The Plasmodium vivax in China: decreased in local cases but increased imported cases from Southeast Asia and Africa

Evaluation of performance for malaria diagnosis in health facilities by five provincial reference laboratories of China

Introduction

The provincial malaria diagnosis reference laboratories review and assess malaria cases diagnosed in health facilities for supporting the malaria elimination efforts and preventing re-transmission of imported malaria. The study aimed to evaluate the detection capability of malaria diagnosis in China from 2014 to 2021.

Methods

Data on malaria cases reported in the provincial-level administrative divisions (PLADs) of Anhui, Henan, Hubei, Guangxi, and Zhejiang from 2014 to 2021 were collected and analyzed.

Results

In total, 5,770 malaria cases were reported from 2014 to 2021, and 99.05% (5,715/5,770) were submitted to the provincial malaria diagnosis reference laboratories. The median time between malaria cases being reported and the samples being received by reference laboratories was 6 days (Interquartile range, IQR:3-12 days) from 2017 to 2021. Diagnosis of 5,680 samples in the laboratory were confirmed by provincial reference laboratories, including 3,970 cases of Plasmodium falciparum, 414 of P. vivax, 1,055 of P. ovale, 158 of P. malariae, 1 of P. knowlesi, and 82 of mixed infections. Plasmodium species of 5,141 confirmed cases were consistent with the initial diagnosis, with a species accuracy rate of 90.53% (5,141/5,679). The accuracy of P. falciparum diagnosis in health facilities was higher than that of non-falciparum species. The inconsistency between microscopy and nested polymerase chain reaction (nPCR) results of confirmatory diagnosis was mainly in malaria-positive versus malaria-negative cases, as well as in mixed versus single infection cases.

Conclusion

The provincial malaria diagnosis reference laboratories have played an important role in ensuring the accuracy and reliability of Plasmodium diagnosis in health facilities. However, the results of this study imply that capacity training for the identification of Plasmodium species in health facilities is warranted.

Molecular detection and species identification of Plasmodium spp. infection among imported cases in Eastern China, 2012-2018

Due to the increasing number of returnees from malaria endemic areas, imported malaria has become a public health challenge in China. To better understand the characteristics of imported Plasmodium species and adjust appropriate strategies for malaria prevention and control in Eastern China, we conducted molecular detection and species identification on 1282 imported malaria cases in Shandong Province between 2012 and 2018. The findings showed that P. falciparum was predominant, particularly in cases imported from Africa. P. vivax was the dominant species imported from Asian countries. Additionally, imported P. ovale and P. malariae emerged in the province. Further surveillance and control of imported malaria among returnees from Africa and Southeast Asia is needed to be strengthened in Eastern China.

Single-nucleotide polymorphisms of artemisinin resistance-related pfubp1 and pfap2mu genes in imported Plasmodium falciparum to Wuhan, China

BACKGROUND

Molecular markers for monitoring resistance could help improve malaria treatment policies. Delayed clearance of Plasmodium falciparum by artemisinin-based combination therapies (ACTs) has been reported in several countries. In addition to PfKelch13 (pfk13), new drug resistance genes, P. falciparum ubiquitin-specific protease 1 (pfubp1) and the eadaptor protein complex 2 mu subunit (pfap2mu), have been identified as being linked to ACTs. This study investigated the prevalence of single-nucleotide polymorphisms (SNPs) in clinical P. falciparum isolates pfubp1 and pfap2mu imported from Africa and Southeast Asia (SEA) to Wuhan, China, to provide baseline data for antimalarial resistance monitoring in this region.

METHODS

Peripheral venous blood samples were collected in Wuhan, China, from August 2011 to December 2019. The Pfubp1 and pfap2mu SNPs of P. falciparum were determined by nested PCR and Sanger sequencing.

RESULTS

In total, 296 samples were collected. Subsequently, 92.23% (273/296) were successfully amplified and sequenced for Pfubp1. There were 60.07% (164/273) wild-type strains and 39.93% (109/273) mutant strains. The pfap2mu gene was divided into three fragments for amplification, and 82.77% (245/296), 90.20% (267/296) and 94.59% (280/296) were sequenced successfully. Genotypes reportedly associated with ACTs resistance detected in this study included pfubp1 D1525E as well as E1528D and pfap2mu S160N. The mutation prevalence rates were 10.99% (30/273), 13.19% (36/273) and 11.24% (30/267), respectively. These are all focused on Congo, Nigeria and Angola. Known delayed-clearance parasite mutations have also been found in SEA.

CONCLUSIONS

The existence of mutation sites of known clearance genes detected in the isolates in this study, including D1525E and E1528D in the pfubp1 gene and S160N in the pfap2mu gene, further proved the risk of ACTs resistance. Constant vigilance is therefore needed to protect the effectiveness of ACTs and to prevent the spread of drug-resistant P. falciparum. Further studies in malaria-endemic countries are needed to further validate potential genetic markers for monitoring parasite populations in Africa and SEA.

Single nucleotide polymorphism analysis of pvmdr-1 in Plasmodium vivax isolated from military personnel of Republic of Korea in 2016 and 2017

Background

Malaria chemoprophylaxis using chloroquine (CQ) and primaquine (PQ) has been administered to resident soldiers in the 3rd Army of Republic of Korea (ROK) to prevent malaria infection since the year 1997. Due to mass chemoprophylaxis against malaria, concern exists about the occurrence of chloroquine resistance (CQR). This study aimed to investigate the single nucleotide polymorphisms (SNPs) of the Plasmodium vivax multi-drug resistance protein-1 (pvmdr-1) gene to monitor the risk of CQR.

Methods

SNPs of the pvmdr-1 gene were analysed in 73 soldiers of the 3^rd Army of ROK diagnosed with infection by P. vivax.

Results

Quintuple mutations (G698S, L845F, M908L, T958M, and F1076L) were detected in 73 soldiers. A newly identified non-synonymous mutation in the Y541C position had been introduced into P. vivax malaria-endemic areas in ROK, at a frequency of 1.3% (1/73). In addition, synonymous mutations were detected at positions K44 (38.4%, 28/73), L493 (26%, 19/73), T529 (61.6%, 45/73), and E1233 (52.1%, 38/73). Based on these SNPs, pvmdr-1 sequences of ROK were classified into 6 haplotypes. The phylogenetic analysis closed to the type of North Korean showed that P. vivax malaria of ROK could be a reason of influx from North Korea.

