Plasmodium vivax serological exposure markers: PvMSP1-42-induced humoral and memory B-cell response generates long-lived antibodies.

Plasmodium vivax serological exposure markers (SEMs) have emerged as promising tools for the actionable surveillance and implementation of targeted interventions to accelerate malaria elimination. To determine the dynamic profiles of SEMs in current and past P. vivax infections, we screened and selected 11 P. vivax proteins from 210 putative proteins using protein arrays, with a set of serum samples obtained from patients with acute P. vivax and documented past P. vivax infections. Then we used a murine protein immune model to initially investigate the humoral and memory B cell response involved in the generation of long-lived antibodies. We show that of the 11 proteins, especially C-terminal 42-kDa region of P. vivax merozoite surface protein 1 (PvMSP1-42) induced longer-lasting long-lived antibodies, as these antibodies were detected in individuals infected with P. vivax in the 1960-1970s who were not re-infected until 2012. In addition, we provide a potential mechanism for the maintenance of long-lived antibodies after the induction of PvMSP1-42. The results indicate that PvMSP1-42 induces more CD73+CD80+ memory B cells (MBCs) compared to P. vivax GPI-anchored micronemal antigen (PvGAMA), allowing IgG anti-PvMSP1-42 antibodies to be maintained for a long time.

Using social media for health education and promotion: a pilot of WeChat-based prize quizzes on China national malaria day.

BACKGROUND: Imported malaria cases remains a key health concern, especially during the COVID-19 pandemic. Providing accurate health information is important to improving people's awareness of malaria. WeChat is an excellent social media tool for health information dissemination, especially during the pandemic. This study explored the effect of malaria knowledge dissemination via a WeChat public account. METHODS: A questionnaire for data collection was constructed using the online survey tool Sojump. Questionnaires were sent to users who followed the Jiangsu institute of Parasitic Disease WeChat public account during the National Malaria Day 2021 period. A small incentive (WeChat Red Packet) was distributed to everyone who answered the questionnaire correctly on time. RESULTS: A total of 13,169 valid questionnaires were collected during the China National Malaria Day period. Questions in which participants focused mainly on information pertaining to themselves, such as infection, symptoms, and epidemic areas, reached highest accuracy (above 90%). Questionnaires were submitted through smartphones and most of them were completed during the period of 4 days from April 23 to April 26, 2021 when a WeChat Red Packet was offered. The accuracy of responses was related to bolded words and location and number of knowledge points that were shown at the beginning of the questionnaire. The number of users of the WeChat public account in question increased from 5961 to 12,339 in just 4 days of the activity. CONCLUSION: A WeChat public account is a convenient and accessible tool for spreading malaria-related health information to the public. Distribution of incentives (Red Packets) can effectively increase public attention to popular science and health information and activities.

Confirmation of the absence of local transmission and geographic assignment of imported falciparum malaria cases to China using microsatellite panel.

BACKGROUND: Current methods to classify local and imported malaria infections depend primarily on patient travel history, which can have limited accuracy. Genotyping has been investigated as a complementary approach to track the spread of malaria and identify the origin of imported infections. METHODS: An extended panel of 26 microsatellites (16 new microsatellites) for Plasmodium falciparum was evaluated in 602 imported infections from 26 sub-Saharan African countries to the Jiangsu Province of People's Republic of China. The potential of the 26 microsatellite markers to assign imported parasites to their geographic origin was assessed using a Bayesian method with Markov Chain Monte Carlo (MCMC) as implemented in the program Smoothed and Continuous Assignments (SCAT) with a modification to incorporate haploid genotype data. RESULTS: The newly designed microsatellites were polymorphic and are not in linkage disequilibrium with the existing microsatellites, supporting previous findings of high rate of recombination in sub-Saharan Africa. Consistent with epidemiology inferred from patients' travel history, no evidence for local transmission was found; nearly all genetically related infections were identified in people who travelled to the same country near the same time. The smoothing assignment method assigned imported cases to their likely geographic origin with an accuracy (Angola: 59%; Nigeria: 51%; Equatorial Guinea: 40%) higher than would be achieved at random, reaching statistical significance for Angola and Equatorial Guinea. CONCLUSIONS: Genotyping using an extended microsatellite panel is valuable for malaria case classification and programme evaluation in an elimination setting. A Bayesian method for assigning geographic origin of mammals based on genetic data was adapted for malaria and showed potential for identification of the origin of imported infections.

