Why do mosquito bites itch by alendar


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									                           LIFE AND LIVING

    Why do mosquito bites itch?
I n t ro d u c t i o n
What is the most dangerous thing alive?
Some might say snakes or scorpions. Maybe
some will suggest a tiger. How about insects?             Lots of people have helped us understand
What insect can harm us the most? Maybe a              more about mosquitoes. Esmond Keogh
wasp, a bee, or perhaps a bull-ant.                    (1895-1970) was researching malaria during
                                                       the Second World War when lots of soldiers
    In fact, one of the most dangerous things          were infected. Why would soldiers be easily
alive must be the mosquito. Who has been               infected? Because they were sent to countries
bitten by a mosquito? What harm did it do?             where there were lots of disease-carrying
Just an itchy swelling? What causes the itch?          mosquitoes and the soldiers had not been
That doesn’t happen when you prick your                able to build up any resistance to the disease.
finger on a pin. The difference between a
pin prick and a mosquito bite is that the                 We don’t get malaria in Australia, but our
mosquito has injected some of its saliva into          mosquitoes do spread Ross River fever and
you to stop your blood clotting around its             the more serious encephalitis, which can be
sharp proboscis. So every time a female                spread by some types of mosquitoes. The best
mosquito sucks out a little bit of your blood,         way to avoid these diseases is to avoid being
it leaves behind some of its saliva. There can         bitten.
be some nasty things in that saliva because
mosquitoes can easily pick up diseases from
the blood of other animals or people.                                       S
                                                       Investigation One
B a c k g ro u n d
Mosquitoes have caused the deaths of                   Mozzie Bite Magn i fication
millions of people through the spread of                     You will need
malaria and yellow fever. Malaria is still one               A hand lens
of the world’s biggest killers. The disease                  Insect specimens
causes a high fever that keeps returning. 200
                                                       Use a microscope to investigate what a
million people develop malaria each year.
                                                       mosquito uses to bite us. Compare a
Malaria has mostly been wiped out from large
                                                       mosquito proboscis with those of a bee
city areas, but still thrives in parts of Asia,
                                                       and a moth or butterfly. Use the specimens
Africa and South America.
                                                       provided to sketch the differences. Notice
   The most effective way to control the               how the moths and butterflies roll up their
disease is to control mosquitoes. But how do           long proboscis that they use to reach the
we do that? We need scientists to help us find         nectar within a flower. Mosquitoes also feed
out more about mosquitoes – where they                 on the sugar in plants. Females of some types
breed; what type of weather they like most;
                                                       must have a meal of blood before they lay
what poisons have the most effect on
                                                       each batch of eggs.
mosquitoes without damaging the
environment too much.

                                 Why do mosquito bites itch?

Investigation Tw o                                          Investigation Thre e
Mozzie Wr iggle r                                           D ip netting
       You will need                                               You will need
       Pond water containing wrigglers                             Nets and containers
Study some baby mosquitoes in some water                    Investigating the life cycle of a mosquito isn’t
in a glass dish. They live and feed under                   very hard because there are usually some in
water but cannot breathe underwater. They                   any water lying around. You can collect them
have a siphon like a snorkel at the end of                  by scooping through the water with a fine net
their body that they breathe through.                       or with an ice-cream container.
    They have to keep wriggling back to the                    Test different places around you with your
surface to breathe. There are four stages in                net or container and mark on a map any
the mosquito’s life. The eggs are laid on little            places where you find examples from a
rafts that float on the water for two to three              mosquito’s life cycle.
days before hatching into the wriggling
larvae. After a week, the larvae grow into
larger pupae from which the mosquitoes
emerge a few days later.

E s mond Ke ogh                    Bullets, shells and bombs are not the only bringers of death
                                   in war. Disease also takes a terrible toll. The work of medical
                               scientists, such as Esmond Keogh, dramatically reduced Australian
                  casualties in World War 2, helping to ensure victory by the Allied forces.
     Keogh started the war as a pathologist attached to the 2/2 Australian General Hospital,
stationed at Gaza and then Kantara, near the Suez Canal, but within a few years was the
Director of Hygiene and Pathology for the whole Australian Army. While in the Middle
East, he investigated diseases such as dysentery, typhoid and malaria, and set up a blood
transfusion service.
   The danger of malaria was revealed in late 1942, when Australian forces were defending
Milne Bay in New Guinea. In one week alone, 1083 soldiers out of a 12 000 strong
contingent were admitted to hospital with the disease. Such losses could not be allowed to
continue. Keogh and others set about the establishment of a Medical Research Unit in
Cairns, where anti-malarial drugs were tested. Eventually, the drug atrebin was shown to be
effective and was prescribed for the armed forces. Others were undertaking research into
safe methods for blood transfusion in malarial regions. Their combined scientific effort was
successful. The number of cases of malaria dropped dramatically.
   It is ironic that at this time of destruction, the Pacific War (1940s) accelerated medical
research in a number of areas, including the production of the ‘wonder drug’ penicillin.
Source: Adapted from the website http://www.asap.unimelb.edu.au/bsparcs/exhib/journal/as_keogh.htm

                          Why do mosquito bites itch?

RECORD SHEETS                                  Your Name ________________________
Investigation 1                 Mozzie Bite Magn i fication

                       Sketch            Shape of            Main features
                                         Mouthparts          of Mouthparts


 Moth or Butterfly



 Your Comments _____________________________________________________________________


RECORD SHEETS                                  Your Name ________________________
Investigation 1                 D ip Netting

                     Mosquito Egg    Mosquito Larvae Mosquito Pupae    Other Water
 Dip Netting         Rafts           or Wrigglers                      Insects

 First Location

 Second Location

 Third Location

                              Why do mosquito bites itch?

                              Review Activities
                        ® Unjumble these words about Esmond Keogh

AAALIRM                 __ __ __ __ __ __ __

DOOBL                   __ __ __ __ __

SEERRHCA                __ __ __ __ __ __ __ __

GADERN                  __ __ __ __ __ __

TIPLAHOS                __ __ __ __ __ __ __ __

SSSUULCCFE              __ __ __ __ __ __ __ __ __ __

(Answers: malaria, blood, research, danger, hospital, successful)

               ® Join these Esmond Keogh words end to end with the last letter of
                                   each word starting the next:

(start) KEOGH           RESEARCH                MALARIA               EFFORT

IDENTIFIES              SCIENTIFIC              HYGIENE               TYPHOID

CARE                    HARM                    LIKE                  ANTIMALARIAL

AUSTRALIA               (and lastly) KEOGH

Find these words from the biography of Esmond Keogh:
                                                  U __ __ __ __ __ __ __ __ N
M __ __ __ __ __ A
                                                  I __ __ __ __ __ __ __ T
O __ __ __ T
                                                  T __ __ __ __ __ __ __ __ __ N
S __ __ __ __ __ __ __ __ L
                                                  O __ __ R
Q F __ __ __ __

Key Learning Are a s
Science         Research the life cycle of a mosquito.
English         Imagine you are a mosquito. Tell your mosquito parents how you have spent your
                day in a short story called “One Day in My Life as a Mosquito”.


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