Molecular identification of Plasmodium species responsible for malaria reveals Plasmodium vivax isolates in Duffy negative individuals from southwestern Nigeria

Epidemiology of Plasmodium vivax in Duffy negatives and Duffy positives from community and health centre collections in Ethiopia

BACKGROUND

Malaria remains a significant cause of morbidity and mortality in Ethiopia with an estimated 3.8 million cases in 2021 and 61% of the population living in areas at risk of malaria transmission. Throughout the country Plasmodium vivax and Plasmodium falciparum are co-endemic, and Duffy expression is highly heterogeneous. The public health significance of Duffy negativity in relation to P. vivax malaria in Ethiopia, however, remains unclear. This study seeks to explore the prevalence and rates of P. vivax malaria infection across Duffy phenotypes in clinical and community settings.

METHODS

A total of 9580 and 4667 subjects from community and health facilities from a malaria endemic site and an epidemic-prone site in western Ethiopia were enrolled and examined for P. vivax infection and Duffy expression from February 2018 to April 2021. Association between Duffy expression, P. vivax and P. falciparum infections were examined for samples collected from asymptomatic community volunteers and symptomatic subjects from health centres.

RESULTS

Infection rate of P. vivax among Duffy positives was 2-22 fold higher than Duffy negatives in asymptomatic volunteers from the community. Parasite positivity rate was 10-50 fold higher in Duffy positives than Duffy negatives among samples collected from febrile patients attending health centres and mixed P. vivax and P. falciparum infections were significantly more common than P. vivax mono infections among Duffy negative individuals. Plasmodium vivax parasitaemia measured by 18sRNA parasite gene copy number was similar between Duffy positives and Duffy negatives.

CONCLUSIONS

Duffy negativity does not offer complete protection against infection by P. vivax, and cases of P. vivax in Duffy negatives are widespread in Ethiopia, being found in asymptomatic volunteers from communities and in febrile patients from health centres. These findings offer evidence for consideration when developing control and intervention strategies in areas of endemic P. vivax and Duffy heterogeneity.

Molecular speciation of Plasmodium and multiplicity of P. falciparum infection in the Central region of Ghana

Malaria is endemic in the Central region of Ghana, however, the ecological and the seasonal variations of Plasmodium population structure and the intensity of malaria transmission in multiple sites in the region have not been explored. In this cross-sectional study, five districts in the region were involved. The districts were Agona Swedru, Assin Central and Gomoa East (representing the forest zone) and Abura-Asebu-Kwamankese and Cape Coast representing the coastal zone. Systematically, blood samples were collected from patients with malaria. The malaria status was screened with a rapid diagnostic test (RDT) kit (CareStart manufactured by Access Bio in Somerset, USA) and the positive ones confirmed microscopically. Approximately, 200 μL of blood was used to prepare four dried blood spots of 50μL from each microscopy positive sample. The Plasmodium genome was sequenced at the Malaria Genome Laboratory (MGL) of Wellcome Sanger Institute (WSI), Hinxton, UK. The single nucleotide polymorphisms (SNPs) in the parasite mitochondria (PfMIT:270) core genome aided the species identification of Plasmodium. Subsequently, the complexity of infection (COI) was determined using the complexity of infection likelihood (COIL) computational analysis. In all, 566 microscopy positive samples were sequenced. Of this number, Plasmodium genome was detected in 522 (92.2%). However, whole genome sequencing was successful in 409/522 (72.3%) samples. In total, 516/522 (98.8%) of the samples contained P. falciparum mono-infection while the rest (1.2%) were either P. falciparum/P. ovale (Pf/Po) (n = 4, 0.8%) or P. falciparum/P. malariae/P. vivax (Pf/Pm/Pv) mixed-infection (n = 2, 0.4%). All the four Pf/Po infections were identified in samples from the Assin Central municipality whilst the two Pf/Pm/Pv triple infections were identified in Abura-Asebu-Kwamankese district and Cape Coast metropolis. Analysis of the 409 successfully sequenced genome yielded between 1-6 P. falciparum clones per individual infection. The overall mean COI was 1.78±0.92 (95% CI: 1.55-2.00). Among the study districts, the differences in the mean COI between ecological zones (p = 0.0681) and seasons (p = 0.8034) were not significant. However, regression analysis indicated that the transmission of malaria was more than twice among study participants aged 15-19 years (OR = 2.16, p = 0.017) and almost twice among participants aged over 60 years (OR = 1.91, p = 0.021) compared to participants between 20-59 years. Between genders, mean COI was similar except in Gomoa East where females recorded higher values. In conclusion, the study reported, for the first time, P. vivax in Ghana. Additionally, intense malaria transmission was found to be higher in the 15-19 and > 60 years, compared to other age groups. Therefore, active surveillance for P. vivax in Ghana and enhanced malaria control measures in the 15-19 year group years and those over 60 years are recommended.

Comparison of Plasmodium Vivax Infections in Duffy Negatives From Community and Health Center Collections in Ethiopia

Background

Malaria remains a significant cause of morbidity and mortality in Ethiopia with an estimated 4.2 million annual cases and 61% of the population living in areas at risk of malaria transmission. Throughout the country Plasmodium vivax and P. falciparum are co-endemic, and Duffy expression is highly heterogeneous. The public health significance of Duffy negativity in relation to P. vivax malaria in Ethiopia, however, remains unclear.

Methods

A total of 9,580 and 4,667 subjects from community and health facilities from a malaria endemic site and an epidemic-prone site in western Ethiopia were enrolled and examined for P. vivax infection and Duffy expression. Association between Duffy expression, P. vivax and P. falciparum infections were examined for samples collected from asymptomatic community volunteers and symptomatic subjects from health centers.

Results

Among the community-based cross-sectional samples, infection rate of P. vivax among the Duffy positives was 2-22 fold higher than among the Duffy negatives. Parasite positivity rate was 10-50 fold higher in Duffy positive than Duffy negatives among samples collected from the health center settings and mixed P. vivax and P. falciparum infections were significantly more common than P. vivax mono infections among Duffy negative individuals. P. vivax parasitemia measured by 18sRNA parasite gene copy number was similar between Duffy positives and Duffy negatives.

Conclusions

Duffy negativity does not offer complete protection against infection by P. vivax, and cases of P. vivax in Duffy negatives are widespread in Ethiopia, being found in asymptomatic volunteers from communities and in febrile patients from health centers. These findings offer evidence for consideration when developing control and intervention strategies in areas of endemic P. vivax and Duffy heterogeneity.

