Prevalence of antifolate drug resistance markers in Plasmodium vivax in China / 医学前沿

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.

Study on the polymorphism in circumsporozoite protein of Plasmodium vivax before the completion on elimination program of malaria, in Hainan province / 中华流行病学杂志

<p><b>OBJECTIVE</b>To explore the polymorphism in circumsporozoite protein of Plasmodium vivax before malaria was eliminated in Hainan island.</p><p><b>METHODS</b>PCR amplification, sequencing, and alignment methodologies were conducted and phylogenetic tree constructed.</p><p><b>RESULTS</b>From all the cases, 19 of them belonged to two types, with 18 as VK210 type and 1 as VK247 type. VK210 type could be divided into seven kinds of subtypes but VK247 had only one type. Ratio of tropical strain with temperate stain in VK210 type was explored between the two stages:control or elimination. Phylogenetic tree was constructed by amino acid sequencing which clearly manifested that VK210 type and VK247 type belonged to different clusters.</p><p><b>CONCLUSION</b>Compared the proportion of two types in the control stage, there was no significant difference seen in the stage of elimination.</p>

A Case of Plasmodium ovale wallikeri Infection in a Chinese Worker Returning from West Africa

In contrast to the gradual reduction in the number of locally transmitted malaria cases in China, the number of imported malaria cases has been increasing since 2008. Here, we report a case of a 39-year-old Chinese man who acquired Plasmodium ovale wallikeri infection while staying in Ghana, West Africa for 6 months in 2012. Microscopic examinations of Giemsa-stained thin and thick blood smears indicated Plasmodium vivax infection. However, the results of rapid diagnostic tests, which were conducted 3 times, were not in agreement with P. vivax. To further check the diagnosis, standard PCR analysis of the small-subunit rRNA gene was conducted, based on which a phylogeny tree was constructed. The results of gene sequencing indicated that this malaria is a variant of P. ovale (P. ovale wallikeri). The infection in this patient was not a new infection, but a relapse of the infection from the one that he had contracted in West Africa.