Competency of malaria laboratory diagnosis at national and provincial levels at the beginning of malaria post-elimination phase, China.

BACKGROUND: Qualified malaria diagnosis competency has contributed to the great achievement of malaria elimination in China. After eliminating malaria, it is still critical to the prevention of re-establishment of malaria transmission in China. This study was aimed to assess the malaria detection competency at national and provincial levels in China at the beginning of malaria post-elimination phase. METHODS: In the present study, different competency assessment activities on the laboratory malaria diagnosis were carried out for national and provincial malaria diagnostic laboratories based on the WHO scoring schedules, including malaria microscopy or nucleic acid amplification tests (NAAT), at the beginning of malaria post-elimination phase (2021-2022) in China. RESULTS: A total of 60 slides for malaria microscopy and 10 specimen for NAAT were included into the WHO External Quality Assessments of malaria parasite qualitative detection and species identification, and the scoring rate was 96.6% (microscopy: 171/177) and 85.0% (NAAT: 17/20), respectively. Moreover, 124 samples were included into the national NAAT quality assessment, and an accuracy of 87.9% (109/124) was found without significance among reference laboratories and non-reference laboratories. CONCLUSIONS: The findings suggest that there is still a need for sustained strengthening of malaria detection competency, particularly in the areas of parasite counting and detection of low-density parasitemia, to ensure prompt detection of the sources of infection and accurate identification of Plasmodium species, and contribute to case management and focus disposal, thereby effectively preventing the malaria re-establishment.

Risk assessment of imported malaria in China: a machine learning perspective.

BACKGROUND: Following China's official designation as malaria-free country by WHO, the imported malaria has emerged as a significant determinant impacting the malaria reestablishment within China. The objective of this study is to explore the application prospects of machine learning algorithms in imported malaria risk assessment of China. METHODS: The data of imported malaria cases in China from 2011 to 2019 was provided by China CDC; historical epidemic data of malaria endemic country was obtained from World Malaria Report, and the other data used in this study are open access data. All the data processing and model construction based on R, and map visualization used ArcGIS software. RESULTS: A total of 27,088 malaria cases imported into China from 85 countries between 2011 and 2019. After data preprocessing and classification, clean dataset has 765 rows (85 * 9) and 11 cols. Six machine learning models was constructed based on the training set, and Random Forest model demonstrated the best performance in model evaluation. According to RF, the highest feature importance were the number of malaria deaths and Indigenous malaria cases. The RF model demonstrated high accuracy in forecasting risk for the year 2019, achieving commendable accuracy rate of 95.3%. This result aligns well with the observed outcomes, indicating the model's reliability in predicting risk levels. CONCLUSIONS: Machine learning algorithms have reliable application prospects in risk assessment of imported malaria in China. This study provides a new methodological reference for the risk assessment and control strategies adjusting of imported malaria in China.

1-3-7 surveillance and response approach in malaria elimination: China's practice and global adaptions.

There has been a significant reduction in malaria morbidity and mortality worldwide from 2000 to 2019. However, the incidence and mortality increased again in 2020 due to the disruption to services during the COVID-19 pandemic. Surveillance to reduce the burden of malaria, eliminate the disease and prevent its retransmission is, therefore, crucial. The 1-3-7 approach proposed by China has played an important role in eliminating malaria, which has been internationally popularized and adopted in some countries to help eliminate malaria. This review summarizes the experience and lessons of 1-3-7 approach in China and its application in other malaria-endemic countries, so as to provide references for its role in eliminating malaria and preventing retransmission. This approach needs to be tailored and adapted according to the region condition, considering the completion, timeliness and limitation of case-based reactive surveillance and response. It is very important to popularize malaria knowledge, train staff, improve the capacity of health centres and monitor high-risk groups to improve the performance in eliminating settings. After all, remaining vigilance in detecting malaria cases and optimizing surveillance and response systems are critical to achieving and sustaining malaria elimination.

Malaria Microscopy Competency in the Subnational Verification, China: Implications for Malaria Elimination and the Prevention of Malaria Reestablishment.

