"Mosquito-borne disease and Life-threatening
disease. Control it Naturally & With Mosquito Net."
"The mosquitoes are a family of small, midge-like
flies: the Culicidae. Although a few species are harmless or even useful to
humanity, most are a nuisance because they consume blood from living
vertebrates, including humans. The females of many species of mosquitoes are
blood-eating pests. In feeding on blood, some of them transmit extremely
harmful human and livestock diseases, such as malaria, yellow fever and
filariasis. Some authorities argue accordingly that mosquitoes are the most
dangerous animals on Earth."
"Mosquitoes are members of a family of nematocerid
flies: the Culicidae (from the Latin culex, genitive culicis meaning
"midge" or "gnat").
The word mosquito (formed by mosca and diminutive ito) is
from the Spanish or Portuguese for "little fly". Superficially,
mosquitoes resemble crane flies (family Tipulidae) and chironomid flies (family
Chironomidae); as a result, casual observers seldom realize the important
differences between the members of the respective families. In particular, the
females of many species of mosquitoes are blood eating pests and dangerous
vectors of diseases, whereas members of the similar-looking Chironomidae and
Tipulidae are not."
"Many species of mosquitoes are not blood eaters,
and many of those that do create a "high to low pressure" in the
blood to obtain it do not transmit disease. Also, in the bloodsucking species,
only the females suck blood. Furthermore, even among mosquitoes that do carry
important diseases, neither all species of mosquitoes, nor or all strains of a
given species transmit the same kinds of diseases, nor do they all transmit the
diseases under the same circumstances; their habits differ."
" For example, some species attack people in houses,
and others prefer to attack people walking in forests. Accordingly, in managing
public health, knowing which species, even which strains, of mosquitoes with
which one is dealing is important."
"Over 3,500 species of mosquitoes have already been
described from various parts of the world. Some mosquitoes that bite humans
routinely act as vectors for a number of infectious diseases affecting millions
of people per year. Others that do not routinely bite humans, but are the
vectors for animal diseases, may become disastrous agents for zoonosis of new
diseases when their habitat is disturbed, for instance by sudden
deforestation"
"Disease"
"Anopheles albimanus mosquito feeding on a human arm
– this mosquito is a vector of malaria, and mosquito control is a very
effective way of reducing the incidence of malaria."
"Mosquito-borne disease and Life-threatening
disease. Control it Naturally."
"Mosquitoes can act as a vector for many
disease-causing viruses and parasites. Infected mosquitoes carry these
organisms from person to person without exhibiting symptoms themselves.
Mosquito-borne diseases include:
"Viral 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."
"Severe dengue can be fatal, but with good
treatment, less than 1% of patients die from dengue."
"The parasitic diseases collectively called malaria,
caused by various species of Plasmodium, carried by mosquitoes of the genus
Anopheles"
"Lymphatic filariasis (the main cause of elephantiasis)
which can be spread by a w
ide variety of mosquito species."
"West Nile virus is a concern in the United States,
but there are no reliable statistics on worldwide cases."
"Eastern equine encephalitis virus is a concern in
the eastern United States."
"Tularemia, a bacterial disease caused by
Francisella tularensis, is variously transmitted, including by biting flies.
Culex and Culiseta, are vectors of tularemia as well as arbovirus infections
such as West Nile Virus.."
"Though originally transmission of HIV was a public
health concern, practical considerations and studies of epidemiological
patterns suggest that any transmission of the HIV virus by mosquitoes is in
practice extremely unlikely at worst"
"Various species of mosquitoes are estimated to
transmit various types of disease to more than 700 million people annually in
Africa, South America, Central America, Mexico, Russia,India, Pakistan, Bangla
Desh and much of Asia, with millions of resultant deaths. At least two million
people annually die of these diseases, and the morbidity rates are many times
higher still."
"Many scientists have suggested complete eradication
of mosquitoes would not have serious ecological consequences"
"Life cycle"
"Anopheles larva from southern Germany, about 8 mm
long
Anatomy of a Culex larva
Image of pitcher plant mosquito Wyeomyia smithii, showing
segmentation and partial anatomy of circulatory system."
"Like all flies, mosquitoes go through four stages
in their life cycle: egg, larva, pupa, and adult or imago. In most species,
adult females lay their eggs in stagnant water; some lay eggs near the water's
edge; others attach their eggs to aquatic plants. Each species selects the
situation of the water into which it lays its eggs and does so according to its
own ecological adaptations. Some are generalists and are not very fussy. Some
breed in lakes, some in temporary puddles. Some breed in marshes, some in
salt-marshes. Among those that breed in salt water, some are equally at home in
fresh and salt water up to about one third the concentration of seawater,
whereas others must acclimatize themselves to the saltiness Such differences
are important because certain ecological preferences keep mosquitoes away from
most humans, whereas other preferences bring them right into houses at
night."
