The Orang Rimba are a sensitive nomadic population at high risk of malaria, and this study comprises the first published data on their perceptions of malaria and preventive methods used. Most participants (77%) had no formal schooling, and all worked in agriculture and/or hunting. Although 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. Reasons for choosing interventions included perceived efficacy, ease of use, and availability, with preference given to those that were free of charge. 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.
Compared to other studies on forest-going populations in Southeast Asia, the Orang Rimba people have relatively lower levels of knowledge on malaria, and higher levels of use of malaria prevention methods [3, 5, 6, 15]. This could be due to their deliberate limited engagement with outsiders, coupled with awareness of the high risks of malaria. Following Indonesia’s subnational elimination approach using various strategies tailored to local contexts [16], enabling the elimination of malaria in this outdoor forest-dwelling population in the coming years should focus on providing education on malaria, particularly amongst pregnant women, and potentially providing additional protective tools that are suitable for use in outdoor settings. Due to the sensitive nature of this population, any engagement should leverage existing relationships that have been formed with local NGOs as well as the Eijkman Institute of Molecular Biology.
In addition to providing education and access to prenatal care, reducing malaria transmission among this population will likely be accelerated using additional malaria prevention methods. The study population expressed their choice of malaria prevention methods to be centered around perceived efficacy, ease of use, and provision free of charge. Following these criteria and the need for interventions appropriate for outdoor nomadic individuals, one option could be the use of topical repellents, which are commercially available and have demonstrated efficacy, reducing the odds of PCR-detectable malaria infection when distributed to 116 villages in Myanmar [17] and reducing malaria infection rates and mosquito density when given to 198 participants in a refugee camp in Northeastern Kenya [18]. Daily compliance may be a challenge however, as speculated when topical repellents were distributed to individuals in 117 villages in the Ratanakiri Province Cambodia [19].
Additional options for outdoor malaria prevention among forest-going populations include the use of insecticide-treated clothes [20], the use of endectocides to treat livestock [21], or the use of volatile pyrethroid spatial repellents, a product class not yet available on the market but that may soon be promising due to high user acceptability amongst villagers [15] and forest-going populations [20] in Mondulkiri Province, that provided 34.1% protective efficacy against related Aedes-borne viral diseases when distributed to 2,907 households in Iquitos, Peru [22]. Volatile pyrethroid spatial repellents may be promising to this population because they are easy to use, being similar to insecticide-treated coils but longer lasting without the need for frequent user activation. The vector control product classes suggested here are safe for humans and have demonstrated an ability to reduce mosquito bites [15, 23–26]. Another option is to provide chemoprophylaxis, a method shown to be effective for forest-going populations in Cambodia [27] that could be delivered with vector control interventions to further improve impact [27, 28].
Once appropriate interventions for outdoor mosquito control are identified for the Orang Rimba people, we recommend the use of social behavior change communication strategies to provide education on malaria as well as the ability of select products to offer protection, an effective method that has shown to be well-liked for malaria education, introducing new interventions, and increasing uptake [20]. Educational efforts should emphasize the risks of malaria during pregnancy as well as the benefits of receiving ITNs and prenatal care, all of which are opportunities for malaria education identified in our maternal health survey. Interventions should be subsidized and ideally made available free of charge, an important factor for the selection of vector control methods identified in our study.
Limitations of our study include our small sample size (n = 39), and that females were not directly interviewed in this study. However, these results offer a substantial contribution to the evidence base on hard-to-reach populations because this study offers the first data in an academic study investigating malaria perceptions and practices on this population. As such it raises awareness on this community and opens avenues for further research to improve the health of members of this sensitive community. Future research on this population can explore the use of culturally sensitive data collection methods that allow for more direct inclusion of female perspectives.
In conclusion, the 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.