Relationship between Duffy Genotype/Phenotype and Prevalence of Plasmodium vivax Infection: A Systematic Review

The Duffy protein, a transmembrane molecule, functions as a receptor for various chemokines and facilitates attachment between the reticulocyte and the Plasmodium Duffy antigen-binding protein. Duffy expression correlates with the Duffy receptor gene for the chemokine, located on chromosome 1, and exhibits geographical variability worldwide. Traditionally, researchers have described the Duffy negative genotype as a protective factor against Plasmodium vivax infection. However, recent studies suggest that this microorganism's evolution could potentially diminish this protective effect. Nevertheless, there is currently insufficient global data to demonstrate this phenomenon. This study aimed to evaluate the relationship between the Duffy genotype/phenotype and the prevalence of P. vivax infection. The protocol for the systematic review was registered in PROSPERO as CRD42022353427 and involved reviewing published studies from 2012 to 2022. The Medline/PubMed, Web of Science, Scopus, and SciELO databases were consulted. Assessments of study quality were conducted using the STROBE and GRADE tools. A total of 34 studies were included, with Africa accounting for the majority of recorded studies. The results varied significantly regarding the relationship between the Duffy genotype/phenotype and P. vivax invasion. Some studies predominantly featured the negative Duffy genotype yet reported no malaria cases. Other studies identified minor percentages of infections. Conversely, certain studies observed a higher prevalence (99%) of Duffy-negative individuals infected with P. vivax. In conclusion, this systematic review found that the homozygous Duffy genotype positive for the A allele (FY*A/*A) is associated with a higher incidence of P. vivax infection. Furthermore, the negative Duffy genotype does not confer protection against vivax malaria.

Indigenous medicinal plants used in folk medicine for malaria treatment in Kwara State, Nigeria: an ethnobotanical study

BACKGROUND

Folk medicine is crucial to healthcare delivery in the underdeveloped countries. It is frequently used as a primary treatment option or as a complementary therapy for malaria. Malaria is a deadly disease which greatly threatens global public health, claiming incredible number of lives yearly. The study was aimed at documenting the medicinal plants used for malaria treatment in folk medicine in Kwara State, Nigeria.

METHODS

Ethnobotanical information was collected from selected consenting registered traditional medicine practitioners (TMPs) through oral face-to-face interviews using in-depth, semi-structured interview guide. The ethnobotanical data were analysed, and descriptive statistical methods were used to compile them.

RESULTS

Sixty-two indigenous medicinal plants, including 13 new plants, used for malaria treatment were identified in this study. The TMPs preferred decoction in aqueous solvent (34%) and steeping in decaffeinated soft drink (19%) for herbal preparations. Oral administration (74%) was the main route of administration, while leaves (40%) and stem barks (32%) were the most dominant plant parts used in herbal preparations. The most cited families were Fabaceae (15%) and Rutaceae (6%), while Mangifera indica (77.14%), Enantia chlorantha (65.71%), Alstonia boonei (57.14%) followed by Cymbopogon citratus (54.29%) were the most used plants. Besides, the antimalarial activities of many of the plants recorded and their isolated phytocompounds have been demonstrated. Furthermore, the conservation status of 4 identified plants were Vulnerable.

CONCLUSION

The study showed strong ethnobotanical knowledge shared by the TMPs in the State and provides preliminary information that could be explored for the discovery of more potent antimalarial compounds.

The temporal dynamics of Plasmodium species infection after artemisinin-based combination therapy (ACT) among asymptomatic children in the Hohoe municipality, Ghana

BACKGROUND

The routine surveillance of asymptomatic malaria using nucleic acid-based amplification tests is essential in obtaining reliable data that would inform malaria policy formulation and the implementation of appropriate control measures.

METHODS

In this study, the prevalence rate and the dynamics of Plasmodium species among asymptomatic children (n = 1697) under 5 years from 30 communities within the Hohoe municipality in Ghana were determined.

RESULTS AND DISCUSSION

The observed prevalence of Plasmodium parasite infection by polymerase chain reaction (PCR) was 33.6% (571/1697), which was significantly higher compared to that obtained by microscopy [26.6% (451/1697)] (P < 0.0001). Based on species-specific analysis by nested PCR, Plasmodium falciparum infection [33.6% (570/1697)] was dominant, with Plasmodium malariae, Plasmodium ovale and Plasmodium vivax infections accounting for 0.1% (1/1697), 0.0% (0/1697), and 0.0% (0/1697), respectively. The prevalence of P. falciparum infection among the 30 communities ranged from 0.0 to 82.5%. Following artesunate-amodiaquine (AS + AQ, 25 mg/kg) treatment of a sub-population of the participants (n = 184), there was a substantial reduction in Plasmodium parasite prevalence by 100% and 79.2% on day 7 based on microscopy and nested PCR analysis, respectively. However, there was an increase in parasite prevalence from day 14 to day 42, with a subsequent decline on day 70 by both microscopy and nested PCR. For parasite clearance rate analysis, we found a significant proportion of the participants harbouring residual Plasmodium parasites or parasite genomic DNA on day 1 [65.0% (13/20)], day 2 [65.0% (13/20)] and day 3 [60.0% (12/20)] after initiating treatment. Of note, gametocyte carriage among participants was low before and after treatment.

CONCLUSION

Taken together, the results indicate that a significant number of individuals could harbour residual Plasmodium parasites or parasite genomic DNA after treatment. The study demonstrates the importance of routine surveillance of asymptomatic malaria using sensitive nucleic acid-based amplification techniques.

Non-falciparum malaria infection and IgG seroprevalence among children under 15 years in Nigeria, 2018

Plasmodium falciparum (Pf) is the dominant malaria parasite in Nigeria though P. vivax (Pv), P. ovale (Po), and P. malariae (Pm) are also endemic. Blood samples (n = 31,234) were collected from children aged 0-14 years during a 2018 nationwide HIV survey and assayed for Plasmodium antigenemia, Plasmodium DNA, and IgG against Plasmodium MSP1-19 antigens. Of all children, 6.6% were estimated to have Pm infection and 1.4% Po infection with no Pv infections detected. The highest household wealth quintile was strongly protective against infection with Pm (aOR: 0.11, 95% CI: 0.05-0.22) or Po (aOR= 0.01, 0.00-0.10). Overall Pm seroprevalence was 34.2% (95% CI: 33.3-35.2) with lower estimates for Po (12.1%, 11.6-12.5) and Pv (6.3%, 6.0-6.7). Pm seropositivity was detected throughout the country with several local government areas showing >50% seroprevalence. Serological and DNA indicators show widespread exposure of Nigerian children to Pm with lower rates to Po and Pv.

CRISPR-Cas13 in malaria parasite: Diagnosis and prospective gene function identification

Malaria caused by Plasmodium is still a serious public health problem. Genomic editing is essential to understand parasite biology, elucidate mechanical pathways, uncover gene functions, identify novel therapeutic targets, and develop clinical diagnostic tools. Recent advances have seen the development of genomic diagnostic technologies and the emergence of genetic manipulation toolbox comprising a host of several systems for editing the genome of Plasmodium at the DNA, RNA, and protein level. Genomic manipulation at the RNA level is critical as it allows for the functional characterization of several transcripts. Of notice, some developed artificial RNA genome editing tools hinge on the endogenous RNA interference system of Plasmodium. However, Plasmodium lacks a robust RNAi machinery, hampering the progress of these editing tools. CRISPR-Cas13, which belongs to the VI type of the CRISPR system, can specifically bind and cut RNA under the guidance of crRNA, with no or minimal permanent genetic scar on genes. This review summarizes CRISPR-Cas13 system from its discovery, classification, principle of action, and diagnostic platforms. Further, it discusses the application prospects of Cas13-based systems in Plasmodium and highlights its advantages and drawbacks.