"Some species of mosquitoes prefer to breed in
phytotelmata (natural reservoirs on plants) such as rainwater accumulated in
holes in tree trunks, or in the leaf-axils of bromeliads. Some specialize in the
liquid in pitchers of particular species of pitcher plants, their larvae
feeding on decaying insects that had drowned there or on the associated
bacteria; the genus Wyeomyia provides such examples — the harmless Wyeomyia
smithii breeds only in the pitchers of Sarracenia purpurea."
"However, some species of mosquito that are adapted
to breeding in phytotelmata are dangerous disease vectors. In nature they might
occupy anything from a hollow tree trunk to a cupped leaf. Such species
typically take readily to breeding in artificial water containers, such as the
odd plastic bucket, flowerpot "saucer", or discarded bottle or tire.
Such casual puddles are important breeding places for some of the most serious
disease vectors, such as species of Aedes that transmit dengue and yellow
fever. Some with such breeding habits are disproportionately important vectors
because they are well placed to pick up pathogens from humans and pass them on.
In contrast, no matter how voracious, mosquitoes that breed and feed mainly in
remote wetlands and salt marshes may well remain uninfected, and if they do
happen to become infected with a relevant pathogen, might seldom encounter
humans to infect in turn."
"The first three stages—egg, larva and pupa—are
largely aquatic. These stages typically last 5–14 days, depending on the
species and the ambient temperature, but there are important exceptions.
Mosquitoes living in regions where some seasons are freezing or waterless spend
part of the year in diapause; they delay their development, typically for
months, and carry on with life only when there is enough water or warmth for
their needs. For instance, Wyeomyia larvae typically get frozen into solid
lumps of ice during winter and only complete their development in spring. The
eggs of some species of Aedes remain unharmed in diapause if they dry out, and
hatch later when they are covered by water."
"Eggs hatch to become larvae, which grow until they
are able to change into pupae. The adult mosquito emerges from the mature pupa
as it floats at the water surface. Bloodsucking mosquitoes, depending on
species, gender, and weather conditions, have potential adult lifespans ranging
from as little as a week to as long as several months."
"Some species can overwinter as adults in
diapause"
"Eggs and oviposition"
"An egg raft of a Culex species, partly broken,
showing individual egg shapes."
"Mosquito habits of oviposition, the ways in which
they lay their eggs, vary considerably between species, and the morphologies of
the eggs vary accordingly. The simplest procedure is that followed by many
species of Anopheles: like many other gracile species of aquatic insects,
females just fly over the water, bobbing up and down to the water surface and
dropping eggs more or less singly. The bobbing behavior occurs among some other
aquatic insects, as well, for example mayflies and dragonflies; it sometimes is
called "dapping". The eggs of Anopheles species are roughly
cigar-shaped and have floats down the sides. Females of many common species of
mosquito can lay 100–200 eggs during the course of the adult phase of their
lifecycle. Even with high egg and intergenerational mortality, over a period of
several weeks a single successful breeding pair can create a population of
thousands."
"Some other species, for example members of the
genus Mansonia, lay their eggs in arrays, attached usually to the under-surfaces
of waterlily pads. Their close relatives, the genus Coquillettidia, lay their
eggs similarly, but not attached to plants. Instead, the eggs form layers
called "rafts" that float on the water. This is a common mode of
oviposition, and most species of Culex are known for the habit, which also
occurs in some other genera, such as Culiseta and Uranotaenia. Anopheles eggs
may on occasion cluster together on the water, too, but the clusters do not
generally look much like compactly glued rafts of eggs."
"In species that lay their eggs in rafts, rafts do
not form adventitiously; the female Culex settles carefully on still water with
her hind legs crossed, and as she lays the eggs one by one, she twitches to
arrange them into a head-down array that sticks together to form the raf"
"Aedes females generally drop their eggs singly,
much as Anopheles do, but not as a rule into water. Instead, they lay their
eggs on damp mud or other surfaces near the water's edge. Such an oviposition
site commonly is the wall of a cavity such as a hollow stump or a container
such as a bucket or a discarded vehicle tire. The eggs generally do not hatch
until they are flooded, and they may have to withstand considerable desiccation
before that happens. They are not resistant to desiccation straight after
oviposition, but must develop to a suitable degree first. Once they have
achieved that, however, they can enter diapause for several months if they dry
out. Clutches of eggs of the majority of mosquito species hatch as soon as possible,
and all the eggs in the clutch hatch at much the same time. In contrast, a
batch of Aedes eggs in diapause tends to hatch irregularly over an extended
period of time. This makes it much more difficult to control such species than
those mosquitoes whose larvae can be killed all together as they hatch. Some
Anopheles species do also behave in such a manner, though not to the same
degree of sophistication."
