Flea, the common name for the
order
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
Siphonaptera, includes 2,500 species of small flightless
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...
s that live as external
parasites of
mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s and
bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
s. Fleas live by
ingesting the blood of their hosts. Adult fleas grow to about long, are usually brown, and have bodies that are "flattened" sideways or narrow, enabling them to move through their hosts' fur or feathers. They lack wings; their hind legs are extremely well adapted for jumping. Their claws keep them from being dislodged, and their mouthparts are adapted for piercing skin and sucking
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...
. They can leap 50 times their body length, a feat second only to jumps made by another group of insects, the
superfamily
SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...
of
froghopper
The froghoppers, or the superfamily Cercopoidea, are a group of hemipteran insects in the suborder Auchenorrhyncha. Adults are capable of jumping many times their height and length, giving the group their common name, but they are best known ...
s. Flea larvae are worm-like, with no limbs; they have chewing mouthparts and feed on organic debris left on their hosts' skin.
Genetic evidence indicates that fleas are a specialised lineage of parasitic
scorpionflies
Mecoptera (from the Greek language, Greek: ''mecos'' = "long", ''ptera'' = "wings") is an Order (biology), order of insects in the superorder Endopterygota with about six hundred species in nine Family (biology), families worldwide. Mecopterans ...
(Mecoptera) ''sensu lato'', most closely related to the family
Nannochoristidae. The earliest known fleas are lived in the Middle
Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
; modern-looking forms appeared in the
Cenozoic
The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...
. Fleas probably originated on mammals first and expanded their reach to birds. Each species of flea specializes, more or less, on one species of host: many species of flea never breed on any other host; some are less selective. Some families of fleas are exclusive to a single host group; for example, the Malacopsyllidae are found only on
armadillo
Armadillos (meaning "little armored ones" in Spanish) are New World placental mammals in the order Cingulata. The Chlamyphoridae and Dasypodidae are the only surviving families in the order, which is part of the superorder Xenarthra, along wi ...
s, the
Ischnopsyllidae only on
bat
Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bi ...
s, and the Chimaeropsyllidae only on
elephant shrews.
The oriental rat flea, ''
Xenopsylla cheopis'', is a
vector of ''
Yersinia pestis'', the
bacterium
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
that causes
bubonic plague
Bubonic plague is one of three types of plague caused by the plague bacterium (''Yersinia pestis''). One to seven days after exposure to the bacteria, flu-like symptoms develop. These symptoms include fever, headaches, and vomiting, as well a ...
. The disease was spread to humans by rodents, such as the
black rat
The black rat (''Rattus rattus''), also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus ''Rattus'', in the subfamily Murinae. It likely originated in the Indian subcontinent, but is n ...
, which were bitten by infected fleas. Major outbreaks included the
Plague of Justinian, about 540, and the
Black Death
The Black Death (also known as the Pestilence, the Great Mortality or the Plague) was a bubonic plague pandemic occurring in Western Eurasia and North Africa from 1346 to 1353. It is the most fatal pandemic recorded in human history, causi ...
, about 1350, each of which killed a sizeable fraction of the world's people.
Fleas appear in human culture in such diverse forms as
flea circuses; poems, such as
John Donne
John Donne ( ; 22 January 1572 – 31 March 1631) was an English poet, scholar, soldier and secretary born into a recusant family, who later became a clergy, cleric in the Church of England. Under royal patronage, he was made Dean of St Paul's ...
's erotic "
The Flea"; works of music, such as those by
Modest Mussorgsky; and a film by
Charlie Chaplin
Sir Charles Spencer Chaplin Jr. (16 April 188925 December 1977) was an English comic actor, filmmaker, and composer who rose to fame in the era of silent film. He became a worldwide icon through his screen persona, the Tramp, and is consider ...
.
Morphology and behavior
Fleas are wingless insects, long, that are agile, usually dark colored (for example, the reddish-brown of the
cat flea
The cat flea (scientific name ''Ctenocephalides felis'') is an extremely common parasitic insect whose principal host is the domestic cat, although a high proportion of the fleas found on dogs also belong to this species. This is despite the wide ...
), with a
proboscis
A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...
, or stylet, adapted to feeding by piercing the skin and sucking their host's blood through their epipharynx. Flea legs end in strong claws that are adapted to grasp a host.
