Clash! This is how many encounters between mosquitoes and humans end. And when the mosquito is swatted, you get rid of both itchy mosquito bites, annoying buzzing and, not least, the dangerous diseases that mosquitoes spread – at least until the next mosquito comes buzzing. And the next one after that again. But even if you squash millions of mosquitoes and use insecticide on them, they always return eventually. In Colombia, they have therefore started to use a completely different strategy against mosquitoes that spread a number of tropical diseases. Instead of trying to kill mosquitoes, since 2015 an organization in Colombia has done the opposite: They have bred and released even more mosquitoes. The new strategy has caused the number of infected people to fall markedly: There are now at least 94 percent fewer cases of dengue fever in the Aburrá valley, where, among other things, the metropolis of Medellín is located. This is shown by an evaluation made by the organization behind the project, the World Mosquito Programme. Bacteria block harmful viruses At first glance, it may seem contradictory that more mosquitoes cause fewer problems. The explanation is that the many millions of mosquitoes that the researchers hatch and release into the open are not quite ordinary mosquitoes. They have been inoculated with a special bacteria called Wolbachia. When the bacterium is inside the mosquito, it prevents the mosquito from spreading a number of viruses, including dengue, zika and chikungunya. The bacterium itself does neither mosquitoes nor humans any harm. It is already found in many other insects, but not normally in mosquitoes that spread diseases. And when mosquitoes with the Wolbachia bacteria are released into an area, the mosquitoes themselves spread the bacteria to other mosquitoes. After a while, most mosquitoes carry the bacteria, and thus the possibility of the virus spreading is also blocked. The new method is on the way, and has already been used in a number of countries, including Australia, Vietnam, Indonesia and Brazil. A study published in the scientific journal Nature Communications shows that this has led to a marked drop in the number of people infected with dengue in the areas. Children get mosquito eggs home from school Before the first mosquitoes are released, the World Mosquito Program informs the locals about how the project works and obtains permission. In Colombia, over nine out of ten Colombians in the affected areas support the project, and many of the residents themselves have helped spread thousands of mosquitoes. Among other things, school pupils have been given small incubators to take home, which hatch lots of mosquitoes in the garden or on the balcony. It may cost a few extra mosquito bites, but in return people can avoid getting dengue fever, which can be an extremely unpleasant disease. In Danish it is also called “knogleknekkerfeber” (knokeknekkefeber editor’s note), because it can make it feel as if you have broken all the bones in your body. Most people recover after about a week, but the disease can also be fatal.
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Mosquito project has almost stopped dengue fever in Colombia
