As if Japan did not have enough worries to try to withstand a new coronavirus outbreak, unpleasant signs have emerged that mosquitoes capable of infecting humans with deadly infectious diseases such as malaria and dengue are building their footing.
Experts cite the effects of climate change for increased sightings of species not yet discovered in Japan, and are equally worrying, in areas farther north than would normally be expected for other species. They warned that global warming might see a more virulent version becoming more common in some regions.
The mosquito in 2015 was linked to the deaths of around 830,000 people worldwide, making it the deadliest insect for humans, according to the Bill and Melinda Gates Foundation, a non-profit organization founded by founder and billionaire Microsoft Corp. Bill Gates and his partner. wife.
The Aedes albopictus mosquito carries a virus that causes dengue fever, which can be fatal.
Mosquitoes are said to live in areas where annual temperatures average 11 degrees or higher. Until about 1950, Aedes albopictus was only found in the southern area of Tochigi Prefecture, which is located north of Tokyo.
However, with rising temperatures, there was confirmation of mosquito sightings in 2000 in Akita and Iwate prefectures in northern Japan. In 2016, the mosquito was seen in Aomori Prefecture at the northernmost tip of the main island of Honshu.
Aedes albopictus triggered a small fear six years ago after dengue spread among people who had visited Tokyo’s Yoyogi Park. It was the first case of mosquito-borne disease reported in Japan in about 70 years. While no one died, 162 people were infected, and they suffered from fever and headaches.
According to the World Health Organization, dengue is widespread throughout the world and the number of confirmed infections has increased 15-fold over the past two decades. Around 390 million people are infected each year with dengue fever and around 500,000 experience serious symptoms. Of that number, 2.5 percent of the cases proved fatal.
The main transmitter of dengue is Aedes aegypti, which is not usually found in Japan. This is a more vicious version of Aedes albopictus and has caused epidemics in Southeast Asia and South America.
Last year, the Philippines recorded a dengue outbreak that killed more than 1,000 people across the country.
There have also been sightings of Aedes aegypti in Japan recently. According to the health ministry, there were confirmed cases at Narita Airport outside Tokyo in 2012. Other sightings occurred at international airports around Japan until 2017.
Aedes aegypti was destroyed whenever it was found in Japan, so it is not believed to have occurred.
But Shinji Kasai, who heads the Medical Entomology Department at the National Institute of Infectious Diseases (NIID), warned that Aedes aegypti might be here to stay if climate conditions continue to be conducive.
“Larvae have been found in various studies, which means mosquitoes breed and leave the next generation in Japan,” Kasai said. “There is a greater threat from mosquitoes that take root in warm areas even in winter, such as airport terminal buildings and around subways in metropolitan areas.”
A Chinese research institute released a projection last year that Aedes aegypti could spread to all parts of Taiwan in 30 years if temperatures rose at the current pace. At present, mosquitoes are only found in southern Taiwan.
The latitude of Taiwan is almost the same as the main island of Okinawa and the nearby island of Ishigakijima. So, if temperatures rise in Japan at current levels, Aedes aegypti can finally take root in Okinawa Prefecture too.
Insecticides are usually used to kill mosquitoes. Incense and insect repellent sprays often include pyrethroids, which attack the insect’s nervous system and kill it.
But experts say it is time for Japan to be on guard because of the finding that some Aedes aegypti mosquitoes have developed resistance to pyrethroids.
There are a number of mutation reports in Vietnam, and Aedes aegypti samples collected at Chubu Centrair International Airport in 2016 and 2017 show very strong resistance.
If mosquitoes finally take root in Japan, wiping them out can be a nightmare.
NIID is continuing research on insecticides that solve pyrethroid immune problems as well as creating a database on the genetic makeup of mosquitoes. However, this work is still in its infancy due to budget and personnel limitations.
“Above the expanded area where Aedes albopictus was found in Japan due to global warming, if Aedes aegypti must also be rooted, the risk of dengue epidemic tends to increase,” Kasai NIID said. “I am worried about another dengue epidemic given the estimates that more people are bringing the virus into Japan because of the increase in tourists who come along with the increasing number of mosquitoes in this country.
Research is being carried out abroad to use genetic engineering to eradicate mosquitoes.
A British company, Oxitec Ltd., created Aedes aegypti men who could not produce offspring. Among mosquitoes born among genetically altered males and female mosquitoes in the wild, larvae die before reaching adulthood. The aim is to release males that have been genetically altered into the wild to eventually eliminate the species.
Experiments in Brazil and the Cayman Islands caused the mosquito population in the Cayman Islands to drop by 80 percent for 23 weeks.
University researchers in Australia have infected Aedes aegypti with Wolbachia bacteria before releasing it into the wild. The infection stops the multiplication of pathogenic viruses in female mosquitoes and renders them powerless to transmit diseases.
However, these efforts are still in the research stage. In addition, the Brazilian experiment by Oxitec found that mosquitoes with modified genes continued to survive.
This story is part of Covering Climate Now, a global collaboration of around 400 news outlets, including The Asahi Shimbun, to strengthen coverage of the climate story. This campaign was started in April 2019 by The Nation, a weekly magazine in the United States, and the Columbia Journalism Review of a feeling that media organizations must change when the world faces a crisis of global warming.