Read the passage below. Use the information in the passage and your own
knowledge to answer the questions that follow.
Mosquitoes and the Zika virus
More than a million people die each year from pathogens spread by mosquitoes.
These pathogens are responsible for causing diseases such as malaria, dengue
fever and yellow fever. The pathogens are spread when a female mosquito feeds
on the blood of an infected person and then flies away to bite another person.
Male mosquitoes do not bite humans.
The Zika virus is also spread by mosquitoes. Recently, this virus has been linked
to a significant increase in the number of babies born with microcephaly in
Brazil. Microcephaly is a condition in which the brain does not develop normally.
The Zika virus can pass from the mother to the developing fetus and babies are
born with a smaller head than usual.
There is no medicine or vaccine to treat people infected with the Zika virus. People
are encouraged to hang mosquito nets over their beds, and also to use other methods
to avoid being bitten by mosquitoes. Some people believe it would be simpler to solve
the problem by specicide. The extinction of 30 disease-carrying mosquito species would
save many lives.
Scientists have genetically modified (GM) the males of the mosquito species,
Aedes aegypti, which carries the Zika virus. These GM males carry a gene that
harms their offspring. The offspring die before they can reproduce and spread
disease. About three million of these GM mosquitoes were released at a site on
the Cayman Islands between 2009 and 2010. Scientists reported a 96% reduction
in mosquitoes compared with nearby areas. Scientists have also tried releasing
large numbers of sterile male mosquitoes to reduce the spread of disease.
Mosquito eradication may affect food chains. Mosquitoes that feed mainly on
plant nectar are important pollinators. Mosquitoes are also a food source for
birds and bats, while mosquito larvae are eaten by fish and frogs.
Rainforests contain a large number of plant and animal species. These habitats
are under threat of deforestation. Some scientists believe that mosquitoes have
reduced this threat because mosquitoes make tropical rainforests almost
uninhabitable for humans.
Scientists in the UK are developing a sound sensor that can detect each different
species of mosquito from the noise made by its unique wing beat. They plan to
give people in rural Indonesia sound sensors to identify mosquitoes that carry
pathogens. The sound sensor triggers the release of insecticide, which helps to
reduce outbreaks of disease.