Introduction: Qualified microscopy competency is a key indicator for certification of malaria elimination. To better prepare the country certification and identify the priorities that need improvement to prevent malaria reestablishment, microscopy competency at different levels were assessed in subnational verification of malaria elimination in China. Methodology. Microscopist representatives from centers for disease control and prevention (CDC)/institutes of parasitic diseases (IPD) and medical institutes for malaria diagnosis at the provincial and county levels in the subnational verification were analyzed. Specifically, five provincial microscopist representatives and ten county-level representatives were assessed in each of previously endemic provinces on qualitative identification (Plasmodium positive or negative) and Plasmodium species identification using standard slides from the National Malaria Diagnosis Reference Laboratory. Results: A total of 100 provincial-level representatives (60 from 42 CDCs/IPDs and 40 from 34 medical institutes) and 200 county-level representatives (61 from 41 CDCs and 139 from 118 medical institutes) were included. The qualitative accuracy was higher than 90% each (P = 0.137), but slides with low parasite density were easy to be misdiagnosed as negative. Furthermore, the accuracy of species identification was 80.0% and 83.6% in medical institutes and centers for disease control and prevention (CDCs) at the provincial level (P = 0.407) with relatively high misdiagnosis of P. vivax as P. ovale in the latter (16.2%) and 82.0% and 85.0% in medical institutes and CDCs at the county level (P = 0.330) for the identification of P. falciparum and non-P. falciparum with higher false-negative in medical institutions (P < 0.001). Conclusions: In conclusion, competent microscopy in subnational verification supported the quality in eliminating malaria in China, while the accurate identification of malaria parasites, especially slides with low parasite density still need to be improved through continuous diagnostic platform construction, continuous technological innovation, and targeted training to prevent reestablishment of malaria transmission.

Epidemiologic Analysis of Efforts to Achieve and Sustain Malaria Elimination along the China-Myanmar Border.

Malaria cases have dramatically declined in China along the Myanmar border, attributed mainly to adoption of the 1-3-7 surveillance and response approach. No indigenous cases have been reported in China since 2017. Counties in the middle and southern part of the border area have a higher risk for malaria importation and reestablishment after elimination.

Characterization of pfmdr1, pfcrt, pfK13, pfubp1, and pfap2mu in Travelers Returning from Africa with Plasmodium falciparum Infections Reported in China from 2014 to 2018.

The artemisinin-based combination therapies (ACTs) used to treat Plasmodium falciparum in Africa are threatened by the emergence of parasites in Asia that carry variants of the Kelch 13 (K13) locus with delayed clearance in response to ACTs. Single nucleotide polymorphisms (SNPs) in other molecular markers, such as ap2mu and ubp1, were associated with artemisinin resistance in rodent malaria and clinical failure in African malaria patients. Here, we characterized the polymorphisms in pfmdr1, pfcrt, pfK13, pfubp1, and pfap2mu among African isolates reported in Shandong and Guangxi provinces in China. Among 144 patients with P. falciparum returning from Africa from 2014 to 2018, pfmdr1 N86Y (8.3%) and pfcrt K76T (2.1%) were the major mutant alleles. The most common genotype for pfcrt was I74E75T76 (8.3%), followed by E75T76 (2.1%). For K13 polymorphisms, a limited number of mutated alleles were observed, and A578S was the most frequently detected allele in 3 isolates (2.1%). A total of 27.1% (20/144) of the isolates were found to contain pfubp1 mutations, including 6 nonsynonymous and 2 synonymous mutations. The pfubp1 genotypes associated with artemisinin resistance were D1525E (10.4%) and E1528D (8.3%). Furthermore, 11 SNPs were identified in pfap2mu, and S160N was the major polymorphism (4.2%). Additionally, 4 different types of insertions were found in pfap2mu, and the codon AAT, encoding aspartic acid, was more frequently observed at codons 226 (18.8%) and 326 (10.7%). Moreover, 4 different types of insertions were observed in pfubp1 at codon 1520, which was the most common (6.3%). These findings indicate a certain degree of variation in other potential molecular markers, such as pfubp1 and pfap2mu, and their roles in either the parasite's mechanism of resistance or the mode of action should be evaluated or elucidated further.

