Mosquitoes
Tropical freshwater or brackish water environments are havens for mosquitoes.
Female mosquitoes require a blood meal (from humans or other animals) to develop
their eggs. In the process of taking a blood meal, mosquitoes may ingest pathogens
(e.g., the parasite causing malaria) from an infected person or animal. At the next
blood meal (mosquitoes go through various cycles of egg production), they then
inject the pathogen into the next person, and this will spread the disease. All mosquitoes go through an aquatic larval stage, but the exact ecological requirements vary
for the different species in different regions.
Two groups of mosquito-borne diseases are of particular public health importance
for those who visit areas where transmission takes place (so-called endemic areas):
malaria and arboviral diseases. (The HIV virus, which causes AIDS, is not transmitted by mosquitoes.)
Malaria is caused by one of four species of parasite belonging to the genus Plasmodium. Malaria parasites are transmitted by Anopheles mosquitoes. These mosquitoes bite between dusk and dawn. Their breeding places are generally in clean fresh
water, standing or slowly running, with some species breeding in brackish water
coastal lagoons. They never breed in polluted water. Unlike Culex mosquitoes (see
below), Anopheles mosquitoes do not produce the typical high-pitched buzz that is
part of the nuisance experienced in mosquito-infested areas. The position of the mosquito body with respect to the wall (at a 45-degree angle) when the insect is resting
is probably the easiest way to distinguish anopheline mosquitoes from culicine ones.
Arboviral diseases (arbo = arthropod-borne) are caused by infections that are exclusively transmitted by mosquitoes. They include yellow fever, dengue and various types
of encephalitis, such as Japanese encephalitis, when it is associated with flooded rice
fields in south, south-east and east Asia. Many of these infections, notably yellow
fever and Japanese encephalitis, are preventable by vaccination. For dengue fever (also
known as break-bone fever in some parts of the world) and its more severe variant,
dengue haemorrhagic fever, there is, however, no vaccine available.
The Aedes mosquitoes, which transmit the dengue virus, breed in small water collections in a human-made environment—hence the urban/human settlement associated distribution of the disease. While dengue haemorrhagic fever is an
important cause of death among children during outbreaks of the disease, classic
dengue is a much less severe but very debilitating disease lasting for 4–6 weeks.
Aedes mosquito species have black and white banded legs, and they (sometimes
ferociously) bite during daytime.
Culex mosquitoes, which breed in organically polluted water, are mainly known
for the transmission of filariasis (which can eventually develop into elephantiasis).
This disease is likely to develop only in people who have been exposed to infectious
bites for many years
Tropical freshwater or brackish water environments are havens for mosquitoes.
Female mosquitoes require a blood meal (from humans or other animals) to develop
their eggs. In the process of taking a blood meal, mosquitoes may ingest pathogens
(e.g., the parasite causing malaria) from an infected person or animal. At the next
blood meal (mosquitoes go through various cycles of egg production), they then
inject the pathogen into the next person, and this will spread the disease. All mosquitoes go through an aquatic larval stage, but the exact ecological requirements vary
for the different species in different regions.
Two groups of mosquito-borne diseases are of particular public health importance
for those who visit areas where transmission takes place (so-called endemic areas):
malaria and arboviral diseases. (The HIV virus, which causes AIDS, is not transmitted by mosquitoes.)
Malaria is caused by one of four species of parasite belonging to the genus Plasmodium. Malaria parasites are transmitted by Anopheles mosquitoes. These mosquitoes bite between dusk and dawn. Their breeding places are generally in clean fresh
water, standing or slowly running, with some species breeding in brackish water
coastal lagoons. They never breed in polluted water. Unlike Culex mosquitoes (see
below), Anopheles mosquitoes do not produce the typical high-pitched buzz that is
part of the nuisance experienced in mosquito-infested areas. The position of the mosquito body with respect to the wall (at a 45-degree angle) when the insect is resting
is probably the easiest way to distinguish anopheline mosquitoes from culicine ones.
Arboviral diseases (arbo = arthropod-borne) are caused by infections that are exclusively transmitted by mosquitoes. They include yellow fever, dengue and various types
of encephalitis, such as Japanese encephalitis, when it is associated with flooded rice
fields in south, south-east and east Asia. Many of these infections, notably yellow
fever and Japanese encephalitis, are preventable by vaccination. For dengue fever (also
known as break-bone fever in some parts of the world) and its more severe variant,
dengue haemorrhagic fever, there is, however, no vaccine available.
The Aedes mosquitoes, which transmit the dengue virus, breed in small water collections in a human-made environment—hence the urban/human settlement associated distribution of the disease. While dengue haemorrhagic fever is an
important cause of death among children during outbreaks of the disease, classic
dengue is a much less severe but very debilitating disease lasting for 4–6 weeks.
Aedes mosquito species have black and white banded legs, and they (sometimes
ferociously) bite during daytime.
Culex mosquitoes, which breed in organically polluted water, are mainly known
for the transmission of filariasis (which can eventually develop into elephantiasis).
This disease is likely to develop only in people who have been exposed to infectious
bites for many years
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