Choosing interventions to eliminate forest malaria: preliminary results of two operational research studies inside Cambodian forests

Abstract

Background Rapid elimination of Plasmodium falciparum malaria in Cambodia is a goal with both national and international significance. Transmission of malaria in Cambodia is limited to forest environments, and the main population at risk consists of forest-goers who rely on forest products for income or sustenance. The ideal interventions to eliminate malaria from this population are unknown. Methods In two forested regions of Cambodia, forest-goers were trained to become forest malaria workers (FMWs). In one region, FMWs performed mass screening and treatment, focal screening and treatment, and passive case detection inside the forest. In the other region, FMWs played an observational role for the first year, to inform the choice of intervention for the second year. In both forests, FMWs collected blood samples and questionnaire data from all forest-goers they encountered. Mosquito collections were performed in each forest. Results Malaria prevalence by PCR was high in the forest, with 2.3–5.0% positive for P. falciparum and 14.6–25.0% positive for Plasmodium vivax among forest-goers in each study site. In vectors, malaria prevalence ranged from 2.1% to 9.6%, but no P. falciparum was observed. Results showed poor performance of mass screening and treatment, with sensitivity of rapid diagnostic tests equal to 9.1% (95% CI 1.1%, 29.2%) for P. falciparum and 4.4% (95% CI 1.6%, 9.2%) for P. vivax. Malaria infections were observed in all demographics and throughout the studied forests, with no clear risk factors emerging. Conclusions Malaria prevalence remains high among Cambodian forest-goers, but performance of rapid diagnostic tests is poor. More adapted strategies to this population, such as intermittent preventive treatment of forest goers, should be considered.

Forest malaria: the prevailing obstacle for malaria control and elimination in India

“…Moreover, in the absence of diagnostic facilities, chemo-preventive strategies such as intermittent preventive treatment for forest goers can be thought of, as being done in Cambodia. 36 Scale-up of detection of asymptomatic and low-parasitemic patients through active case detection in the high transmission areas using molecular techniques has been included in the U.S. President’s Malaria Initiative Thailand, Lao PDR and Regional Malaria Operational Plan FY 2020. 37 These need to be explored in Indian settings as well.…”

Forest malaria and prospects for anti-malarial chemoprophylaxis among forest goers: findings from a qualitative study in Lao PDR

“…Chemoprophylaxis is recommended for international travellers and military personnel visiting endemic areas [ 13 ], but has not been recommended for indigenous populations, such as forest goers, in low transmission settings such as the GMS. In the absence of effective vector-control measures and limited periods of exposure, malaria prophylaxis has been proposed as a promising strategy to protect forest goers [ 14 , 15 ].…”

Forest malaria and prospects for anti-malarial chemoprophylaxis among forest goers: findings from a qualitative study in Thailand

“…Malaria prophylaxis has, however, not generally been recommended for indigenous population living in endemic areas. In light of limited effective vector control strategies and determined periods of exposure during forest visits, it has been proposed as a strategy to protect forest goers [ 9 , 26 – 28 ] and is currently being trialled in Cambodia [ 29 ]. To maximize the impact of this approach, additional information is needed to understand activities of forest goers and their willingness to use different prevention measures, including chemoprophylaxis, and how it could be delivered in their communities.…”