Unlike other insects, fleas do not possess
compound eyes but instead only have simple eyespots with a single biconvex lens; some species lack eyes altogether. Their bodies are laterally compressed, permitting easy movement through the hairs or feathers on the host's body. The flea body is covered with hard plates called sclerites.
These sclerites are covered with many hairs and short spines directed backward, which also assist its movements on the host. The tough body is able to withstand great pressure, likely an
adaptation
In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the po ...
to survive attempts to eliminate them by scratching.
[Fleas](_blank)
Koehler, P.G.; Oi, F.M. Printed July 1993, revised February 2003. Provided by the University of Florida
The University of Florida (Florida or UF) is a public land-grant research university in Gainesville, Florida. It is a senior member of the State University System of Florida, traces its origins to 1853, and has operated continuously on its ...
Fleas lay tiny, white, oval eggs. The larvae are small and pale, have bristles covering their worm-like bodies, lack eyes, and have mouth parts adapted to chewing. The larvae feed on organic matter, especially the feces of mature fleas, which contain dried blood. Adults feed only on fresh blood.
Jumping
Their legs are long, the hind pair well adapted for jumping; a flea can jump vertically up to and horizontally up to ,
making the flea one of the best jumpers of all known animals (relative to body size), second only to the
froghopper
The froghoppers, or the superfamily Cercopoidea, are a group of hemipteran insects in the suborder Auchenorrhyncha. Adults are capable of jumping many times their height and length, giving the group their common name, but they are best known ...
. A flea can jump more than 100 times its length (vertically up to 7 inches and horizontally 13 inches). That's equivalent to an adult human jumping 250 feet vertically and 450 feet horizontally. Rarely do fleas jump from dog to dog. Most flea infestations come from newly developed fleas from the pet's environment. The flea jump is so rapid and forceful that it exceeds the capabilities of muscle, and instead of relying on direct muscle power, fleas store muscle energy in a pad of the elastic protein named
resilin
Resilin is an elastomeric protein found in many insects and other arthropods. It provides soft rubber-elasticity to mechanically active organs and tissue; for example, it enables insects of many species to jump or pivot their wings efficiently ...
before releasing it rapidly (like a human using a bow and arrow).
Immediately before the jump, muscles contract and deform the resilin pad, slowly storing energy which can then be released extremely rapidly to power leg extension for propulsion.
To prevent premature release of energy or motions of the leg, the flea employs a "catch mechanism".
Early in the jump, the tendon of the primary jumping muscle passes slightly behind the coxa-trochanter joint, generating a
torque
In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...
which holds the joint closed with the leg close to the body.
To trigger jumping, another muscle pulls the tendon forward until it passes the joint axis, generating the opposite torque to extend the leg and power the jump by release of stored energy.
The actual take off has been shown by high-speed video to be from the tibiae and tarsi rather than from the
trochantera (knees).
Life cycle and development
Fleas are
holometabolous insects, going through the four
lifecycle
Life cycle, life-cycle, or lifecycle may refer to:
Science and academia
* Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring
*Life-cycle hypothesis ...
stages of
egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
,
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
,
pupa
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...
, and
imago
In biology, the imago (Latin for "image") is the last stage an insect attains during its metamorphosis, its process of growth and development; it is also called the imaginal stage, the stage in which the insect attains maturity. It follows the f ...
(adult). In most species, neither female nor male fleas are fully mature when they first emerge but must feed on blood before they become capable of reproduction.
The first blood meal triggers the maturation of the ovaries in females and the dissolution of the testicular plug in males, and copulation soon follows.
Some species breed all year round while others synchronise their activities with their hosts' life cycles or with local environmental factors and climatic conditions.
Flea populations consist of roughly 50% eggs, 35% larvae, 10% pupae, and 5% adults.
Egg
The number of eggs laid depends on species, with batch sizes ranging from two to several dozen. The
total number of eggs produced in a female's lifetime (fecundity) varies from around one hundred to several thousand. In some species, the flea lives in the host's nest or burrow and the eggs are deposited on the substrate,
[ but in others, the eggs are laid on the host itself and can easily fall off onto the ground. Because of this, areas where the host rests and sleeps become one of the primary ]habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
s of eggs and developing larvae. The eggs take around two days to two weeks to hatch.
