Caso importado de malaria por Plasmodium vivax en El Salvador. Un abordaje epidemiológico / Imported Case of Malaria by Plasmodium vivax in El Salvador. An Epidemiological Approach

Presentación del caso. Paciente masculino de origen guatemalteco con historia de fiebre alta de tipo intermitente, mialgias, artralgias, debilidad generalizada, mareo y vómito de contenido gástrico. Fue tratado inicialmente en un hospital privado con diagnóstico de síndrome febril agudo y referido a un hospital de la red nacional con diagnóstico de dengue con signos de alarma, al tercer día de estancia hospitalaria se diagnostica como un caso de malaria importado por Plasmodium vivax. Intervención terapéutica. Se le dio tratamiento antimalárico con cloroquina y primaquina. Evolución clínica. Presentó mejoría clínica y las pruebas de laboratorio de control reportaron resultados negativos para Plasmodium vivax

Case presentation. Male patient of Guatemalan origin with history of intermittent high fever, myalgia, arthralgia, generalized weakness, dizziness, and vomiting of gastric contents. He was initially treated in a private hospital with a diagnosis of acute febrile illness and referred to a national network hospital with a diagnosis of dengue with warning signs. On the third day of hospital stay a diagnosis of an imported malaria case by Plasmodium vivax was presented. Treatment. The patient was given antimalarial treatment consisting of chloroquine and primaquine. Outcome. The patient presented clinical improvement, and control laboratory tests were negative for Plasmodium vivax.

Characterisation of the merozoite thrombospondin related anonymous protein (MTRAP) of Plasmodium berghei as a transmission-blocking antigen

BACKGROUND Malaria is an infectious disease caused by protozoan parasites belonging to the genus Plasmodium. Human-to-human transmission depends on a mosquito vector; thus, the interruption of parasite transmission from humans to mosquitoes is an important approach in the fight against malaria. The parasite stages infectious to mosquitoes are the gametocytes, sexual stages that are ingested by the vector during a blood meal and transform into male and female gametes in the midgut. Immunity against sexual stage antigens expressed by gametocytes, gametes, and the zygote formed after fertilisation can interrupt the parasite sexual cycle in the mosquito. This transmission blocking immunity is mediated by specific antibodies ingested during the mosquito blood feed, inhibiting the parasite development in the midgut. Merozoite thrombospondin related anonymous protein (MTRAP) is a merozoite and gametocyte surface protein essential for gamete egress from erythrocytes and for parasite transmission to mosquitoes. OBJECTIVES Here, we evaluated the potential of the P. berghei MTRAP to elicit antibodies with the ability to inhibit gamete fertilisation in vitro. METHODS We expressed a soluble recombinant PbMTRAP and used it to immunise BALB/c mice. The transmission blocking activity of the anti-rPbMTRAP antibodies was tested through in vivo challenge experiments followed by in vitro conversion assays. FINDINGS Immunisations with the rPbMTRAP induced a strong antibody response and the antibodies recognised the native protein by Western Blot and IFA. Anti-rPbMTRAP present in the blood stream of immunised mice partially inhibited gamete conversion into ookinetes. CONCLUSION Our results indicate that antibodies to PbMTRAP may reduce but are not sufficient to completely block transmission.

Caracterización molecular del dominio de la hélice del gen k13 de Plasmodium falciparum en muestras de comunidades nativas de Condorcanqui, Amazonas, Perú / Molecular characterization of the Plasmodium falciparum k13 gene helix domain in samples from native communities of Condorcanqui, Amazonas, Perú

Introducción. La resistencia de Plasmodium falciparum a diferentes fármacos antipalúdicos es un obstáculo para eliminar la enfermedad. El genotipo resistente de P. falciparum a la artemisinina puede evaluarse examinando los polimorfismos en el dominio de la hélice del gen Pfk13. La Organización Mundial de la Salud recomienda utilizar estas mutaciones como marcadores moleculares para detectar la resistencia a la artemisinina en países donde la malaria por P. falciparum es endémica. Objetivo. Identificar mutaciones relacionadas con la resistencia a artemisinina presentes en el dominio de la hélice del gen k13 de P. falciparum. Materiales y métodos. Mediante la detección pasiva de casos, se recolectaron 51 muestras positivas por microscopía para Plasmodium, provenientes de seis comunidades del distrito de Río Santiago en Condorcanqui, Amazonas. Se realizó la confirmación molecular de la especie mediante PCR en tiempo real y el dominio de la hélice del gen Pfk13 se amplificó y secuenció por electroforesis capilar. Las secuencias obtenidas se compararon con la cepa de referencia 3D7 de fenotipo silvestre. Resultados. Se confirmó un total de 51 muestras positivas para P. falciparum, provenientes de las comunidades de Ayambis, Chapiza, Palometa, Muchinguis, Alianza Progreso y Caterpiza. Después del alineamiento de las secuencias de ADN, se determinó que las muestras no presentaron mutaciones asociadas con resistencia en el gen K13. Discusión. Los resultados obtenidos son coherentes con estudios similares realizados en otros países de Sudamérica, incluyendo Perú. Estos datos proporcionan una línea base para la vigilancia molecular de resistencia a artemisinina en la región Amazonas y refuerzan la eficacia de la terapia combinada con artemisinina en esta área.

