Can genetically modified mosquitoes curb Dhaka’s dengue menace?

Up to 15 June this year, a total of 5,988 people have been hospitalised with dengue and 30 have died. Photo: Rajib Dhar

By April this year, seven people in Bangladesh had already perished from dengue, even though the traditional dengue season had not even begun yet. 

Just a month later, the country recorded the highest number of dengue cases for the year, but the situation seems to be worsening further, with June already seeing the highest rate of infections. 

According to data by the Directorate General of Health Services (DGHS), in the first 15 days of June, 1,643 people were admitted to hospitals with dengue. In May, 1,773 cases were recorded in total. In January, there were 1,161 cases, while February, March, and April saw 373, 336, and 701 cases respectively.

Up to 15 June this year, a total of 5,988 people have been hospitalised with dengue and 30 have died.

Traditional preventive measures have so far produced minimal results, as evident from previous years' data. In 2024, Bangladesh recorded 575 dengue-related deaths and over 100,000 cases. In 2023, more than 1,700 people died of dengue, with over 321,000 reported cases.

Infecting the carrier

A team of researchers led by Dr Hasan Mohammad Al Amin, a Bangladeshi scientist based in Australia, has discovered a method to turn local mosquitoes against the virus.

In a recent interview with The Business Standard, Dr Al Amin stated that their research could be a turning point in the fight against dengue; however, a field-based pilot project is needed to further validate and advance their findings.

The research, published in the reputable journal Scientific Reports, uses a naturally occurring bacterium — Wolbachia — to block the transmission of the dengue virus.

The application of Wolbachia has previously proven successful in curbing dengue outbreaks in several countries, including Saudi Arabia, Australia and Singapore.

Wolbachia is a type of bacteria that occurs naturally in many insect species but not in Aedes aegypti, the primary mosquito responsible for spreading dengue. 

"When artificially introduced into Aedes aegypti, Wolbachia can prevent the dengue virus from multiplying within the mosquito's body. As a result, the mosquito becomes refractory to dengue virus transmission, meaning it can no longer transmit the virus to humans," Al Amin said. 

As part of the research, Al Amin said, a special strain of Wolbachia called wAlbB was introduced into the Aedes aegypti mosquitoes from Dhaka. The new mosquito strain created in the lab is called wAlbB2-Dhaka. 

The wAlbB2-Dhaka was found showing over 44% reduction of viral presence in their body. On the other hand, virus detection in the saliva, which causes the transmission, was reduced by 92.7%, meaning a near-complete block of dengue transmission.

"Traditional approaches, such as insecticide spraying, have struggled due to two main reasons: limited coverage in overcrowded urban zones, and increasing insecticide resistance in mosquito populations," Al-Amin said. "Given these limitations, Wolbachia offers a sustainable and chemical-free alternative that could be transformative in the fight against dengue." 

The main challenge to this research, Al Amin said, was to create a mosquito strain that is both "Wolbachia-infected and genetically adapted" to survive in Dhaka's environment. 

To achieve this, they crossbred Australian lab-infected mosquitoes with local Aedes aegypti mosquitoes over six generations. This resulted in the wAlbB2-Dhaka strain. 

"It retains 98.44% of the native Dhaka mosquito's genome, ensuring it is well-suited to local conditions. These mosquitoes also maintained resistance to common insecticides, an essential trait for their survival in the wild and for the success of future field deployments," he said. 

When Wolbachia-infected males mate with uninfected females, the resulting eggs fail to hatch. However, when infected females reproduce, all their offspring inherit the Wolbachia bacterium — a phenomenon known as maternal inheritance.

This dual mechanism effectively results in replacement of Aedes aegypti with Wolbachia strains.  "In this study, the wAlbB2-Dhaka strain demonstrated 100% cytoplasmic incompatibility and maternal inheritance, the crucial traits for establishing and sustaining Wolbachia in the field," Al Amin said. 

Heat resilience 

Some strains of Wolbachia, for example wMel, were vulnerable to high temperatures, which limited their effectiveness in hot climates. 

But the wAlbB strain used here, Al Amin said, remained active even at 37°C, making it suitable for Bangladesh's tropical weather. 

"Its successful use in hot regions like Jeddah, Saudi Arabia, further supports its robustness."

The researchers also tested the durability of the mosquito eggs; after 16 weeks of storage, the egg hatch rates matched those of wild mosquitoes, making long-term deployment logistically viable.

What next? 

While the laboratory results are promising, large-scale implementation requires careful planning and testing. Countries like Australia, Malaysia, Indonesia, Singapore, and Brazil have seen success with Wolbachia-based strategies, with dengue incidence declining after mosquito releases.

Al Amin said they are optimistic about wAlbB2-Dhaka's success in the city environment.

"Wolbachia-infected mosquitoes have shown the ability to spread efficiently in high-rise residential areas in Southeast Asia. This bodes well for Dhaka, one of the most densely populated cities in the world," he said. 

Although the wAlbB2-Dhaka strain has shown high effectiveness in the lab, field trials are the next critical step. Monitoring how these mosquitoes interact with wild populations, spread across neighbourhoods, and reduce disease incidence will provide essential data for broader deployment.

The researchers look forward to the government's assistance for a pilot project in the field. 

"We need coordinated government support, timely regulatory approvals, and robust long-term monitoring to ensure the successful deployment of wAlbB2-Dhaka. In addition, strong collaboration between public institutions and private stakeholders will be vital to scaling up the initiative across urban and regional settings," Al Amin said.