/10.1007/s00210-023-02815-9, they describe the efficacy of this hybrid against a drug sensitive strain of P. falciparum and also in vivo in the mouse malaria model.  {How this finding helps overcome drug resistance is not evident from the abstract.}

Plant extracts and traditional treatments

Investigating the antimalarial medicinal plant Clerodendrum polycephalum, Tamuli R & al., Isolation and in vitro and in vivo Activity of Secondary Metabolites from Clerodendrum polycephalum Baker Against Plasmodium Malaria Parasites, J Nat Prod. 2023 Nov 16, https://doi.org/10.1021/acs.jnatprod.3c00743 reports on five compounds isolated, one of which showed considerable in vitro activity against P. falciparum and also against the mouse malaria parasite in vivo.

Campaigns and Policies

 

According to Barat LM & al., “[s]ince its launch in 2005, the U.S. President’s Malaria Initiative’s (PMI) investment in malaria case management has evolved based on lessons learned from its support to countries. An initial focus on updating malaria treatment policies to adopt artemisinin-based combination therapies achieved limited success, in part because of the poor quality of diagnostic and treatment services in targeted countries. In response, the PMI supported the development, refinement, and expansion of Outreach Training and Supportive Supervision (OTSS), a quality improvement approach that combines structured, competency-based supervision with corrective measures, including on-the-job training, coaching, troubleshooting, action planning, and timely follow-up.” Their paper, The U.S. President’s Malaria Initiative’s Support for Improving the Quality of Malaria Case Management Services: Fifteen Years of Progress and Learning, Am J Trop Med Hyg. 2023 Nov 27: tpmd230207, https://doi.org/10.4269/ajtmh.23-0207,“[t]hrough the PMI Impact Malaria Project, launched in 2018, the OTSS approach was expanded beyond case management of uncomplicated malaria to support quality improvement of inpatient management of severe malaria and malaria in pregnancy services delivered through antenatal care clinics. … The OTSS approach has been established as an effective approach to improve the quality of clinical malaria services and can be expanded to cover other health priorities.”

“In 2020, the Zambia National Malaria Elimination Centre targeted the distribution of long-lasting insecticidal nets (LLINs) and indoor-residual spraying (IRS) campaigns based on sub-district micro-planning, where specified geographical areas at the health facility catchment level were assigned to receive either LLINs or IRS. Using data from the 2021 Malaria Indicator Survey (MIS),” Kyomuhangi I & al. “assess[ed] how well the micro-planning was followed in distributing LLINs and IRS, … investigate[d] factors that contributed to whether households received what was planned, and … investigate[d] how overall coverage observed in the 2021 MIS compared to the 2018 MIS conducted prior to micro-planning. They report in Assessing National Vector Control Micro-Planning in Zambia Using the 2021 Malaria Indicator Survey, Malaria J, 2023 Nov 30, 22:365, https://doi.org/10.1186/s12936-023-04807-9 that Overall, 60.0% … of households under a micro-plan received their assigned intervention, with significantly higher coverage of the planned intervention in LLIN-assigned areas … compared to IRS-assigned areas (49.4% … [H]ouseholds falling under the IRS micro-plan had significantly reduced odds of receiving their planned intervention … and significantly reduced odds of receiving any intervention …, compared to households under the LLIN micro-plan. Comparison between the 2021 and 2018 MIS indicated a 27% reduction in LLIN coverage nationally in 2021, while IRS coverage was similar. Additionally, between 2018 and 2021, there was a 13% increase in households that received neither intervention…[Thus,] there was reduced overall vector control coverage in 2021 compared to 2018 before micro-planning.

