Ingrid Chen

Background: Cambodia strives to eliminate all species of human malaria by 2025, requiring that foci among forest-exposed populations in remote settings be addressed. This study explores malaria risks amongst forest-exposed groups in Mondulkiri and Kampong Speu Provinces, Cambodia as part of a multi-stage study on novel mosquito bite prevention tools (Project BITE). Methods: A serial cross-sectional survey explored the demographics, housing structure openness, mosquito bite prevention habits, and protection from malaria amongst three target groups: forest goers who work in the forest, forest dwellers who live in the forest, and forest rangers who patrol forested regions. Malaria prevalence data was collected at three time points using rapid diagnostic tests (RDTs) for febrile individuals and qPCR for all participants. Infection locations and travel patterns of Plasmodium falciparum-infected individuals were analysed for clustering and the potential movement of infections. Results: 2935 participants were enrolled between October 2022 and February 2023, consisting of 1093 (37%) forest goers and 1787 (61%) forest dwellers across both provinces, and 55 (5%) forest rangers in Mondulkiri province. Most worked outdoors as farmers, day labourers, and forest collectors, and reported going to the forest five to seven days a week. For housing, 29% and 39% of participants reported living in partially open primary and secondary structures, respectively. The main methods of mosquito bite protection used were insecticide-treated nets, wearing long sleeves, and burning mosquito coils, with limited protection during the daytime and outside at night. All febrile individuals had negative RDT test results. For qPCR, 24 P. falciparum infections (< 1%) were detected among forest goers and dwellers, clustered in Pu Trom and Pu Nhav villages in Mondulkiri Province, and Banteay Roka and Banteay Roka Kirisenchey (M) villages in Kampong Speu Province. Plasmodium vivax cases were detected (216 cases, 5%) across all enrolled villages. Only two infections were found in forest rangers. Conclusion: Malaria elimination strategies for forest-exposed populations in Cambodia should focus on vector intervention strategies that offer protection during the day and outside at night, and drug-based strategies to clear subpatent infections, targeting forest goers and dwellers in villages where cases are detected.

Background Southeast Asia aims to eliminate malaria by 2030, requiring that risk factors for malaria among hard-to-reach populations be understood and addressed. This is the first study of malaria risks on the Orang Rimba, a culturally unique nomadic ethnic group residing in the lowland rain forests of Sumatra, Indonesia that usually functions outside of the health system. This study characterizes perceptions of malaria and preventive practices used, to inform the selection of interventions that can support malaria elimination efforts for this specific and sensitive population.Methods A small cross-sectional survey was conducted among the Orang Rimba people in the Sarolangun District of Jambi, Indonesia between March and May of 2021. The survey identified participant demographics, their knowledge of malaria, prevention practices in use, and pregnancy-related health behaviors among females. For cultural reasons, questions for women were asked through men.Results We enrolled 39 participants, 87% of which were male. Most participants (77%) had no formal schooling, and all worked in agriculture and/or hunting. Their understanding of malaria was limited, with approximately half understanding that malaria transmission takes place through the bite of an infected mosquito, and 62% citing fever as a symptom of malaria. The vast majority of participants (90%) used mosquito coils and/or insecticide-treated bednets (ITNs) (87%) the night before the survey. Women did not perceive malaria to be a greater health risk in pregnancy, and received limited prenatal care (29%) and ITNs (46%) during their pregnancies.Conclusions Orang Rimba forest dwellers in Sumatra are vulnerable, socioeconomically disadvantaged, and separated from the healthcare system. If Indonesia and the Greater Mekong Subregion are to meet their goal to eliminate malaria by 2030, deliberate and continuous efforts targeted at reducing outdoor transmission among the Orang Rimba communities will be essential. Education on malaria and the provision of prenatal care would likely benefit this community.

Background: Global interest in malaria elimination has prompted research on active test and treat (TaT) strategies. Methods: A systematic review and meta-analysis were conducted to assess the effectiveness of TaT strategies to reduce malaria transmission. Results: A total of 72 empirical research and 24 modelling studies were identified, mainly focused on proactive mass TaT (MTaT) and reactive case detection (RACD) in higher and lower transmission settings, respectively. Ten intervention studies compared MTaT to no MTaT and the evidence for impact on malaria incidence was weak. No intervention studies compared RACD to no RACD. Compared to passive case detection (PCD) alone, PCD + RACD using standard diagnostics increased infection detection 52.7% and 11.3% in low and very low transmission settings, respectively. Using molecular methods increased this detection of infections by 1.4- and 1.1-fold, respectively. Conclusion: Results suggest MTaT is not effective for reducing transmission. By increasing case detection, surveillance data provided by RACD may indirectly reduce transmission by informing coordinated responses of intervention targeting.

