Aedes larvae density at alarming level in dry season too 

Mosquito population will likely grow further in Dhaka city in the coming days as the density of the dengue-carrying Aedes larvae was much higher in the post-monsoon period last year, according to a survey of the health directorate.

The concentration of adult mosquitoes at 11 wards of Dhaka city is alarming. The number of adult mosquitos will increase further if the larvae manage to survive.

Such revelations emerged with the release of a health department survey, titled "Post-monsoon Aedes survey in Dhaka North and South City areas", at a workshop on Sunday. 

The researchers took into account the Breteau Index (BI) to measure the prevalence of larvae. If the BI level goes beyond 20 percent, the presence of mosquito larvae gets to be risky for people.

Entomologists say that in terms of households, BI level of more than 10 percent is poses risks to health. 

Some 100 sites and 1,000 households in Dhaka South and North city corporations were surveyed during December 17-28 last year.

The number of wards marked vulnerable in the latest survey was 11 – of them, five in Dhaka North and six in Dhaka South. 

The density of Aedes larvae was the highest at ward no 12 of Dhaka North and at ward no 42 of Dhaka South.

Besides, the survey found that Aedes larvae of more than expected BI levels were at wards no 1, 16, 20 and 31 of Dhaka North and wards no 5, 6, 11, 16 and 37 in Dhaka South.

The survey revealed that 12 percent sites of Dhaka North and 10 percent of Dhaka South were found were found risky. Some 32 households of Dhaka North and 35 percent of Dhaka South were marked vulnerable. 

The larvae of Aedes mosquitoes were found most in stagnant water in plastic drums at constructions sites. In the earlier survey, the presence of larvae was the highest in water stagnant in tyres. 

Prof Dr Abul Kalam Azad, director general of the health department, said last year dengue had spread outside Dhaka. Therefore, it was important for such mosquito surveys to be conducted in other regions as well. 

Although there is a manpower crisis impeding surveys outside Dhaka, such surveys have to be done after imparting training to health officials, he added.

Brigadier General Mominur Rahman, chief health official of Dhaka North City Corporation, said, "Earlier, we could not draw up a combined plan to control the breeding of Aedes mosquitoes.  This year, we have gone for a year-long planning with the help of experts and entomologists."

It is also necessary to enhance the capacity of city corporation authorities, he added.

Entomologist Kobirul Bashar said a survey will be undertaken from March 1 to assess the mosquito situation this year. 

The last survey was done in 2017.  The density of Aedes larvae was comparatively low in the survey of 2019.