Submicroscopic burden of zoonoticP. knowlesimalaria on Mursala Island andP. falciparumandP. vivaxtransmission in mainland North Sumatra, Indonesia

Accurate molecular tools are essential for estimating zoonotic malaria transmission in Southeast Asia. This study applied ultrasensitive reverse-transcriptase real-time PCR to detect zoonotic malaria in febrile patients from eight mainland health facilities and Mursala Island, spanning three districts in North Sumatra, Indonesia. Among 64 participants on Mursala, 7 (10.9%) had confirmedPlasmodium knowlesisymptomatic infections, including two submicroscopic infections associated with severe anaemia. All were negative by microscopy and pan-pLDH rapid diagnostic tests. NoP. knowlesiinfections were identified among 947 participants from mainland sites; PCR detected malaria in 34%, includingP. vivax(17.5%) andP. falciparum(7.5%). Of these, 30% were submicroscopic infections. NoP. cynomolgiinfections were identified.P. knowlesitransmission is low in North Sumatra, however, may cause serious disease. Molecular diagnostics remain crucial for identifying zoonotic malaria and should be integrated into surveillance systems to inform public health control measures.