What Africa can do to accelerate and sustain progress against malaria

Range dynamics of Anopheles mosquitoes in Africa suggest a significant increase in the malaria transmission risk

Despite a more than 100-year effort to combat malaria, it remains one of the most malignant infectious diseases globally, especially in Africa. Malaria is transmitted by several Anopheles mosquitoes. However, until now few studies have investigated future range dynamics of major An. mosquitoes in Africa through a unified scheme. Through a unified scheme, we developed 21 species distribution models to predict the range dynamics of 21 major An. species in Africa under future scenarios and also examined their overall range dynamic patterns mainly through suitability overlap index and range overlap index. Although future range dynamics varied substantially among the 21 An. species, we predicted large future range expansions for all 21 An. species, and increases in suitability overlap index were detected in more than 90% of the African continent for all future scenarios. Additionally, we predicted high range overlap index in West Africa, East Africa, South Sudan, Angola, and the Democratic Republic of the Congo under future scenarios. Although the relative impacts of land use, topography and climate variables on the range dynamics depended on species and spatial scale, climate played the strongest roles in the range dynamics of most species. Africa might face an increasing risk of malaria transmissions in the future, and better strategies are required to address this problem. Mitigating climate change and human disturbance of natural ecosystems might be essential to reduce the proliferation of An. species and the risk of malaria transmissions in Africa in the future. Our strategies against their impacts should be species-specific.

M. S, N. SN, Shankar G, Tripathi PK, Kashyap H, Jain A, Anvikar A, Chalageri VH. Exploring the hidden mental health consequences of malaria beyond the fever

Malaria morbidity has various presentations and the focus now shifts to uncommon signs and symptoms of malaria infection such as cognitive impairment to address the morbidity when the mortality declines. About 50% of children admitted to hospitals due to malaria experience neurological complications due to factors like low blood sugar, inflammation, elevated pressure, decreased oxygen levels, and excitotoxicity. Malaria during pregnancy negatively also impacts children's cognitive, behavioral, and executive function leading to neurodevelopmental delay due to increased susceptibility which can significantly affect maternal and child health, leading to higher rates of underestimated factors like anxiety, depression, and PTSD. Despite having the world's second-largest tribal population, India's indigenous and tribal communities and their mental health are less explored and less understood. Western psychological tools and neurocognitive assessment tools are not universally applicable, thus necessitating the development of tailored tools to investigate psychological or neurocognitive impairment. This paper has illuminated the hidden mental health consequences of malaria infection, emphasizing the prevalence, nature, and implications of psychological distress among affected individuals. The findings underscore the importance of recognizing and addressing these psychological consequences in the holistic management and prevention of malaria and its mental health consequences.

Entomological survey of sibling species in the Anopheles funestus group in Tanzania confirms the role of Anopheles parensis as a secondary malaria vector

BACKGROUND

Malaria transmission in Tanzania is driven by mosquitoes of the Anopheles gambiae complex and Anopheles funestus group. The latter includes An. funestus s.s., an anthropophilic vector, which is now strongly resistant to public health insecticides, and several sibling species, which remain largely understudied despite their potential as secondary vectors. This paper provides the initial results of a cross-country study of the species composition, distribution and malaria transmission potential of members of the Anopheles funestus group in Tanzania.

METHODS

Mosquitoes were collected inside homes in 12 regions across Tanzania between 2018 and 2022 using Centres for Disease Control and Prevention (CDC) light traps and Prokopack aspirators. Polymerase chain reaction (PCR) assays targeting the noncoding internal transcribed spacer 2 (ITS2) and 18S ribosomal DNA (18S rDNA) were used to identify sibling species in the An. funestus group and presence of Plasmodium infections, respectively. Where DNA fragments failed to amplify during PCR, we sequenced the ITS2 region to identify any polymorphisms.