Conclusions

This study showed that synonymous and non-synonymous mutations of pvmdr-1 were observed in the malaria chemoprophylaxis-executed regions of ROK from 2016 to 2017. Based on the rapid transition of pvmdr-1 SNPs, continuous surveillance for SNPs of pvmdr-1 related to CQR in the malaria-endemic regions of ROK is essential.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04214-6.

Genetic Diversity and Selection of Plasmodium vivax Apical Membrane Antigen-1 in China-Myanmar Border of Yunnan Province, China, 2009-2016

Plasmodium vivax apical membrane antigen-1 (PvAMA-1) is an important vaccine candidate for vivax malaria. However, antigenic variation within PvAMA-1 is a major obstacle to the design of a global protective malaria vaccine. In this study, we analyzed the genetic polymorphism and selection of the PvAMA-1 gene from 152 P. vivax isolates from imported cases to China, collected in the China–Myanmar border (CMB) area in Yunnan Province (YP) during 2009–2011 (n = 71) and 2014–2016 (n = 81), in comparison with PvAMA-1 gene information from Myanmar (n = 73), collected from public data. The overall nucleotide diversity of the PvAMA-1 gene from the 152 YP isolates was 0.007 with 76 haplotypes identified (Hd = 0.958). Results from the population structure suggested three groups among the YP and Myanmar isolates with optimized clusters value of K = 7. In addition, YP (2014–2016) isolates generally lacked some K components that were commonly found in YP (2009–2011) and Myanmar. Meanwhile, PvAMA-1 domain I is found to be the dominant target of positive diversifying selection and most mutation loci were found in this domain. The mutation frequencies of D107N/A, R112K/T, K120R, E145A, E277K, and R438H in PvAMA-1 were more than 70% in the YP isolates. In conclusion, high genetic diversity and positive selection were found in the PvAMA-1 gene from YP isolates, which are significant findings for the design and development of PvAMA-1-based malaria vaccine.

The global burden of Plasmodium vivax malaria is obscure and insidious

J. Kevin Baird and colleagues, examine and discuss the estimated global burden of vivax malaria and it's biological, clinical, and public health complexity.

Molecular surveillance of anti-malarial resistance pfcrt, pfmdr1, and pfk13 polymorphisms in African Plasmodium falciparum imported parasites to Wuhan, China

Background

Imported malaria parasites with anti-malarial drug resistance (ADR) from Africa is a serious public health challenge in non-malarial regions, including Wuhan, China. It is crucial to assess the ADR status in African Plasmodium falciparum isolates from imported malaria cases, as this will provide valuable information for rational medication and malaria control.

Methods

During 2017–2019, a cross-sectional study was carried out in Wuhan, China. Peripheral blood 3 ml of returned migrant workers from Africa was collected. The target fragments from pfcrt, pfmdr1, and k13 propeller (pfk13) genes were amplified, sequenced, and analysed.

Results

In total, 106 samples were collected. Subsequently, 98.11% (104/106), 100% (106/106), and 86.79% (92/106) of these samples were successfully amplified and sequenced for the pfcrt (72–76), pfmdr1, and pfk13 genes, respectively. The prevalence of the pfcrt 76 T, pfmdr1 86Y, and pfmdr1 184F mutations was 9.62, 4.72, and 47.17%, respectively. At codons 72–76, the pfcrt locus displayed three haplotypes, CVMNK (wild-type), CVIET (mutation type), CV M/I N/E K/T (mixed type), with 87.50%, 9.62%, and 2.88% prevalence, respectively. For the pfmdr1 gene, NY (wild type), NF and YF (mutant type), N Y/F, Y Y/F, and N/Y Y/F (mixed type) accounted for 34.91, 43.40, 3.77, 15.09, 0.94, and 1.89% of the haplotypes, respectively. A total of 83 isolates with six unique haplotypes were found in pfcrt and pfmdr1 combined haplotypes, of which NY-CVMNK and NF-CVMNK accounted for 40.96% (34/83) and 43.37% (36/83), respectively. Furthermore, 90 cases were successfully sequenced (84.91%, 90/106) at loci 93, 97, 101, and 145, and 78 cases were successfully sequenced (73.58%, 78/106) at loci 343, 353, and 356 for pfcrt. However, the mutation was observed only in locus 356 with 6.41%. For pfk13, mutations reported in Southeast Asia (at loci 474, 476, 493, 508, 527, 533, 537, 539, 543, 553, 568, 574, 578, and 580) and Africa (at loci 550, 561, 575, 579, and 589) were not observed.

Conclusions

The present data from pfcrt and pfmdr1 demonstrate that anti-malarial drugs including chloroquine, amodiaquine, and mefloquine, remain effective against malaria treatment in Africa. The new mutations in pfcrt related to piperaquine resistance remain at relatively low levels. Another source of concern is the artemether-lumefantrine resistance-related profiles of N86 and 184F of pfmdr1. Although no mutation in pfk13 is detected, molecular surveillance must continue.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03737-8.

The association of CYP2D6 gene polymorphisms in the full-length coding region with higher recurrence rate of vivax malaria in Yunnan Province, China

Background

Accumulating evidence suggest that compromised CYP2D6 enzyme activity caused by gene mutation could contribute to primaquine failure for the radical cure of vivax malaria. The current study aims to preliminarily reveal the association between the recurrence of vivax malaria in Yunnan Province and CYP2D6 gene mutation by analysing polymorphisms in the entire coding region of human CYP2D6 gene.

Methods

Blood samples were collected from patients with vivax malaria, who received "chloroquine and 8-day course of primaquine therapy" in Yunnan Province. The suspected relapsed cases were determined by epidemiological approaches and gene sequence alignment. PCR was conducted to amplify the CYP2D6 gene in the human genome, and the amplified products were then sequenced to compare with the non-mutation “reference” sequence, so as to ensure correct sequencing results and to determine 9 exon regions. Subsequently, the DNA sequences of 9 exons were spliced into the coding DNA sequence (CDS), which, by default, is known as maternal CDS. The paternal CDS was obtained by adjusting the bases according to the sequencing peaks. The mutation loci, haplotypes (star alleles), genotypes and odds ratios (OR) of all the CDSs were analysed.

