He belongs to a group of persons whose occupation resembles the primitive occupation of hunting and gathering. But, he performs a crucial task in the city's civic life.
Early in the morning, 57-year-old G. Mohan quietly walks along the banks of the Buckingham Canal in Kotturpuram and enters a house nearby. Fifteen minutes later; he emerges successful from the house with live mosquitoes confined to a test tube.
“I am one of the few people collecting mosquitoes to make a living. I find it exciting,” beams, Mr. Mohan, who is one of the “insect collectors” employed by the Chennai Corporation. A suction tube, torchlight and test tube are what he carries with him for accomplishing his task. The mosquitoes are collected for calculating the adult mosquito density in all the 10 zones of the Corporation, he says.
“After I spot a mosquito at rest using torchlight, I suck air through the suction tube by placing it close to the mosquito. The mosquito that is trapped in the small net in the suction tube is then transferred to a test tube and sealed with cotton to keep it alive for lab testing,” says Mr.Mohan, who has been in the job for over three decades.
Workers like him also collect mosquito larvae for larval density calculation. The data complied at the Corporation laboratories by entomologists using their assistance remains crucial in tackling the vector borne diseases such as malaria, dengue, chikungunya and filaria by the civic body.
Entomologists at the laboratories also conduct tests by dissecting these mosquitoes to study the parasites carried by them for preventive action, said C. Kalaiamutha, senior entomologist of the civic body.
For instance, if the protozoan parasite Plasmodium falciparum is reported in a locality, the civic body will spray insecticide on war-footing in the locality as it is the most dangerous of malaria infections with the highest rates of complications and mortality.
Thus the lab study of mosquitoes throws light on the areas likely to be affected by an outbreak of the disease and helps in preventive measures by the Chennai Corporation.
But, insect collectors like Mr.Mohan say that they are able to predict an increase in the number of cases of malaria or dengue in a locality just by their observation of mosquitoes at a place for dawn and dusk collection.
“It is just common sense. If we find more male mosquitoes of a particular species in a house, there is a possibility of more breeding and more problems,” says Mr.Mohan.
In a residential locality the insect collectors select a fixed number of houses for collecting mosquito samples and categorise them by the species. The total number of mosquito collected divided by the total time spent in collection gives the adult density in the locality.
“Most of the residents show reluctance in permitting us in their house for collection of mosquitoes. Convincing them is a challenging task,” says R.Vijayarajan, another insect collector of the civic body.
“Areas such as George Town have a large number of closed godowns to which we have no access. This makes the task of collection of mosquitoes in the area tougher. Water collected in this area is breeding source of mosquitoes. So relatively more number of cases is reported here,” says he says.
Our observation during the course of our duty is that there is lack of awareness among residents about their role in control of vector-borne diseases, says Mr. Vijayarajan.