Introduction. Resistance of Plasmodium falciparum to different antimalarial drugs is an obstacle to disease elimination. The artemisinin-resistant genotype of P. falciparum can be assessed by examining polymorphisms in the helix domain of the Pfk13 gene. The World Health Organization recommends these mutations as molecular markers to detect artemisinin-resistant in countries where P. falciparum malaria is endemic. Objective. To identify artemisinin resistance-related mutations present in the helix domain of the P. falciparum k13 gene. Materials and methods. We collected a total of 51 samples through passive case detection, positive for Plasmodium by microscopy, from six communities in the district of Río Santiago in Condorcanqui, Amazonas. Molecular species confirmation was performed by real-time PCR and Pfk13 helix domain was amplified and sequenced by capillary electrophoresis. The obtained sequences were compared with the wild type 3D7 reference strain. Results. A total of 51 positive samples were confirmed for P. falciparum from the communities of Ayambis, Chapiza, Palometa, Muchinguis, Alianza Progreso and Caterpiza. DNA sequences alignment showed the absence of resistance-associated mutations in the k13 gene of the collected samples. Discussion. The obtained results are consistent with similar studies conducted in other South American countries, including Perú, so these data provide a baseline for artemisinin- resistance molecular surveillance in the Amazon region and reinforce the efficacy of artemisinin-based combination therapy in this area.

Perfil de notificações de malária em gestantes de Oiapoque, Amapá / Profile of malaria reports in pregnant women from Oiapoque, Amapá / Perfil de notificaciones de malaria en gestantes de Oiapoque, Amapá

Objetivo: caracterizar as notificações de malária em gestantes no município de Oiapoque. Método: estudo documental, descritivo, retrospectivo e com abordagem quantitativa, realizado a partir de dados secundários do Sistema de Vigilância Epidemiológica da Malária em Oiapoque-Amapá, Brasil, no período de 2013 a 2017. Abordam-se as seguintes variáveis de casos autóctones de malária em gestantes: ano, mês de ocorrência, idade gestacional, espécie infectante de Plasmodium e unidade de notificação. Os dados foram apresentados e analisados mediante estatística descritiva e formulação de mapas de distribuição espacial, gerados pelo software ArcGIS. Resultados: predominaram notificações em áreas urbanas, especialmente no bairro Paraíso (74%), sendo o Plasmodium vivax o principal agente (88%), e de maior incidência entre outubro a dezembro (33%), no terceiro trimestre gestacional (35%). Conclusão: o perfil de notificações de malária em gestante desse munícipio assemelha-se a estudos anteriores nessa região quanto ao local de concentração e período de maior ocorrência. No entanto, a introdução gradativa do protozoário Plasmodium falciparum traz um alerta para a mobilização de gestores e profissionais.

Objective: to characterize the notifications of malaria in pregnant women in the municipality of Oiapoque. Method: documentary, descriptive, retrospective and quantitative study, conducted from secondary data of the Epidemiological Surveillance System of Malaria in Oiapoque-Amapá, Brazil, from 2013 to 2017. The following variables of autochthonous cases of malaria in pregnant women are addressed: year, month of occurrence, gestational age, Plasmodium infecting species and notification unit. Data were presented and analyzed using descriptive statistics and formulation of spatial distribution maps, generated by ArcGIS software. Results: notifications predominated in urban areas, especially in the Paraíso neighborhood (74%), with Plasmodium Vivax being the main agent (88%), and with a higher incidence between October and December (33%), in the third gestational quarter (35%). Conclusion: the profile of reports of malaria in pregnant women of this municipality resembles previous studies in this region, regarding the place of concentration and period of greater occurrence. However, the gradual introduction of the protozoan Plasmodium falciparum brings an alert to the mobilization of managers and professionals.