Results

Of the119 maternal CDS chains in total with 1491 bp in length, 12 mutation sites in the 238 maternal and paternal CDS chains were detected. The c.408G > C mutation was most frequently detected in both suspected relapsed group (SR) and non-relapsed group (NR), reaching 85.2% (75/88) and 76.0% (114/150), respectively. The c.886C > T mutation was most closely related to the recurrence of vivax malaria (OR = 2.167, 95% CI 1.104–4.252, P < 0.05). Among the 23 haplotypes (Hap_1 ~ Hap_23), Hap_3 was non-mutant, and the sequence structure of Hap_9 was the most complicated one. Five star alleles, including *1, *2, *4, *10 and *39, were confirmed by comparison, and CYP2D6*10 allele accounted for the largest percentage (45.4%, 108/238). The frequency of CYP2D6*2 allele in the SR group was significantly higher than that in the NR group (Χ² = 16.177, P < 0.05). Of the defined 24 genotypes, 8 genotypes, including *4/*4, *4/*o, *2/*39, *39/*m, *39/*x, *1/*r, *1/*n, and *v/*10, were detected only in the SR group.

Conclusion

Mutation of CYP2D6*10 allele accounts for the highest proportion of vivax malaria cases in Yunnan Province. The mutations of c. 886C > T and CYP2D6*2 allele, which correspond to impaired PQ metabolizer phenotype, are most closely related to the relapse of vivax malaria. In addition, the genotype *4/*4 with null CYP2D6 enzyme function was only detected in the SR group. These results reveal the risk of defected CYP2D6 enzyme activity that diminishes the therapeutic effect of primaquine on vivax malaria.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03685-3.

From Plasmodium vivax outbreak to elimination: lessons learnt from a retrospective analysis of data from Guantang

BACKGROUND

Malaria was once a serious public health problem in China, with Plasmodium vivax the major species responsible for more than 90% of local transmission. Following significant integrated malaria control and elimination programmes, malaria burden declined, and since 2017 China has not recorded any indigenous case. To understand the historical malaria transmission patterns and epidemic characteristics in China and insights useful to guide P. vivax malaria control and elimination elsewhere, a retrospective study was carried out.

METHODS

Historical data from a pilot study conducted in Guantang, Luyi in central China from 1971-1995, were digitized. The data included monthly numbers of reported cases, febrile cases, parasite carriage rates, the neonatal infection rate, and entomological data regarding Anopheles sinensis.

RESULTS

Following 25 years of continuous integrated malaria control activities, malaria incidence in Guantang decreased from 4,333 cases per 10,000 in 1970 before integrated implementation to 0.23 cases per 10,000 in 1991, and no cases in 1992-1995. Some fluctuations in incidence were observed between 1977 and 1981. During the period parasite rates, antibody levels and the neonatal infection rate also decreased. The pattern of seasonality confirmed that P. vivax in Henan Province was primarily of the long incubation type (temperate) during non-transmission period. The findings retrospectively provide a scientific basis for the implementation of mass campaigns of liver stage hypnozoite clearance. Entomological studies indicated that An. sinensis was the only vector, and it preferred bovine to human hosts, predominantly biting and resting outdoors. Mosquito densities declined between 1971 and 1984.

CONCLUSION

The integrated malaria control approach in Guantang effectively controlled malaria and achieved elimination. Analysis of the effectiveness of the programme can provide guidance to other regions or countries with similar ecological settings aiming to move from malaria control to elimination. There is a potential challenge in the maintenance of non-transmission status owing to imported cases and the long dormancy of liver stage hypnozoites.

Toward the Elimination of Malaria in China: A Retrospective Analysis of Malaria-Endemic Characteristics and Prevention Effects in Yantai, Shandong Province, 1951 to 2017

Objectives: To study the epidemiological characteristics of malaria and the effects of comprehensive malaria control implementation in Yantai, as well as to provide a scientific basis for future malaria elimination. Materials and Methods: A retrospective analysis was conducted to explore the epidemiological changes and prevention effects in Yantai from 1951 to 2017. The malaria data before 2004 were collected from paper-based annual reports, and data after 2004 came from the Infectious Diseases Information Reporting Management System. Results: A total of 81,286 malaria cases were identified in Yantai from 1957 to 2017, with two peaks occurring in 1966 (120.93/100,000) and 1970-1972 (366.12/100,000). From 1951 to 2003, the case classification was mainly Plasmodium vivax (99.80%); the first case attributed to Plasmodium falciparum occurred in 2004, and P. falciparum became the main cause of malaria after 2011. All cases reported since 2010 have been imported cases, and the last indigenous case was caused by P. vivax in 2008. A total of 129 imported cases were reported from 2010 to 2017, most of which originated in Africa (93.80%), mainly in men aged 30-49 years (68.28%). From 1951 to 1973, 73,868 cases of malaria were diagnosed with clinical symptoms, and from 1974 to 2017, 818,943 cases in fever patients were diagnosed with blood tests. Conclusions: To achieve the goal of eliminating malaria by 2020, Yantai should continue to strengthen the management of migrant population, including improving malaria surveillance for returnees and immigrants from overseas endemic areas, and continue to increase the training of medical personnel to improve their diagnostic ability.

Multiple relapses of Plasmodium vivax malaria acquired from West Africa and association with poor metabolizer CYP2D6 variant: a case report

Background

Plasmodium vivax transmission in West Africa, dominant for the Duffy-negative blood group, has been increasingly recognized from both local residents as well as international travelers who contracted P. vivax malaria there. However, the relapsing pattern and sensitivity to antimalarial treatment of P. vivax strains originated from this region are largely unknown. There is evidence that the efficacy of primaquine for radical cure of relapsing malaria depends on host factors such as the hepatic enzyme cytochrome P450 (CYP) 2D6.

