China deploys ‘cannibal' mosquitoes and killer fish to fight chikungunya

Telegraph

08-08-2025

China has deployed 'cannibal' mosquitoes, larvae-eating fish and surveillance drones as it battles to curb an unprecedented outbreak of chikungunya virus.
More than 7,000 cases of the debilitating mosquito-borne disease have been reported across the southern Guangdong province since July – a record number driven by international travel, high temperatures and unusually heavy rains.
'This chikungunya outbreak in China is exceptionally rare and unprecedented,' said Dr Yanzhong Huang, a senior fellow for global health at the Council on Foreign Relations, adding it is the largest since the virus was first seen in China in 2008.
The disease, which is sometimes confused with dengue, is rarely fatal, but it does cause a severe fever, rash and joint pain. The word 'chikungunya' itself comes from a Swahili dialect and roughly translates as 'to bend over' – a reflection of its debilitating symptoms.
So far in China the vast majority of cases have been in the manufacturing hub Foshan, a city of 10 million roughly 105 miles from Hong Kong which reported its first case on Monday. A US advisor urged travellers to take 'increased caution' due to the outbreak.
Now, Chinese authorities have launched a major mosquito-crackdown to suppress chikungunya's spread, alongside 'patriotic public health' measures reminiscent of China's stringent 'zero-Covid' policy.
Predatory prowess
Among the tools deployed are giant, 'compulsive killers' known as elephant mosquitoes (Toxorhynchites, in scientific jargon) whose larvae devour the Aedes mosquito which transmits chikungunya and dengue to people.
Just one larvae can consume a 'staggering' number of the larvae, up to several thousands, according to a paper in the Journal of Tropical Medicine in 2024.
'Their predatory prowess extends beyond direct consumption,' the researchers wrote. 'Toxorhynchites larvae exhibit a fascinating behaviour known as compulsive killing, where they kill mosquito larvae but leave them uneaten.'
Professor Eng Eong Ooi, a researcher at Duke-NUS Medical School's Emerging Infectious Diseases programme in Singapore, said another benefit is that the adult elephant mosquitoes don't suck blood – meaning they don't spread viruses by biting humans.
'It is likely that the health authorities in China are hoping that, by releasing Toxoryhnchites mosquitoes, they would reduce the Aedes mosquito population and thus control the spread of chikungunya virus,' Prof Ooi told the Telegraph.
He added that the policy's effectiveness will be dependent on how often and how many mosquitoes are released, plus the specific species of Toxorhynchites used.
China is not the first country to deploy the killer bugs – America, Malaysia, and India are among countries where releases have been conducted, according to the 2024 paper. Results have been varied, but New Orleans saw a reduction in Aedes mosquitoes of up to 45 per cent, after the cannibal insects were deployed.
Killer fish
Yet this is just one aspect of China's fight against the Aedes mosquito.
A team from the 'Mosquito Factory' at Sun Yat-sen University in Guangdong have also deployed 5,000 larvae-eating fish, which consume the larvae that hatch in the city's lakes, according to local media.
'The idea is to have natural predators of mosquitoes at different stages of the lifecycle, to reduce the overall population, virus transmission and hence disease rates,' said Prof Ooi.
The Aedes mosquito does not only lay its eggs in lakes and ponds. The insect thrives in the hot, rainy conditions that have recently hit southern China, and breeds in any small container of stagnant water, from flowerpots to discarded bottles.
To tackle this, officials are using tools reminiscent of China's controversial 'zero-Covid' policy, which involved mass testing, mandatory quarantines, widespread surveillance and citywide lockdowns.
Locals in Foshan have been told that they could see their electricity cut off or face fines of up to 10,000 yuan (£1,040) if they do not remove potential containers outside their homes, while drones have been used to detect sources of stagnant water across the industrial city.
Dr Huang said that those infected have also been told to stay in hospital beds covered by mosquito nets – evoking the forced isolations seen in Covid – while large-scale insecticide spraying campaigns have seen soldiers fogging streets and parts and workers entering homes without consent, a tactic reminiscent of pandemic-era intrusions.
'China's response echoes its zero-Covid play book, albeit on a more localised scale,' he said.
'This blend of implicit coercion and community enforcement highlights China's enduring 'patriotic public health' model, [which prioritises] rapid containment over individual liberties.'
According to local authorities, while 3,000 cases were reported last week alone, numbers do appear to have peaked and 95 per cent of patients were discharged within seven days.
Explosive outbreaks
The outbreak comes as chikungunya surges across the globe. The virus was first identified in Tanzania in 1952, and has since spread to 110 countries, though it is most regularly seen in sub-Saharan Africa, Southeast Asia and South America.
There have even been cases in the south of France.
'Chikungunya tends to cause sudden explosive outbreaks and then disappear for years, before returning to cause another outbreak,' said Prof Ooi.
This year has been particularly explosive. A surge in cases began in islands in the Indian Ocean in early 2025, including 54,000 cases and 12 deaths in La Réunion, while spikes in cases have also been reported in South America – especially Bolivia.
The World Health Organization (WHO) said patchy data makes it hard to say with certainty that this year has been the worst for chikungunya on record, but every region in the world – including Europe – has reported cases in 2025.
Outbreaks in some of these countries – including France and China – are happening as the Aedes mosquito moves into new territory, as changing climates and urbanisation means they can survive and thrive in different places. In these regions, the chikungunya virus has also found large populations with no prior exposure to the virus.
'For some countries, the proportions of non-immune populations are now large enough to allow for rapid outbreak spread,' a WHO spokesperson said. 'So [the] introduction of chikungunya virus, when Aedes mosquitoes are present, can result in large outbreaks.'
Dr Andre Siqueira, head of the dengue global programme at the Drugs for Neglected Diseases initiative, said countries across the world should brace themselves for more outbreaks as temperatures continue to rise – and rapidly work towards developing countermeasures. Although there are now two chikungunya vaccines, there are no specific antiviral treatments.
He also warned against underestimating the disease, which is rarely deadly but can cause severe illness – especially in newborn babies, the elderly, and people with underlying medical conditions. Symptoms include a fever, rash, headache and joint pain.
'The previous belief that acute chikungunya is a mild disease has been challenged by the severity of joint pain and for reports of complications such as myocarditis and encephalitis, as well as for the evidence for excess mortality in locations experiencing outbreaks,' Dr Siqueira said, pointing to several studies in Brazil.
He added that in as many as 60 per cent of patients, the virus can cause debilitating joint and pain inflammation 'that may last from months to years after the infection'.
'This results in an important burden for the health system, as well as an economic hazard for individuals and affected societies,' said Dr Siqueira.