Molecular surveillance of pfcrt, pfmdr1 and pfk13-propeller mutations in Plasmodium falciparum isolates imported from Africa to China.

BACKGROUND: The emergence and spread of multidrug resistance poses a significant risk to malaria control and eradication goals in the world. There has been no indigenous malaria cases reported in China since 2017, and China is approaching national malaria elimination. Therefore, anti-malarial drug resistance surveillance and tracking the emergence and spread of imported drug-resistant malaria cases will be necessary in a post-elimination phase in China. METHODS: Dried blood spots were obtained from Plasmodium falciparum-infected cases returned from Africa to China between 2012 and 2015, prior to anti-malarial drug treatment. Whole DNA were extracted and known polymorphisms relating to drug resistance of pfcrt, pfmdr1 gene, and the propeller domain of pfk13 were evaluated by nested PCR and sequencing. The haplotypes and prevalence of these three genes were evaluated separately. Chi-squared test and Fisher's exact test were used to evaluate differences among the different sub-regions of Africa. A P value < 0.05 was used to evaluate differences with statistical significance. The maps were created using ArcGIS. RESULTS: A total of 731 P. falciparum isolates were sequenced at the pfcrt locus. The wild type CVMNK was the most prevalent haplotype with prevalence of 62.8% and 29.8% of the isolates showed the triple mutant haplotype CVIET. A total of 434 P. falciparum isolates were successfully sequenced and pfmdr1 allelic variants were observed in only codons 86, 184 and 1246. Twelve haplotypes were identified and the prevalence of the wild type pfmdr1 NYD was 44.1%. The single mutant pfmdr1 in codons 86 and 184 was predominant but the haplotype NYY with single mutation in codon 1246 was not observed. The double mutant haplotype YFD was common in Africa. About 1,357 isolates were successfully sequenced of pfk13-propeller domain, the wild type was found in 1,308 samples (96.4%) whereby 49 samples (3.6%) had mutation in pfk13. Of 49 samples with pfk13 mutations, 22 non-synonymous and 4 synonymous polymorphic sites were confirmed. The A578S was the most common mutation in pfk13-propeller domain and three mutations associated with artemisinin resistance (M476I, R539T, P553L) were identified in three isolates. CONCLUSION: This study provides evidence that could give insight into potential issues with anti-malarial drug resistance to inform national drug policy in China in order to treat imported cases.

Analysis on external competency assessment for malaria microscopists in China.

BACKGROUND: In order to meet the requirement of malaria elimination (ME), three courses of the External Competency Assessment of Malaria Microscopists (ECAMM) were conducted during 2017-2018 in China by facilitators designated by the World Health Organization (WHO-ECAMM). A training course with a model copied from the WHO-ECAMM course was also held a week ahead of ECAMM in March 2018. Thirty-six participants completed these courses and obtained different results. METHODS: The slide structures, agendas, score calculations, and the levels of certifications of the four courses strictly adhered to the WHO guidelines. All the data were collected in Excel 2016 and analysed in Graphpad Prism5 or SPSS 23. Significant differences were evaluated in Graphpad Prism5 by two-tailed paired t tests between the pre-assessment and final-assessment for each of the four courses, as well as one-way ANOVAs with Kruskal-Wallis tests and Dunn's post hoc tests among the final assessments of the four courses. Correlations between participants' competency results and their ages, years working on malaria, and numbers of malaria cases reported in their provinces were evaluated by bivariate correlations (two-tailed) and linear regression (excluding cases pairwise) in SPSS 23. The Pearson correlation coefficients (r values), P values (two tailed), adjusted R square (Adjusted R2), standardized coefficients (ß) and Sig. P values were recorded. The percentages of participants who gave the right answer to each slide (PPS) in the final assessments of the three WHO-ECAMM courses were calculated. Correlation analysis between PPS and parasitaemia (100-2000 parasites/µL) of Plasmodium falciparum slides used in species identification and parasite counting, were also evaluated via bivariate correlations (two-tailed) tests. RESULTS: Among the 36 participants, 16 participants were certificated as Level 1 (two from NRL), 10 were certified as Level 2 (one from NRL). Within the same course, participants had improved their average scores from pre-assessments to final assessments. The numbers of malaria cases reported in participants' provinces were strongly correlated to their species identification (SI) scores; r = 0.45, P = 0.040, n = 21; r = 0.57, P = 0.001, n = 32; r = 0.56, P = 0.007). The parasitaemia of P. falciparum within 100-2000 parasites/µL was correlated significantly (r = 0.44, P = 0.008, n = 36) with the PPS of all counting slides but not with slides for identification (r = - 0.018, P = 0.93, n = 30). CONCLUSIONS: The analysis and comparison of participants' competency results not only verified that the model of the WHO-ECAMM course had strong power in improving and assessing microscopists' competencies but also reflected the correlation between decreased numbers of indigenous malaria cases and microscopists' competencies in certain areas in China.

