Understanding and Targeting the Barriers to Effective Malaria Control and Elimination in the Asia-Pacific Region

Understanding and Targeting the Barriers to Effective Malaria Control and Elimination in the Asia-Pacific Region Project summary Overall, the Asia-Pacific region has achieved impressive reductions in malaria over the last 20 years. However, our current Asia-Pacific ICEMR (2017-2024) has documented strongly diverging regional malaria trends: Cambodia is nearing P. falciparum (Pf) elimination but is confronted with the challenge of stubbornly resilient residual P. vivax (Pv) transmission while Papua New Guinea (PNG) recorded 1.2 million new cases in 2021. Despite their differing progress, both countries face common challenges: optimal allocation of sparse resources in heterogeneous transmission settings driven by asymptomatic infections, environmental change affecting malaria transmission, emerging drug and insecticide resistance and specifically the challenge of eliminating Pv. The renewed Asia-Pacific ICEMR will address these challenges by conducting research that applies new techniques and approaches to achieve translational outcomes. We will i) develop and validate optimized surveillance and response systems that combine traditional epidemiological and vector surveillance with targeted reactive population surveys; ii) understand key drivers of ongoing Pv transmission in a wide range of transmission intensity settings and identify locally optimal combinations of interventions to restrict and eventually interrupt transmission; iii) generate evidence on the ability of novel tools and interventions to improve access to Pv radical cure and target the asymptomatic Pv reservoir; and iv) Determine the threat of emerging drug and insecticide resistance. The renewed ICEMR proposes a coordinated set of field, laboratory and modelling studies across 5 sites including a very low transmission site in Cambodia and 4 low, medium and high transmission PNG sites. In the Epidemiology Project, health facility surveillance, cross-sectional, and reactive case detection studies augmented by novel molecular, genomic and serological diagnostic assays will be used to accurately measure malaria transmission and identify key drivers of residual transmission. Through in-depth molecular surveillance and efficacy monitoring we will map the spread Pf artemisinin resistance (ArtR) in PNG and confirm the emergence of Pv ArtR and mefloquine resistance in Cambodia, while conducting coordinated studies to address barriers to increased access and efficacy of Pv radical cure. The Transmission Project will conduct in-depth vector surveillance coupled with vector genetic studies to better understand the epidemiological observations in Project 1, map the recent emergence of pyrethroid resistance in PNG, document vector range expansions due to the accelerating impacts of environmental and land-use changes, assess the decreasing effectiveness of vector control tools, investigate factors facilitating asymptomatic Pv transmission and evaluate novel transmission blocking interventions. These studies will use innovative diagnostic tests and inform state-of-the-art malaria transmission models provided by two Technical Cores. Throughout the research program policy-relevant scenario modelling will be used to determine locally optimal combinations of interventions. Together, these studies will provide malaria programs with accurate and timely data for action and new solutions to accelerate malaria elimination.