Detection and species determination of malaria parasites by microscopy, antigen detection, polymerase chain reaction, and loop-mediated isothermal amplification assay in a tertiary care hospital

Background: Malaria is a major health issue in tropical and subtropical areas. Out of all subtypes, Plasmodium falciparum (Pf) is the most dangerous form accounting for high mortality and morbidity. It is transmitted by infected female anopheles mosquitoes and infected blood transfusions. Aims and Objectives: The aim of the study is to establish correct diagnosis by direct microscopy, Immunochromatographic test (ICT), and molecular studies. Materials and Methods: This prospective study was conducted in the PG Department of Microbiology, SCB Medical College, Cuttack. Thick blood smears were drawn and then stained with Leishman’s stain to visualize falciparum rings. DNA was extracted from infected blood samples by phenol chloroform method with some modification as described by Sambrook and Russel for molecular analysis. Results: In the present study, 150 cases of malaria were analyzed. The male: female ratio was 1.7:1 and age ranged from 0 to 56 years. The Plasmodium vivax positivity was compared with thin smear to 21 (84%) in ICT, 100% both polymerase chain reaction (PCR) and loop mediated isothermal amplification assay (LAMP) assays followed by the Pf positivity as 76 (92.7%) in ICT, 82 (100%) both PCR and LAMP assays, respectively. The results obtained were statistically significant with P < 0.001. The PCR and LAMP showed 100% response to specificity and positive predictive value. Conclusion: The present study established the role of molecular tests such as PCR and LAMP are highly specific for diagnosis of Plasmodium species whereas they are more or less similar in sensitivity as compared to other diagnostic methods such as ICT and microscopy.

Molecular detection of drug-resistant Plasmodium falciparum mutants in Assam

Background & objectives: The spread of drug-resistant Plasmodium falciparum ( Pf) poses a serious threat to the control and elimination of malaria. The objective of this study was to detect the molecular biomarkers of antimalarial drug resistance in Pf in patients visiting a tertiary care hospital in Assam. Methods: Malaria was first detected in fever cases using microscopy and a rapid diagnostic test (RDT), and then confirmed using PCR. Pf chloroquine resistance transporter (Pfcrt), Pf multidrug resistance-1 (Pfmdr-1), and single-nucleotide polymorphisms linked to delayed parasite clearance after treatment with artemisinin MAL 10-688956 and MAL 13-1718319 and Kelch-13 propeller (PfK-13) genes were evaluated by PCR-restriction fragment length polymorphism (RFLP). Results: Sixty nine cases of malaria were found among 300 cases of fever. Of these, 54 were positive for Pf, 47 of which were confirmed by PCR. Pfcrt-K76T mutation was seen in 96.6 per cent and Pfmdr1-N86Y mutation in 84.2 per cent of cases. Mutation was not detected in MAL10 and MAL13 genes. Sequence analysis of Kelch-13 gene showed the presence of a novel mutation at amino acid position 675. Statistically, no significant association was found between the molecular biomarkers and demographic profile, clinical presentation and outcome of the cases. Interpretation & conclusions: Molecular surveillance is essential to assess the therapeutic efficacy of the drugs against circulating Pf isolates in Assam which are found to be highly resistant to CQ. The role of the new mutation found in the Kelch-13 gene in the development of artemisinin resistance in Assam needs to be thoroughly monitored in future research.

Quality assurance of malaria rapid diagnostic tests: An aid in malaria elimination

Background & objectives: India targets malaria elimination by 2030 in a phased manner, so malaria’s assured diagnosis is crucial. Introduction of rapid diagnostic kits in India in 2010 has revolutionized malaria surveillance. The storage temperature of rapid diagnostic tests (RDTs), kit components and handling in transportations impact the results of RDTs. Therefore, quality assurance (QA) is required before it reaches end-users. The Indian Council of Medical Research-National Institute of Malaria Research (ICMR-NIMR) has a World Health Organization (WHO) recognized lot-testing laboratory facility to assure the quality of RDTs. Methods: The ICMR-NIMR receives RDTs from different manufacturing companies as well as various agencies such as National and State Programmes and Central Medical Services Society. The WHO standard protocol is followed to conduct all the tests, including long-term and post-dispatch testing. Results: A total of 323 lots tested during January 2014-March 2021 were received from different agencies. Amongst them, 299 lots passed the quality of test and 24 failed. In long-term testing, 179 lots were tested and only nine failed. A total of 7741 RDTs were received from end-users for post-dispatch testing of which 7540 qualified the QA test with a score of 97.4 per cent. Interpretation & conclusions: RDTs received for quality testing showed compliance with QA evaluation of malaria RDTs based on the protocol recommended by the WHO. However, continuous monitoring of the quality of RDTs is required under QA programme. Quality-assured RDTs have a major role, especially in areas where low parasitaemia of parasites persists.

A severe case of Plasmodium falciparum malaria imported by a French traveler from Cameroon to French Guiana despite regular intake of Artemisia annua herbal tea

ABSTRACT The use of herbal tea with Artemisia annua by travelers and traditional communities in Africa has increased in recent years as a supposed form of malaria prophylaxis, although its use is not recommended due to lack of efficacy. The risk of severe malaria complications that can lead to death is real regarding said behavior, and awareness needs to be raised. We report a case of severe Plasmodium falciparum malaria imported in the Amazon rainforest by a traveler returning from Cameroon who treated himself with Artemisia annua herbal tea.

