Forest-Going as a Risk Factor for Confirmed Malaria in Champasak Province, Lao PDR: A Case-Control Study

Lao People's Democratic Republic (Lao PDR) has made significant progress in reducing malaria in recent years. In the Greater Mekong Subregion, forest-going is often a risk factor contributing to continuing malaria transmission. This study assessed forest-going and other potential risk factors for malaria cases in Champasak Province, Lao PDR. Routine passive surveillance data from August 2017 to December 2018 were extracted from health facilities in three districts for a case-control study; at the time of presentation, all fever cases were asked to report any recent forest travel. Multivariable logistic regression was used to assess the relationship between forest-going and malaria infection while controlling for other covariates. Of 2933 fever cases with data available on forest-sleeping and malaria diagnosis from 25 health facilities, 244 (8%) tested positive (cases), and 2689 (92%) tested negative (controls). Compared with spending 0-2 nights in the forest, spending 3-7 nights in the forest was associated with 9.7 times the odds of having a malaria infection (95% CI: 4.67-20.31, p < 0.001) when adjusting for gender, occupation, and season. Forest-going, especially longer trips, is associated with increased risk for confirmed symptomatic malaria in southern Lao PDR, and appropriate and targeted intervention efforts are needed to protect this high-risk population.