Sub-RDT Plasmodium vivax infections and G6PD deficiency in Kayin State, Myanmar

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BACKGROUND: In Kayin State (Myanmar), Plasmodium falciparum incidence declined substantially between 2014 and 2020 following intensive elimination efforts, leaving P. vivax as the predominant species. Elimination of P. vivax is challenging due to relapses, presence of low density reservoirs and a high prevalence of glucose-6-phosphate dehydrogenase enzyme (G6PD) deficiency in the area, which constrains the use of 8-aminoquinoline drugs for radical cure. This study assessed the prevalence of low-density, sub-RDT (rapid diagnostic test) P. vivax infections and G6PD deficiency in 23 villages in Kayin State from 2020 to 2021. METHODS: Participants were screened for malaria using malaria RDT (mRDT), a reverse transcriptase real-time polymerase chain reaction (rRT-PCR), an enzyme-linked immunosorbent assay (ELISA) and their G6PD status was assessed using a quantitative point-of-care test. Prevalence estimates with 95% confidence intervals were calculated and stratified by sex and geographic area and group differences were compared using chi-square or Fisher's exact tests. RESULTS: The mRDT detection rate was very low (0.5%), with 26 P. vivax and 1 P. falciparum infections detected among 5509 individuals. Positivity by rRT-PCR for P. vivax was 14.3% (317/2219) followed by P. falciparum 8.3% (185/2219) and unidentified Plasmodium species infections 0.8% (18/2219). The prevalence of sub-RDT P. vivax infections (defined as rRT-PCR positive and mRDT negative) was 14.1% (311/2211). The corresponding figure for P. falciparum was 8.3% (184/2218). Median village prevalence of sub-RDT P. vivax infections was 15.2% [IQR 4.0-23.6, range 0-40.4] and 6.0% [IQR 2.1-16.0, range 0-27.0] for P. falciparum. Hpapun township (north) had a sub-RDT P. vivax prevalence six times higher than Myawaddy township (south). The overall proportion of G6PD deficiency among males was 21.7% and 10.6% in females (P < 0.001). G6PD deficiency showed village-level variation, with a median of 14.4% (IQR 12.3-14.8) in Myawaddy and 17.3% (IQR 14.0-23.1) in Hpapun (P = 0.05). No association was observed between G6PD status and sub-RDT P. vivax infection in either males or females across townships. CONCLUSIONS: The coexistence of sub-RDT P. vivax reservoirs and a high proportion of G6PD deficiency pose a major barrier to elimination. These findings highlight the need for high-sensitivity diagnostics to detect low-density infections and reliable point-of-care G6PD testing to effectively target P. vivax malaria in Kayin State, Myanmar.

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