Fighting Monkey Malaria in Malaysia

Focus on vector-borne disease control

Impact Story

Using K-Othrine^® PolyZone^® insecticide to protect communities and advance mosquito control innovation

The Challenge

In Malaysia’s tropical forests, where people, mosquitoes and monkeys increasingly share the same spaces, a new kind of malaria is emerging. It’s a zoonotic form of the disease — meaning it can be transmitted from animals to humans. In this case, the infection has become widely known as “monkey malaria,” and it is prompting new approaches to mosquito control. Unlike traditional malaria, which spreads between humans through indoor-biting mosquitoes, monkey malaria is transmitted by outdoor-biting mosquitoes that live and feed in forested areas (specifically, the Anopheles leucosphyrus group). The parasite responsible — Plasmodium knowlesi — circulates naturally among macaques, forest-dwelling monkeys often found near human settlements in Southeast Asia. But unlike parasites that infect only animals, P. knowlesi can also cause severe illness in humans.

In 2023, Malaysia experienced a sudden surge in zoonotic malaria cases, with 2,879 infections and 14 deaths reported nationwide — the majority in the forested regions of Sabah and Sarawak. That same year marked Malaysia’s sixth consecutive year without any locally transmitted human malaria, as reported by the World Health Organization. Yet the emergence of monkey malaria has shown that success against one form of the disease does not mean the battle is over — it has simply shifted to a new front.

Zoonotic malaria presents a whole new set of challenges for health experts. Because it originates in monkeys and is spread by outdoor-biting mosquitoes, it cannot be controlled by the same methods that worked for human malaria. Traditional indoor residual spraying is far less effective when mosquitoes feed and rest outside, prompting researchers and public health authorities to explore innovative outdoor control strategies.

The Insight

To address this growing challenge, Malaysia’s Institute for Medical Research (IMR) partnered with Envu to explore outdoor residual spraying (ORS) — an innovative adaptation of existing mosquito-control methods. Envu scientists identified K-Othrine^® PolyZone^®, a polymer-enhanced, weather-resistant insecticide formulation co-developed with the Innovative Vector Control Consortium (IVCC), as a promising candidate for outdoor use in Malaysia’s tropical climate. Its polymer technology allows the active ingredient to remain effective even after heavy rainfall, providing longer-lasting control with reduced environmental impact. Field trials led by IMR and Envu in selected villages across Sabah and Sarawak tested the formulation’s performance and safety. Results confirmed that K-Othrine PolyZone maintained high efficacy over extended periods, significantly reducing outdoor mosquito populations while supporting Malaysia’s broader vector-control objectives.

These findings, published in PLOS One, offered critical data to the WHO Vector Control Working Group and helped inform best practices for managing zoonotic malaria vectors in Southeast Asia.

Impact

Building on the success of the field trials, Malaysia’s Ministry of Health adopted K-Othrine PolyZone for its national malaria-control tender in 2024, expanding the use of outdoor residual spraying nationwide. Under the leadership of Teck Peng Lee, Head of Malaysia and Export Countries, Envu coordinated the timely delivery of 80,000 bottles to public-health teams across the country. To ensure safe and effective application, Envu and IMR collaborated on a series of training sessions across all 14 states, equipping operators with the technical knowledge and stewardship practices required for sustained vector management. This initiative strengthened Malaysia’s capacity to respond to new malaria threats and positioned the country as a regional leader in outdoor vector control innovation. It also demonstrated the value of multi-stakeholder collaboration—linking public institutions, researchers, and private partners in pursuit of shared public health goals.

The experience has underscored a vital truth: progress against disease is never static — new threats demand new thinking, new partnerships, and new tools.