Larva
Flea larvae emerge from the eggs to feed on any available organic material such as dead insects, faeces, conspecific eggs, and vegetable matter. In laboratory studies, some dietary diversity seems necessary for proper larval development. Blood-only diets allow only 12% of larvae to mature, whereas blood and yeast or dog chow diets allow almost all larvae to mature. Another study also showed that 90% of larvae matured into adults when the diet included nonviable eggs. They are blind and avoid sunlight, keeping to dark, humid places such as sand or soil, cracks and crevices, under carpets and in bedding.[ The entire larval stage lasts between four and 18 days.
]
Pupa
Given an adequate supply of food, larvae pupate and weave silk
Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the coc ...
en cocoons after three larval stages. Within the cocoon, the larva molts for a final time and undergoes metamorphosis into the adult form. This can take just four days, but may take much longer under adverse conditions, and there follows a variable-length stage during which the pre-emergent adult awaits a suitable opportunity to emerge. Trigger factors for emergence include vibrations (including sound), heat (in warm-blooded hosts), and increased levels of carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
, all of which may indicate the presence of a suitable host. Large numbers of pre-emergent fleas may be present in otherwise flea-free environments, and the introduction of a suitable host may trigger a mass emergence.[
]
Adult
Once the flea reaches adulthood, its primary goal is to find blood and then to reproduce. Female fleas can lay 5000 or more eggs over their life, permitting rapid increase in numbers. Generally speaking, an adult flea only lives for 2 or 3 months. Without a host to provide a blood meal, a flea's life can be as short as a few days. Under ideal conditions of temperature, food supply, and humidity, adult fleas can live for up to a year and a half. 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 21 °C to 30 °C (70 °F to 85 °F) and optimum humidity is 70%.
Adult female rabbit fleas, ''Spilopsyllus cuniculi
''Spilopsyllus cuniculi'', the rabbit flea, is a species of flea in the family Pulicidae. It is an external parasite of rabbits and hares and is occasionally found on cats and dogs and also certain seabirds that nest in burrows. It can act as a ...
'', can detect the changing levels of cortisol
Cortisol is a steroid hormone, in the glucocorticoid class of hormones. When used as a medication, it is known as hydrocortisone.
It is produced in many animals, mainly by the ''zona fasciculata'' of the adrenal cortex in the adrenal gland ...
and corticosterone
Corticosterone, also known as 17-deoxycortisol and 11β,21-dihydroxyprogesterone, is a 21-carbon steroid hormone of the corticosteroid type produced in the cortex of the adrenal glands. It is of minor importance in humans, except in the very rare ...
hormones in the rabbit's blood that indicate it 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.[ Piper, Ross (2007), ''Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals'', ]Greenwood Press
Greenwood Publishing Group, Inc. (GPG), also known as ABC-Clio/Greenwood (stylized ABC-CLIO/Greenwood), is an educational and academic publisher (middle school through university level) which is today part of ABC-Clio. Established in 1967 as Gr ...
.
Taxonomy and phylogeny
History
Between 1735 and 1758, the Swedish naturalist Carl Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...
first classified insects, doing so on the basis of their wing structure. One of the seven orders into which he divided them was "Aptera", meaning wingless, a group in which as well as fleas, he included spider
Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...
s, woodlice
A woodlouse (plural woodlice) is an isopod crustacean from the polyphyleticThe current consensus is that Oniscidea is actually triphyletic suborder Oniscidea within the order Isopoda. They get their name from often being found in old wood. ...
and myriapods. It wasn't until 1810 that the French zoologist Pierre André Latreille reclassified the insects on the basis of their mouthparts as well as their wings, splitting Aptera into Thysanura (silverfish), Anoplura
Sucking lice (Anoplura, formerly known as Siphunculata) have around 500 species and represent the smaller of the two traditional superfamily (taxonomy), superfamilies of lice. As opposed to the paraphyletic chewing lice, which are now divided amo ...
(sucking lice) and Siphonaptera (fleas), at the same time separating off the arachnids and crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...
s into their own subphyla. The group's name, Siphonaptera, is zoological Latin from the Greek ''siphon'' (a tube) and ''aptera'' (wingless).
