Operational research needs toward malaria elimination in China

Meta-analysis of the diagnostic performance characteristics of three commercial and one in-house nucleic acid amplification tests for malaria screening

Background

A meta-analysis of previously performed evaluation studies of nucleic acid amplification testing (NAT) approaches for the screening for and differentiation of Plasmodium spp. using identical samples was performed to comparatively assess their suitability for the routine diagnostic setting.

Methods

Three commercial NATs for malaria (one loop-mediated isothermal amplification [LAMP] assay, two real-time polymerase chain reactions [PCRs]) and one in-house real-time PCR were comparatively assessed with a collection of 1020 well-characterized ethylenediaminetetraacetic acid (EDTA) blood samples from patients with suspected or confirmed malaria.

Results

Altogether 765 (75%) concordantly negative and 223 (21.9%) concordantly positive results of the four molecular tests were obtained, while discordant results were seen in 32 (3.1%) instances. For genus-specific assays, the observed sensitivity and specificity ranges were 96.4%–98.4% and 99.6%–99.9%, and for species-specific assays, 94.0%–97.6% and 99.6%–100%, respectively. Falsely negative molecular test results comprised microscopically negative samples, samples at the microscopic detection threshold and quantitatively less abundant species in mixed infections.

Conclusions

Excellent test characteristics of all assessed assays with only minor differences encourage molecular malaria screening with genus- and species-specific NAT with discrepancies only within the borderline range of their detection thresholds.

Management of imported malaria cases and healthcare institutions in central China, 2012-2017: application of decision tree analysis

Background

Imported malaria has been an important challenge for China. Fatality rates from malaria increased in China, particularly in Henan Province, primarily due to malpractice and misdiagnoses in healthcare institutions, and the level of imported malaria. This study aims to investigate the relationship between the state of diagnosis and subsequent complications among imported malaria cases at healthcare institutions, based on malaria surveillance data in Henan Province from 2012 to 2017.

Methods

A retrospective descriptive analysis was performed using data from the Centre for Disease Control and Prevention, Zhengzhou City, the capital of Henan Province. A decision tree method was exploited to provide valuable insight into the correlation between imported malaria cases and healthcare institutions.

Results

From 2012 to 2017, there were 371 imported malaria cases, mostly in males aged between 20 and 50 years, including 319 Plasmodium falciparum cases. First visits of 32.3%, 19.9% and 15.9% malaria cases for treatment were to provincial, municipal and county healthcare institutions, respectively. The time interval between onset and initial diagnosis of 284 cases (76.5%) and the time interval between initial diagnosis and final diagnosis of 197 cases (53.1%) was no more than 72 h. An apparent trend was found that there were notably fewer patients misdiagnosed at first visit to healthcare institutions of a higher administrative level; 12.5% of cases were misdiagnosed in provincial healthcare institutions compared to 98.2% in private clinics, leading to fewer complications at healthcare institutions of higher administrative level due to correct initial diagnosis. In the tree model, the rank of healthcare facilities for initial diagnosis, and number of days between onset and initial diagnosis, made a major contribution to the classification of initial diagnosis, which subsequently became the most significant factor influencing complications developed in the second tree model. The classification accuracy were 82.2 and 74.1%, respectively for the tree models of initial diagnosis and complications developed.

Conclusion

Inadequate seeking medical care by imported malaria patients, and insufficient capacity to diagnose malaria by healthcare institutions of lower administrative level were identified as major factors influencing complications of imported malaria cases in Henan Province. The lack of connection between uncommon imported malaria cases and superior medical resources was found to be the crucial challenge. A web-based system combined with WeChat to target imported malaria cases was proposed to cope with the challenge.

