The Times of India                           22.02.2013

Mosquito numbers up though dengue cases drop

CHENNAI: Though the Chennai Corporation has recorded only six cases of dengue
in the past month, reports suggest that more people have shown symptoms
of the disease. Though the civic body says it has taken measures to
control the spread of mosquitoes, its own statistics show that the
number of mosquitoes has risen compared to the same period last year.

The civic body measures mosquito density in different parts of the city
through the year. Between January 17 and 23, the civic body measured a
mosquito density of 72 in Royapuram. For January 24 to 30, the number is
64. Last years, for the same period the corporation numbers stand at
48.

Royapuram is not the only zone that has seen an increase.
Tondiarpet, Teynampet and Anna Nagar too have recorded an increase.
Between January 17 and 23, the density in Anna Nagar recorded was 64 and
between January 24 and 30, it stood at 56, which is far higher than the
40 recorded during the same period last year.

However, experts
say the corporation cannot entirely be blamed for the increase in
mosquitoes. “A reason for the rise is the lack of rain last year,” says
Dr S Elango, former directorate of public health and president of Public Health Association of India.
“Even Cyclone Nilam did not bring much rain,” he says. Though heavy
rain causes water logging and mosquito breeding, infrequent rain also
contributes.

“Canal banks are the main spot for larval
breeding,” says a senior entomologist in the health department. “When it
rains heavily, the water in the canals flows extremely fast, washing
away the eggs laid by mosquitoes. So mosquito density drops during and
just after rain,” he says.

Experts say the civic body should
have foreseen this issue and stepped up its mosquito prevention efforts.
“The officials at the civic body know how the upcoming season will be,”
says Elango. “They could have stepped up activities for fogging and
destruction of breeding sources.”

In some zones such as
Tiruvottriyur, Manali and Kodambakkam, the mosquito density between
January 17 and 23 was 56, 48 and 56 respectively. “These are the same
numbers recorded last year, no increase,” said a corporation official.

The corporation recently said that the number of dengue cases has
reduced drastically in the last few months compared to the same period
last year. They said January’s six cases is a fraction of the 40 dengue
cases recorded during the same period last year. In December 2012 too
only five cases were reported compared to 40 cases during the same
period in 2011.

Officials say they have taken steps to remove
domestic breeding sources such as plastic cups, buckets, drums, coconut
shells and grinding stones. They also carry out intensive fogging
operations every Tuesday.