Repellents being used in Chattogram have lost effectiveness to kill mosquito significantly, a study has found, reports bdnews24.com.
A technical committee formed by Chattogram University at the bidding of Chattogram City Corporation submitted the report on Tuesday.
The authorities decided to conduct the study six months ago after suspicion had aroused over the effectiveness of the repellents.
The findings came as concerns over mosquito-borne dengue fever are growing amid the coronavirus pandemic.
Similar results had been obtained in studies in Dhaka north and south city corporations two years ago as researchers pointed out mosquitos were becoming resilient to the repellents. The authorities later changed the mosquito repellents for the capital.
The researchers in Chattogram used samples of four adulticides and a larvicide from the city corporation in the study on mosquitos and larvae grown in laboratories from samples collected from the port city.
One of the adulticides was light diesel oil or black oil being used by the city corporation. The two others were chemicals for experimental use.
The fourth one, a herbal repellent, was tried as both adulticide and larvicide.
The larvicide spray in use was found only 16 per cent effective to kill mosquitos. The effectiveness rose to 84 per cent when the level of repellent was raised 10 times.
The new herbal sample was able to produce 100 per cent result in two hours as both adulticide and larvicide.
It was made of extracts from various plants, said Dr Rabiul Hasan Bhuiyan, an associate professor at the university's biochemistry and molecular biology department who led the study.
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