Contribution of Plasmodium immunomics: potential impact for serological testing and surveillance of malaria

Introduction: Plasmodium vivax (Pv) and P. knowlesi account together for a considerable share of the global burden of malaria, along with P. falciparum (Pf). However, inaccurate diagnosis and undetectable asymptomatic/submicroscopic malaria infections remain very challenging. Blood-stage antigens involved in either invasion of red blood cells or sequestration/cytoadherence of parasitized erythrocytes have been immunomics-characterized, and are vital for the detection of malaria incidence. Areas covered: We review the recent advances in Plasmodium immunomics to discuss serological markers with potential for specific and sensitive diagnosis of malaria. Insights on alternative use of immunomics to assess malaria prevalence are also highlighted. Finally, we provide practical applications of serological markers as diagnostics, with an emphasis on dot immunogold filtration assay which holds promise for malaria diagnosis and epidemiological surveys. Expert commentary: The approach largely contributes to Pf and Pv research in identifying promising non-orthologous antigens able to detect malaria incidence and to differentiate between past and recent infections. However, further studies to profiling naturally acquired immune responses are expected in order to help discover/validate serological markers of no cross-seroreactivity and guide control interventions. More so, the application of immunomics to knowlesi infections would help validate the recently identified antigens and contribute to the discovery of additional biomarkers of exposure, immunity, or both.

Study roadmap for high-throughput development of easy to use and affordable biomarkers as diagnostics for tropical diseases: a focus on malaria and schistosomiasis

BACKGROUND

Interventions are currently being used against 'infectious diseases of poverty', which remain highly debilitating and deadly in most endemic countries, especially malaria, schistosomiasis, echinococcosis and African sleeping sickness. However, major limitations of current 'traditional' methods for diagnosis are neither simple nor convenient for population surveillance, and showed low sensitivity and specificity. Access to novel technologies for the development of adequate and reliable tools are expressly needed. A collaborative project between African Network for Drugs and Diagnostics Innovation and partner institutions in Africa and China aims to screen suitable serological biomarkers for diagnostic pipelines against these 'diseases of the poor'.

METHODS

Parasite-specific exposed versus unexposed individuals were screened and sera or urine/stools were collected through case-control studies in China and African countries. Target genes/open reading frames were selected, then will be cloned and cell-free expressed, quantified and immuno-detected. Target antigens/epitopes will be probed and screened with sera from exposed or unexposed individuals using a high-throughput antigen screening platform as the study progresses. The specificity and sensitivity of highly immunoreactive biomarkers will be evaluated as well, using enzyme-linked immunosorbent assays or dipsticks.

DISCUSSION

This roadmap explicitly unfolds the integrated operating procedures with focus on malaria and schistosomiasis, for the identification of suitable biomarkers that will aid the prioritization of diagnostics for population use. However, there is need to further validate any new diagnostic through comparison with standard methods in field deployable tests for each region. Our expectations for the future are to seek regulatory approval and promote the use of diagnostics in endemic areas.

Genetic Diversity and Natural Selection in 42 kDa Region of Plasmodium vivax Merozoite Surface Protein-1 from China-Myanmar Endemic Border

Plasmodium vivax merozoite surface protein-1 (PvMSP1) gene codes for a major malaria vaccine candidate antigen. However, its polymorphic nature represents an obstacle to the design of a protective vaccine. In this study, we analyzed the genetic polymorphism and natural selection of the C-terminal 42 kDa fragment within PvMSP1 gene (Pv MSP142) from 77 P. vivax isolates, collected from imported cases of China-Myanmar border (CMB) areas in Yunnan province and the inland cases from Anhui, Yunnan, and Zhejiang province in China during 2009-2012. Totally, 41 haplotypes were identified and 30 of them were new haplotypes. The differences between the rates of non-synonymous and synonymous mutations suggest that PvMSP142 has evolved under natural selection, and a high selective pressure preferentially acted on regions identified of PvMSP133. Our results also demonstrated that PvMSP142 of P. vivax isolates collected on China-Myanmar border areas display higher genetic polymorphisms than those collected from inland of China. Such results have significant implications for understanding the dynamic of the P. vivax population and may be useful information towards China malaria elimination campaign strategies.

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.

Domestic trends in malaria research and development in China and its global influence

Background

Though many countries, including China, are moving towards malaria elimination, malaria remains a major global health threat. Due to the spread of antimalarial drug resistance and the need for innovative medical products during the elimination phase, further research and development (R&D) of innovative tools in both epidemic and elimination areas is needed. This study aims to identify the trends and gaps in malaria R&D in China, and aims to offer suggestions on how China can be more effectively involved in global malaria R&D.