Case presentation

A 49-year-old Chinese man was admitted to the Shanglin County Hospital in Guangxi Province, China, on December 19, 2016, 39 days after he returned from Ghana, where he stayed for one and a half years. He was diagnosed by microscopy as having uncomplicated P. vivax malaria. Treatment included 3 days of intravenous artesunate (420 mg total), and 3 days of chloroquine (1550 mg total), and 8 days of primaquine (180 mg total). Although parasites and symptoms were cleared rapidly and he was malaria-negative for almost two months, he suffered four relapses with relapse intervals ranging from 58 to 232 days. The last relapse occurred at 491 days from his first vivax attack. For the first three relapses, he was treated similarly with chloroquine and primaquine, sometimes supplemented with additional artemisinin combination therapies (ACTs). For the last relapse, he was treated with intravenous artesunate, 3 days of an ACT, and 7 days of azithromycin, and had remained healthy for 330 days. Molecular studies confirmed P. vivax infections for all the episodes. Although this patient was diagnosed to have normal glucose-6-phosphate dehydrogenase (G6PD) activity, his CYP2D6 genotype corresponded to a *2A/*36 allele variant suggesting of an impaired primaquine metabolizer phenotype.

Conclusions

This clinical case suggests that P. vivax malaria originating from West Africa may produce multiple relapses extending beyond one year. The failures of primaquine as an anti-relapse therapy may be attributed to the patient’s impaired metabolizer phenotype of the CYP2D6. This highlights the importance of knowing the host G6PD and CYP2D6 activities for effective radical cure of relapsing malaria by primaquine.

Surveillance of Genetic Variations Associated with Antimalarial Resistance of Plasmodium falciparum Isolates from Returned Migrant Workers in Wuhan, Central China

Antimalarial drug resistance developed in Plasmodium falciparum has become a problem for malaria control. Evaluation of drug resistance is the first step for effective malaria control. In this study, we investigated the gene mutations of P. falciparum using blood samples from returned Chinese migrant workers in order to identify drug resistance-associated molecular markers. These workers returned from Africa and Southeast Asia (SEA) during 2011 to 2016. Polymorphisms in pfcrt, pfmdr1, and k13-propeller genes and the haplotype patterns of Pfcrt and Pfmdr1 were analyzed. The results showed the presence of four haplotypes of Pfcrt codons 72 to 76, including CVMNK (wild type), SVMNT and CVIET (mutation types), and CV M/I N/E K/T (mixed type), with 50.57%, 1.14%, 25.00%, and 23.30% prevalence, respectively. For Pfmdr1, N86Y (22.28%) and Y184F (60.01%) were the main prevalent mutations (mutations are underlined). The prevalence of mutation at position 550, 561, 575, and 589 of K13-propeller were 1.09%, 0.54%, 0.54%, and 0.54%, respectively. These data suggested that Pfcrt, Pfmdr1, and K13-propeller polymorphisms are potential markers to assess drug resistance of P. falciparum in China, Africa, and SEA.

Ready for malaria elimination: zero indigenous case reported in the People's Republic of China

BACKGROUND

Malaria was once one of the most serious public health problems in China. However, the disease burden has sharply declined and epidemic areas have shrunk after the implementation of an integrated malaria control and elimination strategy, especially since 2000. In this review, the lessons were distilled from the Chinese national malaria elimination programme and further efforts to mitigate the challenges of malaria resurgence are being discussed.

METHODS

A retrospective evaluation was performed to assess the changes in malaria epidemic patterns from 1950 to 2017 at national level. The malaria data before 2004 were collected from paper-based annual reports. After 2004, each of the different cases from the Infectious Diseases Information Reporting Management System (IDIRMS) was closely examined and scrutinized. An additional documenting system, the National Information Management System for Malaria, established in 2012 to document the interventions of three parasitic diseases, was also examined to complete the missing data from IDIRMS.

RESULTS

From 1950 to 2017, the occurrence of indigenous malaria has been steeply reduced, and malaria-epidemic regions have substantially shrunk, especially after the launch of the national malaria elimination programme. There were approximately 30 million malaria cases annually before 1949 with a mortality rate of 1%. A total of 5999 indigenous cases were documented from 2010 to 2016, with a drastic reduction of 99% over the 6 years (2010, n = 4262; 2016, n = 3). There were indigenous cases reported in 303 counties from 18 provinces in 2010, but only 3 indigenous cases were reported in 2 provinces nationwide in 2016. While in 2017, for the first time, zero indigenous case was reported in China, and only 7 of imported cases were in individuals who died of Plasmodium falciparum infection.

CONCLUSION

Malaria elimination in China is a country-led and country-owned endeavour. The country-own efforts were a clear national elimination strategy, supported by two systems, namely a case-based surveillance and response system and reference laboratory system. The country-led efforts were regional and inter-sectoral collaboration as well as sustained monitoring and evaluation. However, there are still some challenges, such as the maintenance of non-transmission status, the implementation of a qualified verification and assessment system, and the management of imported cases in border areas, through regional cooperation. The findings from this review can probably help improving malaria surveillance systems in China, but also in other elimination countries.

Diversity pattern of Duffy binding protein sequence among Duffy-negatives and Duffy-positives in Sudan

Background

Vivax malaria is a leading public health concern worldwide. Due to the high prevalence of Duffy-negative blood group population, Plasmodium vivax in Africa historically is less attributable and remains a neglected disease. The interaction between Duffy binding protein and its cognate receptor, Duffy antigen receptor for chemokine plays a key role in the invasion of red blood cells and serves as a novel vaccine candidate against P. vivax. However, the polymorphic nature of P. vivax Duffy binding protein (DBP), particularly N-terminal cysteine-rich region (PvDBPII), represents a major obstacle for the successful design of a DBP-based vaccine to enable global protection. In this study, the level of pvdbpII sequence variations, Duffy blood group genotypes, number of haplotypes circulating, and the natural selection at pvdbpII in Sudan isolates were analysed and the implication in terms of DBP-based vaccine design was discussed.

Methods

Forty-two P. vivax-infected blood samples were collected from patients from different areas of Sudan during 2014–2016. For Duffy blood group genotyping, the fragment that indicates GATA-1 transcription factor binding site of the FY gene (− 33T > C) was amplified by PCR and sequenced by direct sequencing. The region II flanking pvdbpII was PCR amplified and sequenced by direct sequencing. The genetic diversity and natural selection of pvdbpII were done using DnaSP ver 5.0 and MEGA ver 5.0 programs. Based on predominant, non-synonymous, single nucleotide polymorphisms (SNPs), prevalence of Sudanese haplotypes was assessed in global isolates.

