Objective: Rabies is a vaccine-preventable, viral zoonotic disease caused by a lyssavirus. This study was aimed at analyzing the epidemiological characteristics of human rabies in Shanghai to provide valuable information to support accurate prevention and control. Methods: Individual-level data on human rabies and dog bites/attacks in Shanghai were collected from 2006 to 2021. Demographic characteristics, spatial and seasonal patterns, and correlations were analyzed to explore the epidemiological profiles. Infection risk was predicted with a Bayesian aggression model. Results: A total of 43 human rabies cases were registered in Shanghai in 2006–2021; the annual average incidence rate was 0.01/100000. Males and residents at ages of 10 to 19 years and over 50 years had an elevated risk of rabies. All cases were reported in suburban districts and peaked in July. The body parts most frequently injured by dogs were the hands (48.84%). The fatality rate was 100%. Most cases (86.05%) were not treated after exposure. A total of 310 dog bites/attacks were reported and significantly correlated with the number of cases (P=0.010). The predicted risk of human rabies was higher in suburban than urban areas. Conclusion: The incidence of human rabies in Shanghai was relatively low; nevertheless, risk still existed, particularly in suburban areas.

BACKGROUND:Pneumococcal vaccines are effective in preventing pneumococcal diseases in adults. The evaluation of the antibodies persistence to the 23-valent pneumococcal polysaccharide vaccine (PPV23) could provide evidence on PPV23 revaccination. RESEARCH DESIGN AND METHODS:Adults aged ≥ 60 years were selected and vaccinated with PPV23 in Shanghai, and followed up for 5 years with blood samples collection of a 1-year interval. The geometric mean concentrations (GMC) of the IgG against 23 pneumococcal serotypes covered by PPV23 were detected using enzyme-linked immunosorbent assay. The antibodies to 23 pneumococcal serotypes among different groups was analyzed using statistical analysis. RESULTS:Overall, 517 participants completed all six visits over a 5-year period (2013-2018). The GMC of 23 serotypes in adults aged ≥ 60 years decreased slowly after PPV23 vaccination compared to baseline pre-vaccination (P < 0.05), except serotype 3. Additionally, the multiplicative increase in the antibody concentration after PPV23 vaccination was greater, and the antibody levels of serotypes 1 and 6B were significantly higher at visit 5 than at visit 4 (P < 0.05). CONCLUSIONS:The pneumococcal antibodies in elderly after PPV23 vaccination could sustain high levels over long-term follow-up, which suggested that the interval of revaccination with PPV23 in elderly should be at least 5 years after the first vaccination.

China has now achieved the elimination of malaria, but it still faces severe challenges in the post-elimination stage. China continues to be plagued by imported malaria cases, and preventing re-transmission of imported malaria is critical. The effectiveness of antimalarial drugs for malaria control largely depends on the study of drug resistance markers in vitro. Monitoring molecular markers of parasite-associated drug resistance can help predict and manage drug resistance. There is currently a lack of systematic reviews of molecular markers for indigenous and imported malaria in China. Therefore, this review summarizes the published articles related to molecular marker polymorphism of indigenous and imported malaria cases in China in the past two decades, to study the mutation frequency and distribution of crt, mdr1, dhps, dhfr and K13 gene resistance-related loci. This can provide a whole picture of molecular markers and the resistance mutations of imported cases in China, which has certain significance for drug resistance surveillance planning, safe and effective treatment, and preventing the recurrence of local transmission by imported malaria in China in the future.

China was declared malaria free in June of 2021. In the post-elimination setting, vigilant surveillance is essential to sustain malaria free status. Serological surveillance has been recognized as an efficient tool for assessing the immunity levels and exposure risk in a population. In this study, a cross-sectional serological survey was conducted in Yingjiang County, China, in August–September, 2021. The study sites were villages along the borders with Myanmar, which have no local transmission since the last indigenous case registered in 2016. A total of 923 participants from six villages were enrolled. The majority was aged > 36 years (56.12%) and 12.46% (115/923) participants had experienced malaria infection at least once. A magnetic- bead-based assay was used to test antibodies against Plasmodium vivax antigen PvMSP-1 19 to evaluate the prevalence of antibody positive subjects. A reversible catalytic model was used to assess the risk of exposure. The prevalence of anti-PvMSP-1 19 IgG was 12.84% [95% confidence interval (CI): 9.22%–16.47%], 13.93% (95% CI: 10.11%–17.74%), and 3.57% (95% CI: 1.40%–5.75%) in three different line-of-defense areas, which differed significantly ( P < 0.0001). The prevalence of anti-PvMSP-1 19 IgG increased with age and no statistically significant difference was detected between the sexes. The reversible catalytic model indicated that the seropositive conversion rate and seronegative reversion rate were 0.0042, 0.0034, 0.0032 and 0.0024, 0.0004, 0.0065 in the first-, second-line-of-defense area and total areas, respectively, and the fitted value did not differ significantly from the observed value ( P > 0.1). Although this study found the prevalence of antibody-positive subjects and the seroconversion rate in this post-elimination setting were lower than that in transmission setting, the population still had an exposure risk. Serological surveillance should be considered in post-elimination settings to provide valuable information with which to evaluate the risk of malaria re-establishment.

