Scanning electron microscope (SEM) depiction of
a flea
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Aphaniptera
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Fleas are the insects forming the order
Siphonaptera. They are wingless, with mouthparts adapted for piercing
skin and sucking blood. Fleas are external parasites, living by hematophagy off the blood
of mammals (including bats and humans) and birds.
Some flea species include:
- Cat flea (Ctenocephalides felis)
- Dog flea (Ctenocephalides canis)
- Human flea (Pulex irritans)
- Moorhen flea (Dasypsyllus
gallinulae)
- Northern rat flea
(Nosopsyllus fasciatus)
- Oriental rat flea
(Xenopsylla cheopis)
Morphology and behavior
diagram
of a Flea
Fleas are wingless insects (1/16 to 1/8-inch (1.5 to
3.3 mm) long) that are agile, usually dark colored (for example, the
reddish-brown of the cat flea), with tube-like mouth-parts adapted to feeding
on the blood of their hosts. Their legs are long, the hind pair well adapted for
jumping: a flea can jump vertically up to 7 inches (18 cm) and
horizontally up to 13 inches (33 cm).[3] This is around 1200 to 2200 times
their own body length, making the flea one of the best jumpers of all known
animals (relative to body size), second only to the froghopper. According to an article in Science
News, "researchers with the University of Cambridge in England have
shown that fleas take off from their tibiae and tarsi—the insect equivalent of
feet—and not their trochantera, or knees. The researchers report their
conclusion in the March 1 Journal of Experimental Biology."[4]
It has been known that fleas do not use muscle power but energy stored in a
protein named resilin but the researchers used high-speed
video technology and mathematical models to discover where the spring action
actually happens. Their bodies are laterally compressed, permitting easy
movement through the hairs or feathers on the host's body (or in the case of
humans, under clothing). The flea body is hard, polished, and covered with many
hairs and short spines directed backward,[5] which also assist its movements
on the host. The tough body is able to withstand great pressure, likely an
adaptation to survive attempts to eliminate them by mashing or scratching. Even
hard squeezing between the fingers is normally insufficient to kill a flea. It
is possible to eliminate them by pressing individual fleas with adhesive tape
or softened beeswax (or "cheese" wax) or by rolling a flea briskly
between the fingers to disable it then crushing it between the fingernails.
Fleas also can be drowned in water and may not survive direct contact with
anti-flea pesticides
.
Hooke's drawing of a flea in Micrographia
Fleas lay tiny white oval-shaped eggs better viewed through
a loupe. The larva is small, pale, has
bristles covering its worm-like body, lacks eyes, and has mouthparts adapted to
chewing. The larvae feed on various organic matter, especially the feces of
mature fleas. The adult flea's diet consists solely of fresh blood.[6] In the pupal phase, the larva is
enclosed in a silken, debris-covered cocoon.
Life cycle and habitat
Fleas are holometabolous insects, going through the
four life cycle
stages of egg, larva,
pupa,
and imago (adult). The flea life cycle begins
when the female lays after feeding. Adult fleas must feed on blood before they
can become capable of reproduction.[5] Although reproduction is normally
asexual, for at least one specie, under stress conditions, female fleas produce
male fleas. [7]. Eggs are laid in batches of up
to 20 or so, usually on the host itself, which means that the eggs can easily
roll onto the ground. Because of this, areas where the host rests and sleeps
become one of the primary habitats of eggs and
developing fleas. The eggs take around two days to two weeks to hatch.[3]
Micrograph of a flea larva.
Flea larvae emerge from the eggs to feed on any available
organic material such as dead insects, feces, and vegetable matter. They are
blind and avoid sunlight, keeping to dark places like sand, cracks and
crevices, and bedding. Given an adequate supply of food, larvae should pupate and weave a silken
cocoon within 1–2 weeks after 3 larval stages. After another week or two, the
adult flea is fully developed and ready to emerge from the cocoon. They may
however remain resting during this period until they receive a signal that a
host is near - vibrations (including sound), heat, and carbon dioxide are all stimuli indicating
the probable presence of a host.[3] Fleas are known to overwinter in the larval or pupal stages.
Once the flea reaches adulthood, its primary goal is to find
blood and then to reproduce.[8]
Adult fleas only have about a week to find food once they emerge, but after
that they can survive two months to a year between meals. Flea populations are
unevenly distributed, with about 50% eggs, 35% larvae, 10% pupae, and 5%
adults.[3] Their total life cycle can be as
short as two weeks, but may be several months in ideal conditions. Female fleas
can lay 500 or more eggs over their life, allowing for phenomenal growth rates.