RESULTS

The following sibling species of the An. funestus group were found across Tanzania: An. funestus s.s. (50.3%), An. parensis (11.4%), An. rivulorum (1.1%), An. leesoni (0.3%). Sequencing of the ITS2 region in the nonamplified samples showed that polymorphisms at the priming sites of standard species-specific primers obstructed PCR amplification, although the ITS2 sequences closely matched those of An. funestus s.s., barring these polymorphisms. Of the 914 samples tested for Plasmodium infections, 11 An. funestus s.s. (1.2%), and 2 An. parensis (0.2%) individuals were confirmed positive for P. falciparum. The highest malaria transmission intensities [entomological inoculation rate (EIR)] contributed by the Funestus group were in the north-western region [108.3 infectious bites/person/year (ib/p/y)] and the south-eastern region (72.2 ib/p/y).

CONCLUSIONS

Whereas An. funestus s.s. is the dominant malaria vector in the Funestus group in Tanzania, this survey confirms the occurrence of Plasmodium-infected An. parensis, an observation previously made in at least two other occasions in the country. The findings indicate the need to better understand the ecology and vectorial capacity of this and other secondary malaria vectors in the region to improve malaria control.

Lingering challenges in malaria elimination efforts in sub-Saharan Africa: Insights and potential solutions

Introduction

Between 2000 and 2015, significant gains were recorded in reducing the global burden of malaria due to enhanced global collaboration and increased funding. However, progress has stagnated post-2015, and the COVID-19 pandemic seems to have reversed some of these gains, necessitating a critical reevaluation of interventions. This paper aims to analyze the setbacks and offer recommendations for advancement in malaria control and prevention in sub-Saharan Africa.

Methods

We conducted searches on Google Scholar, PubMed, and relevant organization websites to identify relevant studies on malaria control and prevention and associated challenges in sub-Saharan Africa from 2015 to the present. Additionally, studies on individual sub-Saharan African countries were reviewed to ensure comprehensiveness. Data from selected studies were extracted and analyzed using a narrative synthesis approach to offer a concise overview of the evidence.

Findings

We observe that the halt in progress of malaria control in sub-Saharan Africa has deep roots in socioeconomic, political, and environmental factors. These challenges are exacerbated by the population explosion in the region, low coverage of interventions due to funding deficits and incessant crises, and the degradation of the efficacy of existing malaria commodities.

Conclusion

Sub-Saharan Africa is at a crossroads in its fight against malaria. Promising new frontiers such as malaria vaccines, preventive monoclonal antibodies, new-generation insecticide-treated nets, and potentially artificial intelligence-driven technologies offer hope in advancing malaria control and prevention in the region. Through commitment and collaboration, leveraging these opportunities can help surmount challenges and ultimately eliminate malaria in sub-Saharan Africa.

Cabo Verde's malaria-free certification: A blueprint for eradicating malaria in Africa

The World Health Organisation (WHO) officially certified Cabo Verde as a malaria-free country in January 2024, marking a key milestone in world health and demonstrating the efficacy of comprehensive malaria control programs. Cabo Verde is only the third country in the WHO African region to have achieved this designation, highlighting the potential for other nations to successfully eradicate malaria. Despite encountering hurdles like drug-resistant strains and COVID-19 disruptions, Cabo Verde's success after years of strategic planning and multisectoral collaboration highlights the value of long-term public health initiatives. To emulate this achievement, African countries must take a holistic approach that includes strong leadership, effective monitoring systems, and community engagement. Leveraging current resources and embracing breakthroughs, such as the recent introduction of malaria vaccinations, will be critical to achieving a malaria-free Africa. Countries that integrate socioeconomic development into malaria eradication efforts might reduce the burden of malaria on vulnerable communities while also driving progress towards larger development goals. Cabo Verde's success serves as an example of the continent's malaria fight, emphasizing the significance of long-term vigilance, adaptability, and collaborative action in realizing a common goal of a malaria-free future.