Background Malaria is caused by multiple parasitic species of the genusPlasmodium.Plasmodium vivax is the most geographically widespread and poses challenges in elimination due to its unique biological and epidemiological characteristics. The aim of study was to highlight the practices and experience targeting vivax malaria control and elimination in China.Main body P. vivax malaria was historically endemic in more than 70% of counties in China, with reported vivax malaria cases as high as 26 million a year. After around 70 years of effort, China was certified as malaria-free in June of 2021. The key insights into China’s vivax malaria control and elimination were offered, including radical cure strategies, comprehensive but adaptive strategies targeting species ofPlasmodium andAnopheles, mass drug administration, and case-/focus-centred surveillance and response systems.Conclusion The complete global eradication ofP. vivax and eventually malaria will be more difficult, and China’s practices and experience could be a valuable reference in this campaign.

What is already known about this topic? Plasmodium vivax (P. vivax) was the most widely distributed and major human malaria parasite in China, considered the last parasite to be eliminated. What is added by this report? The last domestic P. vivax case was reported in 2016, while hundreds of imported cases were reported annually from 2013???2020, predominantly from What are the implications for public health practice? In the post-elimination phase, adaptive and practical strategies focusing on imported P. vivax cases should be updated and adopted to prevent malaria resurgence.

ABSTRACT. Countries in the Greater Mekong Subregion have committed to eliminate Plasmodium falciparum malaria by 2025. Subclinical malaria infections that can be detected by highly sensitive polymerase chain reaction (PCR) testing in asymptomatic individuals represent a potential impediment to this goal, although the extent to which these low-density infections contribute to transmission is unclear. To understand the temporal dynamics of subclinical malaria in this setting, a cohort of 2,705 participants from three epidemiologically distinct regions of Myanmar was screened for subclinical P. falciparum and P. vivax infection using ultrasensitive PCR (usPCR). Standard rapid diagnostic tests (RDTs) for P. falciparum were also performed. Individuals who tested positive for malaria by usPCR were followed for up to 12 weeks. Regression analysis was performed to estimate whether the baseline prevalence of infection and the count of repeated positive tests were associated with demographic, behavioral, and clinical factors. At enrollment, the prevalence of subclinical malaria infection measured by usPCR was 7.7% (1.5% P. falciparum monoinfection, 0.3% mixed P. falciparum and P. vivax, and 6.0% P. vivax monoinfection), while P. falciparum prevalence measured by RDT was just 0.2%. Prevalence varied by geography and was higher among older people and in those with outdoor exposure and travel. No difference was observed in either the prevalence or count of subclinical infection by time of year, indicating that even in low-endemicity areas, a reservoir of subclinical infection persists year-round. If low-density infections are shown to represent a significant source of transmission, identification of high-risk groups and locations may aid elimination efforts.

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.

The dihydrofolate reductase (dhfr) and dihydropteroate synthetase (dhps) genes of Plasmodium vivax, as antifolate resistance-associated genes were used for drug resistance surveillance. A total of 375 P. vivax isolates collected from different geographical locations in China in 2009–2019 were used to sequence Pvdhfr and Pvdhps. The majority of the isolates harbored a mutant type allele for Pvdhfr (94.5%) and Pvdhps (68.2%). The most predominant point mutations were S117T/N (77.7%) in Pvdhfr and A383G (66.8%) in Pvdhps. Amino acid changes were identified at nine residues in Pvdhfr. A quadruple-mutant haplotype at 57, 58, 61, and 117 was the most frequent (57.4%) among 16 distinct Pvdhfr haplotypes. Mutations in Pvdhps were detected at six codons, and the double-mutant A383G/A553G was the most prevalent (39.3%). Pvdhfr exhibited a higher mutation prevalence and greater diversity than Pvdhps in China. Most isolates from Yunnan carried multiple mutant haplotypes, while the majority of samples from temperate regions and Hainan Island harbored the wild type or single mutant type. This study indicated that the antifolate resistance levels of P. vivax parasites were different across China and molecular markers could be used to rapidly monitor drug resistance. Results provided evidence for updating national drug policy and treatment guidelines.

