1. October 27, 2016
MOSQUITO ARMY
Scientists have been creating spe-
cially modified mosquitoes. They
plan to release millions of these
insects in parts of Colombia and
Brazil. It is hoped that this “mos-
quito army” will reduce the chanc-
es of people being infected with
viruses carried by mosquitoes.
These include: Zika, dengue fever
and chikungunya.
A mosquito called Aedes aegypti
spreads these viruses. This mosqui-
to originally lived in Africa. With
human help, it has spread to most
of the world’s tropical, or warmer,
regions. This mosquito can be easily
recognized by the white markings
on its legs and upper body.
Only female mosquitoes suck
blood. They need it to produce their
eggs. If a mosquito bites a person
who has the Zika, dengue or chi-
kungunya virus in their blood, it
becomes infected. These viruses do
not harm the mosquitoes. Yet the in-
sects can spread them to others. If
the mosquitoes bite and feed on oth-
er people, the virus can enter their
bloodstream. Once this happens, the
virus starts to replicate.
People infected with dengue or
chikungunya become very ill. They
suffer from headaches and fevers.
These illnesses are rarely fatal.
However, they can affect a person’s
health for many years. The Zika vi-
rus causes a different problem. Re-
searchers are now sure that this vi-
rus causes a birth defect, or disorder,
called microcephaly.
Aedes aegypti mosquito
People most at risk from the
Zika virus are expectant mothers.
If a woman gets the virus while
pregnant, her child may have the
disorder. New-born babies with mi-
crocephaly have small heads and
less developed brains. Some babies
with the defect die at a young age.
Others grow up with smaller heads,
but seem to be unaffected. However,
as they age, many suffer from learn-
ing troubles, speech difficulties and
health problems. There is no cure
for microcephaly.
The Zika virus was first discov-
ered in Africa nearly 70 years ago.
It was found in monkeys that lived
in Uganda’s Zika Forest. In 1954, a
person in Nigeria got the virus. This
was the first time that it had been
found in a human. Over the years,
the virus began to appear in other
countries. It does not make people
very ill. It was therefore thought to
be less serious than other mosquito-
carried diseases.
The Zika virus was first recorded
in Brazil 18 months ago. Virolo-
gists, or scientists who study virus-
es, tracked it. During the following
six months, the virus rapidly spread
throughout most of South America
and the Caribbean islands. Now,
Zika is present in over 50 countries.
Since 2015, 2,200 babies have been
born with microcephaly associated
with the Zika virus. Most, or 2,033,
are in Brazil.
The scientists have worked out
how to infect the Aedes aegypti
mosquito with a bacterium called
Wolbachia. This bacterium is found
in many other insect species. It
does not harm humans.
Wolbachia seems to improve a
mosquito’s immune system. It also
competes with any viruses inside
the insect. This means that the virus-
es cannot replicate so easily. There-
fore they are less likely to be passed
to humans. When a mosquito with
Wolbachia breeds, the bacterium is
passed onto its offspring.
Experiments, or trials, have been
carried out in small areas of Aus-
tralia, Vietnam, Indonesia, Colom-
bia, and Brazil. These have reduced
the spread of dengue fever. The
scientists’mosquito army will be re-
leased in large urban areas of Brazil
and Colombia early next year.
Preparatoria 1o.
