Flea

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For other uses, see Flea (disambiguation).

iFleas

SEM of a flea

Scientific classification

Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Subclass:	Pterygota
Infraclass:	Neoptera
Superorder:	Endopterygota
Order:	Siphonaptera

Families

Tungidae – sticktight and chigoe fleas (chiggers)
Pulicidae – common fleas
Coptopsyllidae
Vermipsyllidae – carnivore fleas
Rhopalopsyllidae – marsupial fleas
Hypsophthalmidae
Stephanocircidae
Pygiopsyllidae
Hystrichopsyllidae – rat and mouse fleas
Leptopsyllidae – mouse and rat fleas
Ischnopsyllidae – bat fleas
Ceratophyllidae:-fleas mainly associated with rodents Amphipsyllidae
Malacopsyllidae
Dolichopsyllidae – rodent fleas
Ctenopsyllidae

Flea is the common name for any of the small wingless insects of the order Siphonaptera (some authorities use the name Aphaniptera because it is older, but names above family rank do not follow the rules of priority, so most taxonomists use the more familiar name). Fleas are external parasites, living by hematophagy off the blood of mammals and birds, and 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 the past, however, it was most commonly supposed that fleas had evolved from the flies (Diptera), based on similarities of the larvae.

Note: There is also a genus of foraminiferan Protozoa named Siphonaptera

Some well known flea species include:

Cat flea (Ctenocephalides felis),
Dog flea (Ctenocephalides canis),
Human flea (Pulex irritans),
Northern rat flea (Nosopsyllus fasciatus),
Oriental rat flea (Xenopsylla cheopis).

Flea bites on the back of a human

In most cases, fleas are just a nuisance to their hosts, but some people and some 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. The bites often appear in clusters or lines, 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.

However, fleas can also act as a vector for disease. For example, fleas transmitted the bubonic plague between rodents and humans by carrying Yersinia pestis bacteria. Murine typhus (endemic typhus) fever, and in some cases tapeworms, Hymenolepis, can also be transmitted by fleas.

Flea bites can be treated with Calamine lotion or 0.5-1% conc. hydrocortisone cream. Lufenuron is a veterinary medicine that attacks the larval flea's ability to produce chitin. See also Frontline (medicine).

Hooke's drawing of a flea in Micrographia

Flea "dirt," in the fur of a cat, is actually excess blood (from host) consumed by the adult flea, passed as feces.

[edit] Flea treatments

Flea medicines need to be used with care. Phenothrin (85.7%) in combination with Methoprene was a popular topical flea/tick therapy for felines. Phenothrin kills adult fleas and ticks. Methoprene is an insect growth regulator that interrupts the insect's life cycle by killing the eggs. However, the US EPA has pressured at least one manufacturer of products containing these compounds to voluntarily withdraw some products and include strong cautionary statements on others, warning of adverse feline toxicity.^[1]

A combination of etofenprox (55.0%) and pyriproxyfen (2.2%) is another formulation used in Sergeant's Gold treatment for cats, and possibly others.