Molecular Profiles of Antimalarial Drug Resistance in Plasmodium Species from Asymptomatic Malaria Carriers in Gia Lai Province, Vietnam

Asymptomatic malaria infection is a major concern in the fight against malaria, as it can act as a significant reservoir for its silent spread or transmission. Therefore, surveillance to detect asymptomatic subjects, particularly in regions with high malaria endemicity, is essential. This study aimed to investigate the status of asymptomatic submicroscopic malaria infections in Gia Lai province, Vietnam, and to analyze molecular profiles of antimalarial drug resistance in the parasites from the asymptomatic carriers. A total of 2171 individuals were included from three districts of Gia Lai province, Vietnam, an area where malaria is endemic. Asymptomatic submicroscopic infection was confirmed by quantitative real-time PCR, and the infected <i>Plasmodium</i> species were confirmed by sequencing. Antimalarial drug-resistant genes, including <i>pfk13</i>, <i>pfcrt</i>, <i>pvmdr-1</i>, and <i>pvcrt-o</i>, were analyzed in the parasites from asymptomatic cases. The rate of asymptomatic submicroscopic malaria infection was 2.67%. <i>P. falciparum</i> and <i>P. vivax</i> mono-infections, as well as mixed infections of <i>P. falciparum</i> and <i>P. vivax</i>, were identified, with <i>P. vivax</i> being more prevalent, a significant observation given the challenge of <i>P. vivax</i> relapses and its contribution to sustained malaria transmission. Adults, including young, middle-aged, and older adults, were the predominant affected groups. Asymptomatic infections were more common in females than in males. Interestingly, high frequencies of mutations in genetic markers associated with antimalarial drug resistance, particularly <i>pfk13</i> (C580Y, 100%), <i>pfcrt</i> (M74I/N75E/K76T, 100%), and <i>pvmdr-1</i> (F1076L, 100%), were observed in asymptomatic individuals, which may increase the risk of spreading drug resistance. These findings emphasize the urgent necessity for improved surveillance and targeted intervention to prevent the silent spread of malaria, supporting the National Malarial Control and Elimination Program in formulating malaria elimination strategies for Vietnam.