External phylogeny
It was historically unclear whether the Siphonaptera are sister to the Mecoptera (scorpionflies and allies), or are inside that clade, making "Mecoptera" paraphyletic. The earlier suggestion that the Siphonaptera are sister to the Boreidae
Boreidae, commonly called snow scorpionflies, or in the British Isles, snow fleas (no relation to the snow flea ''Hypogastrura nivicola'') are a very small family of scorpionflies, containing only around 30 species, all of which are boreal or hi ...
(snow scorpionflies) is not supported. A 2020 genetic study recovered Siphonaptera within Mecoptera, with strong support, as the sister group to Nannochoristidae, a small, relictual group of mecopterans native to the Southern Hemisphere. Fleas and nannochoristids share several similarities with each other that are not shared with other mecopterans, including similar mouthparts as well as a similar sperm pump organisation.
Relationships of Siphonaptera per Tihelka et al. 2020.
Fossil history
Fleas likely descended from fluid feeding insects that probably fed on plants. Fossils of large, wingless stem-group fleas with siphonate (sucking) mouthparts from the Middle Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
to Early Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
have been found in northeastern China and Russia, belonging to the families Saurophthiridae and Pseudopulicidae, as well as ''Tarwinia
''Tarwinia'' is an extinct genus of stem-group flea known from a single species, ''T. australis'', from the Early Cretaceous ( Aptian) Koonwarra Fossil Bed of Victoria
Victoria most commonly refers to:
* Victoria (Australia), a state of ...
'' from the Early Cretaceous of Australia. Most flea families formed after the end of the Cretaceous (in the Paleogene
The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...
and onwards). Modern fleas probably arose in the southern continental area of Gondwana
Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...
, and migrated rapidly northwards from there. They most likely evolved with mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
hosts, only later moving to bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
s.
Siphonaptera is a relatively small order of insects: members of the order undergo complete metamorphosis and are secondarily wingless (their ancestors had wings which modern forms have lost). In 2005, Medvedev listed 2005 species in 242 genera, and despite subsequent descriptions of new species, bringing the total up to around 2500 species,[ this is the most complete database available. The order is divided into four infraorders and eighteen families. Some families are exclusive to a single host group; these include the Malacopsyllidae (]armadillo
Armadillos (meaning "little armored ones" in Spanish) are New World placental mammals in the order Cingulata. The Chlamyphoridae and Dasypodidae are the only surviving families in the order, which is part of the superorder Xenarthra, along wi ...
s), Ischnopsyllidae (bat
Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bi ...
s) and Chimaeropsyllidae ( elephant shrews).
Many of the known species are little studied. Some 600 species (a quarter of the total) are known from single records. Over 94% of species are associated with mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
ian hosts, and only about 3% of species can be considered to be specific parasites of bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
s. The fleas on birds are thought to have originated from mammalian fleas; at least sixteen separate groups of fleas switched to avian hosts during the evolutionary history of the Siphonaptera. Occurrences of fleas on reptiles is accidental, and fleas have been known to feed on the hemolymph
Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which ...
(bloodlike body fluid) of tick
Ticks (order Ixodida) are parasitic arachnids that are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, species, and "fullness". Ticks are external parasites, living by ...
s.[
]
Internal phylogeny
Flea phylogeny was long neglected, the discovery of homologies with the parts of other insects being made difficult by their extreme specialization. Whiting and colleagues prepared a detailed molecular phylogeny in 2008, with the basic structure shown in the cladogram. The Hectopsyllidae
Hectopsyllidae is a small family of fleas, containing only the chigoe flea ''Tunga penetrans'' and the genus '' Hectopsylla''. They were formerly known as Tungidae, and by authorities that demote the Pulicoidea to family rank they are treated as ...
, including the harmful chigoe flea or jigger, is sister to the rest of the Siphonaptera.[
]
Relationship with host
Fleas feed on a wide variety of warm-blooded
Warm-blooded is an informal term referring to animal species which can maintain a body temperature higher than their environment. In particular, homeothermic species maintain a stable body temperature by regulating metabolic processes. The onl ...
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
s including dogs, cats, rabbits, squirrels, ferrets, rats, mice birds and sometimes humans. Fleas normally specialise in one host species or group of species, but can often feed but not reproduce on other species. ''Ceratophyllus gallinae
''Ceratophyllus gallinae'', known as the hen flea in Europe or the European chicken flea elsewhere, is an ectoparasite of birds. This flea was first described by the German botanist and entomologist Franz von Paula Schrank in 1803.
