The mosquitoes are back in full-form, bringing with them vector-borne diseases. While dengue has turned out to be the deadliest of the season—two children have already succumbed to the disease in the past week—there are other vector-borne diseases that one should be wary of, warn doctors.

While the health department may be under the impression that filariasis has been eliminated, general practitioners report that the its transmission is still on.

“Studies conducted by the Indian Public Health Association have revealed that blood antigenemia, which are antibodies against the infection, are still high among the general public,” explains Dr S Elango, president, Indian Public Health association.

“Filariasis has been termed a ‘neglected tropical disease’ by the WHO. It is not picked up as the symptoms are quite erratic—it may take years for symptoms to show,” he adds, pointing out that the activity of the culex mosquito that acts as the transmitter of the parasite causing the disease, is now at its highest level.

While the breeding of mosquitoes has stumped health authorities for many years now, cases of dengue and malaria and also a high-risk zone for chikungunya and filariasis have been reported, and it is high time that the state government looked outside its borders for help, avers Dr Elango.

“The health departments of Kerala, TN, Andhra Pradesh and Karnataka should meet and discuss anti-dengue strategies together,” he suggests.

Repellants fail to combat mosquitoes

Don’t waste money on mosquito sprays, mats and coils—doctors have said mosquitoes are resistant to all these repellants, which may end up causing more harm than the perceived benefits.

After decades of being exposed to a cocktail of chemicals from insecticides, most mosquito species have become hard-nosed; they have not only developed a thicker outer cuticle to protect themselves from these repellants, but also produce enzymes to neutralise them.

“We have been repelling mosquitoes with the same chemicals till now and as these insects are highly adaptable, they have developed resistance even to strong insecticides like DDT.

“There is just one group of insecticides now in use, that is still effective against mosquitoes—the pyrethroid group, which are used for fogging operations,” says Dr B.K. Tyagi, director of the Centre for Research in Medical entomology in Madurai.

The pyrethroids however can cause allergies and rashes, and also mess up the endocrine system and interfere with the production of hormones.

The latest Internet fad among Chennaiites is the do-it-yourself mosquito trap, using ‘sugar-baits’.
“There are several models of mosquito-traps developed and tested by the Bill and Melinda Gates Foundation featured on the internet.

We tried a simple one at home, and for the past two weeks, there has been a distinct dip in the mosquito menace,” says Adambakkam resident Ramanathan C.K.

“The trap is made of a plastic bottle, with a solution of sugar and yeast in it.

The sugar and yeast ferment to produce carbon-di-oxide, which attracts the female mosquitoes into the small opening in the bottle. Once they fall in, most of them drown,” he explains.

“Mosquitoes stalk their victims by the scent of carbon-di-oxide; naturally such traps are viable. However, the more effective traps require some strong toxins to be mixed in this water , and it is not advisable to handle such poisonous substances in a home environment,” warns Dr Tyagi. “ The easiest method of controlling vector-borne diseases is to remove all garbage from around the house.

“Even a few ml of water collected in a plastic cover, a paper cup or an old slipper will suffice for dengue mosquitoes to breed; and it is each individual’s responsibility to get rid of such litter, to keep the locality disease-free,” he says.