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.

Mapping transmission foci to eliminate malaria in the People's Republic of China, 2010-2015: a retrospective analysis.

BACKGROUND: China has initiated the National Malaria Elimination Action Plan, which aims to eliminate malaria by 2020. However, the transmission of malaria occurs sporadically or in distinct foci, which greatly hampers progress toward elimination in China and other countries. The object of this study was to foci categorization and evaluates whether the response met the requirements issued by the nation or WHO. METHODS: Residual transmissions were investigated and located with fine spatial resolution mapping from parasitological confirmed malaria cases by use of routine national surveillance data. The "1-3-7" timeframes were monitored for each focus between 2012 and 2015. Each focus was identified, and the application of appropriate measures was evaluated. RESULTS: A total of 5996 indigenous cases were recorded between 2010 and 2015; during this period, the number of cases declined by 99.1% (2010, n = 4262; 2015, n = 39). Most indigenous cases (92.5%) were reported in Anhui (n = 2326), Yunnan (n = 1373), Henan (n = 930), Hubei (n = 459), and Guizhou (n = 458). The temporal distribution showed that the indigenous malaria cases were clustered during the period of May to August. A total of 320 foci were carefully investigated and analyzed: 24 were active foci; 72, residual non-active foci; and 224 cleared-up foci. For the foci response evaluation, all the active foci were investigated within 7 days, while 80.2% of the residual non-active foci were responded within 7 days. In addition, reactive case detection (RACD) was carried out with 92.9% of the active foci and vector investigation carried out with 75%. For residual non-active foci, RACD was carried out with 83.2% and vector investigation with 78.2% of the foci. CONCLUSIONS: This study used nationwide data to categorize foci in China and evaluate the response of these areas during the control and elimination phases. Our approach stratifies future control responses by identifying those locations where the elimination of endemic transmission is needed, such as in the counties at the China-Myanmar border and in Tibet. In addition, this study will help local CDC staff to reassess their needs and responses against different types of foci during the elimination and post-elimination phases.

Malaria in China, 2011-2015: an observational study.

OBJECTIVE: To ascertain the trends and burden of malaria in China and the costs of interventions for 2011-2015. METHODS: We analysed the spatiotemporal and demographic features of locally transmitted and imported malaria cases using disaggregated surveillance data on malaria from 2011 to 2015, covering the range of dominant malaria vectors in China. The total and mean costs for malaria elimination were calculated by funding sources, interventions and population at risk. FINDINGS: A total of 17 745 malaria cases, including 123 deaths (0.7%), were reported in mainland China, with 15 840 (89%) being imported cases, mainly from Africa and south-east Asia. Almost all counties of China (2855/2858) had achieved their elimination goals by 2015, and locally transmitted cases dropped from 1469 cases in 2011 to 43 cases in 2015, mainly occurring in the regions bordering Myanmar where Anopheles minimus and An. dirus are the dominant vector species. A total of United States dollars (US$) 134.6 million was spent in efforts to eliminate malaria during 2011-2015, with US$ 57.2 million (43%) from the Global Fund to Fight AIDS, Tuberculosis and Malaria and US$ 77.3 million (57%) from the Chinese central government. The mean annual investment (US$ 27 million) per person at risk (574 million) was US$ 0.05 (standard deviation: 0.03). CONCLUSION: The locally transmitted malaria burden in China has decreased. The key challenge is to address the remaining local transmission, as well as to reduce imported cases from Africa and south-east Asia. Continued efforts and appropriate levels of investment are needed in the 2016-2020 period to achieve elimination.

