Prevalence of Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency among Malaria Patients in Southern Thailand: 8 Years Retrospective Study.

Erythrocytes deficient in glucose-6-phosphate dehydrogenase (G6PD) is more susceptible to oxidative damage from free radical derived compounds. The hemolysis triggered by oxidative agents such as primaquine (PQ) is used for the radical treatment of hypnozoites of P. vivax. Testing of G6PD screening before malaria treatment is not a common practice in Thailand, which poses patients at risk of hemolysis. This retrospective study aimed to investigate the prevalence of G6PD in malaria patients who live in Southern Thailand. Eight hundred eighty-one malaria patients were collected for 8-year from 2012 to 2019, including 785 (89.1%) of P. vivax, 61 (6.9%) of P. falciparum, 27 (3.1%) of P. knowlesi, and 8 (0.9%) of mixed infections. The DiaPlexC genotyping kit (Asian type) and PCR-RFLP were employed to determine the G6PD variants. The result showed that 5 different types of G6PD variants were identified in 26 cases (2.9%); 12/26 (46.2%) had Mahidol (487G>A) and 11/26 (42.3%) had Viangchan (871G>A) variants, while the rest had Kaiping (1388G>A), Union (1360C>T), and Mediterranean (563C>T) variants. G6PD Songklanagarind (196T>A) variant was not found in the study. Our result did not show a significant difference in the malaria parasite densities in patients between G6PD-deficient and G6PD-normal groups. According to our findings, testing G6PD deficiency and monitoring the potential PQ toxicity in patients who receive PQ are highly recommended.

A LAMP-SNP Assay Detecting C580Y Mutation in Pfkelch13 Gene from Clinically Dried Blood Spot Samples.

Artemisinin resistance (ART) has been confirmed in Greater Mekong Sub-region countries. Currently, C580Y mutation on Pfkelch13 gene is known as the molecular marker for the detection of ART. Rapid and accurate detection of ART in field study is essential to guide malaria containment and elimination interventions. A simple method for collection of malaria-infected blood is to spot the blood on filter paper and is fast and easy for transportation and storage in the field study. This study aims to evaluate LAMP-SNP assay for C580Y mutation detection by introducing an extra mismatched nucleotide at the 3' end of the FIP primer. The LAMP-SNP assay was performed in a water bath held at a temperature of 56°C for 45 min. LAMP-SNP products were interpreted by both gel-electrophoresis and HNB-visualized changes in color. The method was then tested with 120 P. falciparum DNA from dried blood spot samples. In comparing the LAMP-SNP assay results with those from DNA sequencing of the clinical samples, the 2 results fully agreed to detect C580Y. The sensitivity and specificity of the LAMP-SNP assay showed 100%. There were no cross-reactions with other Plasmodium species and other Pfkelch13 mutations. The LAMP-SNP assay performed in this study was rapid, reliable, and useful in detecting artemisinin resistance in the field study.

Genetic Diversity of Plasmodium vivax in Clinical Isolates from Southern Thailand using PvMSP1, PvMSP3 (PvMSP3α, PvMSP3ß) Genes and Eight Microsatellite Markers.

Plasmodium vivax is usually considered morbidity in endemic areas of Asia, Central and South America, and some part of Africa. In Thailand, previous studies indicated the genetic diversity of P. vivax in malaria-endemic regions such as the western part of Thailand bordering with Myanmar. The objective of the study is to investigate the genetic diversity of P. vivax circulating in Southern Thailand by using 3 antigenic markers and 8 microsatellite markers. Dried blood spots were collected from Chumphon, Phang Nga, Ranong and, Surat Thani provinces of Thailand. By PCR, 3 distinct sizes of PvMSP3α, 2 sizes of PvMSP3ß and 2 sizes of PvMSP1 F2 were detected based on the length of PCR products, respectively. PCR/RFLP analyses of these antigen genes revealed high levels of genetic diversity. The genotyping of 8 microsatellite loci showed high genetic diversity as indicated by high alleles per locus and high expected heterozygosity (HE). The genotyping markers also showed multiple-clones of infection. Mixed genotypes were detected in 4.8% of PvMSP3α, 29.1% in PvMSP3ß and 55.3% of microsatellite markers. These results showed that there was high genetic diversity of P. vivax isolated from Southern Thailand, indicating that the genetic diversity of P. vivax in this region was comparable to those observed other areas of Thailand.

Molecular Surveillance of Pfkelch13 and Pfmdr1 Mutations in Plasmodium falciparum Isolates from Southern Thailand.

Artemisinin-based combination therapy (ACT) resistance is widespread throughout the Greater Mekong Subregion. This raises concern over the antimalarial treatment in Thailand since it shares borders with Cambodia, Laos, and Myanmar where high ACT failure rates were reported. It is crucial to have information about the spread of ACT resistance for efficient planning and treatment. This study was to identify the molecular markers for antimalarial drug resistance: Pfkelch13 and Pfmdr1 mutations from 5 provinces of southern Thailand, from 2012 to 2017, of which 2 provinces on the Thai- Myanmar border (Chumphon and Ranong), one on Thai-Malaysia border (Yala) and 2 from non-border provinces (Phang Nga and Surat Thani). The results showed that C580Y mutation of Pfkelch13 was found mainly in the province on the Thai-Myanmar border. No mutations in the PfKelch13 gene were found in Surat Thani and Yala. The Pfmdr1 gene isolated from the Thai-Malaysia border was a different pattern from those found in other areas (100% N86Y) whereas wild type strain was present in Phang Nga. Our study indicated that the molecular markers of artemisinin resistance were spread in the provinces bordering along the Thai-Myanmar, and the pattern of Pfmdr1 mutations from the areas along the international border of Thailand differed from those of the non-border provinces. The information of the molecular markers from this study highlighted the recent spread of artemisinin resistant parasites from the endemic area, and the data will be useful for optimizing antimalarial treatment based on regional differences.