Research progress on stable gene transfection methods of Plasmodium falciparum / 中国热带医学

@#Abstract: Transfection of Plasmodium falciparum is helpful to study the function of its genes, such as drug resistance. However, transgenic manipulation has been very challenging, mainly due to the high A/T base sequence structure (A+T content of about 82%) and low transfection efficiency of the Plasmodium genome. Electroporation-based transfection of Plasmodium falciparum has been successfully applied in the study of certain genes, and electroporation by preloading is currently the preferred method for introducing foreign DNA into Plasmodium falciparum. The site-directed editing of Plasmodium genes mostly adopts the method of two-plasmid transfection. It is generally believed that successful transfection of Plasmodium requires a large amount of high-purity plasmid DNA and an accurate transfection system. In addition to the evaluation of the current commonly used electrotransfection methods, this paper also introduces a new transfection method, namely lyse-reseal erythrocytes for transfection (LyRET). This paper also review the role of factors such as plasmid DNA concentration, the use of transfection reagents, the setting of transfection parameters, the addition of fresh red blood cells, and the markers of successful transfection in improving the success rate and efficiency of Plasmodium transfection, in the hope of providing a reference for study in this field.

Analysis laboratory results of three cases of COVID-19 complicated with falciparum malaria / 中国热带医学

@#Abstract: Objective　To analyze the laboratory indexes of patients infected with malaria patients and COVID-19, so as to provide reliable evidence for the diagnosis of mixed infection of both. Methods　The routine clinical laboratory items such as routine blood, biochemistry and lymphocyte subsets were tested in three cases of COVID-19 complicated with falciparum malaria who admitted to Guangzhou Eighth People's Hospital Affiliated to Guangzhou Medical University from July to December 2020 were tested. Laboratory data were stage-wise analyzed in conjunction with changes in the course of disease. Results　Three patients confirmed COVID-19 infection recruited all had malaria infection history. Fever, headache, and other symptoms emerged on the 4rd to 11th day after admission. Malaria parasite was detected by malaria parasite antigen testing and blood smear testing, and all three patients had re-ignition of malaria after being confirmed COVID-19 infection. In the early stage of malaria relapse, lymphocytes decreased, CRP and SAA increased, and gradually returned to normal level after antimalarial treatment. Interestingly, we only found one patient at the initial stage of malaria detection showed PLT decreased, no other unnormal changes in other routine blood results (WBC, ESO) and liver function results (ALT, AST, GGT, TBIL, DBIL, CG) were found from the beginning to end course of the disease. Conclusion　COVID-19 infection may promote the resurgence of malaria, so the relapse of malaria should be monitored especially for the patient with malaria infection history who begin to develop fever and other symptoms a few days after the diagnosis of COVID-19. The inflammatory indicators would be worth able as an auxiliary judgment basis for the effective treatment of the two combined infection.

Polymorphisms of pvcrt-o and pvmdr1 genes of 48 Plasmodium vivax isolates from the China-Myanmar border / 中国热带医学

@#Abstract: Objective To detect the polymorphisms of drug resistance-related genes pvcrt-o and pvmdr1 of Plasmodium vivax in lazan city in the China-Myanmar border, in order to guide the treatment plan of Plasmodium vivax. Methods A total of 48 Plasmodium vivax samples were collected from Lazan in the China-Myanmar border in 2007, and fragments of pvcrt-o and pvmdr1 genes were amplified by PCR and sequenced. The sequences were aligned with the Salvador I (Sal-I) strain reference genome sequences to determine the presence of SNPs. Results The target fragments of pvcrt-o gene were amplified from 39 Plasmodium vivax samples, while pvmdr1 genes were amplified from 40 samples. Amongst them, 25 samples had AAG insertion before the 10th amino acid (K10 insertion) of pvcrt-o gene, accounting for 64.1%. Non-synonymous mutations were detected at three loci of pvmdr1 gene (T958M, Y976F, and F1076L), the mutation rates were 100%, 22.5%, and 55.0%, respectively. There were three haplotypes of pvmdr1 gene, of which the triple mutant 958M/976F/1076L accounted for 22.5% (9/40), the double mutant 958M/Y976/1076L accounted for 32.5% (13/40), and the single mutant 958M/Y976/F1076 accounted for 45.0% (18/40). The proportion of strains with pvcrt-o and pvmdr1 gene mutation is 63.16%, which is significantly different from those only with pvmdr1 mutation. Conclusions The proportion of pvcrt-o and pvmdr1 gene mutation of 48 Plasmodium vivax isolates is high in the China-Myanmar border, and there is a certain degree of correlation between the two gene mutations. To assess changes in Plasmodium vivax drug resistance in this region, it is required to improve the surveillance of these two molecular markers.