"Mosquito larvae and pupa resting at water
surface"
"The mosquito larva has a well-developed head with
mouth brushes used for feeding, a large thorax with no legs, and a segmented
abdomen."
"Larvae breathe through spiracles located on the
eighth abdominal segment, or through a siphon, and therefore must come to the
surface frequently. The larvae spend most of their time feeding on algae,
bacteria, and other microbes in the surface microlayer. They dive below the
surface only when disturbed. Larvae swim either through propulsion with their
mouth brushes, or by jerky movements of their entire bodies, giving them the
common name of "wigglers" or "wrigglers"."
"Larvae develop through four stages, or instars,
after which they metamorphose into pupae. At the end of each instar, the larvae
molt, shedding their skins to allow for further growth."
"Pupa"
Culex larvae plus one pupa
Culex larva and pupa
Anatomy of an adult mosquito."
"As seen in its lateral aspect, the mosquito pupa is
comma-shaped. The head and thorax are merged into a cephalothorax, with the
abdomen curving around underneath. The pupa can swim actively by flipping its
abdomen, and it is commonly called a "tumbler" because of its
swimming action. As with the larvae, the pupae of most species must come to the
surface frequently to breathe, which they do through a pair of respiratory trumpets
on the cephalothorax. However, pupae do not feed during this stage; typically
they pass their time hanging from the surface of the water by their respiratory
trumpets. If alarmed, say by a passing shadow, they nimbly swim downwards by
flipping their abdomens in much the same way as the larvae do. If undisturbed,
they soon float up again. After a few days or longer, depending on the
temperature and other circumstances, the pupa rises to the water surface, the
dorsal surface of its cephalothorax splits, and the adult mosquito emerges. The
lower activity of the pupa is as compared to the larva is understandable,
bearing in mind that it does not feed, whereas the larva feeds
constantly."
"Adult"
"Adults of the yellow fever mosquito Aedes aegypti,
a typical member of the subfamily Culicinae, the male is on the left, and
females are on the right. Note the bushy antennae and longer palps in the
male."
"The period of development from egg to adult varies
among species and is strongly influenced by ambient temperature. Some species
of mosquitoes can develop from egg to adult in as little as five days, but a
more typical period of development in tropical conditions would be some 40 days
or more for most species. The variation of the body size in adult mosquitoes
depends on the density of the larval population and food supply within the
breeding water."
"Adult mosquitoes usually mate within a few days
after emerging from the pupal stage. In most species, the males form large
swarms, usually around dusk, and the females fly into the swarms to mate."
"Males typically live for about a week, feeding on
nectar and other sources of sugar. After obtaining a full blood meal, the
female will rest for a few days while the blood is digested and eggs are
developed. This process depends on the temperature, but usually takes two to
three days in tropical conditions. Once the eggs are fully developed, the
female lays them and resumes host-seeking."
"The cycle repeats itself until the female dies.
While females can live longer than a month in captivity, most do not live
longer than one to two weeks in nature. Their lifespans depend on temperature,
humidity, and their ability to successfully obtain a blood meal while avoiding
host defenses and predators."
"Length of the adult varies, but is rarely greater
than 16 mm (0.6 in),and weight up to 2.5 milligrams (0.04 grains). All
mosquitoes have slender bodies with three segments: head, thorax and
abdomen."
"The head is specialized for receiving sensory
information and for feeding. It has eyes and a pair of long, many-segmented
antennae. The antennae are important for detecting host odors, as well as odors
of breeding sites where females lay eggs. In all mosquito species, the antennae
of the males in comparison to the females are noticeably bushier and contain
auditory receptors to detect the characteristic whine of the female. The
compound eyes are distinctly separated from one another. Their larvae only
possess a pit-eye ocellus. The compound eyes of adults develop in a separate
region of the head. New ommatidia are added in semicircular rows at the rear of
the eye. During the first phase of growth, this leads to individual ommatidia
being square, but later in development they become hexagonal. The hexagonal
pattern will only become visible when the carapace of the stage with square
eyes is molted The head also has an elongated, forward-projecting
"stinger-like" proboscis used for feeding, and two sensory palps. The
maxillary palps of the males are longer than their proboscises, whereas the
females’ maxillary palps are much shorter. In typical bloodsucking species, the
female has an elongated proboscis."