Classification of induced malaria case in an elimination setting: investigation of transfusion-transmitted malaria cases.

BACKGROUND: Since the National Malaria Elimination Action Plan was launched in China in 2010, local malaria transmission has decreased rapidly. Zero indigenous cases were reported since 2017. However, after 2010, the proportion of imported cases in China increased from 45.7% in 2010 to 99.9% in 2016, and almost all provinces of China have reported imported cases in recent years. Prevention of the reintroduction of malaria into China is crucial for the maintenance of its malaria-free status. Hence, it is of utmost importance to correctly identify the source of malaria infections within the country. CASE INTRODUCTION AND RESPONSE: In 2016 and 2017, three laboratory-confirmed cases of malaria caused by Plasmodium falciparum were identified in patients with no previous travel history to endemic areas were reported in Jiangsu Province, China, where malaria due to P. falciparum was eliminated about 30 years ago. These were diagnosed after 41, 31 and 39 days of seeking treatment, respectively, and all of them had received blood transfusions. Further investigations indicated that two of the cases had received blood from foreign students (from Indonesia and Ghana), and the other had received blood from an individual who had worked in Equatorial Guinea. All three blood donors were traced, and found to be carrying asymptomatic P. falciparum infections by microscopic examination and PCR. Furthermore, five polymorphic microsatellite markers (C1M4, C4M62, C13M13, C14M17, and C13M63) were typed and used to link parasites from the donors with those of the transfusion-receiving patients. CONCLUSIONS: Three transfusion-transmitted malaria cases were identified in China, all of which were due to the transfusion of blood donated by individuals who had contracted malaria outside the country. These cases can provide a reference for those faced with similar challenges in malaria case identification and classification in other regions. In addition, a stricter screening policy including the use of appropriate detection methods for malaria parasites should be developed and adopted for blood donation in regions undergoing malaria elimination.

Implementing parasite genotyping into national surveillance frameworks: feedback from control programmes and researchers in the Asia-Pacific region.

The Asia-Pacific region faces formidable challenges in achieving malaria elimination by the proposed target in 2030. Molecular surveillance of Plasmodium parasites can provide important information on malaria transmission and adaptation, which can inform national malaria control programmes (NMCPs) in decision-making processes. In November 2019 a parasite genotyping workshop was held in Jakarta, Indonesia, to review molecular approaches for parasite surveillance and explore ways in which these tools can be integrated into public health systems and inform policy. The meeting was attended by 70 participants from 8 malaria-endemic countries and partners of the Asia Pacific Malaria Elimination Network. The participants acknowledged the utility of multiple use cases for parasite genotyping including: quantifying the prevalence of drug resistant parasites, predicting risks of treatment failure, identifying major routes and reservoirs of infection, monitoring imported malaria and its contribution to local transmission, characterizing the origins and dynamics of malaria outbreaks, and estimating the frequency of Plasmodium vivax relapses. However, the priority of each use case varies with different endemic settings. Although a one-size-fits-all approach to molecular surveillance is unlikely to be applicable across the Asia-Pacific region, consensus on the spectrum of added-value activities will help support data sharing across national boundaries. Knowledge exchange is needed to establish local expertise in different laboratory-based methodologies and bioinformatics processes. Collaborative research involving local and international teams will help maximize the impact of analytical outputs on the operational needs of NMCPs. Research is also needed to explore the cost-effectiveness of genetic epidemiology for different use cases to help to leverage funding for wide-scale implementation. Engagement between NMCPs and local researchers will be critical throughout this process.

Malaria training for community health workers in the setting of elimination: a qualitative study from China.