[A retrospective analysis on the diagnosis and reporting of imported malaria in Jiangxi Province during 2012-2015].

Objective: To provide scientific basis for malaria surveillance in the elimination phase by retrospectively analyzing the diagnosis and reporting of imported malaria in Jiangxi Province. Methods: Data on malaria endemic situation and individual cases during 2012-2015 were collected through the National Information Management System for Infectious Diseases and the Report and Information Management System for Parasitic Diseases Control and Prevention. Detailed information on primary medical units, laboratory testing units, reporting units, diagnostic methods, time from onset to first medical visit, time from first medical visit to reporting, and time from onset to reporting was analyzed with the descriptive analysis method. Results: A total of 207 malaria cases were reported during 2012-2015 in Jiangxi, all were imported cases and 96.62%(200/207) were diagnosed with laboratory tests. The main primary medical units were found to be county-level (29.95%, 62/207) and prefecture-level (25.60%, 53/207) medical institutions, while the main laboratory testing units were prefecture-level medical institutions(35.27%,73/207) and county-level CDCs (20.29%, 42/207). There was a significant difference in the proportion of different laboratory testing units among the years(P < 0.05). The median time from onset to first medical visit was 1 d (0-149 d), from first medical visit to reporting was 3 d (0-144 d), and from onset to reporting was 5 d (0-149 d). Conclusions: The first visit and the laboratory testing of malaria cases mainly occur in the prefecture-level and county-level medical institutions.

A Single Mutation in K13 Predominates in Southern China and Is Associated With Delayed Clearance of Plasmodium falciparum Following Artemisinin Treatment.

BACKGROUND: Artemisinin resistance in Plasmodium falciparum has emerged in Southeast Asia and poses a threat to malaria control and elimination. Mutations in a P. falciparum gene encoding a kelch protein on chromosome 13 have been associated with delayed parasite clearance following artemisinin treatment elsewhere in the region, but not yet in China. METHODS: Therapeutic efficacy studies of artesunate and dihydroartemisinin-piperaquine were conducted from 2009 to 2012 in the Yunnan Province of China near the border with Myanmar. K13 mutations were genotyped by capillary sequencing of DNA extracted from dried blood spots collected in these clinical trials and in routine surveillance. Associations between K13 mutations and delayed parasite clearance were tested using regression models. RESULTS: Parasite clearance half-lives were prolonged after artemisinin treatment, with 44% of infections having half-lives >5 hours (n = 109). Fourteen mutations in K13 were observed, with an overall prevalence of 47.7% (n = 329). A single mutation, F446I, predominated, with a prevalence of 36.5%. Infections with F446I were significantly associated with parasitemia on day 3 following artemisinin treatment and with longer clearance half-lives. CONCLUSIONS: Plasmodium falciparum infections in southern China displayed markedly delayed clearance following artemisinin treatment. F446I was the predominant K13 mutation and was associated with delayed parasite clearance.

[Exploration of Using One-step Reverse Transcription PCR in Detection of Four Species of Human Malaria Parasites].

Objective: To explore the application and specificity of one-step reverse transcription PCR (RT-PCR) in detecting four species of human Plasmodium parasites. Methods: Blood samples were collected from a falciparum malaria case, a vivax malaria case, an ovale malaria case, and five quartan malaria cases. RNA and DNA were isolated. One-step RT-PCR and one-step real-time RT-PCR were performed on the RNA digested with DNase to amplify the Plasmodium 18S rRNA. Traditional PCR and one-step RT-PCR were used to amplify 18S rRNAs and 18S rDNAs in differentially diluted RNAs (with or without DNase digestion) and DNAs. The lowest detectable dilution concentrations for the two amplification systems were compared. Results: One-step RT-PCR produced specific bands of 310, 394 and 323 bp, which were sequenced to be 18S rRNA of P. falciparum, P. ovale, and P. vivax. No specific band for P. malariare was found. The one-step real-time RT-PCR results showed fluorescence for all the four species, and all had a melting curve with a single peak except for P. malariare. The lowest detectable dilution concentration by one-step RT-PCR varied from 1 to 10-4 based on the DNA or RNA template amount. Specifically, the lowest detectable dilution concentration of DNA was similar to or lower than that of original RNA by an order of magnititude, and both were lower than that of DNase-digested RNA. Further, the sensitivity of one-step RT-PCR evaluated in terms of lowest detectable dilution concentration was 10-1 000 times higher than that of the traditional PCR. Conclusions: The one-step RT-PCR technique can be applied in the detection of P. falciparum, P. ovale, and P. vivax in fresh blood samples. But its use in detecting P. malariae parasites needs further evaluation.

