Difference between revisions of "Flea" - New World Encyclopedia

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{{Taxobox
 
{{Taxobox
 
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| ordo = '''Siphonaptera'''
 
| ordo = '''Siphonaptera'''
 
| subdivision_ranks = Families
 
| subdivision_ranks = Families
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| subdivision =  
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| subdivision =
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[[Tungidae]]&nbsp;– sticktight and [[chigoe flea]]s&nbsp;(chiggers) <br>
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[[Tungidae]]&nbsp;– sticktight and chigoe fleas&nbsp;(chiggers) <br>
 
[[Pulicidae]]&nbsp;– common fleas<br>
 
[[Pulicidae]]&nbsp;– common fleas<br>
 
[[Coptopsyllidae]]<br>
 
[[Coptopsyllidae]]<br>
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[[Vermipsyllidae]]&nbsp;– carnivore fleas<br>
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[[Vermipsyllidae]]&nbsp;– [[carnivore]] fleas<br>
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[[Rhopalopsyllidae]]&nbsp;– marsupial fleas<br>
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[[Rhopalopsyllidae]]&nbsp;– [[marsupial]] fleas<br>
 
[[Hypsophthalmidae]]<br>
 
[[Hypsophthalmidae]]<br>
 
[[Stephanocircidae]]<br>
 
[[Stephanocircidae]]<br>
 
[[Pygiopsyllidae]]<br>
 
[[Pygiopsyllidae]]<br>
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[[Hystrichopsyllidae]]&nbsp;– rat and mouse fleas<br>
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[[Hystrichopsyllidae]]&nbsp;– [[rat]] and [[mouse]] fleas<br>
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[[Leptopsyllidae]]&nbsp;– bird and rabbit fleas<br>
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[[Leptopsyllidae]]&nbsp;– rat and mouse fleas<br>
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[[Ischnopsyllidae]]&nbsp;– bat fleas<br>
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[[Ischnopsyllidae]]&nbsp;– [[bat]] fleas<br>
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[[Ceratophyllidae]]<br>
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[[Ceratophyllidae]]:-fleas mainly associated with [[rodent]]s
 
[[Amphipsyllidae]]<br>
 
[[Amphipsyllidae]]<br>
 
[[Malacopsyllidae]]<br>
 
[[Malacopsyllidae]]<br>
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[[Dolichopsyllidae]]&nbsp;– rodent fleas<br>
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[[Dolichopsyllidae]]&nbsp;– [[rodent]] fleas<br>
 
[[Ctenopsyllidae]]
 
[[Ctenopsyllidae]]
 
}}
 
}}
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'''Flea''' is the [[common name]] for any of the small wingless [[insect]]s of the [[order (biology)|order]] '''Siphonaptera''' (some authorities use the name '''Aphaniptera''' because it is older, but [[circumscriptional name|names above family rank]] do not follow the rules of priority, so most taxonomists use the more familiar name). Fleas are external [[parasite]]s, living by [[hematophagy]] off the [[blood]] of [[mammal]]s and [[bird]]s, 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 [[fly|flies]] ([[Diptera]]), based on similarities of the larvae.
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'''Flea''' is the common name for any of the small, wingless, and laterally compressed [[insect]]s belonging to the order '''Siphonaptera''' (or '''Aphaniptera'''). Fleas thrive in dark and damp (not wet) places and live as ecto-[[parasite]]s of [[warm blooded]] animals like [[bird]]s and [[mammal]]s, feeding on their [[blood]] (hematophagy).  
  
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''Note'': There is also a genus of [[foraminifera]]n [[Protozoa]] named ''[[Siphonaptera]]''
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The intimate association that [[human being]]s often have with their pets, such as household [[cat]]s and [[dog]]s, is sometimes compromised by the infestation of fleas on such pets. In a way, the persistent presence of fleas in pets serves as an indicator for the need for greater care of the pets by the pet owners. 
 +
 
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Fleas can be vectors for serious [[disease]]s, notably [[bubonic plague]]. In the twentieth century, this led to the fleas being a focus for [[biological warfare]]. Kirby (2005), who notes that "plague fleas have a rich military heritage as vectors of disease," records efforts by [[Japan]] during [[World War II]] to develop a weapon using plague fleas. One such weapon was designed to be used against the United States in the Pacific theater in 1944, but apparently was foiled by the sinking of a submarine. Fortunately, after considering to use such weapons of devastating destructiveness against the continental [[United States]], the Chief of Staff of the Imperial Japanese Army canceled the mission in March of 1945, considering it to be ethically unacceptable. Other nations, such as [[Canada]] on behalf of the Allies in World War II (as well as the [[USSR]] and [[Germany]] beginning in the 1930s) were active in this endeavor, and the United States became active after the [[Korean War]], but eventually such programs subsided (Kirby 2005).
  