Taxonomy
'' ...
'' affects poultry as well as wild birds.[ As well as the degree of relatedness of a potential host to the flea's original host, it has been shown that avian fleas that exploit a range of hosts, only parasitise species with low immune responses. In general, host specificity decreases as the size of the host species decreases. Another factor is the opportunities available to the flea to change host species; this is smaller in colonially nesting birds, where the flea may never encounter another species, than it is in solitary nesting birds. A large, long-lived host provides a stable environment that favours host-specific parasites.]
Although there are species named dog fleas ( ''Ctenocephalides canis'' Curtis, 1826) and cat fleas ( ''Ctenocephalides felis''), fleas are not always strictly species-specific. A study in Virginia
Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...
examined 244 fleas from 29 dogs: all were cat fleas. Dog fleas had not been found in Virginia in more than 70 years, and may not even occur in the US, so a flea found on a dog is likely a cat flea (''Ctenocephalides felis'').
One theory of human hairlessness is that the loss of hair helped humans to reduce their burden of fleas and other ectoparasites.
Direct effects of bites
In many species, fleas are principally a nuisance to their hosts, causing an itching sensation which in turn causes the host to try to remove the pest by biting, pecking or scratching. Fleas are not simply a source of annoyance, however. Flea bites cause a slightly raised, swollen, irritating nodule to form on the epidermis at the site of each bite, with a single puncture point at the centre, like a mosquito bite. This can lead to an eczema
Dermatitis is inflammation of the Human skin, skin, typically characterized by itchiness, erythema, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become lichenification, thick ...
tous itchy skin disease called flea allergy dermatitis
Flea allergy dermatitis is an eczematous itchy skin disease of dogs and cats. For both of these domestic species, flea allergy dermatitis is the most common cause of skin disease. Affected animals develop allergic reactions to chemicals in flea sa ...
, which is common in many host species, including dogs and cats. 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 lead to secondary hair loss as a result of frequent scratching and biting by the animal. They can also cause anemia
Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen due to a lower than normal number of red blood cells, or a reduction in the amount of hemoglobin. When anemia comes on slowly, th ...
in extreme cases.
As a vector
Fleas are vectors for viral
Viral means "relating to viruses" (small infectious agents).
Viral may also refer to:
Viral behavior, or virality
Memetic behavior likened that of a virus, for example:
* Viral marketing, the use of existing social networks to spread a marke ...
, bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
l and rickettsia
''Rickettsia'' is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long). The term "rickett ...
l disease
A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
s of humans and other animals, as well as of protozoa
Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...
n and helminth
Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other parasitic worms such as schi ...
parasites. Bacterial diseases carried by fleas include murine or endemic typhus and bubonic plague
Bubonic plague is one of three types of plague caused by the plague bacterium (''Yersinia pestis''). One to seven days after exposure to the bacteria, flu-like symptoms develop. These symptoms include fever, headaches, and vomiting, as well a ...
. Fleas can transmit ''Rickettsia typhi
''Rickettsia typhi'' is a small, aerobic, obligate intracellular, rod shaped gram negative bacterium. It belongs to the typhus group of the ''Rickettsia'' genus, along with ''R. prowazekii''. ''R. typhi'' has an uncertain history, as it may have l ...
'', ''Rickettsia felis
''Rickettsia felis'' is a species of bacterium, the pathogen that causes cat-flea typhus in humans, also known as flea-borne spotted fever. ''Rickettsia felis'' also is regarded as the causative organism of many cases of illnesses generally class ...
'', '' Bartonella henselae'', and the myxomatosis
Myxomatosis is a disease caused by ''Myxoma virus'', a poxvirus in the genus ''Leporipoxvirus''. The natural hosts are tapeti (''Sylvilagus brasiliensis'') in South and Central America, and brush rabbits (''Sylvilagus bachmani'') in North Ame ...
virus. They can carry ''Hymenolepiasis
Hymenolepiasis is infestation by one of two species of tapeworm: ''Hymenolepis nana'' or '' H. diminuta''. Alternative names are dwarf tapeworm infection and rat tapeworm infection. The disease is a type of helminthiasis which is classified as a n ...