Results

Twenty SNPs (14 non-synonymous and 6 synonymous) were identified in pvdbpII among the 42 Sudan P. vivax isolates. Sequence analysis revealed that 11 different PvDBP haplotypes exist in Sudan P. vivax isolates and the region has evolved under positive selection. Among the identified PvDBP haplotypes five PvDBP haplotypes were shared among Duffy-negative as well as Duffy-positive individuals. The high selective pressure was mainly found on the known B cell epitopes (H3) of pvdbpII. Comparison of Sudanese haplotypes, based on 10 predominant non-synonymous SNPs with 10 malaria-endemic countries, demonstrated that Sudanese haplotypes were prevalent in most endemic countries.

Conclusion

This is the first pvdbp genetic diversity study from an African country. Sudanese isolates display high haplotype diversity and the gene is under selective pressure. Haplotype analysis indicated that Sudanese haplotypes are a representative sample of the global population. However, studies with a large number of samples are needed. These findings would be valuable for the development of PvDBP-based malaria vaccine.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2425-z) contains supplementary material, which is available to authorized users.

Case Report: A Cluster of Plasmodium falciparum Malaria Cases among Thai Workers in Gembu, Nigeria

Although falciparum malaria is an important risk among travelers to sub-Saharan Africa, many travelers remain unaware of this risk. In October 2015, we found a cluster of imported Plasmodium falciparum malaria cases among Thai gem mine workers in Nigeria; none had received malaria chemoprophylaxis or information regarding malaria risk. The index case developed fever and visited our hospital on arrival day in Thailand after his 3-week stay in Nigeria. Plasmodium falciparum was found in his blood. He recovered completely 3 days post-admission. After we requested he contact his colleagues in Nigeria regarding malaria risk, we found that three of his five colleagues currently had fever, were diagnosed with malaria, and were being treated in a local hospital. Two were successfully treated in Nigeria. Although their blood films were negative for malaria, we could confirm that they recently had malaria because the polymerase chain reaction (PCR) was still positive for P. falciparum. Tragically, the last febrile case died in Nigeria 6 days post-admission, after developing jaundice and alteration of consciousness. The two colleagues without fever symptoms were also tested by PCR, which was negative for malaria. In conclusion, we found that four of six workers had malaria in this cluster, which was equal to 66.7% attack rate. There is an urgent need to raise awareness of malaria among workers in highly endemic areas. Clinical practice for travelers who are ill on their return should not only focus on individual cases but also consider potential disease clusters.

Malaria in the Guangxi Zhuang Autonomous Region in China: A Twelve-Year Surveillance Data Study

The incidence of an indigenous malaria, defined as malaria acquired by a local mosquito transmission, declined from 2004 to 2015 in the Guangxi Zhuang Autonomous Region. However, imported malaria, defined as malaria acquired from other endemic regions outside of China, has been increasing in the region, as in the rest of the country, particularly the disease caused by Plasmodium falciparum. A retrospective study was conducted to explore malaria-endemic characteristics in Guangxi during the 2004-2015 timeframe; a total of 2,726 confirmed malaria cases were reported, and the majority (90.3%) were due to P. falciparum (N = 1,697 [62.2%]) and Plasmodium vivax (N = 765 [28.1%]). Thirty-four indigenous cases (1.2%) were observed, with no cases of transmission recorded since 2012. Imported P. vivax and Plasmodium ovale infections increased since 2013. The interval between returning to China and the onset of illness was longer for P. vivax and P. ovale infections than for P. falciparum and Plasmodium malariae infections. The difference interval among the species is likely because of the relapse of P. vivax and P. ovale caused by the activation of the latent hypnozoites. Therefore, health clinics should raise awareness and carry out epidemiological studies and follow-up surveys on migrant workers to avoid misdiagnosis and mistreatment. The evaluation of radical treatment should be carried out using a genotyping technology based on glucose-6-phosphate dehydrogenase deficiency levels, and some new drugs active against the hypnozoites should be developed to mitigate malaria in the region.

A study on the epidemiological characteristics and infectious forecast model of malaria at Guangzhou Airport among Chinese returnees from Africa

BACKGROUND

Cross-border malaria transmission in China is a major component of Chinese imported malaria cases. Such cases mostly are travellers returning from malaria endemic countries in Africa. By investigating malaria infectious status among Chinese worker in Africa, this study analysed the malaria risk factors, in order to establish infectious forecast model.

METHODS

Chinese returnees data from Africa were collected at Guangzhou Baiyun International Airport, Guangzhou, China between August 2015 and March 2016 and were included in the cross-sectional and retrospective survey.

RESULTS

A total of 1492 respondents were included in the study with the majority consisting of junior middle school educated male. Most of them are manual and technical workers hired by companies, with average of 37.04 years of age. Overall malaria incidence rate of the population was 8.98% (134/1492), and there were no significant differences regarding age, gender, occupation, or team. Forecast model was developed on the basis of malaria risk factors including working country, local ecological environment type, work duration and intensity of mosquito bite prevention.

CONCLUSIONS

The survey suggested that malaria incidence was high among Chinese travellers who had worked in Africa countries of heavy malaria burden. Further research on the frequency and severity of clinical episodes among Chinese travellers having worked in Africa is needed.