“Outreach Training and Supportive Supervision (OTSS) of malaria services at health facilities has been adopted by numerous malaria-endemic countries. The OTSS model is characterized by a hands-on method to enhance national guidelines and supervision tools, train supervisors, and perform supervision visits.” Ashton RA & al. conducted an independent investigation “to evaluate the effectiveness of OTSS on health worker competence in the clinical management of malaria, parasitological diagnosis, and prevention of malaria in pregnancy. From 2018 to 2021, health facilities in Cameroon, Ghana, Niger, and Zambia received OTSS visits during which health workers were observed directly during patient consultations, and supervisors completed standardized checklists to assess their performance.” They report in Can Outreach Training and Supportive Supervision Improve Competency in Malaria Service Delivery? An Evaluation in Cameroon, Ghana, Niger, and Zambia, Am J Trop Med Hyg. 2023 Dec 4: tpmd230150, https://doi.org/10.4269/ajtmh.23-0150 that “[s]even of eight outcome indicators showed evidence of beneficial effects of increased OTSS visits.” The authors cite “evidence that successive OTSS visits result in meaningful improvements in indicators linked to quality case management of patients attending facilities for malaria diagnosis and treatment, as well as quality malaria prevention services received by women attending antenatal services.”

Utilizing a community-based testing and response approach, described in 2020 (Malaria J, vol 19 art 292, https://doi.org/10.1186/S12936-020-033663-w), Chang W & al. report in Impact of 1,7-Malaria Reactive Community-Based Testing and Response (1,7-mRCTR) Approach on Malaria Prevalence in Tanzania, Infect Dis Poverty, 2023 Dec 18; 12(1):116, https://doi.org/10.1186/S40249-023-01166-0 that “244,771 community-based malaria rapid tests were completed in intervention areas, and each intervention village received an average of 3.85 rounds of 1-7mRCTR. Malaria prevalence declined from 27.4% … to 11.7% … in the intervention areas and from 26.0% to 16.0% in the control areas.”

 

Adhikari B & al. attribute the difference in steady improvement in malaria control in SE Asian countries versus the recent “stalling’ of efforts in Sub-Saharan Africa to the way community health workers (CHWs) are involved in diagnosis and care of people with malaria. They state in Comparing the Roles of Community Health Workers for Malaria Control and Elimination in Camhttpsbodia and Tanzania, BMJ Glob Health. 2023 Dec 9; 8(12):e013593, https://doi.org/10.1136/bmjgh-2023-013593 that in Tanzania, “treatment continues to rely on healthcare facilities, which provide more limited access to early diagnosis and treatment.” The authors advocate increasing the role of trained CHWs in the treatment of malaria. {There is some question in this reviewer’s mind whether the situation in Tanzania can be generalized to Sub-Saharan Africa, as the authors appear to do.}

Epidemiology

 

Climate change, biodiversity and environment

 

In Kalula A & al., Optimal Control and Cost-Effectiveness Analysis of Age-Structured Malaria Model with Asymptomatic Carrier and Temperature Variability, J Biol Dyn. 2023 Dec; 17(1):2199766, https://doi.org/10.1080/17513758.2023.2199766, the authors fitted the “temperature variability function … to the temperature data, and the malaria model [was] then fitted to the malaria cases and validated to check its suitability. Time-dependent controls were considered, including Long Lasting Insecticide Nets, treatment of symptomatic, screening and treatment of asymptomatic carriers and spray of insecticides.” While the paper (not the abstract) alludes to temperature variability and lists the optimal temperature for transmission of malaria at 24.78⁰C to 26.78⁰C, the extensive mathematical analysis kept temperature constant and basically endorsed the WHO recommendations for prophylaxis via LLINs, IRS, and Chemoprevention as well as treatment of those afflicted by the disease.   

“Cyclone Idai in 2019 was one of the worst tropical cyclones recorded in the Southern Hemisphere. The storm caused catastrophic damage and led to a humanitarian crisis in Mozambique. … The housing and infrastructure damage sustained during Cyclone Idai still has not been addressed in all affected communities. This is of grave concern because storm damage results in poor housing conditions which are known to increase the risk of malaria.” Searle KM & al., Long-Lasting Household Damage from Cyclone Idai Increases Malaria Risk in Rural Western Mozambique, Sci Rep. 2023 Dec 7; 13(1):21590, https://doi.org/10.1038/s41598-023-49200-3 documents that in the communities studied, “the odds of malaria infection was nearly threefold higher in participants who lived in households damaged by Cyclone Idai nearly a year after the storm. This highlights the need for long-term disaster response to improve the efficiency and success of malaria control efforts.”

