Inadequate measures repeatedly failing to control mosquitoes

• Dhaka North launched crash programme from Monday
• Drives have relied solely on insecticides
• Experts say Integrated Vector Management is the only way to control mosquitoes
• DSCC allocates Tk 36cr in 2020-21 fiscal year for mosquito control while it was Tk 25.75cr last year
• Dhaka people mostly face Aedes and Culex mosquitoes

In the past few months, as in other years, the afternoons have become suffocating for Dhaka dwellers as hundreds of fogger machines spew out insecticide fumes. And as in other years, these biting pesky insects persist in defying whatever is sprayed.

They only point to one thing – this daily chore of fogging the city is not the solution. And yet the Dhaka North City Corporation is going to start a 'crash programme' to eradicate the city of mosquitoes. The outcome is already known.

There is a catchword, though. Dhaka South Mayor Sheikh Fazle Noor Taposh has said the 'crash programme' is expected to reduce mosquitoes in two weeks.

But experts say that would not be the result of insecticide fogging. Rather in two weeks' time, the rains will likely come and the mosquito population will naturally decline.

But in the meantime, money will be wasted and the environment harmed, with bees dying and the pesticide residues flowing into the rivers. It is undoubtedly evident from the fact that the city corporations' insecticide budget has inflated year after year, and yet mosquitoes have prevailed.

Now entomologists point out that mosquito control is an outcome of a comprehensive programme undertaken by all great cities that have managed to be free of the bug.

On top of it all is cleanliness that Dhaka city so badly lacks.

Entomologists have said that globally there are four important methods for controlling mosquitoes and mosquito born diseases, according to the guidelines of the World Health Organization.

The methods are: environmental management, biological control, use of insecticides, and involving citizens in mosquito control programmes.

Most countries, including India, Malaysia, Thailand and Indonesia, are following Integrated Vector Management (IVM) procedures.

"Both the Dhaka city corporations mainly follow chemical control such as use of larvicide and adulticide, which is only one step among the four IVM procedures. There has to be emphasis on all the steps to control mosquitoes," said Dr Kabirul Bashar, an eminent medical entomologist and a Professor of Jahangirnagar University.

He said that the city corporations had now become active after coming under pressure as mosquitoes have increased. He advised a continuation of insecticide spraying throughout the year.

Answering a question on environmental hazards posed by insecticides, he said, "Yes, any insecticides have environmental hazards. However, the World Health Organization determines the standard doses of insecticides to use that will not be harmful. We have directed the city authorities to maintain the doses."

"Since Culex breeds in dirty water, mosquitoes are less likely to be eradicated until there are rainstorms. However, the reproduction of Culex will naturally decrease in late March. Before that, water bodies, ponds and lakes as well as houses should be kept clean, which is part of environmental management," said Prof Bashar.

Dr Murshida Begum, a Professor of the Zoology department at the University of Dhaka, said, "There is a need to maintain the right doses of insecticides. Sometimes resistance grows to insecticides. So, we have to be aware about the frequent use of a particular insecticide."    

City dwellers are exposed to two mosquito species: Aedes and Culex, making their presence felt in different times of the year.

Now is the time for Culex.

Experts say the city corporations lack comprehensive mosquito control measures and rely solely on insecticides.

The crash programme launched by Dhaka North City Corporation on Monday for a week till March 16 is designed to use larvicide in drains, canals and water bodies while adulticide will be sprayed through fogger machine in various areas. Although such anti-mosquito drives were operated at least four times in the last year, the mosquito menace could not be brought under control.

According to the residents of the areas, mosquitoes are rampant everywhere now, especially in Mirpur, Uttara, Khilgaon, Baridhara, Mohakhali, Gulshan, Dhanmondi, Mohammadpur, Shyamoli, Badda, Rampura, Shanir Akhra, Donia and Shakhari Bazar. 

Lakes, water bodies and under-construction sites in several areas have become mosquito breeding grounds.

Brig Gen Md Jubaidur Rahman, chief health officer of the DNCC, said that now "we are focusing on comprehensive initiatives."

He claimed that the corporation was maintaining proper doses of insecticides.  

What are other countries doing?

Authorities in the Indian city of Kolkata engage entomologists in their drives against mosquitoes. New Town Kolkata Development Authority (NKDA) and entomologists of Kolkata Municipal Corporation jointly work to decide the best way of fogging and spraying larvicide apart from installing mosquito magnet traps, using mosquito nets at construction sites and releasing guppy fish in water bodies on a weekly basis.

Meanwhile, the Malaysian capital Kuala Lumpur has shown how biological control led to a decline in dengue by 40% in the areas where the authorities released Wolbachia-carrying Aedes aegypti mosquitoes. The method also eliminated the need for fogging.

When Aedes aegypti mosquitoes carry natural Wolbachia, the bacteria compete with viruses like dengue, Zika, chikungunya and yellow fever and thus reduce the transmission of these viruses.

A similar trial brought success to Indonesia in mosquito control, resulting in a 77% drop in dengue incidence, reports Berkeley news.