Shanthi*, a domestic worker, who lives in Thideer Nagar near the banks of the Cooum river, fell sick a few days ago. She was diagnosed with dengue.

“We have been living on the river banks for years now as this is the only place where we can find affordable rental houses. Unlike previous years, the mosquito menace in Chennai is very high this year and many of us, mostly children, have been falling sick frequently,” she says.

Being the sole breadwinner of her family, Shanthi lives with her her son, who is in class 10. “The number of mosquitoes that have flourished this year means we cannot sleep at night. When we go to our jobs during the day, it becomes very hard to work as the lack of proper rest leads to exhaustion,” she says.

When Shanthi fell sick with dengue, her son had to take off from school for a couple of weeks to look after her. By the time Shanthi recovered, she was already replaced in her old job and is now working as a construction worker.

Shanthi’s case is not an isolated incident. Reports point out the increasing trend in mosquito menace in Chennai. Notably, the data on the number of vector-borne cases recorded in Chennai in recent times have not been made public yet.

While the civic body has been taking several measures to control the mosquito population, the residents in Chennai stress the need for permanent solutions.

Read more: Dengue in the time of COVID: Stiff challenge ahead for Chennai’s civic and health workers

Major reason for mosquito menace in Chennai

Polluted water bodies and rivers, open drainage systems, discharge of sewage water into the stormwater drains that are meant to carry rainwater, improper execution of civic works, garbage management and the lack of awareness among the public are seen as the major root causes for the increasing number of mosquitoes in Chennai.

Harris Sultan of Arappor Iyakkam says that even after more than a decade of being subsumed to the Greater Chennai Corporation (GCC), many residents in Ambattur have not got underground drainage (UGD) connections, exacerbating the issue of mosquitoes. The same is the case for many suburban areas.

“The works for installing UGD began sometime around 2013 in Ambattur. Since the soil here is composed of clay, the UGD chambers could not be placed as per the plan. While the contractors kept quitting one after the other, it has taken almost a decade for the local body to bring the work to near completion. However, the connections are yet to be given to the households thus resulting in the existence of an open drainage system in the locality,” says Harris Sultan.

An open drainage system becomes the breeding ground for mosquitoes.

“Every time we make a complaint to the local body, they clean the drainage. However, the workers leave the sludge from the drainage on the roadside as they cannot carry the wet sludge. When heavy vehicles pass by the road or during rains, the sludge goes into the sewage again,” says Harris.

Read more: From 1104 cases in August 2017 to just 196 this year: How Chennai is battling dengue

The number of mosquitoes has been on the rise even in areas where there are proper UGD connections but are next to water bodies in Chennai.

C Ramakrishnan, President of the Federation of Adyar Residents Association (FEDARA), says that as the Adyar river is not cleaned properly with weeds growing on the river banks which has become the main source of mosquito breeding in their locality.

This apart, many commercial establishments have also been discharging sewage water into the stormwater drains, adding to the mosquito menace.

“Though the corporation carries out the fumigation process once in a while, it is done only in pockets. Despite making several representations, we have not seen much improvement, ” says Ramakrishnan.

“About five years ago there was absolutely no mosquito issue in Valmiki Nagar. Soon after the stormwater drain works began, we saw a swamp of mosquitoes in the area. The mosquitoes have become more resistant and even the fogging does not work on them. I have never thought of closing the windows at 4 pm or using mosquito repellants at our homes for that matter. Now, we keep all the doors and windows shut as the mosquito can be found even during the day time,” says Jayanthi Premchandar.

With the Buckingham Canal being the major source of a breeding ground for mosquitoes, areas like Gandhi Nagar have seen an increase in mosquitoes, points out Meera Ravikumar.

“The construction of stormwater drains, in which sewage flows now, has only worsened the situation. It has become a major challenge for children, especially those who appear for board exams, as they either fall sick often or could not have a good night’s sleep,” says Meera.

Placing the onus on residents, R Kanagaraj, President of AGS Colony Residents Welfare Association, says that the public should first segregate the household wastes before giving them away to the sanitary workers or throwing them away in the bins.

“Mosquitoes breed only in unsanitary places and we, as citizens, have the responsibility to keep our surroundings clean,” says Kanagaraj.

While the issue of improper disposal of waste, unclean water bodies and open drains continue to be present throughout the year, a key reason given by the local body for the rise in number of mosquitoes is the unexpectedly low temperature during the night and early mornings in Chennai, which has become conducive for mosquito breeding.