'' tapeworms
Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, known as tapeworms. Their bodies consist of man ...
and Trypanosome protozoans. The chigoe flea or jigger ('' Tunga penetrans'') causes the disease tungiasis, a major public health problem around the world. Fleas that specialize as parasites on specific mammals may use other mammals as hosts; thus, humans may be bitten by cat and dog fleas.
Relationship with humans
In literature and art
Fleas have appeared in poetry, literature, music and art; these include Robert Hooke
Robert Hooke FRS (; 18 July 16353 March 1703) was an English polymath active as a scientist, natural philosopher and architect, who is credited to be one of two scientists to discover microorganisms in 1665 using a compound microscope that ...
's drawing of a flea under the microscope
A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisibl ...
in his pioneering book '' Micrographia'' published in 1665, poems by Donne and Jonathan Swift
Jonathan Swift (30 November 1667 – 19 October 1745) was an Anglo-Irish Satire, satirist, author, essayist, political pamphleteer (first for the Whig (British political party), Whigs, then for the Tories (British political party), Tories), poe ...
, works of music by Giorgio Federico Ghedini and Modest Mussorgsky, a play by Georges Feydeau, a film by Charlie Chaplin
Sir Charles Spencer Chaplin Jr. (16 April 188925 December 1977) was an English comic actor, filmmaker, and composer who rose to fame in the era of silent film. He became a worldwide icon through his screen persona, the Tramp, and is consider ...
, and paintings by artists such as Giuseppe Crespi, Giovanni Battista Piazzetta, and Georges de La Tour.
John Donne
John Donne ( ; 22 January 1572 – 31 March 1631) was an English poet, scholar, soldier and secretary born into a recusant family, who later became a clergy, cleric in the Church of England. Under royal patronage, he was made Dean of St Paul's ...
's erotic
Eroticism () is a quality that causes sexual feelings, as well as a philosophical contemplation concerning the aesthetics of sexual desire, sensuality, and romantic love. That quality may be found in any form of artwork, including painting, scul ...
metaphysical poem
The term Metaphysical poets was coined by the critic Samuel Johnson to describe a loose group of 17th-century English poets whose work was characterised by the inventive use of conceits, and by a greater emphasis on the spoken rather than lyric ...
" The Flea", published in 1633 after his death, uses the conceit of a flea, which has sucked blood from the male speaker and his female lover, as an extended metaphor
A metaphor is a figure of speech that, for rhetorical effect, directly refers to one thing by mentioning another. It may provide (or obscure) clarity or identify hidden similarities between two different ideas. Metaphors are often compared wit ...
for their sexual relationship. The speaker tries to convince a lady to sleep with him, arguing that if the mingling of their blood in the flea is innocent, then sex would be also.
The comic poem ''Siphonaptera'' was written in 1915 by the mathematician Augustus De Morgan, It describes an infinite chain of parasitism made of ever larger and ever smaller fleas.
File:HookeFlea01.jpg, Robert Hooke
Robert Hooke FRS (; 18 July 16353 March 1703) was an English polymath active as a scientist, natural philosopher and architect, who is credited to be one of two scientists to discover microorganisms in 1665 using a compound microscope that ...
's drawing of a flea in '' Micrographia'', 1665
File:The development of the flea from egg to adult Wellcome M0016633.jpg, Development of the flea from egg to adult. Antonie van Leeuwenhoek
Antonie Philips van Leeuwenhoek ( ; ; 24 October 1632 – 26 August 1723) was a Dutch microbiologist and microscopist in the Golden Age of Dutch science and technology. A largely self-taught man in science, he is commonly known as " the ...
, c. 1680
Flea circuses
Flea circuses provided entertainment to nineteenth century audiences. These circuses, extremely popular in Europe from 1830 onwards, featured fleas dressed as humans or towing miniature carts, chariot
A chariot is a type of cart driven by a charioteer, usually using horses to provide rapid motive power. The oldest known chariots have been found in burials of the Sintashta culture in modern-day Chelyabinsk Oblast, Russia, dated to c. 2000&nbs ...
s, rollers or cannon
A cannon is a large- caliber gun classified as a type of artillery, which usually launches a projectile using explosive chemical propellant. Gunpowder ("black powder") was the primary propellant before the invention of smokeless powder ...
. These devices were originally made by watchmakers or jewellers to show off their skill at miniaturization. A ringmaster called a "professor" accompanied their performance with a rapid circus patter.