Progress of researches on antimalarial peptides / 中国血吸虫病防治杂志

Malaria remains a major global public health concern, and nearly half of the global populations are still at risk of malaria infection. However, continuous emergence and spread of drug-resistant malaria parasite strains lead to ineffectiveness of conventional antimalarials. Therefore, development of novel antimalarial agents is of urgent need for malaria elimination. As an important component of the host natural immune defense system, antibacterial peptides provide the first line of defense against pathogenic invasion, and the mechanism of preferentially attacking the cell membrane makes them difficult to develop drug resistance. Antimicrobial peptides are therefore considered as a promising candidate for novel antimalarial agents. This review summarizes the advances in researches on antimicrobial peptides with antimalarial actions and discusses the potential of antimalarial peptides as novel antimalarials.

Molecular characterization of Plasmodium Falciparum Kelch-13 among febrile patients in selected Government Hospitals in Nigeria

@#Malaria is a life-threatening disease caused by protozoan Plasmodium species. Plasmodium falciparum is the deadliest species. Reducing and eliminating malaria burden are linked to most of the Sustainable Development Goals (SDG), central to SDG3 targeting the end of malaria by 2030. This study was aimed at assessing the Management of malaria and prevalence of P. falciparum kelch-13 among febrile patients in selected Government Hospitals in Nigeria. Malaria patients (399) attending outpatient clinics of the Hospitals between August, 2019 and January, 2021, were enlisted in the study, following ethical approval and informed consents. Blood (5mL) was collected from patients for microscopic and molecular investigation of malaria parasite. DNA extraction, PCR amplification, BLAST, and alignment were performed. Plasmodium resistance to Artemether/lumefantrine was determined by PCR amplification of extracted DNA using Kelch-13 gene primer. Data obtained were subjected to One-way Analysis of Variance and Linear Regression. The VapA gene primer amplified 55 (68.75%) out of the 80 DNA extracts tested. Twenty-five strains of P. falciparum belonging to 3 clades phylogenetically were identified and they showed evolutionary relationships with others. Plasmodium falciparum resistant Kelch-13 gene was detected in 70% of the isolates. This study observed a high prevalence of resistant gene to ACT drugs in the study area. Monitoring the effectiveness of ACTs must be done routinely to ensure timely changes in National treatment policies.

Monitoring and analysis of kelch13 C580Y mutation in imported Plasmodium falciparum in Wuhan, China / 中国热带医学

@#Abstract: Objective To investigate the prevalence of C580Y mutation of kelch13 gene in the imported P. falciparum cases in Wuhan City, China, and to provide a reference basis for the prevention and treatment of imported falciparum malaria. Methods From 2009 to 2015, blood samples were collected from returnees who infected with P. falciparum in endemic areas of Africa and Southeast Asia in Wuhan City. The P. falciparum DNA was extracted from the blood samples, and kelch13 gene was amplified by loop-mediated isothermal amplification (LAMP), and the distribution of C580Y mutation was analyzed. Results C580Y mutation was detected in 16 of the 208 cases tested by LAMP. No mutations were detected in 69 cases of imported falciparum malaria from Africa during 2009-2012, while 13 cases of the C580Y mutation were detected in 114 cases from 2013 to 2015, with a mutation rate of 11.4%. The mutation rate in South Africa, West Africa, and Central Africa was 12.5%, 9.6%, and 19.0%, respectively, with no mutations detected in cases from North Africa and East Africa. Among the 25 cases of falciparum malaria from Southeast Asia between 2009 and 2013, three cases were positive for the C580Y mutation, all from Myanmar, with a mutation rate of 14.3% (3/21) in Myanmar and 12.0% (3/25) in Southeast Asia. There was no significant difference in the mutation rate between Africa and Southeast Asia after 2013 (P>0.05). Conclusions Our findings highlight the varying degrees of C580Y mutations of kelch13 gene in imported P. falciparum cases in Wuhan and suggest the need for enhanced monitoring and evaluation of related resistance genes.