House Screening Reduces Exposure to Indoor Host-Seeking and Biting Malaria Vectors: Evidence from Rural South-East Zambia

This study evaluated the impact of combining house screens with long-lasting insecticidal nets (LLINs) on mosquito host-seeking, resting, and biting behavior. Intervention houses received house screens and LLINs, while control houses received only LLINs. Centre for Disease Control light traps, pyrethrum spray collections and human landing catches were used to assess the densities of indoor and outdoor host-seeking, indoor resting, and biting behavior of malaria vectors in 15 sentinel houses per study arm per sampling method. The protective efficacy of screens and LLINs was estimated through entomological inoculation rates (EIRs). There were 68% fewer indoor host-seeking Anopheles funestus (RR = 0.32, 95% CI 0.20-0.51, p < 0.05) and 63% fewer An. arabiensis (RR = 0.37, 95% CI 0.22-0.61, p < 0.05) in screened houses than unscreened houses. There was a significantly higher indoor biting rate for unscreened houses (6.75 bites/person/h [b/p/h]) than for screened houses (0 b/p/h) (χ2 = 6.67, df = 1, p < 0.05). The estimated indoor EIR in unscreened houses was 2.91 infectious bites/person/six months, higher than that in screened houses (1.88 infectious bites/person/six months). Closing eaves and screening doors and windows has the potential to reduce indoor densities of malaria vectors and malaria transmission.

China's hidden role in malaria control and elimination in Africa

BACKGROUND

Insufficient funding is hindering the achievement of malaria elimination targets in Africa, despite the pressing need for increased investment in malaria control. While Western donors attribute their inaction to financial constraints, the global health community has limited knowledge of China's expanding role in malaria prevention. This knowledge gap arises from the fact that China does not consistently report its foreign development assistance activities to established aid transparency initiatives. Our work focuses on identifying Chinese-funded malaria control projects throughout Africa and linking them to official data on malaria prevalence. By doing so, we aim to shed light on China's contributions to malaria control efforts, analysing their investments and assessing their impact. This would provide valuable insights into the development of effective financing mechanisms for future malaria control in Africa.

METHODS

Our research used AidData' s recently released Global Chinese Development Finance Dataset V.2.0 providing comprehensive coverage of all official sector Chinese development financing across Africa, from which we identify 224 Chinese-funded malaria projects in Sub-Saharan Africa (SSA) committed between 2002 and 2017. We conducted an analysis of the spending patterns by year, country and regions within Africa and compared it with data on population-adjusted malaria prevalence, sourced from the Malaria Atlas Project.

RESULTS

Chinese-financed malaria projects Africa mainly focused on three areas: the provision of medical supplies (72.32%), the construction of basic health infrastructure (17.86%) and the deployment of anti-malaria experts (3.57%). Moreover, nearly 39% of the initiatives were concentrated in just four countries: the Democratic Republic of Congo, Central African Republic, Uganda and Liberia. Additionally, China's development financing amount showed a weak negative correlation (-0.2393) with population-weighted malaria prevalence. We concluded that the extent and direction of China's support are not adequately tailored to address malaria challenges in different countries.

CONCLUSION

With China's increasing engagement in global health, it is anticipated that malaria control will continue to be a prominent priority on its development assistance agenda. This is attributed to China's vast expertise in malaria elimination, coupled with its substantial contribution as a major producer of malaria diagnostics and treatments.

Key considerations, target product profiles, and research gaps in the application of infrared spectroscopy and artificial intelligence for malaria surveillance and diagnosis

Studies on the applications of infrared (IR) spectroscopy and machine learning (ML) in public health have increased greatly in recent years. These technologies show enormous potential for measuring key parameters of malaria, a disease that still causes about 250 million cases and 620,000 deaths, annually. Multiple studies have demonstrated that the combination of IR spectroscopy and machine learning (ML) can yield accurate predictions of epidemiologically relevant parameters of malaria in both laboratory and field surveys. Proven applications now include determining the age, species, and blood-feeding histories of mosquito vectors as well as detecting malaria parasite infections in both humans and mosquitoes. As the World Health Organization encourages malaria-endemic countries to improve their surveillance-response strategies, it is crucial to consider whether IR and ML techniques are likely to meet the relevant feasibility and cost-effectiveness requirements-and how best they can be deployed. This paper reviews current applications of IR spectroscopy and ML approaches for investigating malaria indicators in both field surveys and laboratory settings, and identifies key research gaps relevant to these applications. Additionally, the article suggests initial target product profiles (TPPs) that should be considered when developing or testing these technologies for use in low-income settings.

