These blood-sucking insects can be picky about ‘food’, say experts
Eveline Gan, Today Online 1 Jul 08;
BLOOD-SUCKING mosquitoes can’t seem to get enough of18-year-old Aza Wee.
A self-professed mosquito magnet, the Serangoon Junior College student said that she tends to be bitten by mosquitoes more frequently than others.
“Wherever I go, I always get bitten,” said Aza.
“If I open the windows, I’ll get bitten almost immediately.My younger sister sleeps in the same room, but she doesn’t have this problem.”
Is Aza’s problem a figment of her imagination? Apparently not.
Like fussy eaters, mosquitoes do display dining preferences,according to experts. This explains why some unfortunate people, such as Aza, may get bitten more frequently than others.
Your natural body odour could be responsible for that barrage of mosquito bites.
“Some people may attract more mosquitoes than others based on how they ‘smell’ to a mosquito,” said Associate Professor Annelies Wilder-Smith, an associate consultant at the National University Hospital’s department of medicine, division of infectious diseases.
“Body odours such as 1-octen-3-ol seem to attract mosquitoes ... but nobody knows how to influence or reduce the amount of this chemical in our body,” she said.
A National Environment Agency (NEA) spokesman told Today that human body odours are “distinctive and specific, and varies from person to person”.
He added: “These differences are believed to be responsible for the uneven biting rates.”
Sweaty people may also get targeted more often by mosquitoes. “Human sweat contains volatiles such as lactic acid and ammonia, which attract mosquitoes. The number of sweat glands present in a person’s body varies, which is why some people tend to perspire more and thus, are more attractive to mosquitoes,” said the spokesman.
He said a higher body mass and higher body temperature may also make a person more attractive to mosquitoes. Being in a place with high humidity also increases the chance of being bitten.
And it’s not all about body chemistry. What you wear may also cause you to look more delicious to some mosquitoes which bite in the day (Aedes mosquitoes are day-feeders with a peak biting period at dusk and dawn).
“People who wear dark-coloured clothes tend to attract more diurnal mosquitoes than those wearing light-coloured ones because these species have been found to respond to visual cues as well,” he said. Diurnal mosquitoes refer to those that feed in the day.
According to Assoc Prof Wilder-Smith, mosquitoes can track potential prey from “tens of metres” away.
“Mosquitoes hunt by detecting carbon dioxide being breathed out from a distance. When they get closer, they can also pick up on the infrared heat being emitted, which identifies the host as a warm-blooded animal,” she explained.
For some people, the problem may stem from their reactions to the bites rather than their attractiveness to mosquitoes, said Assoc Prof Wilder-Smith.
People who are hyper-sensitive to mosquito bites may notice them more and think they get bitten more often, she explained.
“People have a variety of reactions to mosquito bites, and the symptoms change over time, depending on the amount of bites a person has received. These reactions tend to decrease in frequency after one has been bitten by mosquitoes over many years,” said Assoc Prof Wilder-Smith.
“Some adults can become desensitised to mosquitoes and have little or no reaction to their bites, while others can become hyper-sensitive with bites causing blistering, bruising and large inflammatory reactions.”
If you’re one of those unfortunate mosquito magnets, you can minimise bites with a few measures.
Chemical-based repellents have been shown to be superior over natural repellents, said Assoc Prof Wilder-Smith.
Other less commonly used natural mosquito repellents include catnip oil extract, citronella, and eucalyptus oil extract.
The NEA spokesman recommended wearing long-sleeved clothing and pants, and sleeping under a mosquito net.
“In places within your control, such as your home, mosquito breeding should be avoided by removing any potential breeding habitat,” he added.
the Aedes are day-hunters
The mosquitoes responsible for dengue, the Aedes aegypti and the Aedes albopictus, are typically early-morning and early-evening feeders.
“During the heat of the day, the mosquitoes rest in a cool place and wait for evening. They may still bite if they’re disturbed though. On cloudy days, they can feed through the day,” said Assoc Prof Wilder-Smith.
According to the NEA, these two mosquito breeds can also transmit the chikungunya virus, which surfaced here earlier this year. Similar to dengue, its symptoms include fever, headache, fatigue, nausea, vomiting, muscle ache, rash and joint pain.
Over 2,700 dengue cases have been recorded this year.
