Chikungunya epidemic of the season: officials

Ramya Kannan | 24 Aug 2023
The Hindu

CHENNAI: The city is under assault from the air, with swarms of mosquitoes hovering around and swooping down on the citizens of Chennai.

Officially, the breeding season has started, not only in Chennai but the entire State. After the first few showers, mosquito breeding is rampant, public health officials said. There is a difference though, this year: The dengue-chikungunya spreading mosquito Aedes aegypti is multiplying in abnormally high numbers.

In a sample of 100 larvae, the regular malaria causing anopheles mosquito larvae is only one or two, public health department studies have revealed. The density of Aedes aegypti however is 60 per cent higher than last year. Which makes chikungunya — not malaria, not filarial — the epidemic of the season. Chikungunya is transmitted by the bite of the infected female Aedes aegypti mosquito.

According to figures last presented during the health department demand in the Assembly on August 17, 49,567 persons were treated for chikungunya in the State, while blood tests confirmed 618 cases only. In the Chennai Corporation zone, 3,283 `suspected' cases of chikungunya have been detected.

Even though the epidemic is on the wane, the health officials admit that it seems to have eclipsed other diseases normally occurring in epidemic proportions during this time of the year — malaria and dengue.

But high on the list of residents remains the desire to be rid of the mosquito bites. Will fogging and using larvicides help? "Yes, but only temporarily," a top public health official said. "It will only result in a transient reduction of the number of mosquitoes. The permanent solution is to eliminate the sources of breeding." Which in the case of the Aedes aegypti and Anopheles mosquitoes, is fresh, unpolluted water, he explained.

This mostly comprises overhead tanks or containers of water stored within or just outside homes. "The Aedes mosquito is like a pet dog. It only bites those who allow it to breed. It does not travel very far, tries to find its meal in the vicinity of its original breeding ground," he explains.

Community participation

While fogging and larvicide spraying will be continued as usual, public health experts have also called for the community's involvement to bring down mosquito breeding.

Regular cleaning of overhead tanks, spraying of larvicide on non-potable drinking water collection sites are a must at the local level for the purpose. Public health officials have a plan chalked out for rural areas — intensive monitoring and spraying of domestic water collection sources for a month — but admit that it will be more difficult in the urban centres, where reaching out to individual households is a difficult task.

They are clear that for the operations to succeed, the co-operation of residents is essential, especially since `domestic breeding' will increase once the monsoon begins.