Differences in malaria vector biting behavior and changing vulnerability to malaria transmission in contrasting ecosystems of western Kenya

BACKGROUND

Designing, implementing, and upscaling of effective malaria vector control strategies necessitates an understanding of when and where transmission occurs. This study assessed the biting patterns of potentially infectious malaria vectors at various hours, locations, and associated human behaviors in different ecological settings in western Kenya.

METHODS

Hourly indoor and outdoor catches of human-biting mosquitoes were sampled from 19:00 to 07:00 for four consecutive nights in four houses per village. The human behavior study was conducted via questionnaire surveys and observations. Species within the Anopheles gambiae complex and Anopheles funestus group were distinguished by polymerase chain reaction (PCR) and the presence of Plasmodium falciparum circumsporozoite proteins (CSP) determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Altogether, 2037 adult female anophelines were collected comprising the An. funestus group (76.7%), An. gambiae sensu lato (22.8%), and Anopheles coustani (0.5%). PCR results revealed that Anopheles arabiensis constituted 80.5% and 79% of the An. gambiae s.l. samples analyzed from the lowland sites (Ahero and Kisian, respectively). Anopheles gambiae sensu stricto (hereafter An. gambiae) (98.1%) was the dominant species in the highland site (Kimaeti). All the An. funestus s.l. analyzed belonged to An. funestus s.s. (hereafter An. funestus). Indoor biting densities of An. gambiae s.l. and An. funestus exceeded the outdoor biting densities in all sites. The peak biting occurred in early morning between 04:30 and 06:30 in the lowlands for An. funestus both indoors and outdoors. In the highlands, the peak biting of An. gambiae occurred between 01:00 and 02:00 indoors. Over 50% of the study population stayed outdoors from 18:00 to 22:00 and woke up at 05:00, coinciding with the times when the highest numbers of vectors were collected. The sporozoite rate was higher in vectors collected outdoors, with An. funestus being the main malaria vector in the lowlands and An. gambiae in the highlands.

CONCLUSION

This study shows heterogeneity of anopheline distribution, high outdoor malaria transmission, and early morning peak biting activity of An. funestus when humans are not protected by bednets in the lowland sites. Additional vector control efforts targeting the behaviors of these vectors, such as the use of non-pyrethroids for indoor residual spraying and spatial repellents outdoors, are needed.

Resurgence of Malaria Transmission and Incidence after Withdrawal of Indoor Residual Spraying in the District of Koulikoro, Mali

In Mali, malaria vector control relies mostly on long-lasting insecticidal nets and indoor residual spraying (IRS). From 2008 to 2016, an IRS program was implemented in the district of Koulikoro. After a significant reduction in malaria indicators, IRS was stopped in 2016. This study evaluated the effect of IRS withdrawal on entomological parameters of malaria transmission and incidence in children aged 6 months to 10 years in the district of Koulikoro. Entomological parameters of malaria transmission during the last year of IRS implementation in 2016 were compared with those obtained 2 years after IRS withdrawal in 2018 in two villages of Koulikoro. Mosquito vectors were collected by mouth aspiration and pyrethrum spray catches in the villages to monitor these transmission parameters. A sharp increase (10.8 times higher) in vector abundance after IRS withdrawal was observed. The infection rate of Anopheles gambiae sensu lato to Plasmodium falciparum increased from zero during IRS implementation to 14.8% after IRS withdrawal. The average entomological inoculation rate, which was undetectable before, was 1.22 infected bites per person per month 2 years after IRS was withdrawn, and the cumulative malaria incidence rate observed after IRS was 4.12 times (15.2% versus 3.7%) higher than that observed in 2016 in the villages before IRS withdrawal. This study showed a resurgence of malaria transmission and incidence in the Koulikoro health district after IRS was withdrawn. Thus, to manage the potential consequences of malaria transmission resurgence, alternative approaches are needed when stopping successful malaria control interventions.

