Progress and challenges of integrated drug efficacy surveillance for uncomplicated malaria in Thailand

Abstract

Background Integrated drug efficacy surveillance (iDES) was formally introduced nationally across Thailand in fiscal year 2018 (FY2018), building on a history of drug efficacy monitoring and interventions. According to the National Malaria Elimination Strategy for Thailand 2017–2026, diagnosis is microscopically confirmed, treatment is prescribed, and patients are followed up four times to ensure cure. Methods Routine patient data were extracted from the malaria information system for FY2018–FY2020. Treatment failure of first-line therapy was defined as confirmed parasite reappearance within 42 days for Plasmodium falciparum and 28 days for Plasmodium vivax. The primary outcome was the crude drug efficacy rate, estimated using Kaplan–Meier methods, at day 42 for P. falciparum treated with dihydroartemisinin–piperaquine plus primaquine, and day 28 for P. vivax treated with chloroquine plus primaquine; day 60 and day 90 efficacy were secondary outcomes for P. vivax. Results The proportion of patients with outcomes recorded at day 42 for P. falciparum malaria and at day 28 for P. vivax malaria has been increasing, with FY2020 follow-up rates of 61.5% and 57.2%, respectively. For P. falciparum malaria, day 42 efficacy in FY2018 was 92.4% (n = 249), in FY2019 93.3% (n = 379), and in FY2020 98.0% (n = 167). Plasmodium falciparum recurrences occurred disproportionally in Sisaket Province, with day 42 efficacy rates of 75.9% in FY2018 (n = 59) and 49.4% in FY2019 (n = 49), leading to an update in first-line therapy to pyronaridine–artesunate at the provincial level, rolled out in FY2020. For P. vivax malaria, day 28 efficacy (chloroquine efficacy) was 98.5% in FY2018 (n = 2048), 99.1% in FY2019 (n = 2206), and 99.9% in FY2020 (n = 2448), and day 90 efficacy (primaquine efficacy) was 94.8%, 96.3%, and 97.1%, respectively. Conclusions In Thailand, iDES provided operationally relevant data on drug efficacy, enabling the rapid amendment of treatment guidelines to improve patient outcomes and reduce the potential for the spread of drug-resistant parasites. A strong case-based surveillance system, integration with other health system processes, supporting biomarker collection and molecular analyses, and cross-border collaboration may maximize the potential of iDES in countries moving towards elimination.

Leveraging geo-referenced malaria information to increase domestic financial support for malaria elimination in Thailand

“…Foci are assigned to one of four categories of transmission, with different prescribed interventions for each (Table 1 ). Foci classified as A1 and A2 are considered at risk of malaria, with active or residual transmission [ 4 , 5 ].…”

Genetic population of Plasmodium knowlesi during pre-malaria elimination in Thailand

“…Between 2013 and 2020, the overall malaria incidence decreased from 37,741 to 4474 cases (88.1% reduction). The incidence of both Plasmodium falciparum and Plasmodium vivax malaria is declining, but the proportion of the two species has changed, with P. falciparum accounting for 5.7% (257/4474) of cases and P. vivax for 91.6% (4099/4474) in 2020 [ 2 ].…”

Learnings from Thailand in building strong surveillance for malaria elimination

“…Simultaneously, Thailand launched integrated drug efficacy surveillance (iDES) to address multidrug-resistant parasites, which have made elimination challenging and increasingly urgent 5 – 7 . As part of routine malaria care, treated patients are tracked for up to 90 days to confirm parasite clearance and monitor antimalarial drug efficacy 8 . In 2019, after iDES results, triangulated with external findings, documented subpar piperaquine performance, the National Drug Policy Committee approved pyronaridine-artesunate as a new first-line treatment for two provinces 7 , 9 .…”