The gradual rise in temperatures over the past month has brought with it increased complaints of mosquito menace from residents’ welfare associations (RWAs), even as civic officials inspected 900,000 sites and issued 15,000 legal notices to curb the menace.
Officials of the municipality said most of the mosquitoes are of the Culex genus, which causes skin irritation, but acknowledged that April provided favourable breeding conditions and their increased density indicates water stagnation.
They have written to RWAs, market associations, government departments and institutions to tackle mosquito breeding and curb the spread of vector-borne diseases. They said around 4,600 workers are undertaking anti-mosquito drives.
RWAs raise concerns
Atul Goyal, the head of URJA United RWAs Joint Action, an umbrella RWA body, said that there has been a rapid rise in mosquitoes over the past few weeks, probably due to drains not being cleared.
“There are increasing complaints about mosquitoes from RWAs. Fogging is not the solution; civic agencies need to tackle the underlying cause of clogged drains and sanitation,” he said, adding that the mosquito menace is turning into a year-round problem in the Capital.
Ashok Bhasin, head of the North Delhi Residents Welfare Federation, said that areas along the Najafgarh drain are witnessing increased mosquito density. “The major drains have not been cleared, except the one towards Anand Parbat. Mosquitoes are turning out to be big irritants, especially during the night. Sanitation and poor state of drains are the underlying cause.”
BS Vohra, head of the East Delhi RWA Joint Front, concurred that larger drains not being cleared were leading to an increase in mosquitoes. “There is a clogged and dirty drain near Road 57, which is a hot spot for mosquito breeding. Agencies should take precautions early this year as Delhi witnessed many dengue cases last year,” he said.
Annual rise due to weather
A senior civic official, on condition of anonymity, said that April usually witnesses a steep increase in mosquito density due to favourable environmental conditions. “Mosquitoes need temperatures above 30°C, high humidity and stagnant water for breeding. After a period of relative dormancy during winter, an increase is annually witnessed in this period,” the official said.
This April has recorded only one day with a temperature above 40°C, but the rainfall deficit has kept the average around 37°C, which is 0.5°C over the long-period average.
“Most of the mosquitoes that are being detected in the city are of the Culex genus, which do not cause dengue, malaria and chikungunya. Culex mosquitoes cause skin irritation. Their high presence indicates a lot of stagnation and floating material in drains and water bodies. We are not detecting very high presence of disease-causing Anopheles genus, which causes malaria, and Aedes Aegypti genus that causes dengue and chikungunya,” the official said.
Vector-borne disease a year-round threat
On April 2, the municipal commissioner of Delhi wrote to RWAs, market associations and institutions warning that “the season of vector-borne diseases, such as malaria, dengue, chikungunya etc, in Delhi has started” and it has become imperative that all agencies concerned must take preventing measures. The letter cited unpredictable global climate changes for turning vector-borne diseases into a year-round occurrence.
The letter said reports were received regarding high-density mosquito breeding in coolers, overhead tanks, drums, cement haudis, drums and construction sites. MCD has asked institutions and RWAs to ensure that overhead tanks and containers are properly covered with tight lids and that overflow pipe vents are covered, water coolers are repaired, and pads are changed, scrubbed and condemned articles and containers are disposed of.
All institutions, schools and government departments were asked to appoint a nodal officer to oversee anti-mosquito measures on the premises.
The number of mosquito breeding sites detected this year is roughly around the same as in 2023, which witnessed 9,266 dengue cases and 19 deaths: the third worst outbreak of the viral infection in the city, according to annual data on mosquito-borne diseases. However, the severity of the outbreak is obscured as civic bodies have held back weekly data on vector-borne diseases since August 7, 2023, suspending a decades-old exercise that was hitherto conscientiously followed, even during the pandemic.
Action taken, breeding sites identified
Civic officials say that things are under control.
A second civic official said that around 13,000 houses were found to have mosquito breeding spots. “We have also issued more than 15,000 legal notices to owners of premises where favourable mosquito breeding conditions are detected. ’MCD 311’ app is being used to monitor the campaign,” the official said.
“Fogging is carried out in monsoon months. Tackling the source of the breeding is the only viable solution,” the official said.
A year-long mosquito breeding data analysis by the Municipal Corporation of Delhi shows that peri-domestic containers, such as money plants, vases, flower pots, bird pots, tins, tyres and fountain water account for the largest chunk of mosquito breeding sites, accounting for 38%. Domestic water storage containers (drums, buckets and jerry cans) that are usually used in water-stressed regions were a close second, accounting for 33% of breeding spots. Desert coolers, widely used in summer, and overhead water tanks, accounted for a majority of the rest.
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