Please see Sadoine ML & al., Differential Influence of Environmental Factors on Malaria Due to Vector Control Interventions in Uganda, Int J Environ Res Public Health. 2023 Nov 9; 20(22):7042, https://doi.org/10.3390/ijerph20227042 above, in Vector control and protection from vectors.

Risk factors

 

Prior to piloting perennial malaria chemoprevention implementation in southern Togo, Arikawa S & al. conducted “a household survey … to estimate malaria infection prevalence in children under 2 years of age (U2)…. A total of 685 children were included in the survey conducted January-February in 2022 (dry season). … About 80% of the children slept under a bed net the night before the interview. Malaria infection prevalence {based on RDT} was 32.1% … with significant area variation (cluster range: 0.0-73.3). Prevalence of clinical malaria {based on positive RDT and fever} was 15.4% … Children whose caretakers were animist … and those living in mother-headed households … were more likely to have a positive RDT. Living more than 5 km away from the nearest health facility … and presence of two or more under-5-years children in the household … were also associated with increased risk of infection. The paper is Prevalence and Risk Factors Associated with Malaria Infection in Children Under Two Years of Age in Southern Togo Prior to Perennial Malaria Chemoprevention Implementation, Malaria J. 2023 Nov 21; 22:357, https://doi.org/10.1186/s12936-023-04793-y.

Among 526 women admitted for childbirth studied by Tamir Z & al. in a District of Ethiopia, the rate of Plasmodium infection was 14.3%, mostly asymptomatic. The authors report in Plasmodium Infections and Associated Risk Factors Among Parturients in Jawi District, Northwest Ethiopia: A Cross-Sectional Study, Malaria J, 2023 Dec 1, 22:367, https://10.1186/s12936-023-04803-z that infection “was independently predicted by maternal illiteracy …, primigravidity …, lack of antenatal care …, and history of symptomatic malaria during pregnancy … Moreover, the blood group O phenotype was significantly associated with placental malaria among the primiparae.

Meredith HR & al. “worked with four semi-nomadic communities in Central Turkana, Kenya to 1) characterize mobility patterns of travelers from semi-nomadic communities and 2) test the hypothesis that semi-nomadic individuals are at greater risk of exposure to malaria during seasonal migrations than when staying at their semi-permanent settlements.” As reported in Characterizing Mobility Patterns and Malaria Risk Factors in Semi-Nomadic Populations of Northern Kenya, Medrxiv, 2023 Dec 9: 2023.12.06.23299617, https://doi.org/10.1101/2023.12.06.23299617, “[a]fter completing their trips, travelers had a higher prevalence of malaria than those who remained at the household (9.2% vs 4.4%), regardless of gender, age group, and catchment area. These findings highlight the need to develop intervention strategies amenable to mobile lifestyles that can ultimately help prevent the transmission of malaria. {Not peer reviewed, see comment following an article in Vectors above.} 

 

General epidemiology

 

Agbemafle EE & al. “interviewed stakeholders using a semi-structured questionnaire on case detection and reporting [and] assessed the system attributes using the Centers for Disease Control and Prevention updated guidelines for evaluating public health surveillance systems. [They] extracted and reviewed malaria surveillance data from the District Health Management Information System 2” and report in Evaluation of the Malaria Surveillance System – Adaklu District, Volta Region, Ghana, 2019, Public Health Pract (Oxf). 2023 Jul 29; 6:100414, https://doi.org/10.1016/j.puhip.2023.100414 that of “the 80,441 suspected malaria cases recorded in Adaklu District from 2014 to 2018, 47,917 (59.6%) cases were confirmed. The system was meeting its objective of detecting malaria cases and monitoring trends in the population; however, the system missed an epidemic in August 2016. Data generated from the surveillance system is used by the NMCP to aid in the distribution of logistics such as LLINs, RDT test kits, and track malaria control progress in the district. Staff at all levels were able to detect, confirm, treat and report malaria.”