BACKGROUND: Continuous training of health workers is a key intervention to maintain their good performance and keep their vigilance during malaria elimination programmes. However, countries progressing toward malaria elimination have a largely decreased malaria disease burden, less frequent exposure of health workers to malaria patients, and new challenges in the epidemiology of the remaining malaria cases. Moreover, competing health priorities and usually a decline in resources and in political commitment also pose challenges to the elimination programme. As a consequence, the acceptability, sustainability, and impact of malaria training and education programmes face challenges. However, little is known of the perceptions and expectations of malaria training and education programmes of health workers being engaged in countries with malaria elimination programmes. METHODS: This qualitative study provides information on perceptions and expectations of health workers of malaria training programmes from China, which aims to malaria elimination by the year 2020. This study was embedded into a larger study on the challenges and lessons learned during the malaria surveillance strategy in China, involving 42 interviews with malaria experts, health staff, laboratory practitioners, and village doctors at the provincial, city, county, township, and village levels from Gansu province (northwestern China) and Jiangsu province (southeastern China). RESULTS: In the context of an increasing number of imported malaria cases in China, the majority of respondents emphasized the necessity and importance of such programmes and complained about a decreasing frequency of training courses. Moreover, they called for innovative strategies to improve the implementation and sustainability of the malaria training programmes until the elimination goal has been achieved. Perceptions and expectations of health workers from different health centres were quite different. Health workers from higher-level facilities were more concerned about technical training aspects, while health workers from periphery of the health system expected to receive more training on field work coordination and on specific public health actions with regard to case detection and focus investigation. CONCLUSIONS: There is need to guarantee an ongoing good training of health workers in China on malaria aspects until the year 2020 and probably beyond.

Piloting a programme tool to evaluate malaria case investigation and reactive case detection activities: results from 3 settings in the Asia Pacific.

BACKGROUND: Case investigation and reactive case detection (RACD) activities are widely-used in low transmission settings to determine the suspected origin of infection and identify and treat malaria infections nearby to the index patient household. Case investigation and RACD activities are time and resource intensive, include methodologies that vary across eliminating settings, and have no standardized metrics or tools available to monitor and evaluate them. METHODS: In response to this gap, a simple programme tool was developed for monitoring and evaluating (M&E) RACD activities and piloted by national malaria programmes. During the development phase, four modules of the RACD M&E tool were created to assess and evaluate key case investigation and RACD activities and costs. A pilot phase was then carried out by programme implementers between 2013 and 2015, during which malaria surveillance teams in three different settings (China, Indonesia, Thailand) piloted the tool over a period of 3 months each. This study describes summary results of the pilots and feasibility and impact of the tool on programmes. RESULTS: All three study areas implemented the RACD M&E tool modules, and pilot users reported the tool and evaluation process were helpful to identify gaps in RACD programme activities. In the 45 health facilities evaluated, 71.8% (97/135; min 35.3-max 100.0%) of the proper notification and reporting forms and 20.0% (27/135; min 0.0-max 100.0%) of standard operating procedures (SOPs) were available to support malaria elimination activities. The tool highlighted gaps in reporting key data indicators on the completeness for malaria case reporting (98.8%; min 93.3-max 100.0%), case investigations (65.6%; min 61.8-max 78.4%) and RACD activities (70.0%; min 64.7-max 100.0%). Evaluation of the SOPs showed that knowledge and practices of malaria personnel varied within and between study areas. Average monthly costs for conducting case investigation and RACD activities showed variation between study areas (min USD $844.80-max USD $2038.00) for the malaria personnel, commodities, services and other costs required to carry out the activities. CONCLUSION: The RACD M&E tool was implemented in the three pilot areas, identifying key gaps that led to impacts on programme decision making. Study findings support the need for routine M&E of malaria case reporting, case investigation and RACD activities. Scale-up of the RACD M&E tool in malaria-eliminating settings will contribute to improved programme performance to the high level that is required to reach elimination.

The increasing importance of Plasmodium ovale and Plasmodium malariae in a malaria elimination setting: an observational study of imported cases in Jiangsu Province, China, 2011-2014.

