Molecular Epidemiology of Drug Resistance Genes in Plasmodium falciparum Isolates Imported from Nigeria between 2016 and 2020: Continued Emergence of Fully Resistant - Alleles.

Malaria poses public health threats worldwide. Nigeria accounted for the highest numbers of cases (26.8%) and deaths (31.9%) among countries where malaria is endemic in 2020. Currently, monitoring molecular markers in imported malaria cases provides an efficient means to screen for emerging drug resistance in countries where malaria is endemic, particularly in those where field surveillance is challenging. Here, we investigated 165 Plasmodium falciparum infections imported from Nigeria to Zhejiang Province, China, between 2016 and 2020. Multiple molecular markers in , , , , and were detected. The prevalences and patterns of mutations were analyzed. Polymorphism of was limited to 5 of 156 (3.21%) isolates. The wild-type CVMNK allele of became predominant (65.36%) compared with the triple mutation CVIET. A low frequency (4.73%) of double mutations (N86Y and Y184F) in was observed. The dominant haplotypes of and were DI (92.41%) and ISKAA (36.84%), respectively. The newly discovered mutant I431V was identified in 21.71% of isolates. A "fully resistant" combination of , IRN-GE, was found in eight (5.67%) samples, which was hardly seen in Nigeria. The current study demonstrated a high frequency of wild-type . Limited polymorphism of but a high prevalence of and mutations was illustrated. Our data so far serve as comprehensive surveillance of molecular markers of the , , , , and genes. Based on our findings, it has become crucial to evaluate the impact of the emerging fully resistant type of - as well as its combination with I431V on the efficacy of sulfadoxine-pyrimethamine (SP) in Nigeria. Monitoring the current resistance to antimalarial drugs is critical to enable timely action to prevent its spread and limit its impact. The high prevalence of wild-type found in our study is an optimistic signal to reevaluate chloroquine (CQ) sensitivity in Nigeria, which is cost-effective and once played a crucial role in the fight against malaria. Based on the continued emergence of fully resistant - alleles illustrated in the current investigation, actions are needed in Nigeria, such as national systemic surveillance to monitor their updated epidemiology as well as assessments of their influence on SP efficacy to minimize any public health impact. These findings urge a response to the threat of drug resistance to facilitate appropriate drug policies in the study area.