Popkin Hall ZR & al. studied the prevalence of non-P. falciparum malaria in Tanzania by randomly selecting “3,284 of 12,845 samples collected from cross-sectional surveys in 100 health facilities across ten regions of Mainland Tanzania.” As they report in Malaria Species Positivity Rates Among Symptomatic Individuals Across Regions of Differing Transmission Intensities in Mainland Tanzania, J Infect Dis. 2023 Nov 22: jiad522, https://doi.org/10.1093/infdis/jiad522, “P. falciparum was most prevalent, but P. malariae and P. ovale were found in all but one region, with high levels (>5%) of P. ovale in seven regions. The highest P. malariae positivity rate was 4.5% … [They detected only] three P. vivax infections, all in Kilimanjaro. While most non-falciparum malaria-positive samples were co-infected with P. falciparum, 23.6% (n = 13/55) of P. malariae and 14.7% (n = 24/163) of P. ovale spp. were mono-infections. The conclusion mentons implications as far as treatment is concerned.

Oshagbemi OA & al., Estimated Distribution of Malaria Cases Among Children in Sub-Saharan Africa by Specified Age Categories Using Data from the Global Burden of Diseases 2019, Malaria J, 2023 Dec 5, 22:371, https://doi.org/10.1186/s12936-023-04811-z reports the following prevalences stratified by age: “Plasmodium falciparum malaria was 15.4% for ages 0 to < 2 years, 30.5% for 2 to < 6 years, 17.6% for 6 to < 12 years, and 36.5% for ≥ 12 years based on data” from 11 countries of Sub-Saharan Africa.  The article is silent on the prevalence of other forms of malaria.

Spatiotemporal studies

Kane F & al., Modeling Clinical Malaria Episodes in Different Ecological Settings in Mali, 2018-2022, IJID Reg, 2023 Nov 11: 10:24-30, https://doi.org/10.1016/j.ijregi.2023.1

 

Keita S & al., Prognostics of Multiple Malaria Episodes and Nutritional Status in Children Aged 6 to 59 Months from 2013 to 2017 in Dangassa, Mali, Res Sq. 2023 Nov 15: rs.3.rs-3604955, https://doi.org/10.21203/rs.3.rs-3604955/v1

Nour AAI & al., Prevalence of Malaria Parasite Among Pregnant Women Attending to Saudi Kassala Teaching Hospital in Kassala State, Eastern Sudan, J Trop Med, 2023 Nov 30: 2023:2289552, https://doi.org/10.1155/2023/2289552. 

 

Duguma T & al., Malaria Prevalence and Associated Factors Among Symptomatic Children Aged Under Five Years Attending Sheko District Health Center, Southwest Ethiopia: A Cross-Sectional Study, PLoS One. 2023 Dec 1; 18(12):e0295237, https://doi.org/10.1371/journal.pone.0295237

 

 

Malaria Partners Zambia Q1: Achievements and Impact

Malaria Partners Zambia Q1: Achievements and Impact

Malaria Partners Zambia (MPZ) has been diligently working towards malaria eradication during the first quarter of 2024. Malaria Partners Zambia projects remains committed to acknowledging excellence and dedication within the community health workforce through various...

May 2024 Science & Research Report

May 2024 Science & Research Report

By Dr. Derick Pasternak, Ambassador, Malaria Science & Research Coordinator, MPI From the WHO (2024 Apr 25, https://www.afro.who.int/countries/benin/news/major-step-malaria-prevention-three-west-african-countries-roll-out-vaccine): “Cotonou/Freetown/Monrovia — In...

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