The Black Box of Cellular and Molecular Events of Plasmodium vivax Merozoite Invasion into Reticulocytes

Plasmodium vivax is the most widely distributed malaria parasite affecting humans worldwide, causing ~5 million cases yearly. Despite the disease's extensive burden, there are gaps in the knowledge of the pathophysiological mechanisms by which P. vivax invades reticulocytes. In contrast, this crucial step is better understood for P. falciparum, the less widely distributed but more often fatal malaria parasite. This discrepancy is due to the difficulty of studying P. vivax's exclusive invasion of reticulocytes, which represent 1-2% of circulating cells. Its accurate targeting mechanism has not yet been clarified, hindering the establishment of long-term continuous in vitro culture systems. So far, only three reticulocyte invasion pathways have been characterised based on parasite interactions with DARC, TfR1 and CD98 host proteins. However, exposing the parasite's alternative invasion mechanisms is currently being considered, opening up a large field for exploring the entry receptors used by P. vivax for invading host cells. New methods must be developed to ensure better understanding of the parasite to control malarial transmission and to eradicate the disease. Here, we review the current state of knowledge on cellular and molecular mechanisms of P. vivax's merozoite invasion to contribute to a better understanding of the parasite's biology, pathogenesis and epidemiology.

Prevalence of non-Plasmodium falciparum species in southern districts of Brazzaville in The Republic of the Congo

BACKGROUND

Although Plasmodium falciparum infection is largely documented and this parasite is the main target for malaria eradication, other Plasmodium species persist, and these require more attention in Africa. Information on the epidemiological situation of non-P. falciparum species infections is scarce in many countries, including in the Democratic Republic of the Congo (hereafter Republic of the Congo) where malaria is highly endemic. The aim of this study was to determine the prevalence and distribution of non-P. falciparum species infections in the region south of Brazzaville.

METHODS

A cross-sectional survey was conducted in volunteers living in rural and urban settings during the dry and rainy seasons in 2021. Socio-demographic and clinical parameters were recorded. Plasmodium infection in blood samples was detected by microscopic analysis and nested PCR (sub-microscopic analysis).

RESULTS

Of the 773 participants enrolled in the study, 93.7% were from the rural area, of whom 97% were afebrile. The prevalence of microscopic and sub-microscopic Plasmodium spp. infection was 31.2% and 63.7%, respectively. Microscopic Plasmodium malariae infection was found in 1.3% of participants, while sub-microscopic studies detected a prevalence of 14.9% for P. malariae and 5.3% for Plasmodium ovale. The rate of co-infection of P. malariae or P. ovale with P. falciparum was 8.3% and 2.6%, respectively. Higher rates of sub-microscopic infection were reported for the urban area without seasonal fluctuation. In contrast, non-P. falciparum species infection was more pronounced in the rural area, with the associated risk of the prevalence of sub-microscopic P. malariae infection increasing during the dry season.

CONCLUSION

There is a need to include non-P. falciparum species in malaria control programs, surveillance measures and eradication strategies in the Republic of the Congo.

African Plasmodium vivax malaria improbably rare or benign

The overwhelming dominance of Duffy blood group negativity among most people living in sub-Saharan Africa has been considered the basis of their protection from endemic Plasmodium vivax malaria. New evidence demonstrates widespread transmission of P. vivax in Duffy-negative Africa, though currently of unknown distribution, magnitude, or consequences. Other new evidence from outside of Africa demonstrates marked tropisms of P. vivax for extravascular tissues of bone marrow and spleen. Those establish states of proliferative infection with low-grade or undetectable parasitemia of peripheral blood causing acute and chronic disease. This review examines the plausibility of those infectious processes also operating in Duffy-negative Africans and causing harm of unrecognized origin.

Genetic Diversity and Phylogenetic Relatedness of Plasmodium ovale curtisi and Plasmodium ovale wallikeri in sub-Saharan Africa

P. ovale was until recently thought to be a single unique species. However, the deployment of more sensitive tools has led to increased diagnostic sensitivity, including new evidence supporting the presence of two sympatric species: P. ovale curtisi (Poc) and P. ovale wallikeri (Pow). The increased reports and evolution of P. ovale subspecies are concerning for sub-Saharan Africa where the greatest burden of malaria is borne. Employing published sequence data, we set out to decipher the genetic diversity and phylogenetic relatedness of P. ovale curtisi and P. ovale wallikeri using the tryptophan-rich protein and small subunit ribosomal RNA genes from Gabon, Senegal, Ethiopia and Kenya. Higher number of segregating sites were recorded in Poc isolates from Gabon than from Ethiopia, with a similar trend in the number of haplotypes. With regards to Pow, the number of segregating sites and haplotypes from Ethiopia were higher than from those in Gabon. Poc from Kenya, had higher segregating sites (20), and haplotypes (4) than isolates from Senegal (8 and 3 respectively), while nucleotide from Senegal were more diverse (θw = 0.02159; π = 0.02159) than those from Kenya (θw = 0.01452; π = 0.01583). Phylogenetic tree construction reveal two large clades with Poc from Gabon and Ethiopia, and distinct Gabonese and Ethiopian clades on opposite ends. A similar observation was recorded for the phylogeny of Poc isolates from Kenya and Senegal. With such results, there is a high potential that ovale malaria control measures deployed in one country may be effective in the other since parasite from both countries show some degree of relatedness. How this translates to malaria control efforts throughout the continent would be next step deserving more studies.

Nationwide Surveillance of Pfhrp2 Exon 2 Diversity in Plasmodium falciparum Circulating in Symptomatic Malaria Patients Living in Ghana

Reports of increasing false-negative HRP2-based rapid diagnostic test results across Africa require constant monitoring of factors associated with these false-negative outcomes, as failure of this diagnostic tool will have severe consequences on malaria treatment and control programs. This study characterized the extent of genetic diversity in the Plasmodium falciparum histidine-rich protein 2 (Pfhrp2) gene in P. falciparum isolates from symptomatic malaria patients across the regions of Ghana. Exon 2 of Pfhrp2 was amplified from gDNA using polymerase chain reaction. All Pfhrp2-negative samples were subjected to Pf18S rRNA and Pfmsp2 gene amplifications. The amplified Pfhrp2 exon 2 fragments from clonal samples were sent for commercial Sanger sequencing. The type and number of PfHRP2 repeats, classified based on repeat types previously reported, were estimated from the sequence data and compared among geographical regions. About 81% (2,333/2,890) of the original microscopy positive DBS were available and used in this study. The Pfhrp2 exon 2 amplification was successful in 98.5% (2,297/2,333) of the tested samples, with band size ranging from 400 bp to 1,050 bp. A total of 13 out of the 24 previously reported repeat types were identified among the samples, with three samples lacking both type 2 and type 7 repeat motifs. This study suggested that the genetic diversity of Pfhrp2 exon 2 identified in P. falciparum circulating in symptomatic malaria patients in Ghana is unlikely to influence the sensitivity and specificity of HRP2 RDT-based diagnosis.

