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.

Molecular surveillance of artemisinin resistance-related Pfk13 and pfcrt polymorphisms in imported Plasmodium falciparum isolates reported in eastern China from 2015 to 2019.

BACKGROUND: Artemisinin-based combination therapy (ACT) has been recommended as the first-line treatment by the World Health Organization to treat uncomplicated Plasmodium falciparum malaria. However, the emergence and spread of P. falciparum resistant to artemisinins and their partner drugs is a significant risk for the global effort to reduce disease burden facing the world. Currently, dihydroartemisinin-piperaquine (DHA-PPQ) is the most common drug used to treat P. falciparum, but little evidence about the resistance status targeting DHA (ACT drug) and its partner drug (PPQ) has been reported in Shandong Province, China. METHODS: A retrospective study was conducted to explore the prevalence and spatial distribution of Pfk13 and Pfcrt polymorphisms (sites of 72-76, and 93-356) among imported P. falciparum isolates between years 2015-2019 in Shandong Province in eastern China. Individual epidemiological information was collected from a web-based reporting system were reviewed and analysed. RESULTS: A total of 425 P. falciparum blood samples in 2015-2019 were included and 7.3% (31/425) carried Pfk13 mutations. Out of the isolates that carried Pfk13 mutations, 54.8% (17/31) were nonsynonymous polymorphisms. The mutant alleles A578S, Q613H, C469C, and S549S in Pfk13 were the more frequently detected allele, the mutation rate was the same as 9.7% (3/31). Another allele Pfk13 C580Y, closely associated with artemisinin (ART) resistance, was found as 3.2% (2/31), which was found in Cambodia. A total of 14 mutant isolates were identified in Western Africa countries (45.2%, 14/31). For the Pfcrt gene, the mutation rate was 18.1% (77/425). T76T356 and T76 were more frequent in all 13 different haplotypes with 26.0% (20/77) and 23.4% (18/77). The CVIET and CVIKT mutant at loci 72-76 have exhibited a prevalence of 19.5% (15/77) and 3.9% (3/77), respectively. The CVIET was mainly observed in samples from Congo (26.7%, 4/15) and Mozambique (26.7%, 4/15). No mutations were found at loci 97, 101 and 145. For polymorphisms at locus 356, a total of 24 isolates were identified and mainly from Congo (29.2%, 7/24). CONCLUSION: These findings indicate a low prevalence of Pfk13 in the African isolates. However, the emergence and increase in the new alleles Pfcrt I356T, reveals a potential risk of drug pressure in PPQ among migrant workers returned from Africa. Therefore, continuous molecular surveillance of Pfcrt mutations and in vitro susceptibility tests related to PPQ are necessary.

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.

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.

Molecular surveillance of Pfcrt and k13 propeller polymorphisms of imported Plasmodium falciparum cases to Zhejiang Province, China between 2016 and 2018.

BACKGROUND: Resistance to anti-malarial drugs hinders malaria elimination. Monitoring the molecular markers of drug resistance helps improve malaria treatment policies. This study aimed to assess the distribution of molecular markers of imported Plasmodium falciparum infections. METHODS: In total, 485 P. falciparum cases imported from Africa, Southeast Asia, and Oceania into Zhejiang province, China, from 2016 to 2018 were investigated. Most were imported from Africa, and only a few cases originated in Asia and Oceania. Blood samples were collected from each patient. Plasmodium falciparum chloroquine resistance transporter (Pfcrt) at residues 72-76 and Kelch13-propeller (k13) were determined by nested PCR and DNA sequence. RESULTS: Wild-type Pfcrt at residues 72-76 was predominant (72.61%), but mutant and mixed alleles were also detected, of which CVIET (22.72%) was the most common. Mutant Pfcrt haplotypes were more frequent in patients from West Africa (26.92%), North Africa (25%), and Central Africa (21.93%). The number of cases of P. falciparum infections was small in Southeast Asia and Oceania, and these cases involved Pfcrt mutant type. For the k13 propeller gene, 26 samples presented 19 different point mutations, including eight nonsynonymous mutations (P441S, D464E, K503E, R561H, A578S, R622I, V650F, N694K). In addition, R561H, one of the validated SNPs in k13, was detected in one patient from Myanmar and one patient from Rwanda. A578S, although common in Africa, was found in only one patient from Cameroon. R622I was detected in one sample from Mozambique and one sample from Somalia. The genetic diversity of k13 was low in most regions of Africa and purifying selection was suggested by Tajima's D test. CONCLUSIONS: The frequency and spatial distributions of Pfcrt and k13 mutations associated with drug resistance were determined. Wild-type Pfcrt was dominant in Africa. Among k13 mutations correlated with delayed parasite clearance, only the R561H mutation was found in one case from Rwanda in Africa. Both Pfcrt and k13 mutations were detected in patients from Southeast Asia and Oceania. These findings provide insights into the molecular epidemiological profile of drug resistance markers in the study region.