[Malaria Situation in the People's Republic of China in 2015].

The 2015 malaria epidemiological data reported through the annual malaria statistics reporting system were collected and analyzed. Totally 3 288 malaria cases were reported in 664 counties of 31 Provinces/Municipalities/Autonomous Regions （P/M/A） in 2015, which increased by 6.8% in comparison to that of 2014 （3 078 cases）, and the incidence in 2015 was 0.024 0/10 000. The cases were reported primarily from Provinces of Yunnan （18.4%, 606/3 288）, Jiangsu （12.3%, 405/3 288）, Sichuan （8.8%, 290/3 288）, Guangxi （7.2%, 236/3 288） and Shandong（6.4%, 212/3 288）. Of all the cases, 40（1.2%, 40/3 288） were indigenous cases, mainly distributed in the border area of Yunnan （six counties）, Tibet （one county）, Liaoning （one county） and Hainan （one county）. There was one case of whom the source of infection was unknown. The locally-infected falciparum malaria was only found in Cangyuan County of Yunnan（1 case）. The prevalence of indigenous malaria in Motuo County of the Tibet Autonomous Region was over 1/10 000. Meanwhile, there were 3 248（98.8%, 3 248/3 288） abroad-imported cases which widely distributed in the 31 P/M/As. In addition, 3 265（99.3%, 3 265/3 288） of the reported cases were confirmed in reference laboratories, comprising 878 cases of Plasmodium vivax（26.9%, 878/3 265） 1 992 cases of P. falciparum（61.0%, 1 992/3 265）, 76 cases of P. malariae（2.3%, 76/3 265）, 272 cases of P. ovale（8.3%, 272/3 265） and 47 cases of mixed infection（1.4%, 47/3 265）. Furthermore, 163 cases（5.0%, 163/3 288） with severe clinical symptoms were reported in 14 P/M/As, with 20 deaths（0.6%, 20/3 288） in 10 P/M/As. Totally 3 116 malaria cases were reported through the China Information System for Disease Control and Prevention, including 39 indigenous cases. These data reflect achievements in malaria elimination, despite that challenges remain in boarder areas of Yunnan Province and in Motuo County of the Tibet Autonomous Region. Efforts are still needed in risk assesment for malaria re-transmission.

[Research Progress on Risk Assessment of Secondary Transmission of Imported Malaria].

In 2015, WHO issued the Global Technical Strategy for Malaria 2016-2030, which sets the target of reducing global malaria incidence and mortality rates by at least 90% by 2030. Although many countries have successfully achieved malaria elimination, they are facing the risk of imported malaria. In China, despite the acceleration of malaria elimination, imported malaria has become a potential threat to achieving complete malaria elimination. This paper reviews the worldwide research progress on risk assessment of secondary transmission of imported malaria, in the aim of providing reference for risk assessment of imported malaria and preventing secondary transmission in China.

[Risk Assessment for Malaria Transmission in the Border Area of Yunnan Province].