BACKGROUND: Following initiation of China's National Malaria Elimination Action Plan in 2010, indigenous malaria infections in Jiangsu Province decreased significantly. Meanwhile imported Plasmodium infections have increased substantially, particularly Plasmodium ovale and Plasmodium malariae. Given the risk for malaria resurgence, there is an urgent need to understand the increase in imported P. ovale and P. malariae infections as China works to achieve national malaria elimination. METHODS: An observational study of imported malaria cases in Jiangsu Province, China was carried out for the period of 2011-2014. RESULTS: A total of 1268 malaria cases were reported in Jiangsu Province from 2011 to 2014. Although imported Plasmodium falciparum cases (n = 1058) accounted for 83.4 % of all reported cases in Jiangsu, P. ovale cases (14, 19, 30, and 46) and their proportion (3.7, 9.6, 8.8, and 13.0 %) of all malaria cases increased over the 4 years. Similarly, P. malariae cases (seven, two, nine, and 10) and proportion (1.9, 1.0, 2.6, and 2.8 %) of all malaria cases increased slightly during this time. A total of 98 cases of Plasmodium ovale curtisi (47/98, 48 %) and Plasmodium ovale wallikeri (51/98, 52 %) were identified as well. Latency periods were significant among these Plasmodium infections (p = 0.00). Also, this study found that the latency periods of P. ovale sp., P. malariae and Plasmodium vivax were significantly longer than P. falciparum. However, for both P. ovale curtisi and P. ovale wallikeri infections, the latency period analysis was not significant (p = 0.81). Misdiagnosis of both P. ovale and P. malariae was greater than 71.5 and 71.4 %, respectively. The P. ovale cases were misdiagnosed as P. falciparum (35 cases, 32.1 %), P. vivax (43 cases, 39.4 %) by lower levels of CDCs or hospitals. And, the P. malariae cases were misdiagnosed as P. falciparum (ten cases, 35.7 %), P. vivax (nine cases, 32.1 %) and P. ovale sp. (one case, 3.6 %). Geographic distribution of imported P. ovale sp. and P. malariae cases in Jiangsu Province mainly originated from sub-Saharan Africa such as Equatorial Guinea, Nigeria, and Angola. CONCLUSIONS: Although the vast majority of imported malaria cases were due to P. falciparum, the increase in other rare Plasmodium species originating from sub-Saharan Africa and Southeast Asia should be closely monitored at all levels of health providers focusing on diagnosis and treatment of malaria. In addition to a receptive vector environment, long latency periods and misdiagnosis of P. malariae and P. ovale sp. increase the risk of re-introduction of malaria in China.

Transcriptome profiling of pyrethroid resistant and susceptible mosquitoes in the malaria vector, Anopheles sinensis.

BACKGROUND: Anopheles sinensis is a major malaria vector in China and other Southeast Asian countries, and it is becoming increasingly resistant to the insecticides used for agriculture, net impregnation, and indoor residual spray. Very limited genomic information on this species is available, which has hindered the development of new tools for resistance surveillance and vector control. We used the 454 GS FLX system and generated expressed sequence tag (EST) databases of various life stages of An. sinensis, and we determined the transcriptional differences between deltamethrin resistant and susceptible mosquitoes. RESULTS: The 454 GS FLX transcriptome sequencing yielded a total of 624,559 reads (average length of 290 bp) with the pooled An. sinensis mosquitoes across various development stages. The de novo assembly generated 33,411 contigs with average length of 493 bp. A total of 8,057 ESTs were generated with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation. A total of 2,131 ESTs were differentially expressed between deltamethrin resistant and susceptible mosquitoes collected from the same field site in Jiangsu, China. Among these differentially expressed ESTs, a total of 294 pathways were mapped to the KEGG database, with the predominant ESTs belonging to metabolic pathways. Furthermore, a total of 2,408 microsatellites and 15,496 single nucleotide polymorphisms (SNPs) were identified. CONCLUSIONS: The annotated EST and transcriptome databases provide a valuable genomic resource for further genetic studies of this important malaria vector species. The differentially expressed ESTs associated with insecticide resistance identified in this study lay an important foundation for further functional analysis. The identified microsatellite and SNP markers will provide useful tools for future population genetic and comparative genomic analyses of malaria vectors.

Genetic diversity and population structure of Plasmodium vivax in Central China.

BACKGROUND: In Central China the declining incidence of Plasmodium vivax has been interrupted by epidemic expansions and imported cases. The impact of these changes on the local parasite population, and concurrent risks of future resurgence, was assessed. METHODS: Plasmodium vivax isolates collected from Anhui and Jiangsu provinces, Central China between 2007 and 2010 were genotyped using capillary electrophoresis at seven polymorphic short tandem repeat markers. Spatial and temporal analyses of within-host and population diversity, population structure, and relatedness were conducted on these isolates. RESULTS: Polyclonal infections were infrequent in the 94 isolates from Anhui (4%) and 25 from Jiangsu (12%), with a trend for increasing frequency from 2008 to 2010 (2 to 19%) when combined. Population diversity was high in both provinces and across the years tested (H(E) = 0.8 - 0.85). Differentiation between Anhui and Jiangsu was modest (F'(ST) = 0.1). Several clusters of isolates with identical multi-locus haplotypes were observed across both Anhui and Jiangsu. Linkage disequilibrium was strong in both populations and in each year tested (I(A)(S) = 0.2 - 0.4), but declined two- to four-fold when identical haplotypes were accounted for, indicative of occasional epidemic transmission dynamics. None of five imported isolates shared identical haplotypes to any of the central Chinese isolates. CONCLUSIONS: The population genetic structure of P. vivax in Central China highlights unstable transmission, with limited barriers to gene flow between the central provinces. Despite low endemicity, population diversity remained high, but the reservoirs sustaining this diversity remain unclear. The challenge of imported cases and risks of resurgence emphasize the need for continued surveillance to detect early warning signals. Although parasite genotyping has potential to inform the management of outbreaks, further studies are required to identify suitable marker panels for resolving local from imported P. vivax isolates.