Development of loop-mediated isothermal amplification with Plasmodium falciparum unique genes for molecular diagnosis of human malaria

In order to achieve better outcomes for treatment and in the prophylaxis of malaria, it is imperative to develop a sensitive, specific, and accurate assay for early diagnosis of Plasmodium falciparum infection, which is the major cause of malaria. In this study, we aimed to develop a loop-mediated isothermal amplification (LAMP) assay with P. falciparum unique genes for sensitive, specific, and accurate detection of P. falciparum infection. The unique genes of P. falciparum were randomly selected from PlasmoDB. The LAMP primers of the unique genes were designed using PrimerExplorer V4. LAMP assays with primers from unique genes of P. falciparum and conserved 18S rRNA gene were developed and their sensitivity was assessed. The specificity of the most sensitive LAMP assay was further examined using genomic DNA from Plasmodium vivax, Plasmodium yoelii and Toxoplasma gondii. Finally, the unique gene-based LAMP assay was validated using clinical samples of P. falciparum infection cases. A total of 31 sets of top-scored LAMP primers from nine unique genes were selected from the pools of designed primers. The LAMP assay with PF3D7_1253300-5 was the most sensitive with the detection limit 5 parasites/μl, and it displayed negative LAMP assay with the genomic DNA samples of P. vivax, P. yoelii, and T. gondii. The LAMP assay with PF3D7_0112300 (18S rRNA) was less sensitive with the detection limit 50 parasites/μl, and it displayed negative LAMP assay with the genomic DNA samples of P. yoelii and T. gondii, but displayed positive LAMP detection with P. vivax. The positive detection rate of the LAMP assay with PF3D7_1253300-5 was 90% (27/30), higher than that (80%, 24/30) of the positive rate of PF3D7_0112300 (18S rRNA) in examining clinical samples of P. falciparum infection cases. The LAMP assay with the primer set PF3D7_1253300-5 was more sensitive, specific, and accurate than those with PF3D7_0112300 (18S rRNA) in examining P. falciparum infection, and therefore it is a promising tool for diagnosis of P. falciparum infection.

Genome-wide scans for the identification of Plasmodium vivax genes under positive selection

BACKGROUND

The current trend of Plasmodium vivax cases imported from Southeast Asia into China has sharply increased recently, especially from the China-Myanmar border (CMB) area. High recombination rates of P. vivax populations associated with varied transmission intensity might cause distinct local selective pressures. The information on the genetic variability of P. vivax in this area is scant. Hence, this study assessed the genetic diversity of P. vivax genome sequence in CMB area and aimed to provide information on the positive selection of new gene loci.

RESULTS

This study reports a genome-wide survey of P. vivax in CMB area, using blood samples from local patients to identify population-specific selective processes. The result showed that considerable genetic diversity and mean pair-wise divergence among the sequenced P. vivax isolates were higher in some important gene families. Using the standardized integrated haplotype score (|iHS|) for all SNPs in chromosomal regions with SNPs above the top 1% distribution, it was observed that the top score locus involved 356 genes and most of them are associated with red blood cell invasion and immune evasion. The XP-EHH test was also applied and some important genes associated with anti-malarial drug resistance were observed in high positive scores list. This result suggests that P. vivax in CMB area is facing more pressure to survive than any other region and this has led to the strong positive selection of genes that are associated with host-parasite interactions.

CONCLUSIONS

This study suggests that greater genetic diversity in P. vivax from CMB area and positive selection signals in invasion and drug resistance genes are consistent with the history of drug use during malaria elimination programme in CMB area. Furthermore, this result also demonstrates that haplotype-based detecting selection can assist the genome-wide methods to identify the determinants of P. vivax diversity.

Whole-genome sequencing of a Plasmodium vivax clinical isolate exhibits geographical characteristics and high genetic variation in China-Myanmar border area

Background

Currently in China, the trend of Plasmodium vivax cases imported from Southeast Asia was increased especially in the China-Myanmar border area. Driven by the increase in P. vivax cases and stronger need for vaccine and drug development, several P. vivax isolates genome sequencing projects are underway. However, little is known about the genetic variability in this area until now.

Results

The sequencing of the first P. vivax isolate from China-Myanmar border area (CMB-1) generated 120 million paired-end reads. A percentage of 10.6 of the quality-evaluated reads were aligned onto 99.9% of the reference strain Sal I genome in 62-fold coverage with an average of 4.8 SNPs per kb. We present a 539-SNP marker data set for P. vivax that can identify different parasites from different geographic origins with high sensitivity. We also identified exceptionally high levels of genetic variability in members of multigene families such as RBP, SERA, vir, MSP3 and AP2. The de-novo assembly yielded a database composed of 8,409 contigs with N50 lengths of 6.6 kb and revealed 661 novel predicted genes including 78 vir genes, suggesting a greater functional variation in P. vivax from this area.

Conclusion

Our result contributes to a better understanding of P. vivax genetic variation, and provides a fundamental basis for the geographic differentiation of vivax malaria from China-Myanmar border area using a direct sequencing approach without leukocyte depletion. This novel sequencing method can be used as an essential tool for the genomic research of P. vivax in the near future.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3523-y) contains supplementary material, which is available to authorized users.

Malaria control and prevention towards elimination: data from an eleven-year surveillance in Shandong Province, China

BACKGROUND

Shandong Province experienced a declining malaria trend of local-acquired transmission, but the increasing imported malaria remains a challenge. Therefore, understanding the epidemiological characteristics of malaria and the control and elimination strategy and interventions is needed for better planning to achieve the overall elimination goal in Shandong Province.

METHODS

A retrospective study was conducted and all individual cases from a web-based reporting system were reviewed and analysed to explore malaria-endemic characteristics in Shandong from 2005 to 2015. Annual malaria incidence reported in 2005-2015 were geo-coded and matched to the county-level. Spatial cluster analysis was performed to evaluate any identified spatial disease clusters for statistical significance. The space-time cluster was detected with high rates through the retrospective space-time analysis scanning using the discrete Poisson model.

RESULTS

The overall malaria incidence decreased to a low level during 2005-2015. In total, 1564 confirmed malaria cases were reported, 27.1% of which (n = 424) were indigenous cases. Most of the indigenous case (n = 339, 80.0%) occurred from June to October. However, the number and scale of imported cases have been increased but no significant difference was observed during months. Shandong is endemic for both Plasmodium vivax (n = 730) and Plasmodium falciparum (n = 674). The disease is mainly distributed in Southern (n = 710) and Eastern region (n = 424) of Shandong, such as Jinning (n = 214 [13.7%]), Weihai (n = 151 [9.7%]), and Yantai (n = 107 [6.8%]). Furthermore, the spatial cluster analysis of malaria cases from 2005 to 2015 indicated that the diseased was not randomly distributed. For indigenous cases, a total of 15 and 2 high-risk counties were determined from 2005 to 2009 (control phase) and from 2010 to 2015 (elimination phase), respectively. For imported cases, a total of 26 and 29 high-risk counties were determined from 2005 to 2009 (control phase) and from 2010 to 2015 (elimination phase), respectively. The method of spatial scan statistics identified different 13 significant spatial clusters between 2005 and 2015. The space-time clustering analysis determined that the most likely cluster included 14 and 19 counties for indigenous and imported, respectively.

