Molecular Surveillance of Drug Resistance of Plasmodium falciparum Isolates Imported from Angola in Henan Province, China

Geographical Heterogeneity in Antimalarial Resistance Markers Revealed by Genomic Surveillance in Angola, 2023

Plasmodium falciparum malaria remains a leading cause of mortality in Angola, with emerging antimalarial resistance threatening treatment and prevention strategies. Efficacy of artemether-lumefantrine, one of the country's preferred malaria treatments, has been reported below 90% in two provinces, underscoring the need for routine resistance surveillance and efficacy monitoring to guide policy decisions. Between March and July 2023, dried blood spots and demographic data were collected from P. falciparum-positive participants at 16 health facilities across 8 provinces. Multiplexed amplicon deep sequencing was used to characterize single nucleotide polymorphisms in 12 genes linked with resistance, estimate allele frequencies, and detect co-infecting non-falciparum Plasmodium species. Sequence data from 817 samples revealed significant geographic variation in resistance markers. In the southeast, artemisinin partial resistance markers (k13 P574L, P441L), were detected at very low prevalence (<0.1%), while the quintuple dhps/dhfr haplotype, linked to sulfadoxine-pyrimethamine (SP) resistance, was very prevalent (>40% of samples). In the northwest, the sextuple dhps/dhfr haplotype, a marker of higher SP resistance, was most prevalent in Zaire (14.2%). The crt CVIET haplotype, associated with chloroquine resistance, had a national prevalence of 15.9%, detected in over 48% of samples from Zaire and Uíge. The mdr1 N86 genotype, linked to reduced lumefantrine susceptibility, was widespread, detected in 99.3% of samples. Co-infections of P. falciparum and non-falciparum species were rare with no clear geographic distribution. No P. vivax co-infections were detected. These findings highlight the need for continued monitoring to safeguard treatment efficacy, reinforcing the importance of molecular surveillance in malaria control strategies.

An overview of artemisinin-resistant malaria and associated Pfk13 gene mutations in Central Africa

Malaria caused by Plasmodium falciparum is one of the deadliest and most common tropical infectious diseases. However, the emergence of artemisinin drug resistance associated with the parasite's Pfk13 gene, threatens the public health of individual countries as well as current efforts to reduce malaria burdens globally. It is of concern that artemisinin-resistant parasites may be selected or have already emerged in Africa. This narrative review aims to evaluate the published evidence concerning validated, candidate, and novel Pfk13 polymorphisms in ten Central African countries. Results show that four validated non-synonymous polymorphisms (M476I, R539T, P553L, and P574L), directly associated with a delayed therapy response, have been reported in the region. Also, two Pfk13 polymorphisms associated to artemisinin resistance but not validated (C469F and P527H) have been reported. Furthermore, several non-validated mutations have been observed in Central Africa, and one allele A578S, is commonly found in different countries, although additional molecular and biochemical studies are needed to investigate whether those mutations alter artemisinin effects. This information is discussed in the context of biochemical and genetic aspects of Pfk13, and related to the regional malaria epidemiology of Central African countries.

Molecular markers associated with drug resistance in Plasmodium falciparum parasites in central Africa between 2016 and 2021

Objectives

The widespread occurrence of anti-malarial drug resistance threatens the current efforts to control malaria in African regions. Molecular marker surveillance helps to track the emergence and spread of drug-resistant malaria cases.

Methods

A total of 237 Plasmodium falciparum infections imported from central Africa to Zhejiang Province, China, between 2016 and 2021, were investigated. Genomic DNA was extracted from blood samples of each patient and nested PCRs was used to detect molecular markers in k13, Pfcrt, and Pfmdr1 genes. The spatial and temporal distributions of the molecular markers were analyzed.

Results

A limited polymorphism of k13 was observed, including two nonsynonymous (D464E and K503E) and five synonymous mutations. Wild-type CVMNK of Pfcrt predominated (78.5%), whereas 19.5% of the samples harbored the mutant haplotype, CVIET. The point mutation Y184F and the single mutant haplotype NF of Pfmdr1 were the most frequently observed. The geographical distributions of the Pfcrt and Pfmdr1 haplotypes displayed distinct patterns, with the mutant haplotype of Pfcrt more common in Gabon (53.9%) and Congo (50.0%), and wild haplotypes of Pfmdr1 more frequently found in Cameroon, Angola, and Congo. The prevalence of wild-type CVMNK of Pfcrt increased from 68.5-74.6% in 2016-2017 to 81.8-87.5% in 2018-2021. The proportion of wild-type Pfmdr1 also increased from 27.1% in 2016 to 38.5% in 2019.

Conclusion

The geographical and temporal distribution of k13, Pfcrt, and Pfmdr1 polymorphisms in P. falciparum parasites imported from central Africa between 2016 and 2021 are demonstrated. Our data provide updated evidence that can be used to adjust anti-malarial drug policies in central Africa and China.

A review of malaria molecular markers for drug resistance in Plasmodium falciparum and Plasmodium vivax in China

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.

Establishing and applying an adaptive strategy and approach to eliminating malaria: practice and lessons learnt from China from 2011 to 2020

ABSTRACTOn 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.

