The Hindu 06.01.2010
Earning a living out of mosquito collection
G. Mohan, an insect collector of the Chennai Corporation, in Kotturpuram on Wednesday. — Photo: M.Karunakaran
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.