The two city corporations – Dhaka North and Dhaka South – have increased the use of insecticide by 274 percent in the last five years whereas dengue infection by Aedes has gone up by more than 8500 percent.
Insecticide spraying is used for controlling Culex mosquitoes across the world. But, although ineffective for Aedes control, the city corporations have been doing that up to now.
The city corporation authorities have largely ignored the best ways of destroying the sources of Aedes – flower tubs, water in abandoned tyres, plastic drums, buckets, open tanks in under-construction buildings.
Failing to understand the difference between Culex and Aedes, they tend to focus on using insecticide for dengue control, said Kabirul Bashar, an entomologist.
"Spraying insecticide cannot control dengue; it has proved useless over the years," he said.
Kabirul brought up four integrated ways of controlling dengue – source reduction, biological control, chemical control and community involvement.
To control dengue outbreak, they only sprayed insecticide over the years, city corporations' data show.
In 2018, the Dhaka South City Corporation (DSCC) spent Tk20 crore on insecticides, but for destroying Aedes breeding grounds it allocated only Tk30 lakh.
"Either the city corporations do not have the expertise or they do not want to use low-cost options of dengue control," commented Kabirul.
Source reduction and biological control are cheaper options as they only require doing cleanliness operations round the year.
Asked about the issue, DSCC’s Chief Health Officer Brigadier General Dr Sharif Ahmed refused to make any comments.
He, however, said the city corporations will target source reduction from this year.
Preferring anonymity, a senior DSCC official said they know spraying is not effective for Aedes control, but for public satisfaction they continue spraying insecticides.
"There is a public demand for spraying," LGRD Secretary Md Helaluddin also commented in a video conference meeting between Dhaka North City Corporation (DNCC) and Kolkata City Corporation (KCC) last week.
Helaluddin said that in response to Kolkata Deputy Mayor Atin Ghosh's comment that "fogging is useless in controlling Aedes".
The most effective way will be followed from this year although there may be some gaps, DNCC Mayor Atiqul Islam told The Business Standard.
"I have shared experience with the Kolkata City Corporation and have learnt to control dengue," he said.
"Now the Dhaka North City Corporation is working on source reduction and biological control of Aedes," Atiqul said.