Why mosquitoes get attracted towards us
Last Updated: Thursday, December 31, 2009, 00:00

Washington: Do you know why mosquitoes get
attracted towards us? American scientists have found that
humans and birds produce a dominant odour that invites the
blood-sucking insects.

The discovery by scientists at the University of
California, Davis, explained why mosquitoes shifted hosts from
birds to humans and paves the way for key developments in
mosquito and disease control.

The team said they identified the dominant odour --
nonanal -- which naturally produced in humans and birds that
attracts the blood-feeding mosquitoes like Culex, which
transmit West Nile virus and other life-threatening diseases.

The groundbreaking research, published in the journal
of Proceedings of the National Academy of Sciences, showed
that nonanal is the powerful semiochemical, a chemical
substance that carries a message, that triggers the
mosquitoes` keen sense of smell, directing them toward a blood

Authors Walter Leal and Zain Syed said, "Nonanal is how
they find us. The antennae of the Culex are highly developed
to detect even extremely low concentrations of the chemical".

Mosquitoes detect smells with the olfactory receptor
neurons of their antennae, the Science Daily said.

Leal said, "Birds, the main hosts of mosquitoes, serve
as the reservoir for the West Nile virus. When infected
mosquitoes take a blood meal, they transmit the virus to their
hosts, which include birds, humans, horses, dogs, cats, bats,
chipmunks, skunks, squirrels and domestic rabbits".

The researchers tested hundreds of naturally occurring
compounds emitted by people and birds. They collected chemical
odours from 16 adult human subjects, representing multiple
races and ethnic groups.

"We then determined the specificity and sensitivity of
the olfactory receptor neurons to the isolated compounds on
the antennae of the mosquitoes," Syed said, adding "we found
nonanal acts synergistically with carbon dioxide, a known
mosquito attractant".

He said, "We baited mosquito traps with a combination
of nonanal and carbon dioxide and we were drawing in as many
as 2,000 a night in Yolo County, near Davis".

"Nonanal, in combination with carbon dioxide, increased
trap captures by more than 50 percent, compared to traps
baited with carbon dioxide alone," he added.


First Published: Thursday, December 31, 2009, 00:00

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