Fleas

Biology of fleas

Species of fleas

Fleas and diseases

Resources

Fleas are about one thousand species of small insects in the order Siphonaptera, including several hundred species in North America. Adult fleas are external parasites (that is, ectoparasites) of mammals or birds, living on skin or in fur or feathers, and feeding on the blood of their hosts. Some fleas are serious parasites of birds or mammals, and may cause important damage to domestic animals, and sometimes great discomfort to humans. Some species of fleas are vectors of serious diseases of humans or other animals. Infestations of fleas often must be dealt with using topical applications of an insecticide.

Biology of fleas

Fleas have a laterally compressed body, a tough, smooth cuticle with many backward-projecting bristles, and relatively long legs. The mouth parts of fleas include stylets that are used to pierce the skin of the host animal, so that a blood meal can be obtained by sucking.

Fleas have a life cycle characterized by four developmental stages: egg, larva, pupa, and adult. The eggs are usually laid close to the body of the host in a place where the host commonly occurs, for example, on the ground, in a bird or mammal nest, or in carpets or soft furniture in homes. Larval fleas have chewing mouth parts and feed on organic debris and the feces of adult fleas, while adults require meals of bird or mammal blood.

Fleas commonly spend a great deal of time off their hosts, for example, in vegetation or on the ground. They can generally survive for a long time without feeding, while waiting for a suitable opportunity to parasitize a host animal. Fleas are wingless, but they walk well and actively travel over the body of their hosts, and between hosts as well.

Fleas are well known for their jumping ability, with their hind legs providing the propulsive mechanism. As a defensive measure, a flea can propel itself many times its body length through the air. The human flea (Pulex irritans ), for example, can jump as high as 7.9 in (20 cm) and as far as 15 in (38 cm), compared with a body length of only a few millimeters.

Species of fleas

There are numerous species of fleas, occurring in various parts of the world. Although most species of fleas are specific to particular host animals for breeding, they are less specific in their feeding and may use various species of birds or mammals for this purpose.

The cat flea (Ctenocephalides felis ) can be quite abundant during the hotter months of summer, as can the dog flea (C. canis ), when their populations may build up in homes with pet animals. These fleas will also avidly feed on humans, biting especially commonly around the feet and ankles.

The human flea (Pulex irritans ) is an important pest of worldwide distribution that can be quite common in human habitations, especially in tropical and subtropical countries. The oriental rat flea (Xenopsylla cheopis ) is an especially important species, because it is the vector by which the deadly bubonic plague can be spread to humans.

Fleas and diseases

Many of the species of fleas that infest domestic mammals and birds will also utilize humans as a host, although people are not the generally preferred host of these blood-sucking parasites.

The most deadly disease that can be spread to humans by fleas is bubonic plague or black death, caused by the bacterium Pasteurella pestis, and spread to people by various species of fleas, but particularly by the plague or oriental rat flea (Xenopsylla cheopis ). Bubonic plague is an extremely serious disease, because it can occur in epidemics that afflict large numbers of people, and can result in high mortality rates. During the European Black Death of medieval times, millions of people died of this disease. There

KEY TERMS

Vector —Any agent, living or otherwise, that carries and transmits parasites and diseases.

have been similarly serious outbreaks in other places where rats, plague fleas, and humans were all abundant. Bubonic plague is mostly a disease of rodents, which serve as a longer-term reservoir for this disease. However, plague can be transmitted to humans when they serve as an alternate host to rodent fleas during times when rodent populations are large. Plague is mostly spread to humans when infested flea feces are inadvertently scratched into the skin, but transmission can also occur more directly while the fleas are feeding, or when a host accidentally ingests an infected flea.

Another disease that can be spread to humans by fleas is known as endemic or murine flea-borne typhus. This disease is caused by a microorganism known as Rickettsia, and is passed to humans by various species of fleas and lice, but especially by the oriental rat flea. Fleas are also the vector of a deadly disease that afflicts rabbits, known as myxomatosis.

Fleas may also serve as alternate hosts of several tapeworms that can infect humans. These include Dipylidium caninum, which is most commonly a parasite of dogs, but can be passed to humans by the dog flea (Ctenocephalides canis ). Similarly, the tapeworm Hymenolepis diminuta can be passed to people by the rat flea (Xenopsylla cheopis ).

Resources

BOOKS

Carde, Ring, and Vincent H. Resh, eds. Encyclopedia of Insects. San Diego, CA: Academic Press, 2003.