Carriers of plague
Oriental rat flea
The Oriental rat flea (''Xenopsylla cheopis''), also known as the tropical rat flea or the rat flea, is a parasite of rodents, primarily of the genus ''Rattus'', and is a primary vector for bubonic plague and murine typhus. This occurs when a flea ...
s, ''Xenopsylla cheopis'', can carry the coccobacillus '' Yersinia pestis.'' The infected fleas feed on rodent vectors of this bacterium, such as the black rat
The black rat (''Rattus rattus''), also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus ''Rattus'', in the subfamily Murinae. It likely originated in the Indian subcontinent, but is n ...
, ''Rattus rattus'', and then infect human populations with the plague
Plague or The Plague may refer to:
Agriculture, fauna, and medicine
*Plague (disease), a disease caused by ''Yersinia pestis''
* An epidemic of infectious disease (medical or agricultural)
* A pandemic caused by such a disease
* A swarm of pes ...
, as has happened repeatedly from ancient times, as in the Plague of Justinian in 541–542. Outbreaks killed up to 200 million people across Europe between 1346 and 1671. The Black Death
The Black Death (also known as the Pestilence, the Great Mortality or the Plague) was a bubonic plague pandemic occurring in Western Eurasia and North Africa from 1346 to 1353. It is the most fatal pandemic recorded in human history, causi ...
pandemic between 1346 and 1353 likely killed over a third of the population of Europe.
Because fleas carry plague, they have seen service as a biological weapon. During World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
, the Japanese army dropped fleas infested with ''Y. pestis'' in China. The bubonic and septicaemic plagues are the most probable form of the plague that would spread as a result of a bioterrorism attack that used fleas as a vector.
The Rothschild Collection
The banker Charles Rothschild
Nathaniel Charles Rothschild (9 May 1877 – 12 October 1923), known as "Charles", was an English banker and entomologist and a member of the Rothschild family. He is remembered for The Rothschild List, a list he made in 1915 of 284 sites acros ...
devoted much of his time to entomology
Entomology () is the science, scientific study of insects, a branch of zoology. In the past the term "insect" was less specific, and historically the definition of entomology would also include the study of animals in other arthropod groups, such ...
, creating a large collection of fleas now in the Rothschild Collection at the Natural History Museum, London
The Natural History Museum in London is a museum that exhibits a vast range of specimens from various segments of natural history. It is one of three major museums on Exhibition Road in South Kensington, the others being the Science Museum an ...
. He discovered and named the plague
Plague or The Plague may refer to:
Agriculture, fauna, and medicine
*Plague (disease), a disease caused by ''Yersinia pestis''
* An epidemic of infectious disease (medical or agricultural)
* A pandemic caused by such a disease
* A swarm of pes ...
vector flea, '' Xenopsylla cheopis'', also known as the oriental rat flea, in 1903. Using what was probably the world's most complete collection of fleas of about 260,000 specimens (representing some 73% of the 2,587 species and subspecies so far described), he described around 500 species and subspecies of Siphonaptera. He was followed in this interest by his daughter Miriam Rothschild
Dame Miriam Louisa Rothschild (5 August 1908 – 20 January 2005) was a British natural scientist and author with contributions to zoology, entomology, and botany.
Early life
Miriam Rothschild was born in 1908 in Ashton Wold, near Oundle in No ...
, who helped to catalogue his enormous collection of the insects in seven volumes.
Flea treatments
Fleas have a significant economic impact. In America alone, approximately $2.8 billion is spent annually on flea-related veterinary bills and another $1.6 billion annually for flea treatment with pet groomers. Four billion dollars is spent annually for prescription flea treatment and $348 million for flea pest control.
See also
* Chigger
''Trombicula'', known as chiggers, red bugs, scrub-itch mites, or berry bugs, are small arachnids (eight-legged arthropods) in the Trombiculidae family. In their larval stage, they attach to various animals, including humans, and feed on skin, ...
* Louse
Louse ( : lice) is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera has variously been recognized as an order, infraorder, or a parvorder, as a result o ...
References
External links
*
Parasitic Insects, Mites and Ticks: Genera of Medical and Veterinary Importance
{{Authority control
Extant Middle Jurassic first appearances
Hematophages
Insect vectors of human pathogens
Insects in culture
Parasites of cats
Parasites of dogs
Veterinary entomology