Mosquitoes everywhere in north Chennai

Survey finds high density of non-disease spreading Armigeres species; bites a nuisance

A sample survey undertaken by the Indian Public Health Association (IPHA), Tamil Nadu chapter, on mosquito species in the city revealed a high density of the Armigeres species in several pockets of north Chennai.

These mosquitoes, unlike the female Anopheles and Aedes mosquitoes, do not transmit diseases. However, their bites are painful.

The entomology wing of IPHA (TN) — a professional association for public health specialists and workforce — took samples of mosquito species found across the city over a period of two-and-a-half months ending November 15. An analysis of the samples revealed a high prevalence of Armigeres mosquitoes, which do not transmit diseases but are a nuisance, said S. Elango, president of the chapter.

These mosquitoes were found in abundance in several parts of north Chennai, including Korukkupet, Washermenpet, Otteri, Mint, Pulianthope, Vyasarpadi, Pattalam, Tondiarpet and Kasimedu, he said.

“These mosquitoes breed in septic tanks and in piles of sewage. At some places, rain water that has stagnated for more than 10 days could end up mixing with overflowing sewage. Such pools could turn into breeding sources leading to more of these mosquitoes coming up,” Dr. Elango said.

“The Armigeres mosquitoes are a little bigger than the usual ones. They are six millimetres long and have a flying distance of 500 to 750 metres. They can fly up to 500 metres high. They also make some kind of a noise which can disrupt sleep, especially that of infants,” he added.

Entomologists say these mosquitoes enter septic tanks through open vents and can breed in lakhs. “The bites of these mosquitoes are painful. They are active from 6 to 7 p.m.,” an entomologist said.

B. Dhanraj, former chief vector control officer of Chennai Corporation, said a gap of 1.5 mm is enough for these mosquitoes to gain entry into septic tanks.

“The Armigeres mosquitoes breed in sewage and in places that are highly contaminated by human excreta. To prevent them from breeding, the lids of all septic tanks should not have any crevices. Vent pipes should also be covered with a mosquito mesh,” he said.

Entomologists said sewage overflow should be cleared immediately and debris or soil could be dumped on stagnant pools. Fogging will also help, as it can destroy the adult Armigeres mosquito population and anti-larval measures should also be taken up, they say.