Objective: To assess the malaria transmission risk in the border area of Yunnan Province and provide evidence for adjustment of malaria intervention and elimination strategies. Method: Data concerning malaria prevalence, vector distribution, and institutional intervention capacity were collected in 197 towns of 20 counties in the border area of Yunnan Province during 2012-2014. The malaria transmission potential index （TPI）, intervention capacity index (ICI) and malaria risk index (MRI) were calculated for each town, based on the criteria formulated by a professional committee. The towns were categorized according to the indices aforementioned. The risk map was created with GIS software. Results: Based on the TPI, the 197 towns comprised of 2 grade-I towns (including Nabang in Yingjiang and Banlao in Cangyuan) with high transmission potential, 11 grade-II towns with moderate transmission potential and 184 grade-III towns with low transmission potential. Based on the ICI, the 197 towns comprised of 4 grade-III towns (including Zhongke in Ximen, Zhonghe and Diantan in Tengchong, and Menghan in Jinghong) with a weak control capacity, 20 grade-II towns with a moderate control capacity and 173 grade-I towns with a strong control capacity. Based on the MRI, the 197 towns comprised of 2 grade-I towns (including Nabang in Yingjiang, and Banlao in Cangyuan) with a high transmission risk level, 12 grade-II towns with a moderate level and 183 grade-III towns with a low level distributed in 20 counties. Conclusion: The grade I or II towns with moderate and high transmission risk constitute <5% of the 197 towns in the border area, suggesting a relatively low level of malaria transmission risk in most counties.

Evaluation of antimalarial resistance marker polymorphism in returned migrant workers in China.

Imported malaria has been a great challenge for public health in China due to decreased locally transmitted cases and frequent exchange worldwide. Plasmodium falciparum has been mainly responsible for the increasing impact. Currently, artesunate plus amodiaquine, one of the artemisinin combination therapies recommended by the World Health Organization, has been mainly used against uncomplicated P. falciparum malaria in China. However, drug resistance marker polymorphism in returning migrant workers has not been demonstrated. Here, we have evaluated the prevalence of pfmdr1 and pfcrt polymorphisms, as well as the K13 propeller gene, a molecular marker of artemisinin resistance, in migrant workers returned from Ghana to Shanglin County, Guangxi Province, China, in 2013. A total of 118 blood samples were randomly selected and used for the assay. Mutations of the pfmdr1 gene that covered codons 86, 184, 1034, and 1246 were found in 11 isolates. Mutations at codon N86Y (9.7%) were more frequent than at others, and Y(86)Y(184)S(1034)D(1246) was the most prevalent (63.6%) of the four haplotypes. Mutations of the pfcrt gene that covered codons 74, 75, and 76 were observed in 17 isolates, and M(74)N(75)T(76) was common (70.6%) in three haplotypes. Eight different genotypes of the K13 propeller were first observed in 10 samples in China, 2 synonymous mutations (V487V and A627A) and 6 nonsynonymous mutations. C580Y was the most prevalent (2.7%) in all the samples. The data presented might be helpful for enrichment of molecular surveillance of antimalarial resistance and will be useful for developing and updating antimalarial guidance in China.

Amplification of pfmdr1, pfcrt, pvmdr1, and K13 propeller polymorphisms associated with Plasmodium falciparum and Plasmodium vivax isolates from the China-Myanmar border.

Malaria in the China-Myanmar border region is still severe; local transmission of both falciparum and vivax malaria persists, and there is a risk of geographically expanding antimalarial resistance. In this research, the pfmdr1, pfcrt, pvmdr1, and K13-propeller genotypes were determined in 26 Plasmodium falciparum and 64 Plasmodium vivax isolates from Yingjiang county of Yunnan province. The pfmdr1 (11.5%), pfcrt (34.6%), and pvmdr1 (3.1%) mutations were prevalent at the China-Myanmar border. The indigenous samples exhibited prevalences of 14.3%, 28.6%, and 14.3% for pfmdr1 N86Y, pfcrt K76T, and pfcrt M74I, respectively, whereas the samples from Myanmar showed prevalences of 10.5%, 21.1%, and 5.3%, respectively. The most prevalent genotypes of pfmdr1 and pfcrt were Y86Y184 and M74N75T76, respectively. No pvmdr1 mutation occurred in the indigenous samples but was observed in two cases coming from Myanmar. In addition, we are the first to report on 10 patients (38.5%) with five different K13 point mutations. The F446I allele is predominant (19.2%), and its prevalence was 28.6% in the indigenous samples of Yingjiang county and 15.8% in samples from Myanmar. The present data might be helpful for enrichment of the molecular surveillance of antimalarial resistance and useful for developing and updating guidance for the use of antimalarials in this region.