"The thorax is specialized for locomotion. Three
pairs of legs and a pair of wings are attached to the thorax. The insect wing
is an outgrowth of the exoskeleton. The Anopheles mosquito can fly for up to
four hours continuously at 1–2 km/h (0.6–1 mph) traveling up to 12 km (7.5 mi)
in a night. Males beat their wings between 450 and 600 times per second."
"The abdomen is specialized for food digestion and
egg development; the abdomen of a mosquito can hold three times its own weight
in blood.This segment expands considerably when a female takes a blood meal.
The blood is digested over time, serving as a source of protein for the
production of eggs, which gradually fill the abdomen."
"Feeding by adults"
Aedes aegypti, a common vector of dengue fever and yellow
fever
"Typically, both male and female mosquitoes feed on
nectar and plant juices, but in many species the mouthparts of the females are
adapted for piercing the skin of animal hosts and sucking their blood as
ectoparasites. In many species, the female needs to obtain nutrients from a
blood meal before she can produce eggs, whereas in many other species, she can
produce more eggs after a blood meal. Both plant materials and blood are useful
sources of energy in the form of sugars, and blood also supplies more
concentrated nutrients, such as lipids, but the most important function of
blood meals is to obtain proteins as materials for egg production."
"For females to risk their lives on blood sucking
while males abstain is not a strategy limited to the mosquitoes; it also occurs
in some other insect families, such as the Tabanidae. When a female reproduces
without such parasitic meals, she is said to practice autogenous reproduction,
as in Toxorhynchites; otherwise, the reproduction may be termed anautogenous,
as occurs in mosquito species that serve as disease vectors, particularly
Anopheles and some of the most important disease vectors in the genus Aedes. In
contrast, some mosquitoes, for example, many Culex, are partially anautogenous;
they do not need a blood meal for their first cycle of egg production, which
they produce autogenously; however, subsequent clutches of eggs are produced
anautogenously, at which point their disease vectoring activity becomes
operative."
"Here an Anopheles stephensi female is gorged with
blood and beginning to pass unwanted liquid fractions of the blood to make room
for more of the solid nutrients in her gut."
"With regard to host location, female mosquitoes
hunt their blood host by detecting organic substances such as carbon dioxide
(CO2) and 1-octen-3-ol produced from the host, and through optical recognition.
Mosquitoes prefer some people over others. The preferred victim's sweat simply
smells better than others because of the proportions of the carbon dioxide,
octenol and other compounds that make up body odor.
The most powerful semiochemical that triggers the keen
sense of smell of Culex quinquefasciatus is nonanal.
A large part of the mosquito’s sense of smell, or
olfactory system, is devoted to sniffing out blood sources. Of 72 types of odor
receptors on its antennae, at least 27 are tuned to detect chemicals found in
perspiration
In Aedes, the search for a host takes place in two
phases. First, the mosquito exhibits a nonspecific searching behavior until the
perception of host stimulants, then it follows a targeted approach."
"Most mosquito species are crepuscular (dawn or
dusk) feeders. During the heat of the day, most mosquitoes rest in a cool place
and wait for the evenings, although they may still bite if disturbed Some
species, such as the Asian tiger mosquito, are known to fly and feed during
daytime."
"Prior to and during blood feeding, blood-sucking
mosquitoes inject saliva into the bodies of their source(s) of blood. This
saliva serves as an anticoagulant; without it one might expect the female
mosquito's proboscis to become clogged with blood clots. The saliva also is the
main route by which mosquito physiology offers passenger pathogens access to
the hosts' interior. Not surprisingly the salivary glands are a major target to
most pathogens, whence they find their way into the host via the stream of saliva."
"Mosquitoes of the genus Toxorhynchites never drink
bloo. This genus includes the largest extant mosquitoes, the larvae of which
prey on the larvae of other mosquitoes. These mosquito eaters have been used in
the past as mosquito control agents, with varying success."
"Mouthparts"
"Mosquito mouthparts are very specialized,
particularly those of the females, which in most species are adapted to
piercing skin and then sucking blood. Apart from bloodsucking, the females
generally also drink assorted fluids rich in dissolved sugar, such as nectar
and honeydew, to obtain the energy they need. For this, their blood-sucking
mouthparts are perfectly adequate. In contrast, male mosquitoes are not
bloodsuckers; they only drink such sugary fluids as they can find. Accordingly,
their mouthparts do not require the same degree of specialization as those of
females."