Imported malaria definition and minimum data for surveillance

The mobility of malaria-infected individuals poses challenges to elimination campaigns by way of spreading parasite drug resistance, straining country-to-country collaboration, and making routine data collection difficult, especially in resource-poor settings. Nevertheless, no concerted effort has been made to develop a common framework to define the spatial and temporal components of an imported malaria case and recommend the minimum data needed to identify it. We conducted a scoping review of imported malaria literature from 2010 to 2020 which showed that definitions vary widely, and local capabilities of detecting importation are often restricted in low-income countries. Following this, we propose a common definition for imported malaria and the minimum data required to identify a case, depending on the country's capability of conducting an epidemiological investigation. Lastly, we utilize the proposed definition using data from Brazil to demonstrate both the feasibility and the importance of tracking imported cases. The case of Brazil highlights the capabilities of regular surveillance systems to monitor importation, but also the need to regularly use these data for informing local responses. Supporting countries to use regularly collected data and adopt a common definition is paramount to tackling the importation of malaria cases and achieving elimination goals set forth by the World Health Organization.

Pfkelch13 Plasmodium falciparum Mutations in Huambo, Angola

Artemisinin (ART) is recommended as the first-line drug for P. falciparum infections combined with a long-acting partner drug. The emergence of P. falciparum resistance to ART (ARTR) is a concern for malaria. The most feared threat remains the spread of ARTR from Southeast Asia to Africa or the independent emergence of ARTR in Africa, where malaria accounts for 93% of all malaria cases and 94% of deaths. To avoid this worst-case scenario, surveillance of Pfkelch13 mutations is essential. We investigated mutations of Pfkelch13 in 78 P. falciparum samples from Huambo, Angola. Most of the parasites had a wild-type Pfkelch13 allele. We identified one synonymous mutation (R471R) in 10 isolates and one non-synonymous mutation (A578S) in two samples. No Pfkelch13 validated or candidate ARTR mutants were identified. The finding suggests that there is little polymorphism in Pfkelch13 in Huambo. Since cases of late response to ART in Africa and the emergence of ARTR mutations in Rwanda and Uganda have been reported, efforts should be made toward continuous molecular surveillance of ARTR. Our study has some limitations. Since we analyzed P. falciparum parasites from a single health facility, the study may not be representative of all Angolan endemic areas.

Surveillance of Antimalarial Drug-Resistance Genes in Imported Plasmodium falciparum Isolates From Nigeria in Henan, China, 2012-2019

Malaria remains a major public health issue in Nigeria, and Nigeria is one of the main sources of imported malaria in China. Antimalarial drug resistance is a significant obstacle to the control and prevention of malaria globally. The molecular markers associated with antimalarial drug resistance can provide early warnings about the emergence of resistance. The prevalence of antimalarial drug resistant genes and mutants, including PfK13, Pfcrt, Pfmdr1, Pfdhfr, and Pfdhps, was evaluated among the imported Plasmodium falciparum isolates from Nigeria in Henan, China, from 2012 to 2019. Among the 167 imported P. falciparum isolates, the wild-type frequency of PfK13, Pfcrt, Pfmdr1, Pfdhfr, and Pfdhps was 98.7, 63.9, 34.8, 3.1, and 3.1%, respectively. The mutation of PfK13 was rare, with just two nonsynonymous (S693F and Q613H) and two synonymous mutations (C469C and G496G) identified from four isolates. The prevalence of Pfcrt mutation at codon 74–76 decreased year-by-year, while the prevalence of pfmdr1 86Y also decreased significantly with time. The prevalence of Pfdhfr and Pfdhps mutants was high. Combined mutations of Pfdhfr and Pfdhps had a high prevalence of the quadruple mutant I₅₁R₅₉N₁₀₈-G₄₃₇ (39.0%), followed by the octal mutant I₅₁R₅₉N₁₀₈-V₄₃₁A₄₃₆G₄₃₇G₅₈₁S₆₁₃ (17.0%). These molecular findings update the known data on antimalarial drug-resistance genes and provide supplemental information for Nigeria.

Prevalence of Plasmodium falciparum Kelch 13 (PfK13) and Ubiquitin-Specific Protease 1 (pfubp1) Gene Polymorphisms in Returning Travelers from Africa Reported in Eastern China

Delayed clearance of Plasmodium falciparum by artemisinin-based combination therapies (ACTs) has already been observed for African isolates. Here, we aimed to investigate the prevalence, among travelers returning from African countries, of polymorphisms in two genes correlated with delayed parasite clearance (encoding P. falciparum Kelch 13 [PfK13] and ubiquitin-specific protease 1 [pfubp1]) reported in eastern China and to provide baseline data for antimalarial drug resistance (ART) surveillance and evaluation. A total of 153 filter paper blood spots collected in 2017-2019 from patients with uncomplicated P. falciparum cases in Anhui and Shandong Provinces were included in this study. Among them, 3.3% (5/153) of the isolates carried PfK13 mutations, and 3 of them harbored the same synonymous mutation, C469C. A total of 13.1% (20/153) of the isolates were found to contain pfubp1 mutations, and all were nonsynonymous. The pfubp1 genotypes associated with ART that occurred in this study included E1528D (6.5% [10/153]) and D1525E (2.6% [4/153]). However, a high prevalence of the previously unreported mutation E1531D (5.9% [9/153]) was also detected. In addition, two types of deletions (encoding KID and KIE, respectively) and two types of insertions (encoding KYE and KYDKYD, respectively) were found in 16 isolates and 6 isolates, respectively. This study showed limited variation in PfK13 among travelers returning from African countries and suggested other potential molecular markers, such as pfubp1, for use in the surveillance of African isolates in ACT susceptibility studies. Further clinical trial research is under way to investigate these PfK13 and pfubp1 mutations, as well as other candidate molecular markers, and their roles in delaying parasite clearance.