Methods

Quantitative analysis was carried out by collecting data on Chinese malaria-related research programmes between 1985 and 2014, invention patents in China from 1985 to 2014, and articles published by Chinese researchers in PubMed and Chinese databases from 2005 to 2014. All data were screened and extracted for numerical analysis and were categorized into basic sciences, drug/drug resistance, immunology/vaccines, or diagnostics/detection for chronological and subgroup comparisons.

Results

The number of malaria R&D activities have shown a trend of increase during the past 30 years, however these activities have fluctuated within the past few years. During the past 10 years, R&D on drug/drug resistance accounted for the highest percentages of research programmes (32.4%), articles (55.0% in PubMed and 50.6% in Chinese databases) and patents (45.5%). However, these R&D activities were mainly related to artemisinin. R&D on immunology/vaccines has been a continuous interest for China’s public entities, but the focus remains on basic science. R&D in the area of high-efficiency diagnostics has been rarely seen or reported in China.

Conclusions

China has long been devoted to malaria R&D in multiple areas, including drugs, drug resistance, immunology and vaccines. R&D on diagnostics has received significantly less attention, however, it should also be an area where China can make a contribution. More focus on malaria R&D is needed, especially in the area of diagnostics, if China would like to contribute in a more significant way to global malaria control and elimination.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-016-0222-x) contains supplementary material, which is available to authorized users.

Challenges of research and development on antimalarial medicinal products in China: a bibliometric analysis and systematic review

Background

The advancement in any antimalarial medicinal product including vaccines, drugs and diagnostics will have a vital influence on malaria elimination in China and on the global malaria control framework. This study aimed to identify research progress and challenges in China, hoping to better facilitate domestic elimination and for China to be more effectively involved in global malaria research and development.

Methods

A systematic search was conducted for research articles published from 2005 to 2014 in PubMed, CNKI and Wanfang using terms including malaria, diagnosis, drugs and vaccines. In total, 4259 articles from PubMed and 561 references from Chinese databases were included and categorized by topic.

Results

The literature from PubMed was clustered and seven antimalarial medicinal product research hotspots were identified; including drug resistance, diagnostic tests and vaccine antigen screening. The reports related to drugs accounted for the largest proportion in PubMed (57%) and Chinese studies (51%) while references associated with diagnostics accounted for the lowest proportion, 10% in PubMed and 14% in Chinese studies.

Conclusions

Despite continuous effort in malaria research and development, there exist gaps in progressive discoveries on malaria diagnostics and drugs in China. Successive focus on antimalarial medicinal products is essential to facilitate malaria control in China and worldwide.

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.

China's 1-3-7 surveillance and response strategy for malaria elimination: Is case reporting, investigation and foci response happening according to plan?

Background

The China’s 1-3-7 strategy was initiated and extensively adopted in different types of counties (geographic regions) for reporting of malaria cases within 1 day, their confirmation and investigation within 3 days, and the appropriate public health response to prevent further transmission within 7 days. Assessing the level of compliance to the 1-3-7 strategy at the county level is a first step towards determining whether the surveillance and response strategy is happening according to plan. This study assessed if the time-bound targets of the 1-3-7 strategy were being sustained over time. Such information would be useful to improve implementation of the 1-3-7 strategy in China.

Methods

This cross-sectional study involved country-wide programmatic data for the period January 1st 2013 to June 30th 2014. Data variables were extracted from the national malaria information system and included socio-demographic information, type of county, date of diagnosis, date of reporting, date of case investigation, case classification (indigenous, or imported, or unknown), focus investigation, date of reactive case detection (RACD), and date of indoor residual spraying (IRS). Summary statistics and proportions were used and comparisons between groups were assessed using the chi-square test. Level of significance was set at a P-value ≤ 0.05.

Results

Of a total of 5,688 malaria cases from 731 counties, there were 55 (1 %) indigenous cases (only in Type 1 and Type 2 counties) and 5,633 (99 %) imported cases from all types of counties. There was no delay in reporting malaria cases by type of county. In terms of case investigation, 97.5 % cases were investigated within 3 days with the proportion of delays (1.5 %) in type 2 counties, being significantly lower than type 1 counties (4.1 %). Regarding active foci, 96.4 % were treated by RACD and/or IRS.

Conclusions

The performance of 1-3-7 strategy was encouraging but identified some challenges that if addressed can further improve implementation.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-015-0089-2) contains supplementary material, which is available to authorized users.