"Externally, the most obvious feeding structure of
the mosquito is the proboscis. More specifically, the visible part of the
proboscis is the labium, which forms the sheath enclosing the rest of the
mouthparts. When the mosquito first lands on a potential host, her mouthparts
will be enclosed entirely in this sheath, and she will touch the tip of the
labium to the skin in various places. Sometimes, she will begin to bite almost
straight away, while other times, she will prod around, apparently looking for
a suitable place. Occasionally, she will wander for a considerable time, and
eventually fly away without biting. Presumably, this probing is a search for a
place with easily accessible blood vessels, but the exact mechanism is not
known. It is known that there are two taste receptors at the tip of the labium,
which may well play a role."
"The female mosquito does not insert her labium into
the skin; it bends back into a bow when the mosquito begins to bite. The tip of
the labium remains in contact with the skin of the victim, acting as a guide
for the other mouthparts. In total, there are six mouthparts besides the
labium: two mandibles, two maxillae, the hypopharynx, and the labrum."
"The mandibles and the maxillae are used for
piercing the skin. The mandibles are pointed, while the maxillae end in flat,
toothed "blades". To force these into the skin, the mosquito moves
its head backwards and forwards. On one movement, the maxillae are moved as far
forward as possible. On the opposite movement, the mandibles are pushed deeper
into the skin by levering against the maxillae. The maxillae do not slip back
because the toothed blades grip the skin."
"The hypopharynx and the labrum both are hollow.
Saliva with anticoagulant is pumped down the hypopharynx to prevent clotting,
and blood is drawn up the labrum."
"To understand the mosquito mouthparts, it is
helpful to draw a comparison with an insect that chews food, such as a
dragonfly. A dragonfly has two mandibles, which are used for chewing, and two
maxillae, which are used to hold the food in place as it is chewed. The labium
forms the floor of the dragonfly's mouth, the labrum forms the top, while the hypopharynx
is inside the mouth and is used in swallowing. Conceptually, then, the
mosquito's proboscis is an adaptation of the mouthparts that occur in other
insects. The labium still lies beneath the other mouthparts, but also enfolds
them, and it has been extended into a proboscis. The maxillae still
"grip" the "food" while the mandibles "bite" it.
The top of the mouth, the labrum, has developed into a channeled blade the
length of the proboscis, with a cross-section like an inverted "U".
Finally, the hypopharynx has extended into a tube that can deliver saliva at
the end of the proboscis. Its upper surface is somewhat flattened so, when
pressed against it, the labrum forms a closed tube for conveying blood from the
victim."
"Saliva"
"For the mosquito to obtain a blood meal, it must
circumvent the vertebrate physiological responses. The mosquito, as with all
blood-feeding arthropods, has mechanisms to effectively block the hemostasis
system with their saliva, which contains a mixture of secreted proteins. Mosquito
saliva negatively affects vascular constriction, blood clotting, platelet
aggregation, angiogenesis and immunity, and creates inflammation."
"Universally, hematophagous arthropod saliva
contains at least one anticlotting, one antiplatelet, and one vasodilatory
substance. Mosquito saliva also contains enzymes that aid in sugar feeding and
antimicrobial agents to control bacterial growth in the sugar meal. The
composition of mosquito saliva is relatively simple, as it usually contains
fewer than 20 dominant proteins. Despite the great strides in knowledge of
these molecules and their role in bloodfeeding achieved recently, scientists
still cannot ascribe functions to more than half of the molecules found in
arthropod saliva. One promising application is the development of anticlotting
drugs based on saliva molecules, which might be useful for approaching
heart-related diseases, because they are more user-friendly blood clotting
inhibitors and capillary dilators."
"It is now well recognized that feeding ticks,
sandflies, and, more recently, mosquitoes, have an ability to modulate the
immune response of the animals (hosts) on which they feed. The presence of this
activity in vector saliva is a reflection of the inherent overlapping and
interconnected nature of the host hemostatic and inflammatory/immunological
responses and the intrinsic need to prevent these host defenses from disrupting
successful feeding. The mechanism for mosquito saliva-induced alteration of the
host immune response is unclear, but the data have become increasingly
convincing that such an effect occurs. Early work described a factor in saliva
that directly suppresses TNF-α release, but not antigen-induced histamine
secretion, from activated mast cells. Experiments by Cross et al. (1994)
demonstrated the inclusion of Ae. aegypti mosquito saliva into naïve cultures
led to a suppression of interleukin (IL)-2 and IFN-γ production, while the
cytokines IL-4 and IL-5 are unaffected by mosquito saliva. Cellular
proliferation in response to IL-2 is clearly reduced by prior treatment of
cells with SGE Correspondingly, activated splenocytes isolated from mice fed
upon by either Ae. aegypti or Cx. pipiens mosquitoes produce markedly higher
levels of IL-4 and IL-10 concurrent with suppressed IFN-γ production.
