Deadly tiny creature mosquitoes have become more potent and dangerous -- thanks to unplanned urbanisation and the abrupt use of insecticides which has backfired.
Over the last several decades, various initiatives to prevent the spread of mosquitoes have turned out unsuccessful. As a result, mosquitoes are not killed by sprays, coils or other insecticides. Experts predict that mosquitoes will cause more trouble in the future.
Dhaka Tribune spoke to Prof Kabirul Bashar of the Department of Entomology of Jahangirnagar University, where he has established a research centre to study the life cycle of mosquitoes in the country.
As a single creature, mosquitoes are responsible for the most human deaths worldwide. “It is important not to kill mosquitoes but to ensure that mosquitoes do not breed,” said the researcher when asked about the most effective method of fighting against mosquitoes.
Many varieties
According to researcher Prof Kabirul Bashar, there are more than 3,500 species of mosquitoes in the world. In Bangladesh, some 123 species have been recorded so far, and 14 are found in and around Dhaka city.
On the other hand, 200 species of mosquitoes spread diseases to the human body, but the number is 10-12 in Bangladesh.
Commenting on the patterns of behaviour of mosquitoes in various regions, Prof Bashar said mosquitoes in industrial areas are not similar to those in rural areas, while the mosquitoes seen in Bandarban and Rangamati are completely different.
Prof Kabirul Bashar“Almost all species of mosquitoes have characteristic differences, and the germs they carry are also different. However, the prevalence of Aedes mosquitoes is high in Bangladesh. The death toll caused by this mosquito is also high,” he said.
Among the mosquito-borne diseases, malaria, filaria, dengue and chikungunya are common in Bangladesh.
Mosquitoes are the single creature that kills the most number of people in the world. Humans are in the second position. “Controlling the mosquitoes is sometimes difficult. However, it is not the case that it cannot be controlled at all,” Prof Bashar added.
What about Dhaka's mosquitoes?
Highlighting the history of mosquito infestation in Bangladesh, Prof Bashar said that the incidence of dengue from 2000 to 2021 had not been as high as this year.
“Previously, it was more in August and September. I see an unusual situation this year. This has happened due to climate change: the timing of rainfall has changed. Now it is raining intermittently, even in October. This is why Aedes mosquitoes breed in October.
“Another reason is that when dengue cases increase, Aedes mosquitoes increase too. If two things increase at the same time, one of them must be controlled. Only the reduction of mosquitoes can slow down infection. But we have failed on both fronts.”There are two species of Aedes mosquitoes in Dhaka city: Aedes aegypti and Aedes albopictus. The Aedes aegypti mosquito is the main carrier of the dengue disease that spreads in the human body. “This species is also called urban or domestic mosquito. They thrive where there is unplanned urbanization,” Prof Bashar said.
Why all measures failed
This researcher thinks preventing mosquito breeding is more important than killing them to avoid mosquito attacks.
Among the four weapons of mosquito control, the third weapon is insecticide. Malathion is now used to kill flying mosquitoes in our country through fogging. On the other hand, Temifs and Nova Leuron are used to kill mosquito larvae.
Now when this pesticide is used in a place for a long time, mosquitoes develop an immune system against it. And this immune system is transferred to the next generation. “This is why the transfer mechanism has to be examined every few years and the insecticide needs to be changed,” he observed.
Prof Bashar explains that in Bangladesh, most mosquitoes today can tolerate the insecticides that have been used for a long time. Those medicines can restrict their pace to a minimum level. Hence, the mosquitoes recover after some time.
“These pesticides are no longer effective in killing mosquitoes. Instead, the abilities being developed in them are being passed on to new generations through their DNA and genes. As a result, mosquitoes are becoming more powerful,” he told Dhaka Tribune.
How to get rid of mosquitoes
According to the researcher, since mosquitoes spread dengue, mosquito control is the best preventive measure.
Mosquitoes can be controlled in several ways. These include integrated vector management, which has four components: environmental management; biological control or controlling with other organisms; controlling with chemicals or insecticides; and public awareness.
“We can control mosquitoes when we combine the four components into a year-round operation,” he said.
“While people should destroy the mosquito breeding grounds in and around their houses, the city authorities must monitor it and also adopt modern measures to keep the roads, drains, and canals clean,” Prof Bashar added.