Single - nucleotide polymorphisms of artemisinin resistance - related Pfubp1 and Pfap2mu genes in Bioko Island, Equatorial Guinea from 2018 to 2020 / 中国血吸虫病防治杂志

Objective To investigate the prevalence of single nucleotide polymorphisms (SNPs) of artemisinin resistance-related Pfubp1 and Pfap2mu genes in Plasmodium falciparum isolates from Bioko Island, Equatorial Guinea, so as to to provide baseline data for the formulation of malaria control strategies in Bioko Island. Methods A total of 184 clinical blood samples were collected from patients with P. falciparum malaria in Bioko Island, Equatorial Guinea from 2018 to 2020, and genomic DNA was extracted. The Pfubp1 and Pfap2mu gene SNPs of P. falciparum were determined using a nested PCR assay and Sanger sequencing, and the gene sequences were aligned. Results There were 159 wild-type P. falciparum isolates (88.83%) from Bioko Island, Equatorial Guinea, and 6 SNPs were identified in 20 Pfubp1-mutant P. falciparum isolates (11.17%), in which 4 non-synonymous mutations were detected, including E1516G, K1520E, D1525E, E1528D. There was only one Pfubp1gene mutation site in 19 Pfubp1-mutant P. falciparum isolates (95.00%), in which non-synonymous mutations accounted for 68.42% (13/19). D1525E and E1528D were identified as major known epidemic mutation sites in the Pfubp1 gene associated with resistance to artemisinin-based combination therapies (ACTs). At amino acid position 1525, there were 178 wild-type P. falciparum isolates (99.44%) and 1 mutant isolate (0.56%), with such a mutation site identified in blood samples in 2018, and at amino acid position 1528, there were 167 wild-type P. falciparum isolates (93.30%) and 12 mutant isolates (6.70%). The proportions of wild-type P. falciparum isolates were 95.72% (134/140), 79.25% (126/159) and 95.83% (161/168) in the target amplification fragments of the three regions in the Pfap2mu gene (Pfap2mu-inner1, Pfap2mu-inner2, Pfap2mu-inner3), respectively. There were 16 different SNPs identified in all successfully sequenced P. falciparum isolates, in which 7 non-synonymous mutations were detected, including S160N, K199T, A475V, S508G, I511M, L595F, and Y603H. There were 7 out of 43 Pfap2mu-mutant P. falciparum isolates (16.28%) that harbored only one gene mutation site, in which non-synonymous mutations accounted for 28.57% (2/7). For the known delayed clearance locus S160N associated with ACTs, there were 143 wild-type (89.94%) and 16 Pfap2mu-mutant P. falciparum isolates (10.06%). Conclusions Both Pfubp1 and Pfap2mu gene mutations were detected in P. falciparum isolates from Bioko Island, Equatorial Guinea from 2018 to 2020, with a low prevalence rate of Pfubp1 gene mutation and a high prevalence rate of Pfap2mu gene mutation. In addition, new mutation sites were identified in the Pfubp1 (E1504E and K1520E) and Pfap2mu genes (A475V and S508G).

Establishment and preliminary evaluation of a fluorescent recombinase-aided amplification/CRISPR-Cas12a system for rapid detection of Plasmodium falciparum / 中国血吸虫病防治杂志

Objective To establish a fluorescent assay for rapid detection of Plasmodium falciparum based on recombinaseaided amplification (RAA) and CRISPR-Cas12a system,and to preliminarily evaluate the diagnostic efficiency of this system.. Methods The 18S ribosomal RNA (rRNA) gene of P. falciparum was selected as the target sequence, and three pairs of RAA primers and CRISPR-derived RNA (crRNA) were designed and synthesized. The optimal combination of RAA primers and crRNA was screened and the reaction conditions of the system were optimized to create a fluorescent RAA/CRISPR-Cas12a system. The plasmid containing 18S rRNA gene of the P. falciparum strain 3D7 was generated, and diluted into concentrations of 1 000, 100, 10, 1 copy/μL for the fluorescent RAA/CRISPR-Cas12a assay, and its sensitivity was evaluated. The genomic DNA from P. vivax, P. malariae, P. ovum, hepatitis B virus, human immunodeficiency virus and Treponema pallidum was employed as templates for the fluorescent RAA/CRISPR-Cas12a assay, and its specificity was evaluated. Fifty malaria clinical samples were subjected to the fluorescent RAA/CRISPR-Cas12a assay and nested PCR assay, and the consistency between two assays was compared. In addition, P. falciparum strain 3D7 was cultured in vitro. Then, the culture was diluted into blood samples with parasite densities of 1 000, 500, 200, 50, 10 parasites/μL with healthy volunteers’ O-positive red blood cells for the RAA/CRISPR-Cas12a assay, and the detection efficiency was tested. Results The Pf-F3/Pf-R3/crRNA2 combination, 2.5 μL as the addition amount of B buffer, 40 min as the RAA reaction time, 37 °C as the reaction temperature of the CRISPR-Cas12a system were employed to establish the fluorescent RAA/CRISPR-Cas12a system. Such a system was effective to detect the plasmid containing 18S rRNA gene of the P. falciparum strain 3D7 at a concentration of 1 copy/μL, and presented fluorescent signals for detection of P. falciparum, but failed to detect P. ovum, P. malariae, P. vivax, T. pallidum, hepatitis B virus or human immunodeficiency virus. The fluorescent RAA/CRISPR-Cas12a system and nested PCR assay showed completely consistent results for detection of 50 malaria clinical samples (kappa = 1.0, P < 0.001). Following 6-day in vitro culture of the P. falciparum strain 3D7, 10 mL cultures were generated and the fluorescent RAA/CRISPR-Cas12a system showed the minimal detection limit of 50 parasites/μL. Conclusion The fluorescent RAA/CRISPR-Cas12a system is rapid, sensitive and specific for detection of P. falciparum, which shows promising value for rapid detection and risk monitoring of P. falciparum.