Adult female rabbit fleas, Spilopsyllus cuniculi, can
detect the changing levels of cortisol and corticosterone, hormones in the
rabbit's blood that indicate she is getting close to giving birth. This
triggers sexual maturity in the fleas and they start producing eggs. As soon as
the baby rabbits are born, the fleas make their way down to them and once on
board they start feeding, mating, and laying eggs. After 12 days, the adult
fleas make their way back to the mother. They complete this mini-migration
every time she gives birth.[9]
Newly emerged adult fleas live only about one week if a
blood meal is not obtained. However, completely developed adult fleas can live
for several months without eating, so long as they do not emerge from their
puparia. Optimum temperatures for the flea's life cycle are 70°F to 85°F (21°C
to 30°C) and optimum humidity is 70%.[9]
Classification
Cat
flea
Fleas are related to mecoptera,[10] winged insects with good
eyesight. The flightless boreid
(snow scorpionfly) with its rudimentary wings
seems to be close to the common ancestor of the 2000 or so known varieties of
flea, which split off in many directions around 160 million years ago.[10] Their evolution continued to
produce adaptations for their specialized parasitic niche, such that they now
have no wings and their eyes are covered over. The large number of flea species
may be attributed to the wide variety of host species they feed on, which
provides so many specific ecological niches to adapt to.
In the past, it was most commonly supposed that fleas had
evolved from the flies (Diptera),
based on similarities of the larvae. (Some authorities use the name Aphaniptera
because it is older, but names above
family rank need not follow the ICZN
rules of priority, so most taxonomists use the
more familiar name). Genetic and
morphological evidence indicates that they are descendants of the Scorpionfly family Boreidae, which are also flightless;
accordingly it is possible that they will eventually be reclassified as a
suborder within the Mecoptera. In any case,
all these groups seem to represent a clade
of closely related insect lineages, for which the names Mecopteroidea and
Antliophora have been proposed.
Flea systematics are not
entirely fixed. While, compared to many other insect groups, fleas have been
studied and classified fairly thoroughly, details still remain to be learned
about the evolutionary relationships among the
different flea lineages.
- Infraorder
Pulicomorpha
- Superfamily
Pulicoidea
- Family
Hectopsyllidae—sticktight
and chigoe fleas
("chiggers" of Latin America)
- Family Pulicidae—common fleas
- Superfamily Malacopsylloidea
- Family Malacopsyllidae
- Family Rhopalopsyllidae—hosts
- Family Vermipsyllidae—hosts:
carnivores
- Superfamily Coptopsylloidea
- Family Coptopsyllidae
- Superfamily Ancistropsylloidea
- Family Ancistropsyllidae
- Infraorder
Pygiopsyllomorpha
- Superfamily Pygiopsylloidea
- Family Lycopsyllidae
- Family Pygiopsyllidae
- Family Stivaliidae
- Infraorder
Hystrichopsyllomorpha
- Superfamily Hystrichopsylloidea
- Family
Hystrichopsyllidae—hosts: rats and mice. Includes Ctenopsyllidae,
Amphipsyllidae
- Family Chimaeropsyllidae
- Superfamily Macropsylloidea
- Family Macropsyllidae
- Superfamily Stephanocircidoidea
- Family Stephanocircidae
Relationship with host
Flea
bites on the back of a human
Flea
bite on the waist of a human with no reaction
Fleas attack a wide variety of warm-blooded vertebrates including dogs, cats, humans,
chickens, rabbits, squirrels, rats, ferrets, and mice.
Direct effects of bites
Main
article: Pulicosis
Fleas are a nuisance to their hosts, causing an itching
sensation which in turn may result in the host attempting to remove the pest by
biting, pecking, scratching, etc. in the vicinity of the parasite. Fleas are
not simply a source of annoyance, however. Some people and animals suffer allergic reactions to flea saliva resulting in rashes.
Flea bites generally result in the formation of a slightly raised, swollen
itching spot with a single puncture point at the center (similar to a mosquito bite). The bites often appear in
clusters or lines of two bites, and can remain itchy and inflamed for up to
several weeks afterwards. Fleas can also lead to hair loss as a result of
frequent scratching and biting by the animal, and can cause anemia in extreme cases.[11]:126
As a vector
Besides the problems posed by the creature itself, fleas can
also act as a vector
for disease. Fleas transmit not only a variety
of viral, bacterial and rickettsial diseases to humans and other
animals, but also protozoans and helminths.[12]:72–73
- bacteria:
Murine or endemic typhus.[11]:124 Fleas have helped cause
epidemics by transmitting diseases
such as the bubonic
plague between rodents and humans by carrying Yersinia
pestis bacteria.[13] Fleas can transmit Yersinia
pestis, Rickettsia
typhi, Rickettsia
felis, and Bartonella
henselae.
