Dhaka mosquitoes are insecticide-resistant, icddr,b study finds

The insecticides sprayed by the Dhaka city corporations have no effect on the adult mosquitoes as they have become resistant to the varieties of insect repellent used by the authorities, according to icddr,b researchers.

Obaidur Masumbdnews24.com
Published : 26 June 2019, 09:10 PM
Updated : 26 June 2019, 09:10 PM

The findings of the International Centre for Diarrhoeal Disease Research, Bangladesh were presented in a meeting of the two city corporations in May.

The chief health officers of Dhaka North and South city corporations were present.

Funded by the United States Centers for Disease Control and Prevention or CDC, the researchers collected Aedes Aegypti and Culex mosquito eggs between September 2017 and February 2018 from different areas of the city and grew the mosquitoes in laboratory.

The researchers then conducted tests on the mosquitoes in line with World Health Organization or WHO rules, icddr,b researcher Mohammad Shafiul Alam told bdnews24.com.

If the death rate of mosquitoes in a certain period once insecticide is used is below 90 percent, they are assumed to have gained resistance to the insecticides, the researcher said, referring to WHO protocol.   

“But we’ve seen the death rate in most cases is zero. Even doubling the dose doesn’t kill all the mosquitoes,” Shafiul said.  

MM Aktaruzzaman, manager of the malaria and Aedes-transmitted diseases programme at the Directorate General of Health Services, said they also found Culex mosquitoes insecticide-resistant and informed the authorities about the findings.

The insecticides used by the city corporations can kill larvae but not adult mosquitoes, he said.

The two city corporations use 0.5 percent permethrin, 0.2 percent tetramethrin and up to 0.2 percent allethrin per litre of kerosene and apply the mixture through fogging machine to kill mosquitoes for a decade.

The icddr,b researchers have suggested using malathion and deltamethrin instead of permethrin.

Health directorate’s Aktaruzzaman, however, said it would take time to change the substances of the insecticide.

Dhaka North Mayor Mohammad Sayeed Khokon on Wednesday said he was aware of the icddr,b findings.

He said the city corporation was ready to change the substances of the insecticide but they need WHO prescription for this, citing environmental and health concerns.

“We don’t have the scope of going beyond that prescription. We have a seminar on this issue tomorrow (Thursday). We’ll ask for expert opinion there. Let’s see what they say,” he added.

Dhaka North City Corporation Chief Health Officer Mominur Rahman Mamun said they had not found the substances ineffective during tests before purchase.

He added they would welcome changes if the findings of the study on resistance developed among mosquitoes are proven and there are alternatives to the substances in the market.

Toufique Imrose Khalidi
Editor-in-Chief and Publisher