3. The mosquito goes through four separate and distinct stages of its life cycle and they
are as follows: Egg, Larva, pupa, and adult. Each of these stages can be easily
recognized by their special appearance. There are four common groups of mosquitoes
living in the Bay Area. They are Aedes, Anopheles, Culex, and Culiseta.
Egg : Eggs are laid one at a time and they float on the surface of
the water. In the case of Culex and Culiseta species, the eggs are
stuck together in rafts of a hundred or more eggs. Anopheles and
Aedes species do not make egg rafts but lay their eggs
separately. Culex, Culiseta, and Anopheles lay their eggs on
water while Aedes lay their eggs on damp soil that will be flooded
by water. Most eggs hatch into larvae within 48 hours.
Larva : The larva (larvae - plural) live in the water and come to
the surface to breathe. They shed their skin four times growing
larger after each molting. Most larvae have siphon tubes for
breathing and hang from the water surface. Anopheles larvae do
not have a siphon and they lay parallel to the water surface. The
larva feed on micro-organisms and organic matter in the water.
On the fourth molt the larva changes into a pupa.
4. Pupa: The pupal stage is a resting, non-feeding stage. This
is the time the mosquito turns into an adult. It takes about
two days before the adult is fully developed. When
development is complete, the pupal skin splits and the
mosquito emerges as an adult.
The egg, larvae and pupae stages depend on temperature and species characteristics as
to how long it takes for development. For instance, Culex tarsalis might go through its life
cycle in 14 days at 70 F and take only 10 days at 80 F. Also, some species have naturally
adapted to go through their entire life cycle in as little as four days or as long as one
month.
The following pages show a typical mosquito egg raft, larva, pupa, and adult, and explains
more about each stage.
Adult: The newly emerged adult rests on the surface of
the water for a short time to allow itself to dry and all its
parts to harden. Also, the wings have to spread out and
dry properly before it can fly
5. Mosquitoes can act as vectors for many disease-causing viruses and parasites. Infected
mosquitoes carry these organisms from person to person without exhibiting symptoms
themselves. Mosquito-borne diseases include:
âąViral diseases, such as yellow fever, dengue fever and chikungunya, transmitted
mostly by Aedes aegypti. Dengue fever is the most common cause of fever in travelers
returning from the Caribbean, Central America, and South Central Asia. This disease is
spread through the bites of infected mosquitoes and cannot be spread person to person.
âąSevere dengue can be fatal, but with good treatment, less than 1% of patients die from
dengue.
âąThe parasitic diseases collectively called malaria, caused by various species of
Plasmodium, carried by mosquitoes of the genus Anopheles
âąLymphatic filariasis (the main cause of elephantiasis) which can be spread by a wide
variety of mosquito species.
Diseases Caused by Mosquitoes
6. Malaria is caused by a parasite called
Plasmodium, which is transmitted via the bites of
infected mosquitoes. In the human body, the
parasites multiply in the liver, and then infect red
blood cells.
Symptoms of malaria include fever, headache, and
vomiting, and usually appear between 10 and 15
days after the mosquito bite. If not treated, malaria
can quickly become life-threatening by disrupting
the blood supply to vital organs. In many parts of
the world, the parasites have developed resistance
to a number of malaria medicines.
Key interventions to control malaria include:
prompt and effective treatment with artemisinin-
based combination therapies; use of insecticidal
nets by people at risk; and indoor residual
spraying with insecticide to control the vector
MALARIA
8. FILARIA
Filariasis is a parasitic disease
transmitted by blood -feeding
arthropods, mainly black flies and
mosquitoes.
There are eight different types of
thread-like nematodes that cause
filariasis. Most cases of falaria are
caused by the parasite known
as Wuchereria bancrofti.
10. DENGUE
Dengue is transmitted by the bite
of an Aedes mosquito infected with
any one of the four dengue
viruses. It occurs in tropical and
sub-tropical areas of the world.
Symptoms appear 3â14 days
after the infective bite. Dengue
fever is a febrile illness that affects
infants, young children and adults.
12. Chikungunya
Chikungunya is a usually self-limiting
condition due to a virus. It is important to
exclude other dangerous conditions and
symptomatic treatment is usually advocated
Chikungunya is a relatively a rare viral fever
that is caused by the bite of a common
mosquito. Outbreaks have taken place in many
tropical countries. Recently it has resurfaced in
many parts of South India.