Prevalence and risk of Plasmodium vivax infection among Duffy-negative individuals: a systematic review and meta-analysis

A better understanding of the occurrence and risk of Plasmodium vivax infection among Duffy-negative individuals is required to guide further research on these infections across Africa. To address this, we used a meta-analysis approach to investigate the prevalence of P. vivax infection among Duffy-negative individuals and assessed the risk of infection in these individuals when compared with Duffy-positive individuals. This study was registered with The International Prospective Register of Systematic Reviews website (ID: CRD42021240202) and followed Preferred Reporting Items for Systematic review and Meta-Analyses guidelines. Literature searches were conducted using medical subject headings to retrieve relevant studies in Medline, Web of Science, and Scopus, from February 22, 2021 to January 31, 2022. Selected studies were methodologically evaluated using the Joanna Briggs Institute (JBI) Critical Appraisal Tools to assess the quality of cross-sectional, case–control, and cohort studies. The pooled prevalence of P. vivax infection among Duffy-negative individuals and the odds ratio (OR) of infection among these individuals when compared with Duffy-positive individuals was estimated using a random-effects model. Results from individual studies were represented in forest plots. Heterogeneity among studies was assessed using Cochrane Q and I² statistics. We also performed subgroup analysis of patient demographics and other relevant variables. Publication bias among studies was assessed using funnel plot asymmetry and the Egger’s test. Of 1593 retrieved articles, 27 met eligibility criteria and were included for analysis. Of these, 24 (88.9%) reported P. vivax infection among Duffy-negative individuals in Africa, including Cameroon, Ethiopia, Sudan, Botswana, Nigeria, Madagascar, Angola, Benin, Kenya, Mali, Mauritania, Democratic Republic of the Congo, and Senegal; while three reported occurrences in South America (Brazil) and Asia (Iran). Among studies, 11 reported that all P. vivax infection cases occurred in Duffy-negative individuals (100%). Also, a meta-analysis on 14 studies showed that the pooled prevalence of P. vivax infection among Duffy-negative individuals was 25% (95% confidence interval (CI) − 3%–53%, I² = 99.96%). A meta-analysis of 11 studies demonstrated a decreased odds of P. vivax infection among Duffy-negative individuals (p = 0.009, pooled OR 0.46, 95% CI 0.26–0.82, I² = 80.8%). We confirmed that P. vivax infected Duffy-negative individuals over a wide prevalence range from 0 to 100% depending on geographical area. Future investigations on P. vivax infection in these individuals must determine if Duffy-negativity remains a protective factor for P. vivax infection.

Molecular mechanisms of hematological and biochemical alterations in malaria: A review

Malaria is a dangerous disease that contributes to millions of hospital visits and hundreds of thousands of deaths, especially in children residing in sub-Saharan Africa. Although several interventions such as vector control, case detection, and treatment are already in place, there is no substantive reduction in the disease burden. Several studies in the past have reported the emergence of resistant strains of malaria parasites (MPs) and mosquitoes, and poor adherence and inaccessibility to effective antimalarial drugs as the major factors for this persistent menace of malaria infections. Moreover, victory against MP infections for many years has been hampered by an incomplete understanding of the complex nature of malaria pathogenesis. Very recent studies have identified different complex interactions and hematological alterations induced by malaria parasites. However, no studies have hybridized these alterations for a better understanding of Malaria pathogenesis. Hence, this review thoroughly discusses the molecular mechanisms of all reported hematological and biochemical alterations induced by MPs infections. Specifically, the mechanisms in which MP-infection induces anemia, thrombocytopenia, leukopenia, dyslipidemia, hypoglycemia, oxidative stress, and liver and kidney malfunctions were presented. The study also discussed how MPs evade the host's immune response and suggested strategies to limit evasion of the host's immune response to combat malaria and its complications.

Towards malaria control in Nigeria: implications of the malaria parasite rate and spleen rate among children living in a rural community in southwest Nigeria

BACKGROUND

The World Health Organization prioritizes malaria surveillance for accurate tracking of progress of intervention programmes. The malaria parasite rate (PR) and spleen rate (SR) are economical surveillance tools. There has been a global decline in the burden of malaria over the last decade, but most African countries, like Nigeria, have a slow rate of decline. There is a need for adequate malaria surveillance to guide malaria control strategies and policymaking.

METHODS

A community-based cross-sectional study was conducted among 363 children ages 1-15 y in rural southwest Nigeria. The participants' PR was determined by microscopy and the SR was determined by palpation and ultrasonography. The associations between PR and SR and other covariates were assessed.

RESULTS

The PR was 26.7% and the SR was 12.9%. There was no significant association between PR or SR across age groups, but low social class was significantly associated with PR (55 [33.5%], p=0.004) and SR (29 [17.3%], p=0.013). The odds of having splenomegaly doubled with malaria parasitaemia (odds ratio 2.03 [95% confidence interval 1.06 to 3.88).

CONCLUSIONS

The PR and SR suggest that the study area is meso-endemic. The PR in the study area was almost equal across age groups; our findings suggest there may be a need for policy review to plan malaria intervention programmes and include older children, not just children <5 y of age. Routine malaria surveillance using simple tools such as the PR and SR are necessary for reviewing malaria control programmes in the community.

Molecular Identification and Characterization of Plasmodium ovale curtisi in Field Isolates from Symptomatic Children in North-Central Nigeria

PURPOSE

Plasmodium ovale is not usually the focus of most malaria research or intervention programmes and has lately been termed the neglected human malaria parasites. The parasite exists as two genetically distinct sympatric species namely P. ovale curtisi and P. ovale wallikeri but information on the distribution of P. ovale sub-species is lacking in Nigeria. The objective of this study, therefore, was aimed at characterizing the P. ovale sub-species in isolates from symptomatic individuals in North-central Nigeria.

METHODS

Parasites were identified by light microscopy of Giemsa stained thick and thin blood films. Molecular characterization and confirmation of P. ovale sub-species were done by species-specific nested PCR and sequencing of the small subunit ribosomal RNA (SSUrRNA) gene.

RESULTS

A total of 412 children were enrolled into this study of which 88.6% (n = 365) were positive for Plasmodium species by nested PCR and P. falciparum was predominant. Of the 365 isolates, 4 (1.1%) had P. ovale infections and of these, 3 (0.8%) were mixed species infections of P. ovale with P. falciparum. DNA sequence analysis confirmed that all the four P. ovale parasites were P. ovale curtisi as their sequences were 99-100% identical to previously published P. ovale curtisi sequences in the GenBank and they cluster with the P. ovale curtisi sequences by phylogeny.

CONCLUSION

Our findings demonstrate the occurrence of P. ovale curtisi in the study area. This has implications for public health and malaria elimination programmes, since they also serve as potential risk to travellers from malaria-free regions.