Malaria in overseas labourers returning to China: an analysis of imported malaria in Jiangsu Province, 2001-2011.

BACKGROUND: While great success in malaria control has been achieved in China, imported malaria has become a major challenge in the context of malaria elimination. This retrospective study describes the epidemiological profile of imported malaria and identifies the at-risk population during the period of 2001-2011 in Jiangsu Province. METHODS: Data on imported malaria cases in Jiangsu Province from 2001 to 2011 were collected from the infectious disease surveillance system and case investigation reports. Epidemiological trends were described and correlations between trends in exported labour and malaria imported from other countries were explored. RESULTS: From 2001 to 2011, 918 malaria cases and six malaria deaths were due to malaria imported from other countries, accounting for 12.4% of all malaria cases and 100% of all malaria deaths. During this time period the annual number of indigenous cases decreased from 1,163 to 13 while the number of imported cases increased from 86 to 366. The relative proportion of cases imported from other countries versus other provinces also increased from 0.0% (0/86) to 97.0% (350/361). The most affected demographic groups were males (897 cases, 97.7%) and adults (20-50 years old: 857 cases, 93.4%). All 918 cases had a recent travel history to malaria-endemic areas and the main purpose for travel was overseas labour (848 cases, 92.4%). The cases were mainly acquired from African countries (855 cases, 93.1%). Plasmodium falciparum was the most common species (733 cases, 79.8%). The increase in malaria cases imported from other countries was associated with the growth of investment to Africa from Jiangsu (R2 = 0.8057) and the increasing number of exported labourers to Africa from Jiangsu (R2 = 0.8863). CONCLUSIONS: From 2001 to 2011 in Jiangsu Province, there was a consistent increase in the number of malaria cases imported from other countries while the number of locally acquired cases sharply declined. This trend may be ascribed to the increasing investment from China to Africa and the rising number of Chinese labourers working in Africa. Preventative efforts should be targeted to this high-risk group and the surveillance and response system should be strengthened to prevent local resurgence in Jiangsu.

A smartphone-based crowd-sourced real-time surveillance platform (apple snail inspector) for the invasive snails: a design and development study.

BACKGROUND: The large amphibious freshwater apple snail is an important invasive species in China, but there is currently no method available for their surveillance. The development and popularization of smartphones provide a new platform for research on surveillance technologies for the early detection and effective control of invasive species. METHODS: The ASI surveillance system was developed based on the infrastructure of the WeChat platform and Amap. The user can directly enter the game interface through the WeChat port on their mobile phone, and the system automatically obtains their location. The user can then report the location of apple snails. The administrator can audit the reported information, and all information can be exported to Microsoft Excel version 2016 for analysis. The map was generated by ArcGIS 10.2 and was used to characterize the spatial and temporal distribution of apple snails in Jiangsu Province. RESULTS: The architecture of ASI consists of three parts: a mobile terminal, a server terminal and a desktop terminal. We published more than 10 tweets on the official WeChat account of the system to announce it to the public, and a total of 207 users in 2020 and 2021 correctly reported sightings of apple snails. We identified 550 apple snails breeding sites in 2020 and 2021, featuring ponds (81%), parks (17%) and farmland (2%). In addition, most of the locations contained snail eggs, and the reporting times mainly occurred between May and September. CONCLUSIONS: The ASI is an effective surveillance system that can be used to identify the breeding locations of apple snails and provides the basis of prevention and control for its dispersal. Its successful development and operation provide new potential avenues for surveillance of other public health issues.