Unexpectedly, this shift in cytokine expression is observed in splenocytes up
to 10 days after mosquito exposure, suggesting natural feeding of mosquitoes
can have a profound, enduring, and systemic effect on the immune
response."
"T cell populations are decidedly susceptible to the
suppressive effect of mosquito saliva, showing increased mortality and
decreased division rates.
Parallel work by Wasserman et al. (2004) demonstrated
that T- and B-cell proliferation was inhibited in a dose dependent manner with
concentrations as low as 1/7 of the saliva in a single mosquitoDepinay et al.
(2005) observed a suppression of antibody-specific T cell responses mediated by
mosquito saliva and dependent on mast cells and IL-10 expression."
"A recent study suggests mosquito saliva can also
decrease expression of interferon−α/β during early mosquito-borne virus
infection.The contribution of type I interferons (IFN) in recovery from
infection with viruses has been demonstrated in vivo by the therapeutic and
prophylactic effects of administration of IFN-inducers or IFN, and recent
research suggests mosquito saliva exacerbates West Nile virus infection, as
well as other mosquito-transmitted viruses"
"Egg development and blood digestion"
"Female mosquitoes use two very different food
sources. They need sugar for energy, which is taken from sources such as
nectar, and they need blood as a source of protein for egg development. Because
biting is risky and hosts may be difficult to find, mosquitoes take as much
blood as possible when they have the opportunity. This, however, creates
another problem. Digesting that volume of blood takes a while, and the mosquito
will require energy from sugar in the meantime."
"To avoid this problem, mosquitoes have a digestive
system which can store both food types, and give access to both as they are
needed. When the mosquito drinks a sugar solution, it is directed to a crop.
The crop can release sugar into the stomach as it is required. At the same
time, the stomach never becomes full of sugar solution, which would prevent the
mosquito taking a blood meal if it had the chance."
"Blood is directed straight into the mosquito's
stomach. In species that feed on mammalian or avian blood, hosts whose blood
pressure is high, the mosquito feeds selectively from active blood vessels
where the pressure assists in filling the gut rapidly. If, instead of slapping
a feeding mosquito, one stretches one's skin so that it grips the proboscis and
the mosquito cannot withdraw it, the pressure will distend the gut until it
breaks and the mosquito dies. In the unmolested mosquito however, the mosquito
will withdraw, and as the gut fills up the stomach lining secretes a
peritrophic membrane that surrounds the blood. This membrane keeps the blood
separate from anything else in the stomach. However, like certain other insects
that survive on dilute, purely liquid diets, notably many of the Homoptera,
many adult mosquitoes must excrete unwanted aqueous fractions even as they
feed. (see the photograph of a feeding Anopheles stephensi. Note that the
excreted droplet patently is not whole blood, being far more dilute). As long
as they are not disturbed, this permits mosquitoes to continue feeding until
they have accumulated a full meal of nutrient solids. As a result, a mosquito
replete with blood can continue to absorb sugar, even as the blood meal is
slowly digested over a period of several days. Once blood is in the stomach,
the midgut of the female synthesizes proteolytic enzymes that hydrolyze the
blood proteins into free amino acids. These are used as building blocks for the
synthesis of egg yolk proteins."
"In the mosquito Anopheles stephensi Liston, trypsin
activity is restricted entirely to the posterior midgut lumen. No trypsin
activity occurs before the blood meal, but activity increases continuously up
to 30 hours after feeding, and subsequently returns to baseline levels by 60
hours. Aminopeptidase is active in the anterior and posterior midgut regions
before and after feeding. In the whole midgut, activity rises from a baseline
of approximately 3 enzyme units (EU) per midgut to a maximum of 12 EU at 30
hours after the blood meal, subsequently falling to baseline levels by 60
hours. A similar cycle of activity occurs in the posterior midgut and posterior
midgut lumen, whereas aminopeptidase in the posterior midgut epithelium
decreases in activity during digestion. Aminopeptidase in the anterior midgut
is maintained at a constant, low level, showing no significant variation with
time after feeding. Alpha-glucosidase is active in anterior and posterior
midguts before and at all times after feeding. In whole midgut homogenates,
alpha-glucosidase activity increases slowly up to 18 hours after the blood
meal, then rises rapidly to a maximum at 30 hours after the blood meal, whereas
the subsequent decline in activity is less predictable. All posterior midgut
activity is restricted to the posterior midgut lumen. Depending on the time
after feeding, greater than 25% of the total midgut activity of
alpha-glucosidase is located in the anterior midgut. After blood meal
ingestion, proteases are active only in the posterior midgut. Trypsin is the
major primary hydrolytic protease and is secreted into the posterior midgut
lumen without activation in the posterior midgut epithelium. Aminoptidase
activity is also luminal in the posterior midgut, but cellular aminopeptidases
are required for peptide processing in both anterior and posterior midguts.