Survey of ethnobotanical cocktails commonly used in the treatment of malaria in southwestern Nigeria

Background

Combination of different antimalarials has become the popular method of care for malaria morbidity in conventional and traditional treatment approaches due to the need to increase the efficacy and reduce the selection of drug resistance. A worrisome concern is the critical gaps with regards to the information available on antimalarial herbal cocktails. This study presents cocktail herbal remedies in ethnomedicinal approaches to malaria treatment in Oyo and Ogun states, South West Nigeria. Ethnobotanical information on indigenous antimalarials used in combination remedies was collected from herbal practitioners using a semi-structured questionnaire.

Results

Findings showed majority of respondents treat malaria with combination herbal remedies. They sighted their beliefs and customs, the efficacy, affordability and availability of these herbs as reasons for their adoption of herbal medicines as their preferred mode of treating malaria. Enquiry revealed 26 sets of cocktail antimalarials from a variety of plant species. The plants and ingredients are extracted and used as decoction, infusion or steam baths. Oral route was the most popular mode of administration. Respondents reported they drink one to two medium-sized cups of the recipe on an average of two times daily within a duration of about 10 days.

Conclusions

Herbal antimalarial remedies continue to be the popular treatments option in our localities. This study provides knowledge of the diverse ways respondents combine medicinal herbs and other local ingredients for malaria treatment. Pharmacological screening is urgently needed to validate their safety and efficacy in order to protect the health of our locals heavily relying on them to combat high burdens of malaria.

The Pan African Vivax and Ovale Network (PAVON): Refocusing on Plasmodium vivax, ovale and asymptomatic malaria in sub-Saharan Africa

The recent World Malaria report shows that progress in malaria elimination has stalled. Current data acquisition by NMCPs depend on passive case detection and clinical reports focused mainly on Plasmodium falciparum (Pf). In recent times, several countries in sub-Saharan Africa have reported cases of Plasmodium vivax (Pv) with a considerable number being Duffy negative. The burden of Pv and Plasmodium ovale (Po) appear to be more than acknowledged. Similarly, the contribution of asymptomatic malaria in transmission is hardly considered by NMCPs in Africa. Inclusion of these as targets in malaria elimination agenda is necessary to achieve elimination goal, as these harbor hypnozoites. The Pan African Vivax and Ovale Network (PAVON) is a new consortium of African Scientists working in Africa on the transmission profile of Pv and Po. The group collaborates with African NMCPs to train in Plasmodium molecular diagnostics, microscopy, and interpretation of molecular data from active surveys to translate into policy. Details of the mission, rational and modus operandi of the group are outlined.

Comparative analysis of four malaria diagnostic tools and implications for malaria treatment in southwestern Nigeria

OBJECTIVES

One of the problems encountered in malaria control and elimination is inaccurate diagnosis, resulting from the degree of sensitivity of the different malaria diagnostic tools. Even though microscopy remains the gold standard for malaria diagnosis, more sensitive and robust diagnostic tools such as polymerase chain reactions (PCR) are used in research settings to monitor interventions and track sub-microscopic infections due to some of the drawbacks of microscopy. Since diagnosis is a critical determinant for rational malaria treatment, it is imperative that accurate diagnosis must be assured for an effective treatment plan. Therefore, this study compared two routinely used point of care malaria diagnostic tools with two molecular tools and discussed their implication for malaria treatment.

DESIGN

In this study, 436 individuals with suspected malaria were sampled and systematically tested using four methods, namely rapid diagnostic test (henceforth referred to as malaria RDT- mRDT), microscopy, nested PCR (nPCR), and quantitative PCR (qPCR). Test sensitivities and specificities were compared, and their level of concordance was determined.

RESULTS

With nPCR as the gold standard, a false positivity rate of 42.2%, 8.9%, and 57.8% was obtained for mRDT, microscopy, and qPCR. Similarly, false negativity rates of 12.5%, 62.5%, and 0.8% were obtained for each of the methods mentioned above, respectively. Of all the tools assessed, qPCR gave the highest sensitivity (99.2%) and moderate specificity (42.2%), followed by the mRDT kit used (87.5%).

CONCLUSIONS

With the detection of a high false positivity rate based on mRDT and a substantial proportion of sub-microscopic carriers in this study area by nested/quantitative PCR, we recommend that these molecular tools should be in specialized laboratories within the region to (i) track and treat sub-microscopic carriers to prevent their contribution to malaria transmission; (ii) provide reliable epidemiological data using high throughput testing tools for evaluating malaria interventions.

Epidemiological and entomological studies of malaria transmission in Tibati, Adamawa region of Cameroon 6 years following the introduction of long-lasting insecticide nets

BACKGROUND

Malaria remains a serious public health problem in Cameroon. Implementation of control interventions requires prior knowledge of the local epidemiological situation. Here we report the results of epidemiological and entomological surveys carried out in Tibati, Adamawa Region, Cameroon, an area where malaria transmission is seasonal, 6 years after the introduction of long-lasting insecticidal bed nets.

METHODS

Cross-sectional studies were carried out in July 2015 and 2017 in Tibati. Thick blood smears and dried blood spots were collected from asymptomatic and symptomatic individuals in the community and at health centers, respectively, and used for the molecular diagnosis of Plasmodium species. Adult mosquitoes were collected by indoor residual spraying and identified morphologically and molecularly. The infection status of Plasmodium spp. was determined by quantitative PCR, and positivity of PCR-positive samples was confirmed by Sanger sequencing.

RESULTS

Overall malaria prevalence in our study population was 55.0% (752/1367) and Plasmodium falciparum was the most prevalent parasite species (94.3%), followed by P. malariae (17.7%) and P. ovale (0.8%); 92 (12.7%) infections were mixed infections. Infection parameters varied according to clinical status (symptomatic/asymptomatic) and age of the sampled population and the collection sites. Infection prevalence was higher in asymptomatic carriers (60.8%), but asexual and sexual parasite densities were lower. Prevalence and intensity of infection decreased with age in both the symptomatic and asymptomatic groups. Heterogeneity in infections was observed at the neighborhood level, revealing hotspots of transmission. Among the 592 Anopheles mosquitoes collected, 212 (35.8%) were An. gambiae, 172 (29.1%) were An. coluzzii and 208 (35.1%) were An. funestus (s.s.). A total of 26 (4.39%) mosquito specimens were infected by Plasmodium sp. and the three Anopheles mosquitoes transmitted Plasmodium at equal efficiency. Surprisingly, we found an An. coluzzii specimen infected by Plasmodium vivax, which confirms circulation of this species in Cameroon. The positivity of all 26 PCR-positive Plasmodium-infected mosquitoes was successively confirmed by sequencing analysis.

CONCLUSION

Our study presents the baseline malaria parasite burden in Tibati, Adamawa Region, Cameroon. Our results highlight the high malaria endemicity in the area, and hotspots of disease transmission are identified. Parasitological indices suggest low bednet usage and that implementation of control interventions in the area is needed to reduce malaria burden. We also report for the first time a mosquito vector with naturally acquired P. vivax infection in Cameroon.

Comparison of capillary and venous blood for malaria detection using two PCR-based assays in febrile patients in Sierra Leone

Background

Rapid and sensitive diagnostics are critical tools for clinical case management and public health control efforts. Both capillary and venous blood are currently used for malaria detection and while diagnostic technologies may not be equally sensitive with both materials, the published data on this subject are scarce and not conclusive.

