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Innovative Cure For Dengue And Malaria: 'Toxic' Semen From Male Mosquitoes Kills Females

A novel and innovative technique has been found by scientists that could curb the spread of diseases such as malaria and dengue. Australian scientists said that genetically engineered mosquitoes with 'toxic semen' could be an innovative solution for pest control after trying the new method. The study was published in peer-reviewed journal Nature Communications.The "toxic male technique" involves breeding mosquitoes with venomous proteins in their semen, which kill females after mating.It is to be noted that only female mosquitoes bite and drink blood, thereby spreading diseases such as malaria and dengue fever. Male mosquitoes primarily eat plant juices and nectar to get the sugar they need for energy and survival as their proboscis isn't strong enough to pierce skin. Female mosquitoes bite hosts like humans to obtain blood as they need protein present in it to develop their eggs. Doing this can transmit deadly diseases.The lifespan of a male mosquito is much shorter than females - just 6 or 7 days. On the other hand, females can live up to 5 months or longer.Scientist Sam Beach from Australia's Macquarie University said the technique "could work as quickly as pesticides without also harming beneficial species"."This innovative solution could transform how we manage pests, offering hope for healthier communities and a more sustainable future."The first leg of the research experimented on fruit flies. Female fried that bred with 'toxic' males had a significantly reduced lifespan.The second leg of the research would be done on mosquitoes, said Researcher Maciej Maselko."We still need to implement it in mosquitoes and conduct rigorous safety testing to ensure there are no risks to humans or other non-target species," he said.The mosquitoes would be genetically modified so that they could express the toxic semen once they were released into the wild, the researchers said.This can be achieved using "conditional expression" techniques, which activate specific genes with chemical or biological triggers. This approach allows venomous males to mate in labs, producing enough offspring to scale up the method.Genetic engineering has been used for long to control populations of disease-spreading mosquitoes. However, computer models showed techniques actively killing the biting females may be far more effective.

Genetically Engineered Mosquitoes With "toxic" Semen Could Kill Females And Curb Spread Of Disease, Researchers Say

Genetically engineered mosquitoes with toxic semen could be a new weapon against tropical disease, Australian scientists said after trialing the novel pest control method.

The "toxic male technique" aims to breed mosquitoes that express venomous proteins in their semen, killing off females after mating.

Female mosquitoes are targeted because only they bite and drink blood, thereby spreading diseases such as malaria and dengue fever.

Scientist Sam Beach from Australia's Macquarie University said the method "could work as quickly as pesticides without also harming beneficial species."

"This innovative solution could transform how we manage pests, offering hope for healthier communities and a more sustainable future," Beach said.

The first proof-of-concept trials used fruit flies, a common laboratory species favored for its short two-week life cycle.

Female flies that bred with "toxic" males had a significantly reduced lifespan, the scientists found.

Researcher Maciej Maselko said the team would now trial the method in mosquitoes.

"We still need to implement it in mosquitoes and conduct rigorous safety testing to ensure there are no risks to humans or other non-target species," he said.

The mosquitoes would need to be genetically modified so they only expressed the toxic semen once they were released into the wild, the researchers said.

Intergenerational vs intragenerational genetic biocontrol of pest insects. Nature Communications

This could be done through so-called "conditional expression" techniques, which use chemicals or other biological triggers to turn specific genes on or off at will.

This would allow venomous males to successfully mate with females in lab conditions, producing enough viable offspring for the technique to be scaled up.

Genetic engineering has been used for years to control populations of disease-spreading mosquitoes.

Typically, these approaches slow reproduction by releasing hordes of male insects that are genetically modified to be sterile.

Computer models showed techniques actively killing biting females could be far more effective, the research team said.

The research was described in a paper published by peer-reviewed journal Nature Communications on Tuesday evening.

The mosquito has killed as many as 50 billion people over the course of human existence.

Africa bears the brunt of malaria, with 95% of the fatal cases recorded every year, and children under the age of 5 make up about 80% of those deaths. The malaria parasite spreads to people bitten by infected mosquitos, and causes initial symptoms including high fever, headache and chills.

Mosquitoes are responsible for millions of yearly deaths worldwide from malaria, dengue fever and other diseases, according to the World Health Organization.

Eastern equine encephalitis virus is also spread to people by the bite of an infected mosquito. Last year, a New York resident who tested positive for EEE died, and in 2019, the CDC reported at least 15 people died in the U.S. From the rare disease.

Wetter And Warmer: How Does Climate Change Impact Dengue Transmission?

SINGAPORE – 2024 was one of Singapore's wettest and warmest years. Total annual rainfall was 8.1 per cent above the long-term average, and the year tied with 2019 and 2016 for the warmest years on record.

And from Jan 10 to 13, 2025, the Republic was battered by incessant rain associated with a monsoon surge – blasts of cold air from Central Asia. A second monsoon surge is set to hit Singapore this weekend, from Jan 17 to 19.

According to Singapore's third national climate change study, such stormy weather is set to increase in frequency and intensity.

Unfortunately, our changing climate creates conditions ripe for the reproduction of mosquitoes and transmission of the diseases they carry. For instance, the torrential rain creates more stale water bodies which the dengue vector, the Aedes aegypti mosquito, may breed in. More than 13,600 cases of dengue were recorded in Singapore in 2024 – a jump of over 36 per cent from 2023.

