Kill mosquitoes with mosquitoes

2023-11-02

The weather is warmer, the land is alive, and at the same time, the mosquito is resurrected as an inexhaustible nuisance creature that will suck your blood and inject you with venom if you can't slap it to death. If you think that mosquitoes just make you a little itchy and a little upset, it means that you don't understand the power of mosquitoes at all. You must know that the most human beings in the world every year are not snakes and scorpions, not tigers and leopards, not wars, but these little mosquitoes - in 2015 alone, the number of people killed by mosquito bites worldwide reached 830,000! Because mosquitoes can transmit nearly 80 diseases to humans while sucking blood, including the fearsome Japanese encephalitis, dengue fever, malaria, yellow fever, filariasis...

While killing mosquitoes may seem like the best way to control the diseases they spread, there are very few ways to kill them – the least with your bare hands, and the least with your bare hands, and a little more with spraying and lighting mosquito coils. At present, scientists believe that the most effective way to control mosquitoes is biological methods. What kind of biological methods? It sounds a little incredible, and it looks even more terrifying, and lo and behold, these scientists are releasing a lot of mosquitoes into the air!

Use mosquitoes fighting dengue and Zika virus

In late October 2017, in a tree-lined, undulating, middle-class neighborhood in Singapore, senior government officials, community leaders, and a group of media with cameras gathered around a group of scientists to watch them bring an unusual gift: a box of mosquitoes. The scientists opened the box and released 3,000 mosquitoes into the air.

Through the explanations of scientists and the publicity of the media, the local residents were ready for this big gift months in advance. They know that these mosquitoes don't bite people and are part of an important scientific study.

In fact, these released mosquitoes are infected with a bacterium called Wolbachia, which hinders mosquitoes' ability to reproduce, thereby hindering mosquito-borne viruses like Zika. People infected with Zika virus will have symptoms such as low-grade fever, maculopapular rash, joint and muscle pain, conjunctivitis, weakness and, most frighteningly, pregnant women infected with Zika virus are prone to giving birth to babies with deformed heads. Since the first case of Zika virus infection was detected in 2014, outbreaks have now been reported in more than 20 countries and territories, and are likely to spread globally.

In addition to infecting mosquitoes with Wolbachia, scientists have also studied biological modification of mosquitoes by radiation and genetic modification. These new methods of controlling mosquito-borne diseases by releasing modified mosquitoes originated a few years ago when people were first hit by dengue fever. The main symptoms of dengue fever are high fever, headache, severe muscle and joint soreness, while severe dengue fever can kill people within 24 hours and is the fastest spreading tropical disease in the world. According to the World Health Organization, dengue fever has expanded from a severe epidemic in just nine countries before 1970 to more than 100 countries today, mostly in Asia and Latin America.

While Singapore is not the only country to drop mosquitoes into the air, in Asia and Latin America, scientists are also trying to use this new method to defeat the Aedes aegypti and Aedes albopictus mosquitoes – the very ones that spread dengue, chikungunya and Zika viruses that have claimed many lives and the happiness of many families.

However, in some cases, it is more difficult to convince people to believe and accept "releasing mosquitoes for mosquito control" than to biologically modify mosquitoes. The reason is that in the mid-20th century, in order to stop mosquitoes from spreading epidemics such as malaria and yellow fever, it once led to the abuse of DDT, which caused cancer in some people, and at the same time, DDT caused great pollution to the natural environment, and greatly reduced carnivorous birds. Therefore, people are worried that these new biological methods, like DDT, are "three parts poisonous".

World Mosquito Program

The ban on DDT, coupled with the explosion of global transportation and tourism, is prompting a resurgence of mosquito-borne diseases. Although China's mosquito nets became popular abroad through the 2016 Rio Olympics and are known as mosquito prevention artifacts, we can't stay in mosquito nets all the time, and we have to face mosquitoes when we get out of them. Scientists believe that the popularization of biological mosquito control methods is imminent, and the use of Wolbachia to control mosquito-borne diseases is the most important thing after DDT is banned.

Wolbachia is relatively safe because it is not transmitted to humans or animals, but only from insect to insect. In addition to affecting the reproduction of insect hosts, Wolbachia can cause a variety of serious neurological complications in the new host when it is transferred to a new species. In 2009, scientists discovered that Wolbachia prevents the dengue virus from replicating and multiplying in mosquitoes, thereby blocking the spread of dengue fever.

In 2011, Australian scientists introduced a method of releasing mosquitoes to control mosquitoes through the World Mosquito Programme (formerly known as the Dengue Eradication Project). They release infected mosquitoes into the air, where the male mosquitoes are unable to fertilize the female mosquitoes properly, thus blocking the mosquito from reproducing; Female mosquitoes, on the other hand, pass the virus on to their next generation, preventing them from reproducing properly and carrying dengue fever and Zika viruses. However, female mosquitoes still bite.

Singapore and China, on the other hand, have tried to suppress mosquito populations by releasing only male mosquitoes. Male mosquitoes do not bite, but this method is more expensive because it requires the males to be sorted in a laboratory. In 2016, following a successful trial, China set up a mosquito retrofit factory in Guangzhou, producing 5 million Wolbachia-infected mosquitoes per week.

Wolbachia is a bacterium that occurs naturally in the environment, not an artificial bacterium, and although the long-term ecological effects are unknown, it can be said that in the short term it is harmless and adaptable to humans and animals. Now, more and more countries have adopted projects to release Wolbachia-carrying mosquitoes. Hopefully, one day, humans will actually be able to say goodbye to these little vampires.