Sri Lanka is facing a serious public health challenge in 2025, as dengue fever continues to spread across the island at alarming rates. With urban centres overwhelmed and rural communities increasingly affected, scientists and health authorities are turning to biological control strategies as a sustainable and environmentally responsible solution. Professor M. W. Amarasiri de Silva, a leading voice in this field, has outlined the key dynamics driving the epidemic and the promising role that nature-based interventions can play in bringing it under control.
Understanding Sri Lanka's Dengue Hotspot Pattern in 2025
The dengue hotspot pattern observed across Sri Lanka in 2025 is not random. It reflects a complex web of interconnected factors rooted in urbanisation, shifting climate conditions, and increased human mobility. Colombo stands out as the country's most intense hotspot, and for good reason. The capital city's dense housing clusters, ongoing construction activity, and the constant daily movement of large numbers of people create near-perfect breeding conditions for the Aedes aegypti mosquito, the primary vector responsible for transmitting the dengue virus.
Stagnant water collecting in construction sites, discarded containers, and poorly maintained drainage systems provides ideal larval habitats. Meanwhile, the sheer volume of people moving in and out of Colombo each day accelerates the spread of the virus from one neighbourhood to another. These realities make conventional mosquito control methods, such as chemical fogging and insecticide spraying, increasingly insufficient on their own.
What Is Biological Control and Why Does It Matter?
Biological control refers to the use of living organisms or naturally derived agents to reduce the population of disease-carrying pests. Unlike chemical pesticides, biological control methods are targeted, environmentally friendly, and less likely to trigger insecticide resistance in mosquito populations. In the context of dengue control in Sri Lanka, several biological approaches are being explored and implemented with encouraging results.
One of the most widely discussed methods involves the introduction of Wolbachia bacteria into Aedes aegypti mosquito populations. When infected with Wolbachia, mosquitoes become significantly less capable of transmitting the dengue virus to humans. This approach has been successfully trialled in several countries, including Australia, Indonesia, and Colombia, showing dramatic reductions in dengue incidence. Sri Lanka's health authorities are now examining the feasibility of scaling this intervention across high-risk urban zones.
Natural Predators and Larvicidal Agents
Another key component of biological dengue control involves the use of natural predators that feed on mosquito larvae. Certain species of fish, particularly Gambusia affinis (commonly known as the mosquitofish) and native Poecilia species, are known to consume large quantities of mosquito larvae in standing water bodies. Introducing these fish into water storage tanks, ornamental ponds, and other larval habitats can significantly reduce mosquito populations without the need for chemical treatment.
Additionally, the bacterium Bacillus thuringiensis israelensis (Bti) is gaining attention as a highly effective and safe larvicide. Bti produces toxins that are lethal to mosquito larvae but completely harmless to humans, animals, and other aquatic organisms. Its application in water bodies across dengue-prone areas of Sri Lanka offers a practical and scalable solution that can complement existing vector control programmes.
Climate and Urbanisation: Compounding the Challenge
Professor de Silva emphasises that no single intervention can address the dengue crisis in isolation. The interaction between climate change and rapid urbanisation is fundamentally reshaping the epidemiological landscape. Rising temperatures and increasingly erratic rainfall patterns are extending the mosquito breeding season and pushing Aedes populations into previously unaffected highland areas. Communities that once considered themselves safe from dengue are now reporting outbreaks for the first time.
Urban expansion without adequate sanitation infrastructure further exacerbates the problem. As more people migrate to cities and peri-urban areas in search of economic opportunity, informal settlements grow rapidly, often lacking proper waste management and clean water supply systems. These conditions are a breeding ground — quite literally — for the dengue vector.
A Coordinated, Community-Driven Approach
Experts agree that the most effective dengue control strategies combine biological methods with strong community participation and government coordination. Public awareness campaigns that educate citizens about eliminating standing water, properly storing water, and supporting biological control initiatives are essential. Local health workers play a critical role in monitoring larval sites and ensuring that biological agents are deployed correctly and consistently.
Sri Lanka has a strong tradition of community health engagement, and this social infrastructure can be leveraged to support biological control programmes at the grassroots level. Schools, religious institutions, and local government bodies all have a role to play in sustaining these efforts over the long term.
The Path Forward
Biological control alone will not eliminate dengue from Sri Lanka, but it represents a vital and underutilised tool in the country's public health arsenal. With continued investment in research, community education, and policy support, Sri Lanka has a genuine opportunity to reduce the burden of dengue significantly. The 2025 epidemic serves as a powerful reminder that sustainable solutions rooted in ecological science are not just desirable — they are urgently necessary.