Background: Southeast Asia is making tremendous progress towards their 2030 malaria elimination goal but needs new interventions to stop forest malaria. This study trials two new vector control tools, a volatile pyrethroid spatial repellent (VPSR) and insecticide-treated clothing (ITC), amongst forest-exposed populations in Mondulkiri Province Cambodia to inform their potential use for eliminating forest malaria. Methods: 21 forest-exposed individuals were given a questionnaire on their perceptions of malaria and preventive practices used, after which they trialed two products sequentially. Clothes was treated with ITC by the study team. Mixed methods were used to understand their experience, attitudes, and preferences regarding the products trialed. Quantitative data was summarized and qualitative insights were analysed using thematic analysis, applying the Capability, Opportunity, and Motivation Behaviour Change (COM-B) model and Behaviour Change Wheel Framework to identify intervention functions to support tailored product rollout amongst these populations. Results: Study participants reported a need for protection from mosquito bites in outdoor and forest-exposed settings and perceived both products trialed to be effective for this purpose. The VPSR product was preferred when travel was not required, whereas ITC was preferred for ease of use when going to the forest, especially in rainy conditions. COM-B analysis identified that key enablers for use of both products included their perceived efficacy and ease of use, which required no skill or preparation. For barriers to use, the odour of ITC was sometimes perceived as being toxic, as well as its inability to protect uncovered skin from mosquito bites, while the perceived usefulness of the VPSR product trialed was limited by its water sensitivity in rainy forest settings. Intervention components to encourage appropriate and sustained use of these products include education about how to use these products and what to expect, persuasion to use them from community leaders and targeted channels, and enablement to facilitate convenient and affordable access. Conclusion: The rollout of VPSRs and ITC amongst forest-exposed populations can be useful for eliminating malaria in Southeast Asia. Study findings can be applied to increase product uptake among forest exposed populations in Cambodia, while manufacturers can aim to develop products that are rainproof, easy to use in forest settings, and have favourable odour profiles to target users.

Background: Southeast Asia is making tremendous progress towards their 2030 malaria elimination goal but needs new interventions to stop forest malaria. This study trials two new vector control tools, a volatile pyrethroid spatial repellent (VSPR) and insecticide-treated clothing (ITC), amongst forest-exposed populations in Mondulkiri Province Cambodia to inform their potential use for eliminating forest malaria. Methods: 21 forest-exposed individuals were given a questionnaire on their perceptions of malaria and preventive practices used, after which they trialed two products sequentially. Mixed methods were used to understand their experience, attitudes, and preferences regarding the products trialed. Quantitative data was summarized and qualitative insights were analyzed using thematic analysis, applying the Capability, Opportunity, Motivation Behavior Change (COM-B) model and Behavior Change Wheel Framework to identify intervention functions to support tailored product rollout amongst these populations. Results: Study participants reported a need for protection from mosquito bites in outdoor and forest-exposed settings and perceived both products trialed to be effective for this purpose. The VPSR product was preferred when travel was not required, whereas ITC was preferred for ease of use when going to the forest, especially in rainy conditions. COM-B analysis identified that key enablers for use of both products included their perceived efficacy and ease of use, which required no skill or preparation. For barriers to use, the odor of ITC was sometimes perceived as being toxic, as well as its inability to protect uncovered skin from mosquito bites, while the perceived usefulness of the VPSR product trialed was limited by its water sensitivity in rainy forest settings. Intervention components to encourage appropriate and sustained use of these products include education about how to use these products and what to expect, persuasion to use them from community leaders and targeted ads, and enablement to guarantee access. Conclusion: The rollout of VPSRs and ITC amongst forest-exposed populations can be useful for eliminating malaria in Southeast Asia. Study findings can be applied to increase product uptake in Cambodia, while research efforts can aim to develop products that are rainproof, easy to use in forest settings, and have favorable odor profiles to target users.