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 and birds.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), making the flea one of the best jumpers of all known animals (relative to body size), second only to the
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." It has been known that fleas do not use muscle power but energy stored in a protein named resilin, with researchers using high-speed video technology and mathematical models to discover where the spring action actually happens.
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
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.
bacteria: Murine or endemic typhus.:124 Fleas have helped cause epidemics by transmitting diseases such as the bubonic plague between rodents and humans by carrying Yersinia pestis bacteria. Fleas can transmit Yersinia pestis, Rickettsia typhi, Rickettsia felis, and Bartonella henselae.
helminth: infestation of Hymenolepiasis tapeworm.
protozoa: Trypanosome protozoans such as those of the subgenus Herpetosoma, use a variety of flea species opportunistically as vectors.: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.
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.