Did you know:
While there are more than 3500 species
of mosquitoes which feast on blood from a
range of hosts, including mammals, birds, reptiles,
amphibians, and fish, only female mosquitoes bite, primarily to
acquire protein for egg production. Male and female mosquitoes
feed on nectar or other forms of plant sugars for food.
你知道嗎：
雖然有超過3,500種類的蚊蟲，吸取的血液來自
不同的勳物，包括：哺乳類、鳥類、爬行動物和魚類等；不過，
只有雌蚊才會吸血，以取得產卵所須的蛋白質。雄蚊和雌蚊都是以花蜜或其他植物糖為食物。
As
residents of Hong Kong, we are all too
familiar with the infuriating little pests that feed on
our blood through their tube-like mouths. Not only
do they suck our blood, but they also leave behind
unwanted signatures in the form of itchy rashes on
the exposed skin of victims. Itchy welts are not even
the end of it. Mosquitoes are carriers of a number of
devastating diseases such as dengue fever, yellow
fever, and malaria. While some of us are busy
swatting away these nasty creatures in the summer
heat, others remain unfazed and unaffected.
Could it be that these pests are selective of their
victims?
With the large number of compounds to
examine, researchers have yet to pinpoint exactly
what factors mosquitoes use to determine their
ideal feeding target. There are, however, several
factors that may attract mosquitoes, including
carbon dioxide output, body temperature, and
body odour related chemical compounds [1].
We are more likely targets when participating in
physical activity, which increases our CO
2
output
and body temperature. In addition, expectant
mothers exhale 21% more CO
2
than the average
person and have a higher body temperature
around the navel, and is reported to be more
attractive targets for mosquitoes [2]. Another
study suggests that among humans who secrete
blood type substances on their skin
(approximately 76%
of the
population), mosquitoes seem to have a significant
preference for individuals with blood type O than
for people with blood type A, possibly due to the
release of chemical odourant markers [3,4].
Several chemosensory receptor families are
related to the ability of mosquitoes to sense odours.
Orco is an obligate co-receptor for one such family.
A recent study at The Rockefeller University used
genetically engineered
Aedes aegypti
mosquitoes
that lack the orco gene to study the effects of these
proteins on mosquitoes’ odour-sensing abilities.
Mosquitoes naturally feed on nectar to satisfy their
metabolic needs. However, the ones with mutated
orco genes lost their odour-sensing abilities and
were unable to distinguish between honey and
glycerol (glycerol has a similar viscosity to honey
but is odour less). In addition, cer tain species
of mosquitoes (
Aedes aegypti
and
Anopheles
gambiae
), which have a natural tendency toward
selecting human blood over other warm-blooded
vertebrae lost their evolutionary preference even
in the presence of CO
2
. Modified mosquitoes were
not attracted to human scent when no CO
2
was
present [5].
Resea rch i nto mosqu i to prefe rences a re
essential for curbing diseases such as dengue,
ye l l ow feve r, and ma l a r i a,
which are more devastating
i n devel opi ng count r ies.
T h e a b o v em e n t i o n e d
research does not aim to
release genetically
eng i nee red
Genetically Modified
Mos uitoes
By Jacqueline Aw
歐婷梅