Alpha-glucosidase activity is elevated in the posterior midgut after feeding in
response to the blood meal, whereas activity in the anterior midgut is
consistent with a nectar-processing role for this midgut region"
"Distribution"
"Female Ochlerotatus notoscriptus feeding on a human
arm, Tasmania, Australia"
"Mosquitoes are very widespread, occurring in all
regions of the world except for Antarctica. In warm and humid tropical regions,
they are active for the entire year, but in temperate regions they hibernate
over winter. Arctic mosquitoes may be active for only a few weeks as pools of
water form on top of the permafrost. During that time, though, they exist in
huge numbers and can take up to 300 mL of blood per day from each animal in a
caribou herd."
"Eggs from strains in the temperate zones are more
tolerant to the cold than ones from warmer regions.They can even tolerate snow
and subzero temperatures. In addition, adults can survive throughout winter in
suitable microhabitats."
"Means of dispersal"
"Worldwide introduction of various mosquito species
over large distances into regions where they are not indigenous has occurred
through human agencies, primarily on sea routes, in which the eggs, larvae, and
pupae inhabiting water-filled used tires and cut flowers are transported.
However, apart from sea transport, mosquitoes have been effectively carried by
personal vehicles, delivery trucks, trains and aircraft. Sufficient quarantine
measures have proven difficult to implement."
"Methods used to prevent the spread of disease, or
to protect individuals in areas where disease is endemic, include:
" Vector control aimed at mosquito control or
eradication
Disease prevention, using prophylactic drugs and
developing vaccines
Prevention of mosquito bites, with insecticides, nets and
repellents."
"Since most such diseases are carried by
"elderly" female mosquitoes, some scientists have suggested focusing
on these to avoid the evolution of resistance.[57]
Control.
"Mosquito control"
"Many methods are used for mosquito control.
Depending on the situation, the most important usually include:
source reduction (e.g., removing stagnant water)
biocontrol (e.g. importing natural predators such as
dragonflies)
trapping, and/or insecticides to kill larvae or adults
exclusion (mosquito nets and window screening)."
"Source reduction"
"World War II era pamphlet aimed to discourage
creation of stagnant water."
"Source reduction means elimination of breeding
places of mosquitoes. It includes engineering measures such as filling,
leveling and drainage of breeding places, and water management (such as
intermittent irrigation). Source reduction can also be done by making water
unsuitable for mosquitoes to breed, for example, by changing salinity of water.
Some specific measures are:
For Culex: abolition of domestic and peridomestic sources
of water suitable for breeding, for example removal and disposal of sewage and
other waste water
For Aedes: eliminating incidental containers such as
discarded tins, crockery, pots, broken bottles, and coconut shells
For Anopheles: abolish breeding places by filling or
drainage
For Mansonia: removal of aquatic plants manually or by
application of herbicides
Details of the biology of different species of mosquitoes
differ too widely for any limited set of rules to be sufficient in all
circumstances. However, the foregoing are the most economical and practical
measures for most purposes. The importance of peridomestic control arises
largely because most species of mosquitoes rarely travel more than a few
hundred meters unless the wind is favorable."
"Exclusion"
"In combination with scrupulous attention to control
of breeding areas, window screens and mosquito nets are the most effective
measures for residential areas. Insecticide-impregnated mosquito nets are
particularly effective because they selectively kill those insects that attack
humans, without affecting the general ecology of the area."
"An ideal mosquito net is white in color (to allow
easy detection of mosquitoes), rectangular, netted on sides and top, without a
hole. The size of opening in net should not exceed 1.2mm (0.0475 inches) in
diameter, or about 23 holes per square centimeter (150 per square inch).
"Window screens should have copper or bronze gauze
with 16 meshes to an inch."