No evidence of amplified Plasmodium falciparum plasmepsin II gene copy number in an area with artemisinin-resistant malaria along the China-Myanmar border.

BACKGROUND: The emergence and spread of artemisinin resistance in Plasmodium falciparum poses a threat to malaria eradication, including China's plan to eliminate malaria by 2020. Piperaquine (PPQ) resistance has emerged in Cambodia, compromising an important partner drug that is widely used in China in the form of dihydroartemisinin (DHA)-PPQ. Several mutations in a P. falciparum gene encoding a kelch protein on chromosome 13 (k13) are associated with artemisinin resistance and have arisen spread in the Great Mekong subregion, including the China-Myanmar border. Multiple copies of the plasmepsin II/III (pm2/3) genes, located on chromosome 14, have been shown to be associated with PPQ resistance. METHODS: The therapeutic efficacy of DHA-PPQ for the treatment of uncomplicated P. falciparum was evaluated along the China-Myanmar border from 2010 to 2014. The dry blood spots samples collected in the efficacy study prior DHA-PPQ treatment and from the local hospital by passive detection were used to amplify k13 and pm2. Polymorphisms within k13 were genotyped by capillary sequencing and pm2 copy number was quantified by relative-quantitative real-time polymerase chain reaction. Treatment outcome was evaluated with the World Health Organization protocol. A linear regression model was used to estimate the association between the day 3 positive rate and k13 mutation and the relationship of the pm2 copy number variants and k13 mutations. RESULTS: DHA-PPQ was effective for uncomplicated P. falciparum infection in Yunnan Province with cure rates > 95%. Twelve non synonymous mutations in the k13 domain were observed among the 268 samples with the prevalence of 44.0% and the predominant mutation was F446I with a prevalence of 32.8%. Only one sample was observed with multi-copies of pm2, including parasites with and without k13 mutations. The therapeutic efficacy of DHA-PPQ was > 95% along the China-Myanmar border, consistent with the lack of amplification of pm2. CONCLUSION: DHA-PPQ for uncomplicated P. falciparum infection still showed efficacy in an area with artemisinin-resistant malaria along the China-Myanmar border. There was no evidence to show PPQ resistance by clinical study and molecular markers survey. Continued monitoring of the parasite population using molecular markers will be important to track emergence and spread of resistance in this region.

Prevalence of molecular markers associated with drug resistance of Plasmodium vivax isolates in Western Yunnan Province, China.

BACKGROUND: Plasmodium vivax is the most widely distributed malaria parasite, and its drug resistance poses unique challenges to malaria elimination. The Greater Mekong Subregion (GMS) is known as the global epicenter of multidrug resistance. Surveillance of molecular markers associated with drug resistance in this area will help to inform drug policy. METHODS: Dry blood spots from 58 patients out of 109 with P. vivax infection between 2017, December and 2019, March were obtained from Yingjiang County, Yunnan Province, along the China-Myanmar border. Pvdhfr, Pvdhps, Pvmdr1 and Pvcrt-o were amplified and sequenced to assess gene mutations. The polymorphism and prevalence of these molecular markers were analyzed. RESULTS: Mutations in Pvdhfr at codons 57, 58, 61, 99 and 117 were detected in 27.59, 48.28, 27.59, 32.76 and 48.28% of the isolates, respectively. Single mutant haplotype (I13F57S58T61S99S117I173) was the most frequent (29.31%, 17/58), followed by double mutant haplotype (20.69%, 12/58). Of three types of tandem repeat variations of Pvdhfr, deletion type was the most common. Pvdhps showed a lower prevalence among mutation genotypes. Single mutant was dominant and accounted for 34.48% (20/58). Prevalence of Pvmdr1 mutations at codons 958 and 1076 were 100.00% and 84.48%, respectively. The proportion of double and single mutant types was 84.48% (49/58) and 15.52% (9/58), respectively. Eleven samples (18.97%, 11/58) showed K10 "AAG" insertion in chloroquine resistance transporter gene Pvcrt-o. CONCLUSIONS: There was moderate diversity of molecular patterns of resistance markers of Pvdhfr, Pvdhps, Pvmdr1 and Pvcrt-o in imported P. vivax cases to Yingjiang county in Western Yunnan, along the China-Myanmar border. Prevalence and molecular pattern of candidate drug resistance markers Pvdhfr, Pvdhps, Pvmdr1 and Pvcrt-o were demonstrated in this current study, which would help to update drug policy.