Dengue cases in Singapore have been on the rise since the 1990s, with the largest recorded outbreaks occurring in 2020 and 2022, said the National Environment Agency in response to queries from The Straits Times.

Globally, the link between climate change and dengue incidence is becoming ever more salient, with case numbers rising exponentially. In 2023, more than five million cases were reported worldwide, according to the World Health Organisation (WHO).

As the planet warms, that number has more than doubled, with more than 14 million dengue cases recorded worldwide in 2024, as reported by the European Centre for Disease Prevention and Control.

ST Explains how climate change affects dengue incidence.

1. How changing weather patterns affect dengue spread

With climate change, the world is both warmer and wetter.

Traditionally, dengue disproportionately impacts tropical and sub-tropical regions around the world, which have hot and humid climates primed for mosquitoes to thrive.

But with climate change, dengue cases are rising even in temperate regions such as North America and Europe, which are now seeing shorter and warmer winters.

Mosquitoes are increasingly inhabiting environments at higher altitudes and latitudes, expanding their geographical range in a phenomenon called climate-driven range shifts.

In 2023, 130 dengue cases were reported in the European Economic Area, as compared with 71 in 2022, reported the European health agency. This was a marked increase from 2020 and 2021, when a total of 73 cases were reported in the region.

"Climate change extends the periods in which mosquitoes can thrive in temperate regions – so what used to be a three- to five-month period when there could be transmission is now longer," said Dr Ooi Eng Eong, a professor specialising in emerging infectious diseases at Duke-NUS Medical School.

With every 1 deg C of warming, the earth's atmosphere can store and release 7 per cent more water, according to the US Department of Agriculture. This means that we are likely to see more frequent and heavy rainfall in the future.

More rain also creates more stale water bodies and receptacles that mosquitoes may breed in. Three of the four stages of the mosquito life cycle take place in water – eggs are laid in pools of stagnant water, which hatch into larvae and pupae which develop within them.

When asked how climate change may impact dengue trends in Singapore, Dr Ooi said: "With warmer temperatures and more unseasonal rains, peak dengue season may stretch for longer during the year, rather than just between May and September, when it usually peaks in Singapore.

"Perhaps it becomes spread out over a longer period – that's one possibility."

Another driver of dengue is how humans move as a result of our changing climate.

With climate change, there is an increased risk of extreme weather events, which can displace communities, said Dr Kimberly Fornace, an associate professor from the Saw Swee Hock School of Public Health at NUS.

After a natural disaster, people may move into makeshift homes, which lack proper water or sanitation facilities. Improper water storage practices and increased population density are both risk factors for dengue, said the WHO.

2. How climate change affects virus replication

Aside from creating more viable habitats for mosquitoes to breed, climate change also speeds up the physical maturation of the mosquito, while also enabling the virus to develop faster within it, said Dr Fornace.

The dengue virus is a very simple organism – it has only 10 genes. It thus infects both mosquitoes and humans, which have tens of thousands of genes, and utilises their replication machinery to make new copies of itself.

For the virus to grow, it needs to interact with other proteins and factors in the host cell – a process which requires energy.

When the temperature is warmer, molecules move more, and are more likely to meet and react with each other. With global warming, bodily chemical processes thus speed up, resulting in more efficient replication of the dengue virus.

After the mosquito takes its blood meal, the virus infects its midgut and travels to its salivary glands over about eight to 12 days. The time the virus takes to become infectious within its mosquito host is also temperature-dependent, said Dr Fornace.

"This means that it takes a shorter time for mosquitoes to become infectious after getting the virus," she added.

3. Challenges to suppressing dengue in Singapore

Singapore's vector control programme, which seeks to control population numbers of the dengue vector, was officially introduced in 1970.

According to Dr Ooi, the Ministry of Health (MOH) focused on trying to control Aedes aegypti because among mosquito-borne infections, dengue was the most common cause of death in children, overtaking even malaria.

In its early years, the programme was very effective.

Dr Ooi said: "Between 1975 and 1990, Singapore had no outbreaks, even when the rest of South-east Asia had outbreaks once every three or four years.

"But since the 1990s we've had repeated outbreaks once every five to eight years."

This is because with successful vector control, overall dengue transmission is very low. Singapore's herd immunity levels thus kept dropping, resulting in a low population immunity to the disease.

"Over time, paradoxically, your population becomes more vulnerable to dengue," said Dr Ooi.

However, dengue vaccines are notoriously difficult to perfect, as the serotypes of the dengue virus are genetically quite distinct, making it difficult for one vaccine to target all four.

Two vaccines – Dengvaxia and Qdenga – currently exist on the market. According to MOH, only the former is approved for use in Singapore. It is also recommended only for those aged 12 to 45 years who have had a previous dengue infection.

When asked what might be the best way forward, both Dr Fornace and Dr Ooi suggested a multi-pronged solution.

Dr Fornace said: "You need good diagnosis and treatment.

"Ideally, you kind of have some sort of vaccination strategy, outreach and public awareness, alongside vector control."

Dr Ooi also stressed the importance of continuing with vector control efforts, while fortifying Singapore's dengue vaccination strategy.

Find out more about climate change and how it could affect you on the ST microsite here .

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