"Natural predators"
"Dragonfly and damselfly nymphs and various other
aquatic insect predators eat mosquitoes at all stages of development and dense
populations can be useful in reducing mosquito problems.[58] Various small
fishes, such as species of Galaxias and members of the Poeciliidae, such as
Gambusia (so-called mosquitofish) and guppies (Poecilia), eat mosquito larvae
and sometimes may be worth introducing into ponds to assist in control. Many
other types of fish are also known to consume mosquito larvae, including bass,
bluegills, piranhas, Arctic char, salmon, trout, catfish, fathead minnows,
goldfish, and killifish."
"Although bats and purple martins can be prodigious
consumers of insects, many of which are pests, less than 1% of their diet
typically consists of mosquitoes. Neither bats nor purple martins are known to
control or even significantly reduce mosquito population."
"Some cyclopoid copepods are predators on
first-instar larvae, killing up to 40 Aedes larvae per day.Larval
Toxorhynchites mosquitoes are known as natural predators of other Culicidae.
Each larva can eat 10 to 20 mosquito larvae per day. During its entire
development, a Toxorhynchites larva can consume an equivalent of 5,000 larvae
of the first-instar (L1) or 300 fourth-instar larvae However, Toxorhynchites
can consume all types of prey, organic debris, or even exhibit cannibalistic
behavior.
"Other natural predators and parasitoids include
fungi and nematodes. Though important at times, their effectiveness varies with
circumstances."
"Bacillus thuringiensis israelensis has also been
used to control them as a biological agent."
"Mosquito bites and treatment"
"Mosquito bite wounds"
"Visible, irritating bites are due to an immune
response from the binding of IgG and IgE antibodies to antigens in the
mosquito's saliva. Some of the sensitizing antigens are common to all mosquito
species, whereas others are specific to certain species. There are both
immediate hypersensitivity reactions (types I and III) and delayed
hypersensitivity reactions (type IV) to mosquito bites. Both reactions result
in itching, redness and swelling. Immediate reactions develop within a few
minutes of the bite and last for a few hours. Delayed reactions take around a
day to develop, and last for up to a week. Several anti-itch medications are
commercially available, including those taken orally, such as Benadryl, or
topically applied antihistamines and, for more severe cases, corticosteroids,
such as hydrocortisone and triamcinolone. Tea tree oil has been shown to be an
effective anti-inflammatory, reducing itching."
“Insect Repellent."
"Insect repellents are applied on skin and give
short time protection against mosquito bites. The chemical DEET repels some
mosquitoes and other insects.[68] Some CDC-recommended repellents are
picaridin, Eucalyptus oil (PMD) and IR3535. Others are indalone, dimethyl
pthalate, dimethyl carbate and ethyl hexanediol."
"Evolution"
"The oldest known mosquito with an anatomy similar
to modern species was found in 79-million-year-old Canadian amber from the
Cretaceous.[70] An older sister species with more primitive features was found
in amber that is 90 to 100 million years old. Two mosquito fossils have been
found that show very little morphological change in modern mosquitoes against
their counterpart from 46 million years ago."
"Genetic analyses indicate the Culicinae and
Anophelinae clades may have diverged about 150 million years ago.The Old and
New World Anopheles species are believed to have subsequently diverged about 95
million years ago."
"The mosquito Anopheles gambiae is currently
undergoing speciation into the M and S molecular forms. This means some
pesticides that work on the M form will not work anymore on the S form."
"Taxonomy of the Culicidae"
"Over 3,500 species of the Culicidae have already
been described. They are generally divided into two subfamilies which in turn
comprise some 43 genera. These figures are subject to continual change, as more
species are discovered, and as DNA studies compel rearrangement of the taxonomy
of the family. The two main subfamilies are the Anophelinae and Culicinae, with
their genera as shown in the subsection below."
"Within you there are not only weaknesses,
helplessness and misconceptions in abundance. Infinite capability, infinite
wisdom and boundless joy are also present."
" If there is a disease within us, then its cure is
also within us. You must recognize the power within and its influence. Be established
within the self and burn down our defects through " The DIVINE BITA (SEED)
MANTRA of Vedanta."
*Consciousness of Unconditional Love & Peace is
Unique one among All Human Being & Non living Of UNIVERSE,"One for All
& All for One"
"COMPETENCE means the ABILITY of human beings of
universe to swim across the RIVER of LIFE and reach to SHORE of LORD'S
CONSCIOUSNESS."
"When it can be so said about our knowledge of the
Physical Plane much more can be said about the Higher Spheres still Unexplored.
The Metaphysics and Occult Sciences have already given Glimpses in that Direction.
We see that this Universe is a Divine Play of two kinds of Forces - Secular
& Spiritual, Physical & Metaphysical. Physical Science gives us
information of the Former & over the other it possesses no
Jurisdiction."
.jpg)
.jpg)