Dengue mosquito developed resistance against insecticides: Entomologists

Entomologists of late found the conventional insecticides appeared ineffective against dengue Aedes mosquitoes saying they visibly developed a natural resistance to two traditional toxicants used to kill the deadly insects or destroy their larva.

"Toxic substances (insecticides) have turned sub-insecticide, losing their efficacy against mosquitoes," National Institute of Prevalence and Social Medicine or NIPSOM's entomology department chief Professor Dr Md Golam Sharower told BSS today.

The entomologist attributed the phenomenon to anti-mosquito workers inefficacy in applying the insecticides to kill the mosquitoes or destroy the larva with their traditional fogger machines.

NIPSOM entomologists said two particular insecticides, Malathion and Temephos, were currently being used to respectively kill mosquitoes and their larva.

But, Sharower said, workers assigned by two city corporations visibly could not properly spray the insecticides in appropriate doses for want of their knowledge, which largely made the dengue-carrying mosquitoes resistant to the pesticides.

Jahangirnagar University's Zoology professor Dr Kabirul Bashar, an entomologist by background, asserted that "it is very important to understand the reproductive nature and life cycle of Aedes mosquito (in particular) to take effective measures to halt dengue assaults to save human lives".

Bashar also echoed Sharower expressing his doubts about the practice of traditional methods to destroy Aedes.

City corporations of Dhaka north and south – both under the purview of the Local Government Ministry (LGD) of the local government ministry -- are mainly entrusted with the task of eradicating mosquitoes in the capital.

The LGD ministry recently sent a delegation of Dhaka North City Corporation (DNCC) including four deputy secretaries to Germany to learn the proper use of the fogger machines. A spray man supervisor and a ward councilor however were in the delegation to visit Germany to acquire the mosquito annihilation skills through fogger machines.

DNCC's Chief Executive Officer Mohammad Selim Reza, meanwhile, said they separately sent at least three teams to Germany and France while all their team members were technical persons who were directly involved in the anti-mosquito campaign.

DNCC officials said they recently bought 100 fogging machines from Germany's PulseFog while works were underway to provide continued training to the persons engaged to operate state of art fogging machines procured recently to spray insecticides in appropriate doses at precise locations.

Dengue this year broke an all time record claiming so far 650 deaths with experts and officials accusing the city corporations of failure to discharge their responsibility in combating mosquitoes.

Sharower, however, said the city corporations largely failed but they alone could not perform the job without community engagements and coordination of relevant organisations.

Bashar said since the Aedes mosquito is found generally in residential areas "it is actually a domestic species and its management system must be different from other mosquito species".

"We need to recruit health workers to oversee a specific number of houses in particular areas in Dhaka throughout the year," Bashar said, adding a year-long monitoring system must be introduced to destroy potential breeding sources of Aedes mosquitoes.

The entomologist said areas under the purview of both the city corporations and the two municipal authorities in the capital must strengthen the interaction or cooperation to control the dengue.