Methods

Paired clinical samples of venous and capillary blood from 141 febrile individuals in Bo, Sierra Leone, were obtained between January and May 2019 and tested for the presence of Plasmodium parasites using two multiplexed PCR assays: the FilmArray-based Global Fever Panel (GFP) and the TaqMan-based Malaria Multiplex Sample Ready (MMSR) assay.

Results

No significant differences in Plasmodium parasite detection between capillary and venous blood for both assays were observed. The GFP assay was more sensitive than MMSR for all markers that could be compared (Plasmodium spp. and Plasmodium falciparum) in both venous and capillary blood.

Conclusions

No difference was found in malaria detection between venous and capillary blood using two different PCR-based detection assays. This data gives support for use of capillary blood, a material which can be obtained easier by less invasive methods, for PCR-based malaria diagnostics, independent of the platform.

High frequency of the Duffy-negative genotype and absence of Plasmodium vivax infections in Ghana

Background

Recent studies from different malaria-endemic regions including western Africa have now shown that Plasmodium vivax can infect red blood cells (RBCs) and cause clinical disease in Duffy-negative people, though the Duffy-negative phenotype was thought to confer complete refractoriness against blood invasion with P. vivax. The actual prevalence of P. vivax in local populations in Ghana is unknown and little information is available about the distribution of Duffy genotypes. The aim of this study was to assess the prevalence of P. vivax in both asymptomatic and symptomatic outpatients and the distribution of Duffy genotypes in Ghana.

Methods

DNA was extracted from dried blood spots (DBS) collected from 952 subjects (845 malaria patients and 107 asymptomatic persons) from nine locations in Ghana. Plasmodium species identification was carried out by nested polymerase chain reaction (PCR) amplification of the small-subunit (SSU) rRNA genes. For P. vivax detection, a second PCR of the central region of the Pvcsp gene was carried out. Duffy blood group genotyping was performed by allele-specific PCR to detect the presence of the FY^ES allele.

Results

No cases of P. vivax were detected in any of the samples by both PCR methods used. Majority of infections (542, 94.8%) in the malaria patient samples were due to P. falciparum with only 1 infection (0.0017%) due to Plasmodium malariae, and 2 infections (0.0034%) due to Plasmodium ovale. No case of mixed infection was identified. Of the samples tested for the FY^ES allele from all the sites, 90.5% (862/952) had the FY^ES allele. All positive samples were genotyped as FY*B-33/FY*B-33 (Duffy-negative homozygous) and therefore classified as Fy(a−b−).

Conclusions

No cases of P. vivax were detected by both PCRs and majority of the subjects tested carried the FY^ES allele. The lack of P. vivax infections observed can be attributed to the high frequency of the FY^ES allele that silences erythroid expression of the Duffy. These results provide insights on the host susceptibility for P. vivax infections that had not been investigated in Ghana before.

Plasmodium malariae, current knowledge and future research opportunities on a neglected malaria parasite species

Plasmodium malariae is often reported as a benign malaria parasite. There are limited data on its biology and disease burden in sub-Saharan Africa (sSA) possibly due to the unavailability of specific and affordable tools for routine diagnosis and large epidemiology studies. In addition, P. malariae occurs at low parasite densities and in co-infections with other species, predominately P. falciparum. The paucity of data on P. malariae infections limits the capacity to accurately determine its contribution to malaria and the effect of control interventions against P. falciparum on its prevalence. Here, we summarise the current knowledge on P. malariae epidemiology in sSA - overall prevalence ranging from 0-32%, as detected by different diagnostic methods; seroprevalence ranging from 0-56% in three countries (Mozambique, Benin and Zimbabwe), and explore the future application of next-generation sequencing technologies as a tool for enriching P. malariae genomic epidemiology. This will provide insights into important adaptive mechanisms of this neglected non-falciparum species, including antimalarial drug resistance, local and regional parasite transmission patterns and genomic signatures of selection. Improved diagnosis and genomic surveillance of non-falciparum malaria parasites in Africa would be helpful in evaluating progress towards elimination of all human Plasmodium species.

Allelic diversity of MSP1 and MSP2 repeat loci correlate with levels of malaria endemicity in Senegal and Nigerian populations

BACKGROUND

Characterizing the genetic diversity of malaria parasite populations in different endemic settings (from low to high) could be helpful in determining the effectiveness of malaria interventions. This study compared Plasmodium falciparum parasite population diversity from two sites with low (pre-elimination) and high transmission in Senegal and Nigeria, respectively.

METHODS

Parasite genomic DNA was extracted from 187 dried blood spot collected from confirmed uncomplicated P. falciparum malaria infected patients in Senegal (94) and Nigeria (93). Allelic polymorphism at merozoite surface protein 1 (msp1) and merozoite surface protein- 2 (msp2) genes were assessed by nested PCR.

RESULTS

The most frequent msp1 and msp2 allelic families are the K1 and IC3D7 allelotypes in both Senegal and Nigeria. Multiplicity of infection (MOI) of greater that 1 and thus complex infections was common in both study sites in Senegal (Thies:1.51/2.53; Kedougou:2.2/2.0 for msp1/2) than in Nigeria (Gbagada: 1.39/1.96; Oredo: 1.35/1.75]). The heterozygosity of msp1 gene was higher in P. falciparum isolates from Senegal (Thies: 0.62; Kedougou: 0.53) than isolates from Nigeria (Gbagada: 0.55; Oredo: 0.50). In Senegal, K1 alleles was associated with heavy than with moderate parasite density. Meanwhile, equal proportions of K1 were observed in both heavy and moderate infection types in Nigeria. The IC3D7 subtype allele of the msp2 family was the most frequent in heavily parasitaemic individuals from both countries than in the moderately infected participants.

CONCLUSION

The unexpectedly low genetic diversity of infections high endemic Nigerian setting compared to the low endemic settings in Senegal is suggestive of possible epidemic outbreak in Nigeria.

DNA analysis reveals non-falciparum malaria in the Democratic Republic of the Congo

BACKGROUND

The World Health Organization (WHO) attributes the entirety of malaria infection and transmission in the Democratic Republic of the Congo (DRC) to Plasmodium falciparum, one of the several species of malaria known to infect humans. Recent studies have put forth some evidence that transmission of Plasmodium vivax may also be occurring in the DRC. As interventions and treatments differ between malaria species, it is crucial to maintain the most accurate understanding of malaria species diversity in each region.

METHODS

Blood samples were taken from aymptomatic children 0-5 years old living in three regions of the DRC in 2014. For this study, samples were taken from a larger pool of samples, collected as part of a population-based survey in three regions. Plasmodium infection was screened for using nested polymerase chain reaction (PCR) assays and species were confirmed by cloning and DNA sequencing.