CONCLUSIONS

In order to cope with the requirements of malaria elimination phase, the surveillance system should be strengthened particularity on the frequent migration regions as well as the effective multisectoral cooperation and coordination mechanisms. Specific response packages should be tailored among different types of cities and capacity building should also be improved mainly focus on the emergence response and case management. Fund guarantees for scientific research should be maintained both during the elimination and post-elimination phase to consolidate the achievements of malaria elimination.

Spatial and space-time distribution of Plasmodium vivax and Plasmodium falciparum malaria in China, 2005-2014

BACKGROUND

Despite the declining burden of malaria in China, the disease remains a significant public health problem with periodic outbreaks and spatial variation across the country. A better understanding of the spatial and temporal characteristics of malaria is essential for consolidating the disease control and elimination programme. This study aims to understand the spatial and spatiotemporal distribution of Plasmodium vivax and Plasmodium falciparum malaria in China during 2005-2009.

METHODS

Global Moran's I statistics was used to detect a spatial distribution of local P. falciparum and P. vivax malaria at the county level. Spatial and space-time scan statistics were applied to detect spatial and spatiotemporal clusters, respectively.

RESULTS

Both P. vivax and P. falciparum malaria showed spatial autocorrelation. The most likely spatial cluster of P. vivax was detected in northern Anhui province between 2005 and 2009, and western Yunnan province between 2010 and 2014. For P. falciparum, the clusters included several counties of western Yunnan province from 2005 to 2011, Guangxi from 2012 to 2013, and Anhui in 2014. The most likely space-time clusters of P. vivax malaria and P. falciparum malaria were detected in northern Anhui province and western Yunnan province, respectively, during 2005-2009.

CONCLUSION

The spatial and space-time cluster analysis identified high-risk areas and periods for both P. vivax and P. falciparum malaria. Both malaria types showed significant spatial and spatiotemporal variations. Contrary to P. vivax, the high-risk areas for P. falciparum malaria shifted from the west to the east of China. Further studies are required to examine the spatial changes in risk of malaria transmission and identify the underlying causes of elevated risk in the high-risk areas.

Analysis of Pvama1 genes from China-Myanmar border reveals little regional genetic differentiation of Plasmodium vivax populations

Background

With the premise of diminishing parasite genetic diversity following the reduction of malaria incidence, the analysis of polymorphic antigenic markers may provide important information about the impact of malaria control on local parasite populations. Here we evaluated the genetic diversity of Plasmodium vivax apical membrane antigen 1 (Pvama1) gene in a parasite population from the China-Myanmar border and compared it with global P. vivax populations.

Methods

We performed evolutionary analysis to examine the genetic diversity, natural selection, and population differentiation of 73 Pvama1 sequences acquired from the China-Myanmar border as well as 615 publically available Pvama1 sequences from seven global P. vivax populations.

Results

A total of 308 Pvama1 haplotypes were identified among the global P. vivax isolates. The overall nucleotide diversity of Pvama1 gene among the 73 China-Myanmar border parasite isolates was 0.008 with 41 haplotypes being identified (Hd = 0.958). Domain I (DI) harbored the majority (26/33) of the polymorphic sites. The McDonald Kreitman test showed a significant positive selection across the ectodomain and the DI of Pvama1. The fixation index (F_ST) estimation between the China-Myanmar border, Thailand (0.01) and Myanmar (0.10) showed only slight geographical genetic differentiation. Notably, the Sal-I haplotype was not detected in any of the analyzed global isolates, whereas the Belem strain was restricted to the Thai population. The detected mutations are mapped outside the overlapped region of the predicted B-cell epitopes and intrinsically unstructured/disordered regions.

Conclusions

This study revealed high levels of genetic diversity of Pvama1 in the P. vivax parasite population from the China-Myanmar border with DI displaying stronger diversifying selection than other domains. There were low levels of population subdivision among parasite populations from the Greater Mekong Subregion.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1899-1) contains supplementary material, which is available to authorized users.

Lessons on malaria control in the ethnic minority regions in Northern Myanmar along the China border, 2007-2014

BACKGROUND

For many countries where malaria is endemic, the burden of malaria is high in border regions. In ethnic minority areas along the Myanmar-China border, residents have poor access to medical care for diagnosis and treatment, and there have been many malaria outbreaks in such areas. Since 2007, with the support of the Global Fund to Fight AIDS, Tuberculosis and Malaria (GFATM), a malaria control project was introduced to reduce the malaria burden in several ethnic minority regions.

METHODS

A malaria control network was established during the period from 2007 to 2014. Multiple malaria interventions, including diagnosis, treatment, distribution of LLINs and health education, were conducted to improve the accessibility and quality of malaria control services for local residents. Annual cross-sectional surveys were conducted to evaluate intervention coverage and indicators of malaria transmission.

RESULTS

In ethnic minority regions where a malaria control network was established, both the annual malaria incidence (19.1 per thousand per year, in 2009; 8.7, in 2014) and malaria prevalence (13.6 % in 2008; 0.43 % in 2014) decreased dramatically during the past 5-6 years. A total of 851 393 febrile patients were detected, 202 598 malaria cases (including confirmed cases and suspected cases) were treated, and 759 574 LLINs were delivered to populations at risk. Of households in 2012, 73.9 % had at least one ITNs/LLINs (vs. 28.3 %, in 2008), and 50.7 % of children less than 5 years and 50.3 % of pregnant women slept under LLINs the night prior to their visit. Additionally, malaria knowledge was improved in 68.4 % of residents.

CONCLUSION

There has been great success in improving malaria control in these regions from 2007 to 2014. Malaria burdens have decreased, especially in KOK and WA. The continued maintenance of sustainable malaria control networks in these regions may be a long-term process, due to regional conflicts and the lack of funds, technology, and health workers. Furthermore, information and scientific support from the international community should be offered to these ethnic minority regions to uphold recent achievements.

