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Vol. XXXII No. 21, February 16-28, 2023
It is usually the rainy seasons that bring forth mosquitoes, but Chennai is troubled by an unusual infestation that shows no signs of waning, even months later in February. Areas adjoining water bodies tend to be affected the most, but the current scenario seems to buck this trend, too – no place it seems, public or private, adjacent to water bodies or otherwise, is spared the scourge of mosquitoes. While there has not been a particularly notable increase in dengue cases, experts worry that the disease is no longer a seasonal illness as it was a mere five years ago, but a chronic one present throughout the year. There has also been a fractional increase in malaria, a disease spread by the Anopheles mosquito; while the case numbers are low at present, it is feared that this could foreshadow a bigger spike.
The Hindu quotes Mr. B. Dhanraj, who retired from the Corporation as the Chief Vector Control Officer, as explaining that waterways account for 50 per cent of the mosquito population, stormwater drains 40 per cent and domestic spaces, 10 per cent. Significantly, it is the SWDs that are now reported to be responsible for an influx of Culex mosquitoes that thrive in the sewage water present in the stormwater drains and canals. Tondiarpet, Old Washermanpet, Korukkupet and Mint alongside the Buckingham Canal are said to be the worst affected by the presence of Culex mosquitoes. A study conducted by the authorities found the presence of 10 larvae of culex mosquitoes per dip compared to 2 per dip of the Aedes variety that breeds in fresh water. In a quote to the Times of India, virologist T. Jacob John said, “The value should be zero. Culex grows in sewage water. This shows we live in a dirty environment. Culex can transmit deadly viral infections like Japanese encephalitis (JE) and West Nile infection.”
There are other factors worsening the problem at hand – plots lying vacant or under construction are turning into breeding grounds, as is the indisciplined dumping of household waste. It was just in October last year that a city-wide study identified over 10,000 houses – largely from Tondiarpet, Royapuram and Central Chennai – to be directly responsible for breeding mosquitoes due to untended stagnant water on the premises. Revised fines for mosquito breeding were imposed at the time, with authorities reportedly empowered to levy penalties on both residential and commercial properties. Given the circumstances today, perhaps the findings should have triggered a more intensive, focused study into the problem.
As it stands, several areas in the city have raised complaints that fogging operations have either lapsed or reduced in frequency despite the severity of the issue. The Corporation seems to be reacting on a war footing. Six drones have been deployed along waterways such as the Cooum and the Buckingham Canal to spray repellants; repellant balls and bottles filled with repellant oils have been introduced to kill larvae in the water. Commissioner Gagandeep Singh Bedi announced that fogging will be doubled as well, with operations to be conducted both in the morning and evening. The Corporation is gearing up its resources for the challenge – it is reported to have on stand-by 3,200 malaria staff, 229 hand-operating fog machines, eight smaller machines, 412 hand-operated insecticide sprayers, 67 vehicle-mounted fumigations and 10 boats to spray waterways. The next ten days, they say, are crucial to cull the problem.
The question arises, however – are there other solutions the city can explore? After all, unpredictable seasonal changes suggest that mosquito proliferation may well be a long-term or chronic civic challenge. Science has shown that innovative solutions can better battle this menace. Singapore’s Project Wolbachia, for instance, releases non-infectious male mosquitoes carrying the Wolbachia bacteria to control the breeding of the Aedes Aegypti – eggs resulting from the mating of these males with females are infertile and do not hatch. A similar solution has been mooted in India too. Oxitec Ltd – a UK-based biotech company – proposes to execute an anti-Aedes Aegypti project in Maharashtra which will release genetically modified mosquitoes whose larvae will overproduce protein and kill them before they reach adulthood. The idea is not new to Chennai. Such measures were under consideration as far back as 2016 but were dropped in favour of using repellents instead, for fear that the plan may not work over a large terrain. With successful case studies on hand, perhaps it is time to reconsider this scientific measure for vector control.