Mass drug administration for the control and elimination of Plasmodium vivax malaria: an ecological study from Jiangsu province, China.

BACKGROUND: Recent progress in malaria control has caused renewed interest in mass drug administration (MDA) as a potential elimination strategy but the evidence base is limited. China has extensive experience with MDA, but it is not well documented. METHODS: An ecological study was conducted to describe the use of MDA for the control and elimination of Plasmodium vivax in Jiangsu Province and explore the association between MDA and malaria incidence. Two periods were focused on: 1973 to 1983 when malaria burden was high and MDA administered to highly endemic counties province-wide, and 2000 to 2009, when malaria burden was low and a focal approach was used in two counties. All available data about the strategies implemented, MDA coverage, co-interventions, incidence, and adverse events were collected and described. Joinpoint analysis was used to describe trends in incidence and the relationship between MDA coverage and incidence was explored in negative binomial regression models. RESULTS: From 1973 to 1983, MDA with pyrimethamine and primaquine was used on a large scale, with up to 30 million people in target counties covered in a peak year (50% of the total population). Joinpoint analyses identified declines in annual incidence, -56.7% (95% CI -75.5 to -23.7%) from 1973-1976 and -12.4% (95% CI -24.7 to 2.0%) from 1976-1983. Population average negative binomial models identified a relationship between higher total population MDA coverage and lower monthly incidence from 1973-1976, IRR 0.98 (95% CI 0.97 to 1.00), while co-interventions, rainfall and GDP were not associated. From 2000-2009, incidence in two counties declined (annual change -43.7 to -14.0%) during a time when focal MDA using chloroquine and primaquine was targeted to villages and/or individuals residing near passively detected index cases (median 0.04% of total population). Although safety data were not collected systematically, there were rare reports of serious but non-fatal events. CONCLUSIONS: In Jiangsu Province, China, large-scale MDA was implemented and associated with declines in high P. vivax malaria transmission; a more recent focal approach may have contributed to interruption of transmission. MDA should be considered a potential key strategy for malaria control and elimination.

Chromosome-level genome assembly defines female-biased genes associated with sex determination and differentiation in the human blood fluke Schistosoma japonicum.

Schistosomiasis is a neglected tropical disease of humans caused by blood flukes of the genus Schistosoma, the only dioecious parasitic flatworm. Although aspects of sex determination, differentiation and reproduction have been studied in some Schistosoma species, almost nothing is known for Schistosoma japonicum, the causative agent of schistosomiasis japonica. This mainly reflects the lack of high-quality genomic and transcriptomic resources for this species. As current genomes for S. japonicum are highly fragmented, we assembled and report a chromosome-level reference genome (seven autosomes, the Z-chromosome and partial W-chromosome), achieving a substantially enhanced gene annotation. Utilizing this genome, we discovered that the sex chromosomes of S. japonicum and its congener S. mansoni independently suppressed recombination during evolution, forming five and two evolutionary strata, respectively. By exploring the W-chromosome and sex-specific transcriptomes, we identified 35 W-linked genes and 257 female-preferentially transcribed genes (FTGs) from our chromosomal assembly and uncovered a signature for sex determination and differentiation in S. japonicum. These FTGs clustering within autosomes or the Z-chromosome exhibit a highly dynamic transcription profile during the pairing of female and male schistosomula, thereby representing a critical phase for the maturation of the female worms and suggesting distinct layers of regulatory control of gene transcription at this development stage. Collectively, these data provide a valuable resource for further functional genomic characterization of S. japonicum, shed light on the evolution of sex chromosomes in this highly virulent human blood fluke, and provide a pathway to identify novel targets for development of intervention tools against schistosomiasis.

Elicitation of T-cell-derived IFN-γ-dependent immunity by highly conserved Plasmodium ovale curtisi Duffy binding protein domain region II (PocDBP-RII).

