Asymptomatic malaria infections and associated risk factors in malaria-eliminating settings of Nong District, Savannakhet Province, Lao People's Democratic Republic.

Abstract

Background: As the Lao People's Democratic Republic is nearing malaria elimination, asymptomatic malaria infections remain a challenge to address. Control measures focusing on symptomatic persons do not effectively work for asymptomatic infections which often go undetected by conventional diagnostic tools. It is therefore crucial to understand the burden of asymptomatic malaria for tailored interventions to eliminate the disease. This study assessed the prevalence of asymptomatic malaria infections with associated risk factors in an endemic district of Savannakhet province.

Methods: In March 2024, a cross-sectional study was conducted in three villages of Nong District. Blood samples were collected from the fingertips of the participants for Plasmodium parasite identification using microscopy and Loop-mediated Isothermal Amplification (LAMP); those aged 13 years and above were also interviewed. Mann-Whitney U test and Fisher's exact test were performed to compare the medians of different age and temperature groups and determine the association between predictor variables and outcome variables respectively.

Results: A total of 622 individuals participated in this survey; Plasmodium parasites were detected in 2.1% (13/622) of participants. The prevalence of asymptomatic malaria was 1.8% (11/622). Plasmodium vivax accounted for 15.4% (2/13) of all positive cases. The remaining species could not be identified. Farmers aged 15 years and above accounted for 81.8% of the asymptomatic infections. Ninety percent (90%) of the participants used bed nets in the village. Among interviewed participants, 23.6% reported not using mosquito bed nets in the forest; 21.3% of the participants who had been to the forest were nighttime forest workers.

Conclusions: This study revealed a prevalence of 1.8% of asymptomatic malaria infections in the study areas with the majority of the infections clustered among farmers, and an important proportion of these populations not using protective measures in the forest. These findings showed that malaria reservoirs are notable with a lack of use of protective measures, which could threaten malaria control and elimination efforts. Therefore, malaria elimination in Lao PDR by 2030 would need interventions targeting high-risk adult populations for screening with sensitive tools coupled with sensitization on protective measures and asymptomatic malaria.