Background Anti-malarial drug resistance is still a major threat to malaria elimination in the Great Mekong Sub-region. Plasmodium vivax parasites resistant to anti-malarial drugs are now found in Myanmar. Molecular surveillance on drug resistance genes in P. vivax parasites from northeastern Myanmar was aimed at estimating the underlying drug resistance in this region. Methods Blood samples from patients with vivax malaria were collected from Laiza city in northeastern Myanmar in 2020. Drug resistance genes including Pvcrt-o, Pvmdr1 , Pvdhfr and Pvdhps were amplified and sequenced. Genetic polymorphisms and haplotypes were analysed to evaluate the prevalence of mutant alleles associated with drug resistance. Results A total of 149 blood samples from P. vivax patients were collected. The prevalence of Pvmdr1 mutations at codons 958 and 1076 was 100.0% and 52.0%, respectively, whereas no single nucleotide polymorphism was present at codon 976. The proportions of single and double mutant types were 48.0% and 52.0%, respectively. A K10 “AAG” insertion in the Pvcrt-o gene was not detected. Mutations in Pvdhfr at codons 57, 58, 61, 99 and 117 were detected in 29.9%, 54.3%, 27.6%, 44.9% and 55.1% of the samples, respectively. Wild type was predominant (46.3%), followed by quadruple and double mutant haplotypes. Of three types of tandem repeat variations of Pvdhfr , Type B, with three copies of GGDN repeats, was the most common. Pvdhps mutations were only detected at codons 383 and 553 and the wild type Pvdhps was dominant (78.0%). Eleven haplotypes were identified when combining the mutations of Pvdhfr and Pvdhps , among which the predominant one was the wild type (33.9%), followed by double mutant alleles S58R/S117N /WT (24.6%). Conclusions This study demonstrated resistant P. vivax phenotypes exists in northeastern Myanmar. Continued surveillance of drug resistance markers is needed to update treatment guidelines in this region.

Although the total number of malaria cases and fatalities have declined globally since 2010, there were still 241 million malaria cases identified across 85 countries and territories in 2020. As the global malaria eradication process accelerates, more countries have launched their own initiatives of elimination. Notably, China achieved this goal by 2021, ending thousands of years of endemic. Undoubtedly, tremendous experience and vital lessons have been accrued en route to the malaria-free goal in malaria-eliminated countries including China. To enhance prospects of a malaria-free world by bridging the key evidence from a malaria-eliminated country to the contexts of affected, this personal view highlights concerted commitments and universal investment in healthcare, improved surveillance and response system, constant capacity building, demand-oriented scientific research, and multiway cooperation, which have helped China to eliminate this ancient scourge. We discuss how these key takeaways could be leveraged to different contexts. We also argue the long-term challenges and barriers on the pathway to malaria elimination and underline the needs for consistent efforts to maintain zero indigenous cases and prevent re-introduction of malaria. Through concerted efforts from global collaboration, a malaria-free world can become a reality.

Abstract Background Transmission-blocking vaccines (TBVs) target the sexual stages of malaria parasites to reduce or interrupt the transmission cycle in human and mosquito populations. The genetic diversity of TBVs candidate antigens, Pvs25 and Pvs28, in Plasmodium vivax could provide evidence for the development of TBVs. Methods Dry blood spots from P. vivax patients were collected from Dandong, Suining, Hainan, Nyingchi, Tengchong, and Yingjiang in China. The pvs25 and pvs28 genes were amplified and sequenced. The genetic diversity of pvs25 and pvs28 were analyzed using DNASTAR, MEGA6, and DnaSP 5.0 programs. Results A total of 377 samples were collected, among which 324 and 272 samples were successfully amplified in the pvs25 and pvs28 genes, respectively. Eight haplotypes were identified in Pvs25, for which the predominant mutation was I130T with 100% prevalence. A variety of 22 haplotypes in Pvs28 were identified. The number of GSGGE/D repeats of Pvs28 was a range of 4–8, among which, high (7–8) and low (4–5) copy numbers of tandem repeats were found in haplotypes H2 and H17, respectively. The nucleotide diversity of pvs28 (π = 0.00305 ± 0.00061) was slightly higher than that of pvs25 (π = 0.00146 ± 0.00007), thus they were not significantly different (P > 0.05). The Tajima's D value of pvs25 was positive whereas pvs28 was negative, which indicated that both genes were affected by natural selection. Conclusion The genetic diversity of pvs25 and pvs28 genes in China was relatively limited, which provided valuable information for TBVs design and optimization.