Defining operational research priorities to improve malaria control and elimination in sub-Saharan Africa: results from a country-driven research prioritization setting process

BACKGROUND

In order to reignite gains and accelerate progress toward improved malaria control and elimination, policy, strategy, and operational decisions should be derived from high-quality evidence. The U.S. President's Malaria Initiative (PMI) Insights project together with the Université Cheikh Anta Diop of Dakar, Senegal, conducted a broad stakeholder consultation process to identify pressing evidence gaps in malaria control and elimination across sub-Saharan Africa (SSA), and developed a priority list of country-driven malaria operational research (OR) and programme evaluation (PE) topics to address these gaps.

METHODS

Five key stakeholder groups were engaged in the process: national malaria programmes (NMPs), research institutions in SSA, World Health Organization (WHO) representatives in SSA, international funding agencies, and global technical partners who support malaria programme implementation and research. Stakeholders were engaged through individual or small group interviews and an online survey, and asked about key operational challenges faced by NMPs, pressing evidence gaps in current strategy and implementation guidance, and priority OR and PE questions to address the challenges and gaps.

RESULTS

Altogether, 47 interviews were conducted with 82 individuals, and through the online survey, input was provided by 46 global technical partners. A total of 33 emergent OR and PE topics were identified through the consultation process and were subsequently evaluated and prioritized by an external evaluation committee of experts from NMPs, research institutions, and the WHO. The resulting prioritized OR and PE topics predominantly focused on generating evidence needed to close gaps in intervention coverage, address persistent challenges faced by NMPs in the implementation of core strategic interventions, and inform the effective deployment of new tools.

CONCLUSION

The prioritized research list is intended to serve as a key resource for informing OR and PE investments, thereby ensuring future investments focus on generating the evidence needed to strengthen national strategies and programme implementation and facilitating a more coordinated and impactful approach to malaria operational research.

Effects of vegetation densities on the performance of attractive targeted sugar baits (ATSBs) for malaria vector control: a semi-field study

BACKGROUND

Attractive targeted sugar baits (ATSBs) control sugar-feeding mosquitoes with oral toxicants, and may effectively complement core malaria interventions, such as insecticide-treated nets even where pyrethroid-resistance is widespread. The technology is particularly efficacious in arid and semi-arid areas. However, their performance remains poorly-understood in tropical areas with year-round malaria transmission, and where the abundant vegetation constitutes competitive sugar sources for mosquitoes. This study compared the efficacies of ATSBs (active ingredient: 2% boric acid) in controlled settings with different vegetation densities.

METHODS

Potted mosquito-friendly plants were introduced inside semi-field chambers (9.6 m by 9.6 m) to simulate densely-vegetated, sparsely-vegetated, and bare sites without any vegetation (two chambers/category). All chambers had volunteer-occupied huts. Laboratory-reared Anopheles arabiensis were released nightly (200/chamber) and host-seeking females recaptured using human landing catches outdoors (8.00 p.m.-9.00 p.m.) and CDC-light traps indoors (9.00 p.m.-6.00 a.m.). Additionally, resting mosquitoes were collected indoors and outdoors each morning using Prokopack aspirators. The experiments included a "before-and-after" set-up (with pre-ATSBs, ATSBs and post-ATSBs phases per chamber), and a "treatment vs. control" set-up (where similar chambers had ATSBs or no ATSBs). The experiments lasted 84 trap-nights.

RESULTS

In the initial tests when all chambers had no vegetation, the ATSBs reduced outdoor-biting by 69.7%, indoor-biting by 79.8% and resting mosquitoes by 92.8%. In tests evaluating impact of vegetation, the efficacy of ATSBs against host-seeking mosquitoes was high in bare chambers (outdoors: 64.1% reduction; indoors: 46.8%) but modest or low in sparsely-vegetated (outdoors: 34.5%; indoors: 26.2%) and densely-vegetated chambers (outdoors: 25.4%; indoors: 16.1%). Against resting mosquitoes, the ATSBs performed modestly across settings (non-vegetated chambers: 37.5% outdoors and 38.7% indoors; sparsely-vegetated: 42.9% outdoors and 37.5% indoors; densely-vegetated: 45.5% outdoors and 37.5% indoors). Vegetation significantly reduced the ATSBs efficacies against outdoor-biting and indoor-biting mosquitoes but not resting mosquitoes.

