Most mosquitoes breeding in clean stagnant water are dengue-spreading Aedes

Concealed spots like water-holding trays underneath some refrigerators can be a potential breeding ground for the Aedes mosquitoes, responsible for the spread of dengue fever.

Mosquitoes hatch eggs wherever they find stagnant water. This includes, but is not limited to, water-filled containers and abandoned tires in and around households in Dhaka. Over 80 percent of these mosquitoes breeding in clean stagnant water could be the infamous dengue-spreading Aedes aegypti, indicates an icddr,b study published in PLoS One.

This is a strong reminder that simple precautions can reduce dengue fever this monsoon.

The threat of dengue fever looms over Bangladesh as the monsoon progresses, hitting the country early this year with higher levels of rainfall, thus stagnant water sources are widespread in the capital – Dhaka, where dengue is most-reported.

Recently published findings from the study survey conducted in 12 selected city wards during 2011-2013 suggests that refrigerator trays were mostly responsible for Aedes production during wet seasons. Plastic drums were the most productive habitats for breeding during dry and monsoon seasons while vehicle parts and discarded construction materials were the most efficient.

Photo: James L. Occi / AFPMB. CC BY-NC-ND 2.0

“It was not too surprising that the low socio-economic zones of Dhaka had slightly higher presence of Aedes mosquitoes, perhaps because sanitation standards and awareness about mosquito-breeding in these areas were below par,” says Dr Kishor Kumar Paul, author of the study and senior research investigator at icddr,b.

Dr C Emdad Haque, co-author of the study and professor at the Natural Resources Institute, University of Manitoba, Canada, observes that people are usually afraid of dengue during monsoon rainfall. “Our study has also indicated that too much rainfall may actually reduce mosquitoes as the larvae are washed away, especially from containers exposed to rainfall outdoors,” he adds.

Earlier studies have shown that mosquito breeding is more likely to thrive well in warmer climates, however the contrary may also happen, observes the researchers, noting that further research may ascertain how temperature variations affect breeding.

Hence regardless of the climatic context, maintaining household cleanliness in all households, is key to reducing mosquito breeding. Proper use and disposal of containers, communal awareness, regular surveillance and effective source management are recommended by this study.

City dwellers and the city corporation authorities must increase their vigilanceto ensure that breeding grounds for mosquitoes are not created by discarded items across the country.