Influx of Culex mosquito compounds sufferings of Dhaka residents

Highlights

• The problem may reach its peak in March
• Uttara has the highest number of mosquitoes
• Number of mosquitoes trapped daily in January: Uttara 450, Dakshinkhane 410, Mirpur 350, Rayerbagh 350, Jatrabari 200
• 99% of trapped mosquitoes are Culex, 1% Aedes and others
• Culex mosquito transmits filariasis
• There is no information about the infection of filarial disease in Dhaka and surrounding areas

An influx of Culex mosquitoes has caused a new menace for Dhaka city dwellers, who have been experiencing a recent wane in Ades-infected dengue fever.

With evening setting in, the mosquito menace rises abruptly in most areas of the capital.

Shahida Begum, who lives on the 6th floor of a residential building in Badda, now has a scarred skin caused by mosquito bites. She has to keep her six-month-old baby in a mosquito net from the afternoon.

"I've been sick for the last few days because of the menace. The skin of all my family members has been scarred by mosquito bites," she told The Business Standard.

She held the city corporation responsible for its failure to curb the sharp rise in mosquito population as she has not recently seen any city corporation workers spraying chemicals to kill the insects.

A rickshaw-puller in Eskaton, Subrata Dhar, also came up with similar observations, saying while pulling the rickshaw, he cannot stop anywhere for even two minutes because of the mosquitoes.

Culex mosquito infestation has marked a sharp rise in most areas of the bustling city, according to the residents.

A study by the Zoology Department of Jahangirnagar University finds that the density of this general type of mosquitoes has increased in the capital in the last four months.

On average, more than 300 adult mosquitoes were caught in traps per day in January, whereas the number was 250 in December and less than 200 in October and November last year, according to a study.

Of the trapped mosquitoes, 99% were Culex, while the rest 1% were Aedes, Anopheles, Armigeres and Mansonia types.

The research data also suggest that the menace may reach its peak in March, if this trend continues.

Prof Kabirul Bashar, who spearheaded the study, told TBS that of the areas surveyed, Uttara has the highest mosquito population, where more than 450 mosquitoes were trapped every day. "Such a high number of mosquitoes have not been seen anywhere in the city."

Besides, 410 adult mosquitoes were caught in Dakshinkhan and 350 in Mirpur, he added.

The researcher noted that the mosquito menace is low in the southern part of the city compared to the northern part as the number of water bodies is low in that part.

The maximum number of 350 mosquitoes was found Rayerbagh area of the south city, followed by 200 in Dania area of Jatrabari.

Kabirul says Culex mosquitoes cause disturbance to people more than creating health hazards.

However, he acknowledged that there is evidence of Culex mosquitoes spreading filariasis in some parts of the country, but there is no information about the transmission of this disease in Dhaka and its surrounding areas.

Urban experts believe that though both the city corporations are talking about various plans to control mosquitoes, their initiatives have not been sufficient and appropriate.

Although the city authorities are trying to clean the drainage systems and spray mosquito repellents, experts think that it is not enough to bring the situation under control. Apart from these moves, larvae should be killed by larvicide to prevent adult mosquitoes, they pointed out.

Entomologists say that there are 123 species of mosquitoes in the country. Among them, 16 species are more common. Culex is more than 95% of the few species that exist throughout the year in different parts of the country, including the capital.

The country usually sees Culex infestation from October, which recedes with the increase in the severity of winter.

However, the problem intensifies in February every year when rainfall is absent for many days and the density of water in ponds, drains and water bodies increases. Reproduction of Culex mosquitoes gets a boost at that time as they get a lot of food from increased organic matter in the water, according to experts.

Lt Col Rubayet Ismat, Dhaka north city deputy chief health officer, told TBS, "The density of mosquitoes has increased in those places where canals and drains have remained clogged for many days."

He added that the ongoing development projects have blocked the mouths of drains in many places of Dhaka city.

He claimed that even medicine did not work much in those places. "We're conducting cleaning drives in those places. Hopefully, the density will decrease in a few days."

Dr Fazle Shamsul Kabir, acting chief health officer of Dhaka south city, claimed that the mosquito density in the south city is lower this year than in any other year.

"We managed to keep it under control. Earlier, people had to face a huge mosquito infestation at this time. But no complaints have been lodged from any area this year," he told TBS.

He also claimed that the authorities were able to keep the Adi Buriganga river, canals and water bodies clean this year.