CONCLUSION

While vegetation can influence the performance of ATSBs, the devices remain modestly efficacious in both sparsely-vegetated and densely-vegetated settings. Higher efficacies may occur in places with minimal or completely no vegetation, but such environments are naturally unlikely to sustain Anopheles populations or malaria transmission in the first place. Field studies therefore remain necessary to validate the efficacies of ATSBs in the tropics.

Antimalarial potential of Moringa oleifera Lam. (Moringaceae): A review of the ethnomedicinal, pharmacological, toxicological, and phytochemical evidence

Several regions of the world frequently use the species Moringa oleifera Lam. (Moringaceae) in traditional medicine. This situation is even more common in African countries. Many literature reports point to the antimalarial potential of this species, indicating the efficacy of its chemical compounds against malaria-causing parasites of the genus Plasmodium. From this perspective, the present study reviews the ethnobotanical, pharmacological, toxicological, and phytochemical (flavonoids) evidence of M. oleifera, focusing on the treatment of malaria. Scientific articles were retrieved from Google Scholar, PubMed^®, ScienceDirect^®, and SciELO databases. Only articles published between 2002 and 2022 were selected. After applying the inclusion and exclusion criteria, this review used a total of 72 articles. These documents mention a large use of M. oleifera for the treatment of malaria in African and Asian countries. The leaves (63%) of this plant are the main parts used in the preparation of herbal medicines. The in vivo antimalarial activity of M. oleifera was confirmed through several studies using polar and nonpolar extracts, fractions obtained from the extracts, infusion, pellets, and oils obtained from this plant and tested in rodents infected by the following parasites of the genus Plasmodium: P. berghei, P. falciparum, P. yoelii, and P. chabaudi. Extracts obtained from M. oleifera showed no toxicity in preclinical tests. A total of 46 flavonoids were identified in the leaves and seeds of M. oleifera by different chromatography and mass spectrometry methods. Despite the scarcity of research on the antimalarial potential of compounds isolated from M. oleifera, the positive effects against malaria-causing parasites in previous studies are likely to correlate with the flavonoids that occur in this species.

Perennial malaria chemoprevention with and without malaria vaccination to reduce malaria burden in young children: a modelling analysis

BACKGROUND

A recent WHO recommendation for perennial malaria chemoprevention (PMC) encourages countries to adapt dose timing and number to local conditions. However, knowledge gaps on the epidemiological impact of PMC and possible combination with the malaria vaccine RTS,S hinder informed policy decisions in countries where malaria burden in young children remains high.

METHODS

The EMOD malaria model was used to predict the impact of PMC with and without RTS,S on clinical and severe malaria cases in children under the age of two years (U2). PMC and RTS,S effect sizes were fit to trial data. PMC was simulated with three to seven doses (PMC-3-7) before the age of eighteen months and RTS,S with three doses, shown to be effective at nine months. Simulations were run for transmission intensities of one to 128 infectious bites per person per year, corresponding to incidences of < 1 to 5500 cases per 1000 population U2. Intervention coverage was either set to 80% or based on 2018 household survey data for Southern Nigeria as a sample use case. The protective efficacy (PE) for clinical and severe cases in children U2 was calculated in comparison to no PMC and no RTS,S.

RESULTS

The projected impact of PMC or RTS,S was greater at moderate to high transmission than at low or very high transmission. Across the simulated transmission levels, PE estimates of PMC-3 at 80% coverage ranged from 5.7 to 8.8% for clinical, and from 6.1 to 13.6% for severe malaria (PE of RTS,S 10-32% and 24.6-27.5% for clinical and severe malaria, respectively. In children U2, PMC with seven doses nearly averted as many cases as RTS,S, while the combination of both was more impactful than either intervention alone. When operational coverage, as seen in Southern Nigeria, increased to a hypothetical target of 80%, cases were reduced beyond the relative increase in coverage.

