JMIR Publications

ABSTRACT

Background:

Cambodia is targeting elimination of malaria by 2025. The last remaining pockets of malaria in Cambodia are concentrated among populations exposed to forested areas, but the size of these populations is not well understood. In order to plan for procurement and distribution of vector control tools, chemoprophylaxis, and other commodities for malaria prevention and surveillance, a robust estimation of the size of the most at-risk populations is required.

Objective:

To estimate the size of the population at highest-risk of malaria exposure in two operational districts in Cambodia.

Methods:

In April 2023, a multi-stage, in-person survey was conducted among residents in the two operational districts (OD) in Cambodia with the highest malaria burden at the time of the study: Sen Monorom in Mondulkiri province and Phnom Srouch in Kampong Speu province. In each OD, 10 villages were randomly selected for inclusion in the study, and 35 households were randomly selected for inclusion from each village. To estimate the number of individuals at high risk of malaria—defined as residing within 1km of a forest—the survey collected information on the distance of their primary residence to forested areas and their travel patterns to forested areas. The survey also collected data on whether the individuals surveyed had received a BITE forest pack as part of the larger BITE project, in order to develop smaller scale estimates of the number of individuals exposed to forests in each of four randomly selected villages in Sen Monorom OD, via the "multiplier method".

Results:

In Sen Monorom, 138 households and 872 individuals were enrolled in the study, and in Phnom Srouch 163 households and 844 individuals were enrolled. In both ODs, the ratio of males to females was approximately equal, with median age of 22.0 years in Sen Monorom, 24.5 years in Phnom Srouch (total age range 3-86)). The first-stage survey indicated that approximately 79% of residents in Sen Monorom, representing an estimated 17,315 individuals, are at high risk for malaria exposure. In Phnom Srouch, just 25% of the population fit the high-risk criteria, representing an estimated 1,945 individuals. Between 125 and 186 individuals were estimated to be at high risk of malaria in each of the four villages where the multiplier method could be applied.

Conclusions:

This study provides an estimate of the number of individuals in two operational districts in Cambodia who are considered to be at high risk for malaria infection. These estimates can be used to help plan malaria control and elimination efforts in the future. This paper provides a relatively simple method for undertaking additional at-risk population size estimate studies in other areas in Cambodia and beyond.