A silver bullet against the mosquito-borne menace? | Sunday Observer

A silver bullet against the mosquito-borne menace?

23 April, 2023
Dengue hotspots in  the world
Dengue hotspots in the world

Since Sri Lanka reported its first cases of dengue in the early 60s, the country suffered periodic outbreaks of the disease which had since become endemic to the island.

Rapid urbanisation has also contributed to the upsurge of dengue by the decades and Sri Lanka’s health services spend millions of rupees combatting the disease which could be mitigated if proper precautions are taken.

However, like non-communicable diseases which can be curbed my simple things such as diet and exercise, the best way to tackle dengue is prevention. Although significant progress has been made in dengue treatment such as a vaccine which provides partial protection against the viral disease its use has been limited due to safety concerns for those who have not had a previous dengue infection.

What makes dengue hard to combat lies in the fact that the disease thrives in urban environments. As national statistics show the dengue hotspots are concentrated in and around our biggest cities.

Serious complications

Technology Transfer Expert Lemuel Melamed

Due to the lack of a specific antiviral treatment for dengue, the emphasis remains on symptom management and supportive care, such as fluid replacement and fever control. Early detection and treatment can significantly reduce the risk of serious complications.

Dengue can be fatal if it progresses to Dengue Haemorrhagic Fever (DHF), a more severe form seen in only a small percentage of those infected. DHF is typically characterised by a high continuous fever lasting less than seven days, bleeding from various parts of the body (including the nose, mouth, and gums, or skin bruising), severe continuous abdominal pain caused by an enlarged liver, and, in severe cases, shock. This can result in death. Children are more vulnerable to DHF.

Sri Lanka had experienced large outbreaks of dengue with many DHF cases in 2002 and 2012, which mobilised islandwide dengue prevention campaigns at the community level. Another project has been conducted by the World Mosquito Programme (WMP) using its Wolbachia method where mosquitoes infected with the Wolbachia bacteria are introduced to the environment. Wolbachia is a naturally occurring bacteria that inhibits dengue virus replication within the mosquito, reducing the mosquito’s ability to transmit the virus to humans.

Since 2011, the WMP has been conducting field trials using the Wolbachia method. However, according to the WMP website, Wolbachia is not an emergency measure, but rather a long-term, self-sustaining solution to mosquito-borne disease reduction. It can be used in conjunction with other methods such as insecticides and vaccines.

The WMP’s method relies on releasing more Wolbachia-infected aphids (male mosquitoes) into the environment. Although this method stops female mosquito from laying eggs, this suppression method is tricky. As it happens — and for reasons that are not well understood — mosquitoes can successfully breed when both partners are infected with Wolbachia.

Another solution that was promoted since the large outbreaks is introducing fish to water bodies. Although this is a novel idea, Sri Lanka’s many urban waterways are not the most ideal places for aquatic creatures by and large due to the enormous amounts of waste and pollution present. Even the WHO and local authorities have not listed fish as a feasible method to tackle mosquito breeding.


As the world becomes more connected, tourism has become a lifeline for many nations such as Sri Lanka, fuelling our economic growth and providing countless job opportunities. However, the persistent threat of diseases such as dengue has left many travellers wary of visiting tropical regions.

The risk of contracting dengue in Sri Lanka is high, particularly during the rainy season. Tourists are at an increased risk of infection as they are likely to spend more time outdoors, and their immune systems may be less equipped to deal with the disease.

But what if there were proactive measures Sri Lanka could take to control the spread of dengue? The impact would be nothing short of transformative. The country will become even safer to travel and a more attractive destination for tourists.

The Government and tourism industry have taken steps to mitigate the spread of dengue, such as conducting awareness campaigns, clearing breeding sites, and introducing new technologies to control mosquito populations. However, the persistence of the disease and the growing prevalence of dengue strains resistant to traditional insecticides have made it difficult to eliminate the risk entirely.

Dead Sea Medica

A breakthrough solution has been developed in Israel that uses organic compounds to create a physical buffer against mosquito breeding spots called Mosquito Natural Killer-HD-373.

HD-373 is a liquid application derived from medicinal herb extracts and minerals from the Dead Sea region, the lowest area above sea level in the world. The company, Dead Sea Medica, developed HD-373 to help countries with mosquito problems and health regulations regarding disease control of viral and other pathogen effects on the population. HD-373 was tested as non-toxic thanks to its organic composition.

HD-373 is spread on water surfaces to form a thin natural film; creating a buffer that stops mosquito larva and adults to pass and develop in the water.

We asked a technology transfer expert from Israel, Lemuel Malamed, about the advantages of HD-373 over other solutions.

Melamed said the compound is safe for humans, animals, wildlife, and the environment compared to chemical alternatives. Sri Lanka has used natural extracts such as citronella oil as mosquito repellents for centuries and HD-373 is no exception.

“HD-373 is also quick acting: The solution can reduce mosquito populations in a few hours by preventing larvae and adult mosquitos from developing in the water and the air, with noticeable results in three to four days if applied correctly. Melamed said that the product has been tested and used in Colombia, and will show similar results Sri Lanka, which has a similar warm and humid climate.

Referring to the efficacy of the World Mosquito Programme’s Wolbachia solution, Melamed said that HD-373 can be used alongside other mosquito prevention methods, to enhance their effectiveness. “If applied correctly, it could complement the Wolbachia method by providing a safe product that eradicates mosquitoes from water bodies.”

Positive results

HD-373 trials in Colombia

Melamed commented further on the Wolbachia method, “While the Wolbachia method has shown promise in controlling mosquito-borne diseases, it is not a standalone solution. Dengue outbreaks can still occur due to factors such as climate change, urbanisation, and inadequate waste management, which create favourable breeding conditions for mosquitoes.”

He said HD-373 is less likely to cause any water pollution since it is non-toxic and derived from natural ingredients, as results from the trials in Colombia had proved. “The positive results in Israel and in other locations indicate that HD-373 can be an effective solution in fighting the dengue mosquito population.”

“For the product to be tested and licensed in Sri Lanka, it is recommended to engage with an expert in the country who can help obtain the approvals, creating a protocol for testing, conducting the tests, and generating a report on the results. This process will help ensure that the product is suitable for use in Sri Lanka and meets local regulations,” Melamed added.

Although massive outbreaks of dengue come and go, putting a stop to the disease by way of prevention is an imperative for a developing economy such as Sri Lanka. Urbanisation will continue and the prevalence of dengue will put an enormous burden on our healthcare system. But since urbanisation expands metropolitan areas such as Colombo and Gampaha, we cannot always rely on massive clean-up efforts to keep the mosquitoes in check, especially since the country receives regular monsoonal rains.

The best hope could be in synergy; combining the Wobachia method and HD-373. The first will have a short-term effect fighting the seasonal growth of mosquitoes, while the spread of Wolbachia-infected mosquitoes will help in the long run. However, this needs further research and all stakeholders need to be invited to a dialogue.