BACKGROUND: Infections with Plasmodium ovale are widely distributed but rarely investigated, and the resulting burden of disease has been underestimated. Plasmodium ovale curtisi Duffy binding protein domain region II (PocDBP-RII) is an essential ligand for reticulocyte recognition and host cell invasion by P. ovale curtisi. However, the genomic variation, antigenicity and immunogenicity of PocDBP-RII remain major knowledge gaps. METHODS: A total of 93 P. ovale curtisi samples were collected from migrant workers who returned to China from 17 countries in Africa between 2012 and 2016. The genetic polymorphism, natural selection and copy number variation (CNV) were investigated by sequencing and real-time PCR. The antigenicity and immunogenicity of the recombinant PocDBP-RII (rPocDBP-RII) protein were further examined, and the humoral and cellular responses of immunized mice were assessed using protein microarrays and flow cytometry. RESULTS: Efficiently expressed and purified rPocDBP-RII (39 kDa) was successfully used as an antigen for immunization in mice. The haplotype diversity (Hd) of PocDBP-RII gene was 0.105, and the nucleotide diversity index (π) was 0.00011. No increased copy number was found among the collected isolates of P. ovale curtisi. Furthermore, rPocDBP-RII induced persistent antigen-specific antibody production with a serum IgG antibody titer of 1: 16,000. IFN-γ-producing T cells, rather than IL-10-producing cells, were activated in response to the stimulation of rPocDBP-RII. Compared to PBS-immunized mice (negative control), there was a higher percentage of CD4+CD44highCD62L- T cells (effector memory T cells) and CD8+CD44highCD62L+ T cells (central memory T cells) in rPocDBP-RII­immunized mice. CONCLUSIONS: PocDBP-RII sequences were highly conserved in clinical isolates of P. ovale curtisi. rPocDBP-RII protein could mediate protective blood-stage immunity through IFN-γ-producing CD4+ and CD8+ T cells and memory T cells, in addition to inducing specific antibodies. Our results suggested that rPocDBP-RII protein has potential as a vaccine candidate to provide assessment and guidance for malaria control and elimination activities.

Case-based malaria surveillance and response: implementation of 1-3-7 approach in Jiangsu Province, China.

Following initiation of China's National Malaria Elimination Action Plan (NMEAP) in 2010, China's 1-3-7 surveillance and response approach was developed and rolled out in China to facilitate the malaria control programme and accelerate the progress of malaria elimination. Innovative strategies and interventions have been developed and implemented in Jiangsu Province to facilitate case-based malaria surveillance and response. A total of 9879 malaria cases were reported in Jiangsu Province from 2001 to 2020. Since 2012, no indigenous malaria cases have been reported in Jiangsu Province. However, in recent years, there has been a substantial increase of imported cases from abroad. To continue improving the malaria surveillance and response system, Jiangsu Province has conducted population-based health education to improve the healthcare seeking behaviour of malaria patients, strengthened the capacity of health facilities to improve the performance of malaria diagnosis and treatment, and strengthened health workforce capacity to improve the implementation of 1-3-7 approach. Continually improving surveillance and response system can play a critical role in the early detection and rapid response of individual malaria cases and prevent the re-establishment of malaria.

Prevalence of pvmrp1 Polymorphisms and Its Contribution to Antimalarial Response.

As more sporadic cases of chloroquine resistance occur (CQR) in Plasmodium vivax (P. vivax) malaria, molecular markers have become an important tool to monitor the introduction and spread of drug resistance. P. vivax multidrug resistance-associated protein 1 (PvMRP1), as one of the members of the ATP-binding cassette (ABC) transporters, may modulate this phenotype. In this study, we investigated the gene mutations and copy number variations (CNVs) in the pvmrp1 in 102 P. vivax isolates from China, the Republic of Korea (ROK), Myanmar, Papua New Guinea (PNG), Pakistan, the Democratic People's Republic of Korea (PRK), and Cambodia. And we also obtained 72 available global pvmrp1 sequences deposited in the PlasmoDB database to investigate the genetic diversity, haplotype diversity, natural selection, and population structure of pvmrp1. In total, 29 single nucleotide polymorphisms reflected in 23 non-synonymous, five synonymous mutations and one gene deletion were identified, and CNVs were found in 2.9% of the isolates. Combined with the antimalarial drug susceptibility observed in the previous in vitro assays, except the prevalence of S354N between the two CQ sensitivity categories revealed a significant difference, no genetic mutations or CNVs associated with drug sensitivity were found. The genetic polymorphism analysis of 166 isolates worldwide found that the overall nucleotide diversity (π) of pvmrp1 was 0.0011, with 46 haplotypes identified (Hd = 0.9290). The ratio of non-synonymous to synonymous mutations (dn/ds = 0.5536) and the neutrality tests statistic Fu and Li's D* test (Fu and Li's D* = −3.9871, p < 0.02) suggests that pvmrp1 had evolved under a purifying selection. Due to geographical differences, genetic differentiation levels of pvmrp1 in different regions were different to some extent. Overall, this study provides a new idea for finding CQR molecular monitoring of P. vivax and provides more sequences of pvmrp1 in Asia for subsequent research. However, further validation is still needed through laboratory and epidemiological field studies of P. vivax samples from more regions.