Read more: What makes it hard to manage waste in the Koyambedu market?

Is climate change a reason for the mosquito menace in Chennai?

Every year, the GCC receives the highest number of public complaints about mosquitoes in November and December months. They used to receive more than 1,200 complaints a month during monsoon. It usually reduces in January and February.

“After January there should have been a temperature change but it seemed to have continued to remain at levels that are almost the same as the monsoon. The temperature is very low during the night and the mornings continue to be misty in Chennai. While the temperature should have touched 27°C to 28°C by now, the minimum temperature hovers between 21°C and 24°C. This not only becomes a favourable condition for mosquitoes to breed but also increases its longevity,” says S Selvakumar, Chief Vector Control Officer of GCC.

Explaining the challenges further, he says, “If the lifetime of a mosquito is 21 days, the low temperature increases the lifetime to 28 to 30 days. By this time, another fresh batch of mosquitoes would have matured. Now the challenge is in controlling the adult mosquitoes.”

Steps by GCC to addressing mosquito menace in Chennai

To address the issue of mosquitoes and vector-borne diseases in Chennai, the GCC has initiated a drive to control the existing adult mosquitoes, says Selvakumar.

We have carried out fogging in the entire stretch of the stormwater drain which is around 2,100 km. At points of water stagnation in the stormwater drains, we have also been spraying the mosquito larvicides. As many as 68 vehicle-mounted fogging machines and 240 hand-held fogging machines are being used in addition to the use of drones to spray the larvicides on the 247 kilometres of river stretches and the canals for the third round,” he says, adding that the larval density has reduced considerably.

The number of mosquitoes will eventually reduce in the coming days but exterminating the existing adult mosquitoes is a challenge for the civic body at present.

“This apart, in areas like North Chennai where people hardly raise the complaints, we are coordinating with the respective councillors,” says Selvakumar .

Acknowledging the mixing of sewage in stormwater drains, Selvakumar, also says that the engineering department of the GCC has plugged around 1,400 illegal sewage connections in the past two weeks.

“In low-lying areas, the metro water manuals are also connected to the stormwater drains. When the water becomes full in the manual, it drains into the stormwater drains. This is yet another challenge and we are coordinating with the Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) to address this issue,” he says.

Selvakumar says that the GCC has been using bio larvicides in water bodies in which the water quality was good and those that have fish breeding in it, while the chemical larvicides are used in polluted water bodies.

While GCC’s role in controlling the mosquito menace has some limitations, it is also the responsibility of the PWD to ensure the canals and rivers are clean. Besides, the CMWSSB also has the responsibility to ensure the sewage is not mixed into the stormwater drains.

An interdepartmental approach is the need of the hour, say the residents hit hardest by the issue.

Permanent fix for mosquito menace necessary

Noting that the measures taken by the GCC have been cosmetic, Meera points out that the larvicides used to spray on the water bodies are chemicals.

“At times when the groundwater is already contaminated and dipping, the government should rather take an environmentally friendly approach like garlic spray to control the mosquito menace in Chennai,” she says.

There are 32 natural canals and three rivers in Chennai. Drainage water flows through all these water bodies. Had clean water flowed through these water bodies, the mosquito menace would have been prevented. Since the drainage flows through these water bodies now, the mosquitoes have been able to thrive.

“When complaints are raised, the corporation workers fog in the area or spray some liquid pesticides to control the mosquito population. However, this is not effective enough and a temporary measure,” says Harris.

Infrastructural changes are needed in the long run to prevent largescale breeding of mosquitoes.

“The government should ensure that the drainage water does not get discharged into the water bodies and rivers. Each street should have an underground drainage system. Solid waste should be handled properly. These are the infrastructural needs we need not only to prevent mosquito menace but also to help in better water management,” says Harris, adding that realistic plans should be made for this.

For instance, if 1,000 streets in Chennai have open drainage, then the local body could target to provide underground drainage for 200 to 300 streets in a year. In the next couple of years, they could complete the works for all 1,000 streets.

“When such infrastructural works are carried out, the increasing population should also be taken into account and the investment should be made in a way that the infrastructure is built for the next 50 years,” says Harris.

The planned execution of infrastructural works in line with an environmentally friendly approach to cleaning the water bodies will go a long way in controlling the mosquito population in Chennai.

(*name changed on request)

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