This is an image of an arm torn apart by hundreds of mosquitoes at the same time. That arm belongs to Perran Ross, an entomologist at the University of Melbourne, Australia.
In a net cage, dozens of mosquitoes are sitting on his skin, they find a thin spot to be able to penetrate the nozzle into Ross capillaries. Sips of his blood began to flow through the mosquitoes’ stomachs. After they are full, the mosquitoes take off and fly, making room for others in the flock that have not found a place to park.
As part of an ambitious research strategy to eradicate dengue around the world, this afternoon Ross again served himself a free buffet to more than 5,000 Aedes aegypti. They will take away 16 ml of his blood.
Record: Researcher gives 5,000 mosquito bites a day for science
People who have ever had dengue fever will not be able to stop being haunted by the mosquitoes Aedes aegypti, also known as the black and white striped mosquito. They are the vectors for the transmission of the dengue virus, which tortures them with headaches, vomiting, muscle aches, skin rashes, and especially high fever that cannot be stopped for days in a row. .
A small proportion of patients with dengue may develop severe dengue fever or shock syndrome – causing bleeding under the skin and severe, life-threatening vomiting. Each year, the World Health Organization (WHO) still records more than 4 million severe dengue cases worldwide, killing more than 22,000 people.
Yet in some places like Australia, dengue fever epidemic has become a thing of the past.
Although dengue has never been officially circulated in mainland Australia, in North Queensland, dengue outbreaks sometimes occur sporadically. The virus was transferred here from tourists with dengue fever. The native mosquitoes would suck their blood and within that short one week they could pass the disease on to an unlucky Queensland.
Only in the past few years, the number of dengue cases in Australia has fallen sharply. From the beginning of 2020 until now, the whole continent has only confirmed 2 cases positive for dengue virus.
Dr Richard Gair, Director of Tropical Public Health Services in Cairns, said: “Far North Queensland is fundamentally a dengue free zone, and it is the first milestone we have achieved in more than 100 years. ”
And that achievement is all thanks to science, with researchers like Perran Ross. They are working to produce Wolbachia infected Aedes aegypti mosquitoes to release them into the wild in Northern Queensland.
Wolbachia is an infectious bacterium that is very widely distributed in insect populations. A study in the 1990s found that 17% of the insect species tested were infected with Wolbachia, it is likely that the true number of untested species is more than that.
Wolbachia bacteria naturally stop the transmission of dengue, so that they cannot be passed in mosquito populations from generation to generation. Even better, Wolbachia doesn’t seem to affect people at all, a trait that makes it a compelling choice for worldwide dengue elimination efforts.
When the idea came up with Wolbachia infection in wild mosquito populations, scientists faced only one problem: the Aedes aegypti, the infectious dengue agent could not mass Wolbachia. .
Instead, scientists must inject Wolbachia into each A. aegypti mosquito egg. They have to do it manually, under the microscope. “We put the eggs on a slide, and then use the microwave to pierce the eggs with a very small needle“Explained Ross.
“Then we suck Wolbachia-containing cells from one egg and inject it into another. If you’re lucky, that egg will survive and the bacteria will be passed on to the next generation.“.
It is hard work. A researcher can only inject a few hundred eggs a day, while it can take about 200 to 10,000 eggs to find a single Wolbachia-infected female mosquito, which can be released into the environment. to transmit bacteria to the next generation.
“It can take us six months of full-time work to get a stable Wolbachia mosquito population“Said Ross.”But really, that’s a small price to pay for a strain of Wolbachia-carrying mosquitoes.
Once you have the strain of mosquitoes, you can start breeding them in the lab. And if you want to get enough mosquitoes to effectively reproduce with the wild mosquito populations in your area, you have to get a female mosquito infected with Wolbachia per 3-10 homes.
“You have to feed hundreds of thousands of mosquitoes in the lab and then release them everywhere“Said Ross.”These particular mosquitoes don’t really get far. ”
His daily lab work is to monitor the long-term effects and stability of Wolbachia on Australian mosquito populations. Part of that surveillance is feeding the thousands of mosquitoes. And the blood source is no different, is the natural blood in Ross.
A picture of his bitten arm went viral on social media in May, after Ross fed 5,000 mosquitoes in a single day:
Sharing his feelings after that record, Ross said: “Sometimes the bites can be a bit stinging if the mosquitoes are bitten right in the wrong place, but for the most part they are only mildly irritating. After that, of course, they were still terribly itchy. Right after I pulled my arm out of the cage, I had to resist the thought of wanting to scratch my arm “.
The good news is that what Ross had to endure paid off. Scientists discovered that Wolbachia infected Aedes aegypti not only reduced dengue infection rate but also other mosquito-borne diseases.
Wolbachia-infected A. aegypti mosquitoes also have a shortened lifespan, reducing the chance they can transmit disease or cause discomfort to humans.
In the world, there are also many countries pursuing the strategy of releasing Wolbachia infected mosquitoes into the wild to fight out dengue fever, Zika and chikungunya fever. In 2019, scientists published a study showing they had wiped out mosquitoes on two Chinese islands, using a strain of Wolbachia bacteria combined with a dose of radiation directed at mosquitoes.
Another Wolbachia mosquito release is currently underway in Malaysia in the hope that it will stop the spread of the three dengue viruses, Zika and chikungunya.
Ross explained: “They released mosquitoes in Kuala Lumpur, which is endemic to high dengue fever. And that action brought about 40 to 60 percent reduction in the epidemic. The results are remarkable “.
Just last year, the Malaysian Ministry of Health expanded this experimental research program thanks to its unexpected success.
A Vietnamese scientist in the Wolbachia mosquito release project in Vinh Luong, Nha Trang.
A non-profit organization called the World Mosquito Program is working to bring more Wolbachia-infected mosquitoes to other virus-affected areas. Up to this point, they have released Wolbachia infected mosquitoes in 12 countries around the world including Vietnam.
As for Ross’s team, work at this time has revealed that Wolbachia appears to remain stable in the population, so even in locations where COVID-19 affected program implementation, The released mosquitoes can still stay.
Despite the ongoing challenges, Ross remains optimistic about the role Wolbachia plays in preventing dengue worldwide. “The work will be expensive and require a lot of community participation and planning“, I said. “But I think that idea is quite possible.