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.

Monitoring and evaluation of intervals from onset of fever to diagnosis before "1-3-7" approach in malaria elimination: a retrospective study in Shanxi Province, China from 2013 to 2018.

BACKGROUND: China's 1-3-7 approach was extensively implemented to monitor the timeframe of case reporting, case investigation and foci response in the malaria elimination. However, activities before diagnosis and reporting (before '1') would counteract the efficiency of 1-3-7 approach but few data have evaluated this issue. This study aims to evaluate the timelines between onset of fever and diagnosis at healthcare facilities in Shanxi Province. METHODS: Routine data were extracted from IDIRMS and NMISM database from 2013 to 2018. Time intervals between onset of fever and healthcare-seeking and between healthcare-seeking and diagnosis were calculated. Each of the documented malaria cases was geo-coded and paired to the county-level layers of polygon. RESULTS: A total of 90 cases were reported in 2013-2018 in Shanxi Province, and 73% of cases reported at provincial health facilities. All malaria cases were imported from Africa (90%) and Southeast Asia (10%) especially around the Chinese Spring Festival (n = 46, 51%). The median days between fever and healthcare-seeking and between healthcare-seeking and diagnosis of malaria were 3 and 2, respectively. CONCLUSIONS: The current "1-3-7" approach is well executed in Shanxi Province, but delays intervals observed in case finding before 1-3-7 approach occurred in all levels of facilities in Shanxi Province, which imply that more efforts are highlighted for timely case finding. Health education should be provided for improving awareness of healthcare-seeking, and various technical training aiming at the physicians should be carried out to improve diagnosis of malaria.

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.

Receptivity to malaria in the China-Myanmar border in Yingjiang County, Yunnan Province, China.

BACKGROUND: The re-establishment of malaria has become an important public health issue in and out of China, and receptivity to this disease is key to its re-emergence. Yingjiang is one of the few counties with locally acquired malaria cases in the China-Myanmar border in China. This study aimed to understand receptivity to malaria in Yingjiang County, China, from June to October 2016. METHODS: Light-traps were employed to capture the mosquitoes in 17 villages in eight towns which were categorized into four elevation levels: level 1, 0-599 m; level 2, 600-1199 m; level 3, 1200-1799 m; and level 4, > 1800 m. Species richness, diversity, dominance and evenness were used to picture the community structure. Similarity in species composition was compared between different elevation levels. Data of seasonal abundance of mosquitoes, human biting rate, density of light-trap-captured adult mosquitoes and larvae, parous rate, and height distribution (density) of Anopheles minimus and Anopheles sinensis were collected in two towns (Na Bang and Ping Yuan) each month from June to October, 2016. RESULTS: Over the study period, 10,053 Anopheles mosquitoes were collected from the eight towns, and 15 Anopheles species were identified, the most-common of which were An. sinensis (75.4%), Anopheles kunmingensis (15.6%), and An. minimus (3.5%). Anopheles minimus was the major malaria vector in low-elevation areas (< 600 m, i.e., Na Bang town), and An. sinensis in medium-elevation areas (600-1200 m, i.e., Ping Yuan town). In Na Bang, the peak human-biting rate of An. minimus at the inner and outer sites of the village occurred in June and August 2016, with 5/bait/night and 15/bait/night, respectively. In Ping Yuan, the peak human-biting rate of An. sinensis was in August, with 9/bait/night at the inner site and 21/bait/night at the outer site. The two towns exhibited seasonal abundance with high density of the two adult vectors: The peak density of An. minimus was in June and that of An. sinensis was in August. Meanwhile, the peak larval density of An. minimus was in July, but that of An. sinensis decreased during the investigation season; the slightly acidic water suited the growth of these vectors. The parous rates of An. sinensis and An. minimus were 90.46 and 93.33%, respectively. CONCLUSIONS: The Anopheles community was spread across different elevation levels. Its structure was complex and stable during the entire epidemic season in low-elevation areas at the border. The high human-biting rates, adult and larval densities, and parous rates of the two Anopheles vectors reveal an exceedingly high receptivity to malaria in the China-Myanmar border in Yingjiang County.

Trends of imported malaria in China 2010-2014: analysis of surveillance data.