RESULTS

Of 336 samples screened by PCR, 62.2% (n=209) initially tested positive for P. falciparum and 14.6% (n=49) initially tested positive for P. vivax. Sanger sequencing was performed on PCR-positive Plasmodium samples to confirm identity of Plasmodium species. Sequencing showed Plasmodium malariae in one blood sample and Plasmodium ovale in another sample. Plasmodium vivax was detected in 12/65 cases (18.5%). Overall, 14/65 sequenced cases (21.5%) were infected with a non-falciparum malaria. 330bp 18s P. vivax DNA sequences were obtained.

CONCLUSIONS

This study reveals Plasmodium vivax and other non-falciparum malaria across several regions of the DRC, and enforces the importance of further testing and more precise diagnostics when testing for and treating malaria in the DRC. Here, we find a higher proportion of cases of P. vivax malaria than found in previous studies. This is the most robust DNA sequencing of Plasmodium vivax in the DRC to date.

Seroprevalence and Parasite Rates of Plasmodium malariae in a High Malaria Transmission Setting of Southern Nigeria

Although Plasmodium falciparum continues to be the main target for malaria elimination, other Plasmodium species persist in Africa. Their clinical diagnosis is uncommon, whereas rapid diagnostic tests (RDTs), the most widely used malaria diagnostic tools, are only able to distinguish between P. falciparum and non-falciparum species, the latter as “pan-species.” Blood samples from health facilities were collected in southern Nigeria (Lagos and Calabar) in 2017 (October–December) and Calabar only in 2018 (October–November), and analyzed by several methods, namely, microscopy, quantitative real-time PCR (qPCR), and peptide serology targeting candidate antigens (Plasmodium malariae apical membrane antigen, P. malariae lactose dehydrogenase, and P. malariae circumsporozoite surface protein). Both microscopy and qPCR diagnostic approaches detected comparable proportions (∼80%) of all RDT-positive samples infected with the dominant P. falciparum malaria parasite. However, higher proportions of non-falciparum species were detected by qPCR than microscopy, 10% against 3% infections for P. malariae and 3% against 0% for Plasmodium ovale, respectively. No Plasmodium vivax infection was detected. Infection rates for P. malariae varied between age-groups, with the highest rates in individuals aged > 5 years. Plasmodium malariae–specific seroprevalence rates fluctuated in those aged < 10 years but generally reached the peak around 20 years of age for all peptides. The heterogeneity and rates of these non-falciparum species call for increased specific diagnosis and targeting by elimination strategies.

Large Variations in Malaria Parasite Carriage by Afebrile School Children Living in Nearby Communities in the Central Region of Ghana

Background

Indicators of successful malaria control interventions include a reduction in the prevalence and densities of malaria parasites contained in both symptomatic and asymptomatic infections as well as a reduction in malaria transmission. Individuals harboring malaria parasites in asymptomatic infections serve as reservoirs for malaria transmission. This study determined the prevalence of asymptomatic malaria parasite carriage in afebrile children attending six different schools in two districts, the Cape Coast Metropolitan Assembly (CCMA) and the Komenda Edina Eguafo Abirem (KEEA) of the Central Region of Ghana.

Methods

This cross sectional study recruited afebrile children aged between 3 and 15 years old from six randomly selected schools in the Central Region of Ghana. Finger-pricked blood was collected and used to prepare thick and thin blood smears as well as spot a strip of filter paper (Whatman #3). Nested PCR was used to identify Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale, and Plasmodium vivax in DNA extracted from the filter paper spots. The multiplicity of P. falciparum infection was determined using merozoite surface protein 2 genotyping.

Results

Out of the 528 children sampled, PCR identified 27.1% to harbor Plasmodium parasites in asymptomatic infections, whilst microscopy identified malaria parasites in 10.6% of the children. The overall PCR estimated prevalence of P. falciparum and P. malariae was 26.6% and 1.3%, respectively, with no P. ovale or P. vivax identified by PCR or microscopy. The RDT positivity rate ranged from 55.8% in Simiw to 4.5% in Kuful. Children from the Simiw Basic School accounted for 87.5% of all the asymptomatic infections. The multiplicity of P. falciparum infection was predominantly monoclonal and biclonal.

Conclusions

The low prevalence of asymptomatic malaria parasite carriage by the children living in the Cape Coast Metropolis suggests that the malaria control interventions in place in CCMA are highly effective and that additional malaria control interventions are required for the KEEA district to reduce the prevalence of asymptomatic malaria parasite carriers. No molecular evidence of P. ovale and P. vivax was identified in the afebrile children sampled from the selected schools.

Presence of additional Plasmodium vivax malaria in Duffy negative individuals from Southwestern Nigeria

Background

Malaria in sub-Saharan Africa (sSA) is thought to be mostly caused by Plasmodium falciparum. Recently, growing reports of cases due to Plasmodium ovale, Plasmodium malariae, and Plasmodium vivax have been increasingly observed to play a role in malaria epidemiology in sSA. This in fact is due to the usage of very sensitive diagnostic tools (e.g. PCR), which have highlighted the underestimation of non-falciparum malaria in this sub-region. Plasmodium vivax was historically thought to be absent in sSA due to the high prevalence of the Duffy negativity in individuals residing in this sub-continent. Recent studies reporting detection of vivax malaria in Duffy-negative individuals from Mali, Mauritania, Cameroon challenge this notion.

Methods

Following previous report of P. vivax in Duffy-negative individuals in Nigeria, samples were further collected and assessed RDT and/or microscopy. Thereafter, malaria positive samples were subjected to conventional PCR method and DNA sequencing to confirm both single/mixed infections as well as the Duffy status of the individuals.

Results

Amplification of Plasmodium gDNA was successful in 59.9% (145/242) of the evaluated isolates and as expected P. falciparum was the most predominant (91.7%) species identified. Interestingly, four P. vivax isolates were identified either as single (3) or mixed (one P. falciparum/P. vivax) infection. Sequencing results confirmed all vivax isolates as truly vivax malaria and the patient were of Duffy-negative genotype.

Conclusion

Identification of additional vivax isolates among Duffy-negative individuals from Nigeria, substantiate the expanding body of evidence on the ability of P. vivax to infect RBCs that do not express the DARC gene. Hence, such genetic-epidemiological study should be conducted at the country level in order to evaluate the true burden of P. vivax in Nigeria.

Use of real-time multiplex PCR, malaria rapid diagnostic test and microscopy to investigate the prevalence of Plasmodium species among febrile hospital patients in Sierra Leone

Background

Malaria continues to affect over 200 million individuals every year, especially children in Africa. Rapid and sensitive detection and identification of Plasmodium parasites is crucial for treating patients and monitoring of control efforts. Compared to traditional diagnostic methods such as microscopy and rapid diagnostic tests (RDTs), DNA based methods, such as polymerase chain reaction (PCR) offer significantly higher sensitivity, definitive discrimination of Plasmodium species, and detection of mixed infections. While PCR is not currently optimized for routine diagnostics, its role in epidemiological studies is increasing as the world moves closer toward regional and eventually global malaria elimination. This study demonstrates the field use of a novel, ambient temperature-stabilized, multiplexed PCR assay in a small hospital setting in Sierra Leone.