Major parasitic diseases of poverty in mainland China: perspectives for better control

Significant progress has been made in the prevention, control, and elimination of human parasitic diseases in China in the past 60 years. However, parasitic diseases of poverty remain major causes of morbidity and mortality, and inflict enormous economic costs on societies.In this article, we review the prevalence rates, geographical distributions, epidemic characteristics, risk factors, and clinical manifestations of parasitic diseases of poverty listed in the first issue of the journal Infectious Diseases of Poverty on 25 October 2012. We also address the challenges facing control of parasitic diseases of poverty and provide suggestions for better control.

Shrinking the malaria map in China: measuring the progress of the National Malaria Elimination Programme

Background

Remarkable progress has been made towards the elimination of malaria in China since the National Malaria Elimination Programme (NMEP) was launched in 2010. The incidence of locally-acquired malaria cases has declined rapidly and endemic areas have also dramatically shrunk. In total, 3 078 malaria cases were reported in 2014, but only 56 cases were indigenous. In order to further promote the elimination programme, we reviewed the progress of and experiences associated with malaria elimination in China, and identified the challenges and priorities for the next stage of the programme.

Methods

Data were collected from the web-based China Information System for Disease Control and Prevention, and the China Annual Report of Malaria Elimination. The progress towards the elimination of malaria from 2010 to 2014 was measured.

Results

During the implementation of the NMEP from 2010 to 2014, local malaria incidence has declined continuously, only remaining in the Yunnan Province and Tibet Autonomous Region in 2014. By the end of 2015, 75.6 % (1 636/2 163) of the malaria-endemic counties passed the sub-national elimination assessment. The main challenges are cases of border malaria and imported malaria from other countries. Sustainable support and investment from the government, the establishment of an effective surveillance and response system, and risk assessments for the potential reintroduction of malaria are priorities for the next stage of the elimination programme.

Conclusions

The NMEP in China has been successfully implemented thus far and the malaria map has shrunk dramatically. The priorities for malaria elimination are interventions to block transmission at border areas, management of imported malaria cases, preventing malaria reintroduction, capacity building, and sustainability of malaria surveillance and response.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-016-0146-5) contains supplementary material, which is available to authorized users.

Whole-genome sequencing of a Plasmodium vivax isolate from the China-Myanmar border area

Currently, there is a trend of an increasing number of Plasmodium vivaxmalaria cases in China that are imported across its Southeast Asia border, especially in the China-Myanmar border area (CMB). To date, little is known about the genetic diversity of P. vivax in this region. In this paper, we report the first genome sequencing of a P. vivaxisolate (CMB-1) from a vivax malaria patient in CMB. The sequencing data were aligned onto 96.43% of the P. vivax Salvador I reference strain (Sal I) genome with 7.84-fold coverage as well as onto 98.32% of 14 Sal I chromosomes. Using the de novo assembly approach, we generated 8,541 scaffolds and assembled a total of 27.1 Mb of sequence into CMB-1 scaffolds. Furthermore, we identified all 295 known virgenes, which is the largest subtelomeric multigene family in malaria parasites. These results provide an important foundation for further research onP. vivax population genetics.

Predicting malaria vector distribution under climate change scenarios in China: Challenges for malaria elimination

Projecting the distribution of malaria vectors under climate change is essential for planning integrated vector control activities for sustaining elimination and preventing reintroduction of malaria. In China, however, little knowledge exists on the possible effects of climate change on malaria vectors. Here we assess the potential impact of climate change on four dominant malaria vectors (An. dirus, An. minimus, An. lesteri and An. sinensis) using species distribution models for two future decades: the 2030 s and the 2050 s. Simulation-based estimates suggest that the environmentally suitable area (ESA) for An. dirus and An. minimus would increase by an average of 49% and 16%, respectively, under all three scenarios for the 2030 s, but decrease by 11% and 16%, respectively in the 2050 s. By contrast, an increase of 36% and 11%, respectively, in ESA of An. lesteri and An. sinensis, was estimated under medium stabilizing (RCP4.5) and very heavy (RCP8.5) emission scenarios. in the 2050 s. In total, we predict a substantial net increase in the population exposed to the four dominant malaria vectors in the decades of the 2030 s and 2050 s, considering land use changes and urbanization simultaneously. Strategies to achieve and sustain malaria elimination in China will need to account for these potential changes in vector distributions and receptivity.

RC, Battle KE, Longbottom J, Mappin B, Ordanovich D, Tatem AJ, Drakeley C, Gething PW, Zimmerman PA, Smith DL, Hay SI. Plasmodium vivax Transmission in Africa

Malaria in sub-Saharan Africa has historically been almost exclusively attributed to Plasmodium falciparum (Pf). Current diagnostic and surveillance systems in much of sub-Saharan Africa are not designed to identify or report non-Pf human malaria infections accurately, resulting in a dearth of routine epidemiological data about their significance. The high prevalence of Duffy negativity provided a rationale for excluding the possibility of Plasmodium vivax (Pv) transmission. However, review of varied evidence sources including traveller infections, community prevalence surveys, local clinical case reports, entomological and serological studies contradicts this viewpoint. Here, these data reports are weighted in a unified framework to reflect the strength of evidence of indigenous Pv transmission in terms of diagnostic specificity, size of individual reports and corroboration between evidence sources. Direct evidence was reported from 21 of the 47 malaria-endemic countries studied, while 42 countries were attributed with infections of visiting travellers. Overall, moderate to conclusive evidence of transmission was available from 18 countries, distributed across all parts of the continent. Approximately 86.6 million Duffy positive hosts were at risk of infection in Africa in 2015. Analysis of the mechanisms sustaining Pv transmission across this continent of low frequency of susceptible hosts found that reports of Pv prevalence were consistent with transmission being potentially limited to Duffy positive populations. Finally, reports of apparent Duffy-independent transmission are discussed. While Pv is evidently not a major malaria parasite across most of sub-Saharan Africa, the evidence presented here highlights its widespread low-level endemicity. An increased awareness of Pv as a potential malaria parasite, coupled with policy shifts towards species-specific diagnostics and reporting, will allow a robust assessment of the public health significance of Pv, as well as the other neglected non-Pf parasites, which are currently invisible to most public health authorities in Africa, but which can cause severe clinical illness and require specific control interventions.