On 30 June 2021, China was certified malaria-free by the World Health Organization. In this study, the evolution, performance, outcomes, and impact of China’s adaptive strategy and approach for malaria elimination from 2011 to 2020 were analysed using 10-year data. The strategy and approach focused on timely detection and rapid responses to individual cases and foci. Indigenous cases declined from 1,308 in 2011 to 36 in 2015, and the last one was reported from Yunnan Province in April 2016, although thousands of imported cases still occur annually. The “1–3–7” approach was implemented successfully between 2013 and 2020, with 100% of cases reported within 24 h, 94.5% of cases investigated within three days of case reporting, and 93.4% of foci responses performed within seven days. Additionally, 81.6% of patients attended the first healthcare visit within 1–3 days of onset and 58.4% were diagnosed as malaria within three days of onset, in 2017–2020. The adaptive strategy and approach, along with their universal implementation, are most critical in malaria elimination. In addition to strengthening surveillance on drug resistance and vectors and border malaria collaboration, a further adapted three-step strategy and the corresponding “3–3–7” model are recommended to address the risks of re-transmission and death by imported cases after elimination. China’s successful practice and lessons learnt through long-term efforts provide a reference for countries moving towards elimination.

Traditionally, malaria has always been considered one of the tropical diseases. This only has changed in the late 1990s, with the World Health Organization (WHO) profiling HIV, tuberculosis (TB), and malaria as priority “poverty-related” killing diseases (1). This has led to the creation of the Global Fund to Fight AIDS, Tuberculosis, and Malaria (2), that has mobilized substantial resources to advance the control of all three diseases, even if mostly in a siloed manner. Around the same time, efforts were undertaken to solicit international attention for an entire group of other tropical diseases, currently still affecting over 1.7 billion people worldwide, that had been left “neglected” (3). The global response that was mounted to advance the control/elimination of neglected tropical diseases (NTDs) — that are more disabling than killing diseases — was based on a different logic. It profiled NTDs as a group of diseases that 1) together represented a similar burden as HIV, TB, or malaria; 2) were treatable or preventable by similar interventions that could be delivered as integrated packages; and 3) were entrenched in poverty as no other diseases, urging the international community to prioritize the deployment of development efforts focused on the poorest sections of society. Both global strategies have worked well, even though with vastly different levels of resources. Impressive global progress has been made in the fight against malaria over the last two decades. The malaria case incidence rate (cases per 1,000 population at risk) has decreased from 80 in 2000 to 57 in 2019, a reduction of almost 30%. The mortality incidence rate (deaths per 100,000 population at risk) was reduced from 25 in 2000 to 10 in 2019, or a reduction of 60%. As a result, the global number of deaths due to malaria has fallen from 736,000 in 2000 to 409,000 in 2019, a decrease of over 40%. Over the same period, the number of countries with fewer than 100 indigenous malaria cases increased from 6 to 27, with 21 countries — including China — reporting zero indigenous malaria cases for at least three consecutive years, and 10 of these countries being certified malariafree by the WHO (4). In 2019, an estimated 3.0 billion USD was spent globally on malaria control and elimination (5). Interventions for NTDs, especially large-scale preventive treatments for lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminthiasis, and trachoma, have scaled up massively over the last decade with over a billion people reached yearly from 2015 to 2019. This has led, at the end of 2020, to already 600 million fewer people needing interventions for NTDs and 42 countries having eliminated at least one NTD. A complex disease such as sleeping sickness has been brought to the verge of elimination, elimination of visceral leishmaniasis is close to being achieved in South-East Asia, and the global number of reported cases of Chagas disease has decreased by 40% between 2011 and 2019. During the same period, 90 million people have been freed from the risk of vector transmission of Chagas disease, and universal blood screening for the disease implemented at 100% in Latin-America (6–7). The yearly amount of Overseaos Development Aid (ODA) funding has been estimated to be in the order of 300 million USD per year since 2014, leveraging a contribution in medicines donated by the pharmaceutical sector with a value of approximately 1.5 billion USD per year (8–9). Despite good progress, both program areas face challenges. The global gains in combating malaria have levelled off in recent years. The emergence of resistance to insecticides and medicines is threatening malaria control and elimination (10), and the quest for novel technological solutions is hardly coping with the need. Redistributing resources toward control or eliminationspecific interventions, such as diagnosis and treatments, vector control, preventive treatments in pregnant women and children, and strengthening surveillance systems to identify and investigate foci, may produce economic efficiencies (5). Hence the increasing awareness that something more fundamentally preventive needs to be done, and new program and policy interventions to be developed, such as integrated vector management along with China CDC Weekly

