The malaria burden in Cambodia has been greatly reduced over the past few years, with confirmed malaria cases experiencing a general decline since 2009. However, of Cambodia’s 25 provinces, 21 are still considered to be endemic, and an estimated 48% of the population, or approximately 7.4 million people, live in high transmission areas.
Malaria incidence is highest in the northeastern regions of the country. The proportion of cases due to Plasmodium falciparum (Pf) versus Plasmodium vivax (Pv) is variable across the country, with Pf cases being more common in the southwest and northeast, and Pv cases dominating the northwest and central regions. Transmission of malaria in Cambodia is associated with the rainy season, which occurs from May until October, peaking around August/September.
A history of the national treatment guidelines
In response to the development of multi-drug resistant malaria, Cambodia designed and implemented a number of policy and strategy changes to improve coverage of appropriate case management. In 2000, Cambodia switched its first-line national malaria treatment policy for Pf malaria to an ACT of artesunate and mefloquine (ASMQ) and stipulated diagnostic testing prior to treatment. Since 2000, the Cambodian government provided first-line artemisinin-based combination therapy (ACT) for free in public health facilities, and parasitological diagnosis was promoted through the introduction of malaria rapid diagnostic tests (mRDT) and by strengthening the capacity of skilled microscopists. Over the years there have been a series of changes in the national treatment guidelines following recommendations from the World Health Organization (WHO) to change treatments when resistance to the drug is detected. In 2008, due to high failure rates with ASMQ, the first-line treatment for uncomplicated Pf malaria was changed from co-blistered ASMQ to fixed-dose dihydroartemisinin piperaquine (DHA-PPQ) in specific areas of the country where artemisinin resistance had been identified; DHA-PPQ became the nationwide first-line treatment for both Pf malaria and Pv malaria in 2010. However, subsequent DHA-PPQ treatment failure rates prompted the use of atovaquone proguanil to treat cases in key areas of western Cambodia in 2012. Less than a year after adopting atovaquone proguanil, resistance-conferring mutations were detected in Pf malaria, so fixed dose combination (FDC) ASMQ was reintroduced as the first-line treatment in areas with drug resistance in March 2015.