CONCLUSIONS

PMC can substantially reduce clinical and severe cases in the first two years of life in areas with high malaria burden and perennial transmission. A better understanding of the malaria risk profile by age in early childhood and on feasible coverage by age, is needed for selecting an appropriate PMC schedule in a given setting.

Changes in the associations between malaria incidence and climatic factors across malaria endemic countries in Africa and Asia-Pacific region

Empirical evidence supporting the associations between malaria incidence and climatic factors has remained controversial, buffering the progress in the Global Malaria Program that aims to eliminate 90% of the world malaria burden by 2030. This study has aimed to evaluate the nature and extent at which these relations are maintained across all the malaria endemic countries of Africa and Asia-Pacific region. We have utilized the last two decades of malaria incidence, annual minimum temperature, and annual precipitation time series data (2000-2020) for the two most malaria-impacted regions. These data were fitted in the generalized linear model and the mixed effects model. The results showed that there exists a large heterogeneity in malaria incidence across the countries, and between the regions. Last two decadal tendencies showed significant reductions in the disease burden in almost all the countries in the Asia Pacific, with several exceptions or relatively slowed reductions in the Africa. We found significant changes in the positive linear associations between malaria incidence, annual minimum temperature, and annual precipitation across African countries. Many Asia-Pacific countries namely Bangladesh, Bhutan, Indonesia, South Korea, Nepal, Thailand, Vietnam showed negative effects in the associations with the annual precipitation. This study indicates that increasing temperature within the range of 12-30 °C can generate positive effects on malaria incidence, but the nature and extent of precipitation effects vary across countries and at a large regional scale.

Field evaluation of the novel One Step Malaria Pf and Pf/Pv rapid diagnostic tests and the proportion of HRP-2 gene deletion identified on samples collected in the Pwani region, Tanzania

Background

Malaria rapid diagnostic tests (mRDTs) have played an important role in the early detection of clinical malaria in an endemic area. While several mRDTs are currently on the market, the availability of mRDTs with high sensitivity and specificity will merit the fight against malaria. We evaluated the field performance of a novel One Step Malaria (P.f/P.v) Tri-line and One Step Malaria (P.f) rapid test kits in Pwani, Tanzania.

Methods

In a cross-sectional study conducted in Bagamoyo and Kibiti districts in Tanzania, symptomatic patients were tested using the SD BIOLINE, One Step Malaria (P.f/P.v) Tri-line and One Step Malaria (P.f) rapid test kits, microscope, and quantitative Polymerase Chain Reaction (qPCR). An additional qPCR assay was carried out to detect Histidine-Rich Protein 2 (HRP-2) gene deletion on mRDT negative but microscope and qPCR positive samples. Microscope results confirmed by qPCR were used for analysis, where qPCR was used as a reference method.

Results

The sensitivity and specificity of One Step P.f/P.v Tri-line mRDTs were 96.0% (CI 93.5-97.7%) and 98.3% (CI 96.8-99.2%), respectively. One Step P.f mRDT had sensitivity and specificity of 95.2% (CI 92.5-97.1%) and 97.9% (CI 96.3-99.0%) respectively. Positive predictive value (PPV) was 97.6% (CI 95.4-98.7%) and negative predictive value (NPV) was 96.2% (CI 95.5-98.3%) for the One Step P.f/P.v Tri-line mRDTs respectively, while One Step P.f mRDT had positive predictive value (PPV) and negative predictive value (NPV) of 97.0% (CI 94.8-98.3%) and 96.7 (CI 94.9-97.9%) respectively. 9.8% (CI 7.84-11.76) of all samples tested and reported to be malaria-negative by mRDT had HRP-2 gene deletion.

Conclusion

One Step Malaria P.f/P.v Tri-line and One Step Malaria P.f rapid test kits have similar sensitivity and specificity as the standard mRDT that is currently in the market, demonstrating the potential to contribute in the fight against malaria in endemic settings. However, the identified malaria parasites population with HRP-2 gene deletion pose a threat to the current mRDT usability in the field and warrants further investigations.