BACKGROUND: To describe the epidemiologic profile and trends of imported malaria, and to identify the populations at risk of malaria in China during 2010-2014. METHODS: This is a descriptive analysis of laboratory confirmed malaria cases during 2010-2014. Data were obtained from surveillance reports in the China Information System for Disease Control and Prevention (CISDCP). The distribution of imported malaria cases over the years was analysed with X(2) for trend analysis test. All important demographic and epidemiologic variables of imported malaria cases were analysed. RESULTS: Malaria incidence in general reduced greatly in China, while the proportion of Plasmodium falciparum increased threefold from 0.08 to 0.21 per 100,000 population during the period 2010-2014. Of a total 17,725 malaria cases reported during the study period, 11,331 (64%) were imported malaria and included an increasing trend: 292 (6%), 2103 (63%), 2151 (84%), 3881 (96%), 2904 (97%), respectively, (X(2) = 2110.70, p < 0.01). The majority of malaria cases (imported and autochthonous) were adult (16,540, 93%), male (15,643, 88%), and farming as an occupation (11,808, 66%). Some 3027 (94%) of imported malaria cases had labour-related travel history during the study period; 90% (6340/7034) of P. falciparum infections were imported into China from Africa, while 77% of Plasmodium vivax infections (2440/3183) originated from Asia. CONCLUSIONS: Malaria elimination in China faces the challenge of imported malaria, especially imported P. falciparum. Malaria prevention activities should target exported labour groups given the increasing number of workers returning from overseas.

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.

[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.

Establishing a China malaria diagnosis reference laboratory network for malaria elimination.

BACKGROUND: In China, the prevalence of malaria has reduced dramatically due to the elimination programme. The continued success of the programme will depend upon the accurate diagnosis of the disease in the laboratory. The basic requirements for this are a reliable malaria diagnosis laboratory network and quality management system to support case verification and source tracking. METHODS: The baseline information of provincial malaria laboratories in the China malaria diagnosis reference laboratory network was collected and analysed, and a quality-assurance activity was carried out to assess their accuracies in malaria diagnosis by microscopy using WHO standards and PCR. RESULTS: By the end of 2013, nineteen of 24 provincial laboratories have been included in the network. In the study, a total of 168 staff were registered and there was no bias in their age, gender, education level, and position. Generally Plasmodium species were identified with great accuracy by microscopy and PCR. However, Plasmodium ovale was likely to be misdiagnosed as Plasmodium vivax by microscopy. CONCLUSIONS: China has established a laboratory network for primary malaria diagnosis which will cover a larger area. Currently, Plasmodium species can be identified fairly accurately by microscopy and PCR. However, laboratory staff need additional trainings on accurate identification of P. ovale microscopically and good performance of PCR operations.

[Malaria Situation in the People' s Republic of China in 2014].

The 2014 malaria epidemiological data reported through the annual malaria statistics reporting system were collected and analyzed. A total of 3 078 malaria cases were reported in 680 counties of 30 Provinces/ Municipalities/Autonomous Regions (P/M/A)(except Inner Mongolia) in 2014, decreased by 25.4% compared with the 4 128 cases in 2013. The incidence rate was 0.022 6/10 000. More cases distributed in Yunnan (17.3%, 533/3 078), Jiangsu (11.5%, 355/3 078), Sichuan (8.6%, 266/3 078), Henan (7.0%, 216/3 078) and Zhejiang (7.0%, 215/3 078) Provinces. Of all the cases, 56 (1.8%) were indigenous cases, mainly from the border area of Yunnan (comprising 9 counties) and the Tibet Autonomous Region (one county). Locally-infected falciparum malaria was only found in Yingjiang County (4 cases) and Cangyuan County (2 cases) of Yunnan. Indigenous malaria prevalence was of over 1/10 000 in Motuo County and Yingjiang County. There were 3 021 abroad-imported cases of malaria (98.1% ), which widely distributed in the 30 P/M/As. In addition, one case of quartan malaria with long latency was reported' in Guangdong Province. Of all the reported cases, 3 057 (99.3%) were further confirmed by plasmodium species, comprising 846 cases of vivax malaria (27.7%), 1 882 cases of falciparum malaria (61.6%), 3 cases of quartan malaria (1.7%), 231 cases of ovale malaria (7.6%), 44 cases of mixed infections, and one case of P. knowlesi malaria. Furthermore, 170 cases (5.5%) with severe conditions were reported in 16 P/M/As, and 25 deaths were reported in 15 P/M/As. In summary, remarkable achievements have been made in eliminating malaria in China, despite increases in imported cases. The border areas of Yunnan and Motuo County of Tibet Autonomous Region remain the key regions for malaria elimination. Efforts are needed to reinforce the management of imported cases and the treatment of complicated malaria.