Methods

Blood samples from 534 febrile individuals reporting to a hospital in Bo, Sierra Leone, were tested using three methods: a commercial RDT, microscopy, and a Multiplex Malaria Sample Ready (MMSR) PCR designed to detect a universal malaria marker and species-specific markers for Plasmodium falciparum and Plasmodium vivax. A separate PCR assay was used to identify species of Plasmodium in samples in which MMSR detected malaria, but was unable to identify the species.

Results

MMSR detected the presence of any malaria marker in 50.2% of all tested samples with P. falciparum identified in 48.7% of the samples. Plasmodium vivax was not detected. Testing of MMSR P. falciparum-negative/universal malaria-positive specimens with a panel of species-specific PCRs revealed the presence of Plasmodium malariae (n = 2) and Plasmodium ovale (n = 2). The commercial RDT detected P. falciparum in 24.6% of all samples while microscopy was able to detect malaria in 12.8% of tested specimens.

Conclusions

Wider application of PCR for detection of malaria parasites may help to fill gaps existing as a result of use of microscopy and RDTs. Due to its high sensitivity and specificity, species coverage, room temperature stability and relative low complexity, the MMSR assay may be useful for detection of malaria and epidemiological studies especially in low-resource settings.

Molecular epidemiology of malaria parasite amongst patients in a displaced people's camp in Sudan

BACKGROUND

Despite the importance of epidemiological studies in the development of effective control strategies and provision of basic health services for refugees and internally displaced persons (IDPs), data on the prevalence of malaria are limited. Thus, this study was conducted to estimate the molecular prevalence of malaria amongst the displaced population in Ardamata IDP camp in Al-Geneina City, Sudan.

METHODS

A cross-sectional study was conducted from July 2018 to December 2018 to estimate malaria prevalence amongst the displaced population in Ardamata IDP camp in Al-Geneina City, Sudan. A total of 380 patients with suspected malaria were recruited. Nested polymerase chain reaction (nPCR) assays were performed to detect the Plasmodium genus and species.

RESULTS

Of 380 patients, 232 (61.1%) were positive for malaria. Plasmodium falciparum was the only prevalent species detected amongst the study population. nPCR analysis revealed that none of the samples had Plasmodium vivax, Plasmodium ovale or Plasmodium malariae. The malaria prevalence rate was higher amongst males (67.1%) than in females (56.8%), and gender was the only risk factor that was significantly associated with malaria infection (p = .042).

CONCLUSIONS

Despite control programmes, malaria remains a significant cause of illness amongst a displaced population. The high prevalence of malaria infection in this study indicates that additional health facilities and control strategies should be implemented in displaced camps and the surrounding areas.

Probing the composition of Plasmodium species contained in malaria infections in the Eastern region of Ghana

BACKGROUND

Asymptomatic falciparum and non-falciparum malaria infections are major challenges to malaria control interventions, as they remain a source of continual infection in the community. This becomes even more important as the debate moves towards elimination and eradication. This study sought to quantify the burden of Plasmodium malaria infection in seven communities in the Eastern Region of Ghana.

METHODS

The cross-sectional study recruited 729 participants aged 85 years old and below from 7 closely linked communities. Finger pricked blood was used to prepare thick and thin blood smears as well as spot filter paper and an histidine rich protein 2 (HRP2) rapid diagnostic test kit (RDT). Genomic DNA was extracted from the filter paper dry blood spot (DBS) and used in PCR to amplify the Plasmodium 18S rRNA gene using species specific PCR.

RESULTS

96.6% of the participants were identified as afebrile, with axillary temperatures below 37.5 °C. PCR identified 66% of the participants to harbor malaria parasites, with 9 P. malariae and 7 P. ovale mono-infections accounting for 2.2% and P. falciparum combined with either 36 P. malariae or 25 P. ovale infections, accounting for 13.3%. Parasite prevalence by microscopy (32%) was similar to the RDT positivity rate (33%). False positive RDT results ranged from 64.6% in children aged between 5 and 9 years to 10% in adults aged 20 years and above. No significant differences were observed in falciparum and non-falciparum parasite carriage at the community level, however young adults aged between 15 and 19 years had the highest prevalence (34.8% (16/46)) of P. falciparum and P. malariae parasite carriage whilst children aged between 5 and 9 years had the highest level (11.4% (14/123)) of P. ovale carriage.

CONCLUSION

The high rate of misidentification of non-falciparum parasites and the total absence of detection of P. ovale by microscopy suggests that more sensitive malaria diagnostic tools including molecular assays are required to accurately determine the prevalence of carriers of non-falciparum parasites and low density P. falciparum infections, especially during national surveillance exercises. Additionally, malaria control interventions targeting the non-falciparum species P. malariae and P. ovale parasites are needed.

Genetic diversity, natural selection and haplotype grouping of Plasmodium vivax Duffy-binding protein genes from eastern and western Myanmar borders

Background

Merozoite proteins of the malaria parasites involved in the invasion of red blood cells are selected by host immunity and their diversity is greatly influenced by changes in malaria epidemiology. In the Greater Mekong Subregion (GMS), malaria transmission is concentrated along the international borders and there have been major changes in malaria epidemiology with Plasmodium vivax becoming the dominant species in many regions. Here, we aimed to evaluate the genetic diversity of P. vivax Duffy-binding protein gene domain II (pvdbp-II) in isolates from the eastern and western borders of Myanmar, and compared it with that from global P. vivax populations.

Methods

pvdbp-II sequences were obtained from 85 and 82 clinical P. vivax isolates from the eastern and western Myanmar borders, respectively. In addition, 504 pvdbp-II sequences from nine P. vivax populations of the world were retrieved from GenBank and used for comparative analysis of genetic diversity, recombination and population structure of the parasite population.

Results

The nucleotide diversity of the pvdbp-II sequences from the Myanmar border parasite isolates was not uniform, with the highest diversity located between nucleotides 1078 and 1332. Western Myanmar isolates had a unique R391C mutation. Evidence of positive natural selection was detected in pvdbp-II gene in P. vivax isolates from the eastern Myanmar area. P. vivax parasite populations in the GMS, including those from the eastern, western, and central Myanmar as well as Thailand showed low-level genetic differentiation (F_ST, 0.000–0.099). Population genetic structure analysis of the pvdbp-II sequences showed a division of the GMS populations into four genetic clusters. A total of 60 PvDBP-II haplotypes were identified in 210 sequences from the GMS populations. Among the epitopes in PvDBP-II, high genetic diversity was found in epitopes 45 (379-SIFGT(D/G)(E/K)(K/N)AQQ(R/H)(R/C)KQ-393, π = 0.029) and Ia (416-G(N/K)F(I/M)WICK(L/I)-424], Ib [482-KSYD(Q/E)WITR-490, π = 0.028) in P. vivax populations from the eastern and western borders of Myanmar.

Conclusions

The pvdbp-II gene is genetically diverse in the eastern and western Myanmar border P. vivax populations. Positive natural selection and recombination occurred in pvdbp-II gene. Low-level genetic differentiation was identified, suggesting extensive gene flow of the P. vivax populations in the GMS. These results can help understand the evolution of the P. vivax populations in the course of regional malaria elimination and guide the design of PvDBP-II-based vaccine.