- virus:
myxomatosis.[12]:73
- helminth:
infestation of Hymenolepiasis
tapeworm.[14]
- protozoa:
Trypanosome protozoans such as those
of the subgenus Herpetosoma,
use a variety of flea species opportunistically as vectors.[12]:74
Fleas that specialize as parasites on specific mammals may
use other mammals as hosts; therefore humans are susceptible to the predation
of more than one species of flea.[15]
A misconception concerning the carrying/transmission of the
HIV/AIDS by fleas has been debunked by the Centers for Disease Control and
Prevention (CDC 2003), which stated that fleas cannot carry the virus and
spread it to other humans.
For humans
Fleas can settle in a person's hair in less than ten
minutes, causing soreness and itching. The itching associated with flea bites
can be treated with anti-itch creams,
usually antihistamines
or hydrocortisone.[16]
Calamine lotion has been shown to be
effective for itching.[17]
For pets
Flea
and tick repellant powder being applied to a dog
Modern flea control is approached using Integrated
Pest Management (IPM) protocols at the host (pet) level. IPM is
achieved by targeting fleas during at least two separate life stages, with at
least two separate molecules. This is typically achieved using an adulticide to kill adult fleas and an
insect development inhibitor (IDI), like lufenuron, or insect growth regulator
(IGR), like methoprene, to prevent development of
immature stages. Flea adults, larvae, or eggs can be controlled with insecticides. Lufenuron is a veterinary preparation
(Program) that attacks the larval flea's ability to produce chitin but does not kill fleas. Flea medicines need to
be used with care because many of them also affect mammals.
Cedar oil, a
non-toxic natural substance, has been proven effective in the eradication of
infestations in pets. Cedar oil is being used to treat sand-flea infestation of
US Military forces in the Persian Gulf.[18]
Since more than three quarters of a flea's life is spent
somewhere other than on the host animal, it is not adequate to treat only the
host; it is important also to treat the host's environment. Thorough vacuuming,
washing linens in hot water, and treating all hosts in the immediate
environment (the entire household, for example) are essential and if possible
on a regular basis.[19]
Contemporary commercial products for the topical treatment
of flea infestations on pets contain pesticides such as imidacloprid, permethrin, and (S)-methoprene. All flea control products are
recommended to be used at least half-yearly because the lifecycle
of flea and tick can last to up to 6 months, and by using one of the flea and
tick control products for so long, the infestation is highly prevented and, in
the end, stopped. Although all these products are effective in fighting against
flea and tick infestations, they have different active
ingredients and, because cats cannot metabolize some of the compounds of the
product, care must be taken in their use.
For the home
Combatting a flea infestation in the home takes patience
because for every flea found on an animal, there could be many more developing
in the home. A spot-on insecticide will kill the fleas on the pet and in turn
the pet itself will be a roving flea trap and mop up newly hatched fleas. The
environment should be treated with a fogger or spray insecticide containing an insect growth regulator, such as pyriproxyfen or methoprene to kill eggs and pupae, which
are quite resistant against insecticides. Frequent vacuuming is also helpful,
but the vacuum bag must be disposed of immediately afterwards. Fleas tend to
breed exponentially in piles of shoes.
Flea
"dirt" in the fur of a cat is actually excess blood from the host
consumed by the adult flea and passed as feces
Diatomaceous earth
can also be used as a home flea treatment in lieu of acetylcholinesterase
inhibitory treatments or insecticides which carry with them a risk of poisoning
for both humans and animals. However, diatomaceous earth is at least
potentially dangerous to pets and people when inhaled, so care in use is
recommended.
Dried pennyroyal has been
suggested as a natural flea control,[20]
but is not recommended in homes with pets due to its high toxicity to mammals.[21]
Borax is sold as a "Natural Laundry
Booster" and can also be used as another home treatment for flea
infestations. Borax contains sodium borate which kills
fleas by dehydrating them, but its safety for pets is untested.[22]
Using dehumidifiers with
air
conditioning and vacuuming all may interrupt the flea life cycle.
Humidity is critical to flea survival. Eggs need relative humidity of at least
70–75% to hatch, and larvae need at least 50% humidity to survive. In humid
areas, about 20% of the eggs survive to adulthood; in arid
areas, less than 5% complete the cycle.[23] Fleas thrive at higher
temperatures, but need 70° to 90°F (21° to 32°C) to survive. Lower temperatures
slow down or completely interrupt the flea life-cycle. A laboratory study done
at the University of
California showed that vacuuming catches about 96% of adult fleas. A
combination of controlled humidity, temperature, and vacuuming should eliminate
fleas from an environment. Altering even one of these environmental factors may
be enough to drastically lower and eliminate an infestation.
See also
- Pulicosis (Flea bites)
- Anti-itch drug
- Bubonic plague
- Cat flea
- Echidnophaga
gallinacea
- Flea circus
- Use
of DNA in forensic entomology
Sumber : http://en.wikipedia.org/wiki/Flea
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