Improving the surveillance and response system to achieve and maintain malaria elimination: a retrospective analysis in Jiangsu Province, China.

BACKGROUND: Following initiation of China's National Malaria Elimination Action Plan (NMEAP) in 2010, the '1-3-7' approach was developed and rolled out in China to facilitate the malaria elimination programme and accelerate malaria elimination. This study aims to summarize and condense these experiences through a retrospective analysis in Jiangsu Province, which could be adapted and applied in other malaria elimination settings worldwide. METHODS: A retrospective analysis of imported malaria cases into China identified through an improved surveillance and response system in Jiangsu Province was carried out for the period of 2001-2020. To improve the malaria surveillance and response system, Centers for Diseases Control and Prevention from the prefectures and counties in Jiangsu province conducted population-level health education to improve healthcare seeking behavior, strengthened capacity of health facilities to improve performance of malaria diagnosis and treatment, and raised the capacity of public health providers to improve implementation of the '1-3-7' approach. Categorical variables were carried out by Chi square tests with Fisher's exact correction. RESULTS: From 2001 to 2020, a total of 9,879 malaria cases were reported in Jiangsu Province. Since 2012, no indigenous malaria cases have been reported in Jiangsu Province. However, in recent years, there has been a substantial increase of imported falciparum malaria cases. Between 2012 and 2020, an estimated 61.57 million individuals have benefited from population-level health education in Jiangsu Province. For healthcare-seeking services among the 2,423 imported malaria cases, 687 (28.4%) and 1,104 (45.6%) cases visited hospitals on the first day and the second day from symptom onset, respectively. A total of 1,502 (61.9%) cases were diagnosed on the first day at medical facilities. Jiangsu Province achieved 100%, 99.4% and 98.3% completion rate in terms of case detection and notification (within one day), case investigation (within three days) and foci response and disposition (within seven days), respectively. The improved surveillance and response system in Jiangsu Province plays an important role in preventing the re-introduction of malaria and maintaining the malaria-free status. CONCLUSIONS: Jiangsu Province has maintained its malaria-free status since 2012. The continuous improvement of a surveillance and response system plays an important role in the early detection and rapid response of potential malaria-related outbreaks in Jiangsu, China, and has important lessons for other malaria eliminating settings. Remaining vigilant in the detection of imported malaria cases and maintaining an active surveillance and response system is critical to sustain the success of malaria elimination.

Disparate selection of mutations in the dihydrofolate reductase gene (dhfr) of Plasmodium ovale curtisi and P. o. wallikeri in Africa.

Plasmodium ovale curtisi and P. ovale wallikeri are both endemic in sub-Saharan Africa, the Middle East and Southeast Asia. Molecular surveillance data for drug resistance in P. ovale spp. is limited at present. We analysed polymorphisms in the podhfr, pocrt and pocytb genes of P. ovale spp. in 147 samples collected from travelers returning to China from Africa. Two podhfr mutations, S58R and S113N/T were detected in P. ovale curtisi with high/moderate frequencies of 52.17% and 17.39%, respectively. Evidence of positive selection (dN/dS = 2.41) was found for podhfr in P. ovale curtisi and decreased diversity (He) of microsatellite markers flanking the mutant alleles suggests that selective sweeps have occurred for both. Mutations E34G (1.50%) and L43V (1.50%) in pocrt of P. ovale curtisi, and E34G (3.70%), I102M (1.80%) and V111F (1.80%) of P. ovale wallikeri were found at low frequencies. Mutations R66K (6.20%), R75K (11.63%) and R95K (3.88%) of pocytb were found in both P. ovale curtisi and P. ovale wallikeri. These results suggest that the podhfr gene of P. ovale curtisi may be subject to drug selection in Africa, warranting further attention. We observed significant differences in the prevalence and distribution of podhfr mutations between the two P. ovale species, suggestive of fundamental biological differences between them.