Genome-wide in silico analysis for novel regulators of gametocyte development critical for transmission of Plasmodium falciparum

@#Malaria, caused by the unicellular Apicomplexan protozoa of the genus Plasmodium, is an infectious disease transmitted via female Anopheles mosquitoes. The sexual stage (gametocytes) of malaria parasites is the key to the transmission of parasites from vertebrate hosts to mosquitoes, representing critical bottleneck of the parasite life cycle. This study has established a systematic computational pipeline to achieve the genome-wide in silico analysis and find 708 novels potentially indispensable genes for gametocyte development, consisting of 644 protein coding genes, 56 ncRNA genes and 8 pseudogenes, with a total of 191 genes in the transmembrane, 29 protein coding genes to be exported proteins, and 58 genes in apicoplast regions. Furthermore, Gene Ontology analysis showed that the largest cluster was cellular processes with nucleus and cytosol highest, followed by molecular function with binding and oxidoreductase activities abundant. Meanwhile, when a text searched, using PlasmoDB, there were 300 genes with annotations of “putative”, and 196 genes with annotations of “unknown function”. These data would be helpful to provide potential targets for effective malaria transmission-blocking strategies.

Multiplicity of infection of Plasmodium knowlesi in Malaysia: an application of Pkmsp-1 block IV

@#In Malaysia presently, the main cause of human malaria is by the zoonotic monkey parasite Plasmodium knowlesi. A previous study has suggested that the P. knowlesi merozoite surface protein 1 (Pkmsp-1) block IV to be a suitable multiplicity of infection (MOI) genotyping marker for knowlesimalaria. This study therefore aimed to investigate the usefulness of Pkmsp-1 block IV in assessing the MOI of P. knowlesi in clinical isolates from Malaysia. Two allele-specific PCR primer pairs targeting the two allelic families of block IV (T1 and T2) were designed, and used to genotype P. knowlesi in 200 blood samples (100 from Peninsular Malaysia and 100 from Malaysian Borneo). Results showed that the mean MOI in Malaysian Borneo was slightly higher as compared to Peninsular Malaysia (1.58 and 1.40, respectively). Almost half of the total blood samples from Malaysian Borneo (52%) had polyclonal infections (i.e., more than one allele of any family type) as compared to Peninsular Malaysia (33%) samples. The T1 allelic family was more prevalent in Peninsular Malaysia (n=75) than in Malaysian Borneo (n=60). The T2 allelic family, however, was more prevalent in the Malaysian Borneo (n=87 vs n=53 respectively). This study shows that the single locus Pkmsp-1 block IV can serve as a simple alternative genetic marker for estimating knowlesi malaria MOI in a population. Future MOI studies should focus on macaque populations as macaques are the natural host of P. knowlesi.

Quality of blood smear examinations for malaria parasites in Chenzhou City after malaria elimination / 中国血吸虫病防治杂志

Objective To analyze the quality of blood smear examinations for malaria parasites in Chenzhou City, so as to provide insights into sustainable consolidation of malaria elimination achievements. Methods All positive blood smears from fever patients were irregularly sampled from each county (district) of Chenzhou City from 2018 to 2022 and reexamined, and no less than 3% negative blood smears were reexamined. The preparation, dyeing, cleanliness and microscopic examination results of blood smear were reexamined, and the quality of blood smear reexaminations was assessed using a descriptive statistical method. Results A total of 13 625 fever patients received blood smear examinations for malaria parasites in Chenzhou City from 2018 to 2022, of which 21 were positive and 13 604 were negative; 687 blood samples were reviewed, and the percentage of negative blood smear reexaminations was 4.90% (666/13 604), with a 63.51% rate of qualified negative blood smears preparation, a 67.87% rate of qualified dyeing and a 76.13% rate of qualified cleanliness, and no missing diagnosis found. There were 21 positive blood smears reexamined, and the proportions of qualified blood smears preparation, dyeing and cleanliness were all 85.71%, with 2 smears mistaking Plasmodium species (9.52%). The percentage of qualified negative blood smears preparation was 51.41% in 2022, which reduced by 31.61% in relative to that (75.17%) in 2019 (χ2 = 9.033, P < 0.05), and the percentage of qualified negative blood smears dyeing was 60.19% in 2022, which reduced by 28.82% in relative to that (84.56%) in 2019 (χ2 = 19.498, P < 0.05), while the percentage of qualified negative blood smears cleanliness was 62.96% in 2022, which reduced by 28.93% in relative to that (88.59%) in 2019 (χ2 = 23.826, P < 0.001). In addition, there were no significant differences in the proportion of qualified negative blood smears preparation (χ2 = 0.260, P > 0.05) or dyeing (χ2 = 1.094, P > 0.05) among the three years, while a significant difference was detected in the percentage of qualified negative blood smears cleanliness (χ2 = 12.175, P < 0.05). Conclusions No missing diagnosis was seen in blood smear examinations for malaria parasites among fever patients in Chenzhou City after malaria elimination; however, there were reductions in proportions of qualified blood smears preparation, dyeing and cleanliness. Quality control of blood smear examinations is recommended to be reinforced in key regions of Chenzhou City.

