Ensure vigilance in the malaria response in Cambodia
Over the past ten years, malaria morbidity and mortality have dramatically decreased in Cambodia. Although in 2018, the country declared for the first time that there had been no malaria-related deaths, elimination of the disease continues to be compromised.
Indeed, Cambodia and the five other countries in the Greater Mekong region, a few years ago, began seeing the appearance of resistance from malaria parasites to drugs derived from artemisinin, the first-line treatment and most effective for disease management. It is now a priority to research resistance to strengthen control programs and move toward malaria elimination.
Researchers at Institut Pasteur in Cambodia hypothesized that forests are the main source of malaria transmission. Indeed, the persistence of malaria in rural areas is largely attributed to people crossing or living in forests. However, the malaria transmission mechanisms in forests have not yet been studied, and there are likely to be several specific features that would involve specific control measures relating to the forest and its populations.
Reaching remote populations
In Cambodia, forest workers are considered the group most at risk for malaria infection. This mobile and migrant population comes from the remote provinces of the country and also from neighboring countries (Vietnam, Thailand, and Laos). About 7,000 forest workers have been identified in the country, 90% of whom are men.
These workers leave their village in the morning to work in the forests. When they cannot return home or when it is necessary to stay, they can spend several days there. Yet, in Cambodia, the main risk factor associated with malaria is spending the night in the forest, when the mosquitoes that carry malaria are most active.
The families of these workers, estimated at 30,000 people for the forests studied by Institut Pasteur, live in or around forests. Despite having access to the health system, many of them suffer from malnutrition and diseases such as tuberculosis and malaria. In addition, forest dwellings are often completely or partially open to the outside, and impregnated mosquito nets are not used properly. The risk of infection by malaria imported from the forest is therefore increased.
In light of this, Institut Pasteur in Cambodia decided to study the malaria transmission mechanisms in forests in order to improve strategies to rapidly eliminate the reservoir of parasites through community interventions in forests. The project has a budget of 958,000 Euros over a period of 33 months and is implemented in partnership with the National Malaria Control Program and the NGO Partners for Development.
A community network to document and prevent the transmission of malaria
In 2019, Institut Pasteur and its partners set up the first network of forest workers specializing in combatting malaria in forests. Almost 600 km² of forest areas in Mondulkiri, Stung Treng, and Kratie were covered by 30 agents. These agents, recruited from among the inhabitants of the forest, have been trained in prevention, screening, and health care related to malaria. They worked closely with the communities and have been able to collect data from 3,179 workers. These data provided a better understanding of the epidemiology of malaria within the forest areas studied.
In 2020, the network agents worked with their peers to provide tests: people testing positive for malaria were treated. At the same time, monthly intermittent preventive treatment was prescribed to forest workers. The effectiveness of preventive treatment was evaluated in three cross-sectional studies in September and November 2020 and in January 2021. In October 2020, following the rainy season, which usually presents the highest annual rates of malaria, only 28 cases of Plasmodium falciparum were identified in all health centers in Cambodia!
The first results of the study, as well as recommendations to reduce the incidence of malaria in forest areas in Cambodia, have been published by Institut Pasteur.
Resistance to malaria: a regional threat
At a general level, the development of resistance to antimalarial drugs in the Greater Mekong region poses a major threat to regional and global efforts to respond to malaria and to eliminate the disease.
To stem the pandemic, the Global Fund has been supporting the Regional Artemisinin-resistance Initiative (RAI) since 2013, which was the first regional grant to combat malaria and the emergence of resistance to artemisinin in Southeast Asia.
In 2015, RAI was evaluated, which highlighted the “need to better understand the populations most at risk of malaria and target them more effectively” and to further extend RAI’s support to the response to malaria in forest areas, where access to malaria control services is low, particularly among mobile populations, soldiers, and migrants.”