Bill Freedman

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flea, common name for any of the small, wingless insects of the order Siphonaptera. The adults of both sexes eat only blood and are all external parasites of mammals and birds. Fleas have hard bodies flattened from side to side and piercing and sucking mouthparts. Their legs are powerful and adapted for fast movement and jumping, enabling them to find new hosts as well as to escape quickly the attempts of the hosts to remove them. The adults can survive away from a host for several weeks without eating. Flea eggs are usually laid in dirt or in the nest of the host; the larvae feed on organic material and the feces of adult fleas. Metamorphosis is complete; the larvae spin silken cocoons when ready to pupate. Many species are not specific to a particular host species, and cat and dog fleas, as well as the human flea of the warmer parts of Europe and Asia, attack humans. Certain rat fleas transmit typhus and bubonic plague to humans, and another species transmits tularemia from rabbits. Fleas also transmit several species of tapeworms that sometimes infest humans. The chigoe is a flea. Water fleas and beach fleas are crustaceans and not closely related to the insects. Fleas are classified in the phylum Arthropoda, class Insecta, order Siphonaptera.

Siphonaptera (fleas; class Insecta, subclass Pterygota) An order of wingless, parasitic insects in which the adult body is flattened laterally. The larvae (maggots) feed on organic debris, undergo complete metamorphosis, and hatch from the pupa when this is disturbed by a possible host. Most adults are host-specific, although some have a wide range of hosts and others will feed on any host when very hungry. There are 1400–1500 species, of world-wide distribution, grouped in two suborders: Pulicida and Apulicida. The Pulicida includes the families Pulicidae (most flea parasites of mammals, some of which are vectors for serious diseases, e.g. pneumonic plague) and Tungidae (the jigger or sand flea).

flea the flea is often taken as the type of something small and contemptible, or as a sign of dirt and degradation.
as fit as a flea in very good health. Recorded from the late 19th century, an example of the emphasis given by alliteration (compare as fit as a fiddle).
flea bite an insignificant inconvenience or cost (literally, a small red mark caused by the bite of a flea).
a flea in one's ear a sharp reproof administered to someone.

see also big fleas have little fleas, lie down with dogs, you will get up with fleas, nothing should be done in haste but gripping a flea.

FLEA

FLEA (Heb. פַּרְעֹשׁ, parosh). The flea symbolizes an insignificant, loathsome creature (i Sam. 24:15; 26:20). Nevertheless, the ancients did not refrain from calling themselves "parosh," and this was the name of a Judahite family that came with Ezra to Ereẓ Israel from Babylonia (Ezra 2:3), as well as of a Moabite prince (Neh. 10:15). The common flea, Pulex irritans, is a parasite living on human beings and other mammals. Another species is the Chenopsylla cheopsis, which attaches itself to rats. The flea is mentioned several times in talmudic literature where it is stated that contrary to several insects regardedas formed through spontaneous generation, its propagation is sexual (Shab. 107b). In modern times the flea has disappeared almost entirely from the inhabited regions of Israel.

bibliography:

F.S. Bodenheimer, Ha-Ḥai be-Arẓot ha-Mikra, 2 (1956), 292ff.; Tristram, Nat Hist, 305.

[Jehuda Feliks]

Siphonaptera An order of secondarily wingless insects comprising the fleas. The body of a flea is laterally compressed and bears numerous backward-directed spines. Fleas live as blood-sucking ectoparasites of mammals and birds, having mouthparts adapted to piercing their host, injecting saliva to prevent clotting, and sucking up the blood. The long bristly legs can transmit energy stored in the elastic body wall to leap relatively long distances (over 300 mm horizontally). Apart from causing irritation, fleas can transmit disease organisms, most notably bubonic plague bacteria, which can be carried from rats to humans by the rat flea (Xenopsylla cheopsis). The whitish wormlike legless larvae feed on organic matter. After two moults the larva spins a cocoon and undergoes metamorphosis into the adult.

flea / flē/ • n. a small wingless jumping insect (order Siphonaptera) that feeds on the blood of mammals and birds, including the human flea (Pulex irritans) and the cat flea (Ctenocephalides felis). ∎  a water flea (see daphnia).

flea (flee) n. a small wingless bloodsucking insect with a laterally compressed body and long legs adapted for jumping. Adult fleas are temporary parasites on birds and mammals and those species that attack humans (Pulex, Xenopsylla, and Nosopsyllus) may be important in the transmission of various diseases. Their bites may become a focus of infection.