Fixation of pfcrt chloroquine resistance alleles in Plasmodium falciparum clinical isolates collected from unrest tribal agencies of Pakistan / Fixação de alelos de resistência à cloroquina pfcrt em isolados clínicos de Plasmodium falciparum coletados de agitações de agências tribais do Paquistão

Plasmodium falciparum resistance to Chloroquine (CQ) is a significant cause of mortality and morbidity worldwide. There is a paucity of documented data on the prevalence of CQ-resistant mutant haplotypes of Pfcrt and Pfmdr1 genes from malaria-endemic war effected Federally Administered Tribal Areas of Pakistan. The objective of this study was to investigate the prevalence of P. falciparum CQ-resistance in this area. Clinical isolates were collected between May 2017 and May 2018 from North Waziristan and South Waziristan agencies of Federally Administrated Trial Area. Subsequently, Giemsa-stained blood smears were examined to detect Plasmodium falciparum. Extraction of malarial DNA was done from microscopy positive P. falciparum samples, and P. falciparum infections were confirmed by nested PCR (targeting Plasmodium small subunit ribosomal ribonucleic acid (ssrRNA) genes). All PCR confirmed P. falciparum samples were sequenced by pyrosequencing to find out mutation in Pfcrt gene at codon K76T and in pfmdr1 at codons N86Y, Y184F, N1042D, and D1246Y. Out of 121 microscopies positive P. falciparum cases, 109 samples were positive for P. falciparum by nested PCR. Pfcrt K76T mutation was found in 96% of isolates, Pfmdr1 N86Y mutation was observed in 20%, and 11% harboured Y184F mutation. All samples were wild type for Pfmdr1 codon N1042D and D1246Y. In the FATA, Pakistan, the frequency of resistant allele 76T remained high despite the removal of CQ. However, current findings of the study suggest complete fixation of P. falciparum CQ‑resistant genotype in the study area.

A resistência do Plasmodium falciparum à cloroquina (CQ) é uma causa significativa de mortalidade e morbidade em todo o mundo. Há uma escassez de dados documentados sobre a prevalência de haplótipos mutantes CQ-resistentes dos genes Pfcrt e Pfmdr1 da guerra endêmica da malária em áreas tribais administradas pelo governo federal do Paquistão. O objetivo deste estudo foi investigar a prevalência de resistência a CQ de P. falciparum nesta área. Isolados clínicos foram coletados entre maio de 2017 e maio de 2018 nas agências do Waziristão do Norte e do Waziristão do Sul da Área de Ensaio Administrada Federalmente. Posteriormente, esfregaços de sangue corados com Giemsa foram examinados para detectar Plasmodium falciparum. A extração do DNA da malária foi feita a partir de amostras de P. falciparum positivas para microscopia, e as infecções por P. falciparum foram confirmadas por nested PCR (visando genes de ácido ribonucleico ribossômico de subunidade pequena de Plasmodium (ssrRNA)). Todas as amostras de P. falciparum confirmadas por PCR foram sequenciadas por pirosequenciamento para descobrir a mutação no gene Pfcrt no códon K76T e em pfmdr1 nos códons N86Y, Y184F, N1042D e D1246Y. De 121 microscopias de casos positivos de P. falciparum, 109 amostras foram positivas para P. falciparum por nested PCR. A mutação Pfcrt K76T foi encontrada em 96% dos isolados, a mutação Pfmdr1 N86Y foi observada em 20% e 11% abrigou a mutação Y184F. Todas as amostras eram do tipo selvagem para o códon N1042D e D1246Y de Pfmdr1. No FATA, Paquistão, a frequência do alelo resistente 76T permaneceu alta apesar da remoção de CQ. No entanto, as descobertas atuais do estudo sugerem a fixação completa do genótipo resistente a CQ de P. falciparum na área de estudo.