准确的监测数据对开展疟疾控制、消除和消除后防止再传播工作至关重要.近年来高灵敏度的血清学监测方法不断发展和优化,特别是基于磁珠和蛋白质芯片的多重免疫分析技术,使得评估低流行区疟疾暴露风险、分析暴露的相关因素和空间异质性等成为可能.本文综述了血清学监测方法在疟疾控制与消除中的研究和应用进展,以为疟疾消除和消除后监测提供更适合的方法学工具.

Introduction: Antimalarial drug resistance, especially artemisinin resistance, has been a global threat to reduce morbidity and mortality and to eliminate malaria. Antimalarial drug resistance surveillance could provide evidence for the efficacy of a national drug policy for treatment of all reported malaria cases. Methods: The therapeutic efficacy of dihydroartemisinin-piperaquine (DHA-PPQ) and chloroquine (CQ) for the treatment of uncomplicated Plasmodium falciparum and Plasmodium vivax infection, respectively, was evaluated by enrolling patients between 2016 and 2020. Surveillance of molecular markers involved collecting blood samples by passive or active detection and amplifying the drug resistance genes Pfcrt, Pfmdr1, Pfdhfr, Pfdhps, and PfK13 . Results: DHA-PPQ and CQ were effective for the treatment of P. falciparum and P. vivax infections, with cure rates > 90% and 100%, respectively. Among the 2,492 samples, the Pfcrt wild-type CVMNK was the most frequent haplotype (70.1%, 1,747/2,492), while 19.4% (484/2,492) displayed the triple mutant haplotype CVIET. In total of 228 isolates with sequencing in Pfdhfr and Pfdhps, high mutant prevalence of 98.7% and 95.2% were detected, respectively. A total of 54 non-synonymous mutations in the PfK13 propeller domain were confirmed with a prevalence of 3.5% (87/2,483), and the most common mutation was A5785, with a proportion of 16.1% (14/87), followed by Q613E (6.9%, 6/87). Conclusion and Implications for Public Health Practice: DHA-PPQ and CQ, the first line drugs for P. falciparum and P. vivax treatment, showed efficacy in China. Molecular markers showed high levels of polymorphism and resistance, which revealed an early warning of drug resistance in imported cases.

目的 分析中国消除疟疾监测响应系统的实施和工作成效,为消除后防止疟疾输入再传播工作提供科学依据.方法 系统收集整理消除疟疾监测响应相关的方案和活动记录,以及基于国家传染病报告信息管理系统和寄生虫病防治信息管理系统中2011-2020年全国疟疾病例个案信息和监测指标数据,使用SPSS 25.0和GraphPad Prism 8.4.3软件进行统计分析.结果 2011-2020年,全国共报告疟疾病例30278例,中国籍28448例(93.96％).本地原发感染病例1732例(5.72％),为2011-2016年报告;境外输入性病例28173例(93.05％);输血感染病例9例(0.03％);长潜伏期三日疟5例(0.02％);输入继发间日疟4例(0.01％);来源不明病例355例(1.17％),为2011-2013年报告.病例以恶性疟(17960例,59.32％)为主;主要集中在云南(5415例,17.88％)、广西(3193例,10.55％)、江苏(2797例,9.24％)等省(自治区);全年均有病例报告,主要集中在5-7月(9689例,32.00％).输入性病例主要来自缅甸(4856例,17.24％)、加纳(2957例,10.50％)、尼日利亚(2693例,9.56％)等国.被动监测、人群主动病例侦查和线索追踪病例侦查的血检阳性率分别为0.76％(28452/37500291)、0.03％ (35/1215309)和0.30％ (32/105384).2013-2020年,病例诊断后1日内报告率为100％ (23114/23114),报告后3日内流行病学个案调查率为94.49％ (21840/23114),7日内疫点调查和处置率为93.30％ (20294/21751),病例发病到初诊以及初诊到确诊间隔时间中位数均为1d(四分位距:0～3d).中华按蚊分布广泛,且普遍对溴氰菊酯产生抗性.体内疗效观察双氢青蒿素哌喹片对恶性疟、氯伯喹对间日疟的治愈率分别为92.31％ (36/39)和100％ (21/21).结论 建设敏感有效的监测响应系统是中国消除疟疾的成功经验,在消除疟疾后应继续把监测响应作为核心措施,积极开展部门合作,加强能力建设,防止输入再传播,巩固消除成果.

Yingjiang County, which is on the China–Myanmar border, is the main focus for malaria elimination in China. The epidemiological characteristics of malaria in Yingjiang County were analysed in a retrospective analysis. A total of 895 malaria cases were reported in Yingjiang County between 2013 and 2019. The majority of cases occurred in males (70.7%) and individuals aged 19–59 years (77.3%). Plasmodium vivax was the predominant species (96.6%). The number of indigenous cases decreased gradually and since 2017, no indigenous cases have been reported. Malaria cases were mainly distributed in the southern and southwestern areas of the county; 55.6% of the indigenous cases were reported in Nabang Township, which also had the highest risk of imported malaria. The “1–3–7” approach has been implemented effectively, with 100% of cases reported within 24 h, 88.9% cases investigated and confirmed within 3 days and 98.5% of foci responded to within 7 days. Although malaria elimination has been achieved in Yingjiang County, sustaining elimination and preventing the re-establishment of malaria require the continued strengthening of case detection, surveillance and response systems targeting the migrant population in border areas.

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 CV IET . 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 NY Y with single mutation in codon 1246 was not observed. The double mutant haplotype YF D 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.

Background: Sulfadoxine-pyrimethamine (SP) is recommended for intermittent preventive treatment in Africa against Plasmodium falciparum infection. However, increasing SP resistance (SPR) of P. falciparum affects the therapeutic efficacy of SP, and pfdhfr (encoding dihydrofolate reductase) and pfdhps (encoding dihydropteroate synthase) genes are widely used as molecular markers for SPR surveillance. In the present study, we analyzed single nucleotide polymorphisms (SNPs) of pfdhfr and pfdhps in P. falciparum isolated from infected Chinese migrant workers returning from Africa. Methods: In total, 159 blood samples from P. falciparum-infected workers who had returned from Africa to Anhui, Shangdong, and Guangxi provinces were successfully detected and analyzed from 2017 to 2019. The SNPs in pfdhfr and pfdhps were analyzed using nested PCR. The genotypes and linkage disequilibrium (LD) were analyzed using Haploview. Results: High frequencies of the Asn51Ile (N51I), Cys59Arg(C59R), and Ser108Asn(S108N) mutant alleles were observed, with mutation frequencies of 97.60, 87.43, and 97.01% in pfdhfr, respectively. A triple mutation (IRN) in pfdhfr was the most prevalent haplotype (86.83%). Six point mutations were detected in pfdhps DNA fragment, Ile431Val (I431V), Ser436Ala (S436A), Ala437Gly (A437G), Lys540Glu(K540E), Ala581Gly(A581G), Ala613Ser(A613S). The pfdhps K540E (27.67%) was the most predominant allele, followed by S436A (27.04%), and a single mutant haplotype (SGKAA; 62.66%) was predominant in pfdhps. In total, 5 haplotypes of the pfdhfr gene and 13 haplotypes of the pfdhps gene were identified. A total of 130 isolates with 12 unique haplotypes were found in the pfdhfr-pfdhps combined haplotypes, most of them (n = 85, 65.38%) carried quadruple allele combinations (CIRNI-SGKAA). Conclusion: A high prevalence of point mutations in the pfdhfr and pfdhps genes of P. falciparum isolates was detected among Chinese migrant workers returning from Africa. Therefore, continuous in vitro molecular monitoring of Sulfadoxine-Pyrimethemine combined in vivo therapeutic monitoring of artemisinin combination therapy (ACT) efficacy and additional control efforts among migrant workers are urgently needed.