 
Some well known flea species include:
 
Some well known flea species include:
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* [[Cat flea]] (''Ctenocephalides felis''),
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* Cat flea (''Ctenocephalides felis''),
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* [[Dog flea]] (''Ctenocephalides canis''),
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* Dog flea (''Ctenocephalides canis''),
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* [[Human flea]] (''Pulex irritans''),
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* Human flea (''Pulex irritans''),
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* [[Northern rat flea]] (''Nosopsyllus fasciatus''),
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* Northern rat flea (''Nosopsyllus fasciatus''),
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* [[Rat flea|Oriental rat flea]] (''Xenopsylla cheopis'').
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* Oriental rat flea (''Xenopsylla cheopis'').
  
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[[Image:Flea_bites.jpg|thumb|left|Flea bites on the back of a human]]
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Siphonaptera also is the name of a [[genus]] of foraminiferan [[protozoa]].
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In most cases, fleas are just a nuisance to their hosts, but some people and some animals suffer [[allergic reaction]]s to flea [[saliva]] resulting in [[rash]]es. 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.
 
  
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However, fleas can also act as a [[vector]] for [[disease]].  One possible example of this was the [[bubonic plague]], which may have been transmitted between rodents and humans. Murine typhus (endemic typhus) fever, and in some cases [[tapeworm]]s, ''[[Hymenolepis]]'', can also be transmitted by fleas.
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==Morphology and Behavior==
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==Fleas ==
 
 
[[Image:HookeFlea01.jpg|thumb|left|[[Robert Hooke|Hooke's]] drawing of a flea in ''[[Micrographia]]'']]
 
[[Image:HookeFlea01.jpg|thumb|left|[[Robert Hooke|Hooke's]] drawing of a flea in ''[[Micrographia]]'']]
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Fleas pass through a complete life cycle consisting of egg, larva, pupa and adult. Completion of the life cycle from egg to adult varies from two weeks to eight months depending on the temperature, humidity, food, and species. Normally after a blood meal, the female flea lays about 15 to 20 eggs per day — up to 600 in its lifetime — usually on the host ([[dog]]s, [[cat]]s, [[rat]]s, [[rabbit]]s, [[mouse|mice]], [[squirrel]]s, [[chipmunk]]s, [[raccoon]]s, [[opossum]]s, [[fox]]es, [[chicken]]s, [[human]]s, etc.). Eggs loosely laid in the hair coat drop out almost anywhere, especially where the host rests, sleeps or nests (rugs, carpets, upholstered furniture, cat or dog boxes, kennels, sand boxes, etc.).  
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Fleas are small (1.5 to five mm long), agile, usually dark colored (e.g. the cat flea is reddish-brown), wingless insects. Their bodies are oval and laterally compressed, (i.e., flattened side to side) permitting easy movement through the hairs (or [[feather]]s, etc.) on the host's body.  
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Eggs hatch between two days to two weeks into [[larva]]e found indoors in and along floor cracks, crevices, along baseboards, under rug edges and in furniture or beds. Outdoor development occurs in [[sand]]y [[gravel]] [[soil]]s (moist sand boxes, dirt crawlspace under the house, under shrubs, etc.) where the host may rest or sleep. Sand and gravel are very suitable for larval development which is the reason fleas are erroneously called "[[sand flea]]s".
 
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[[Image:Fleadirt.jpg|thumb|right|Flea dirt in the fur of a cat]]Larvae are blind, avoid light, pass through three larval [[instar]]s and take a week to several months to develop. Their food consists of digested blood from adult flea [[feces]], dead [[skin]], [[hair]], [[feather]]s, and other organic debris; larvae do not suck blood. [[Pupa]]e mature to adulthood within a silken [[cocoon]] woven by the larva to which pet hair, carpet fiber, dust, grass cuttings, and other debris adheres. In about five to fourteen days, adult fleas emerge or may remain resting in the cocoon until the detection of vibration (pet and people movement), pressure (host animal lying down on them), heat, noise, or [[carbon dioxide]] (meaning a potential blood source is near). Most fleas overwinter in the larval or pupal stage with survival and growth best during warm, moist winters and spring. "Flea season" is traditionally at the end of summer and in the early fall, but in warmer areas can last year round.
 
  
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Flea [[bite]]s 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)]].
+
The head and thorax are relatively small compared to the enlarged abdomen. Fleas have short and thick [[antenna (biology)|antennae]], only a pair of simple [[eye]]s or ocelli, and piercing and sucking type of mouthparts adapted to feeding on the blood of their hosts.The thorax consists of three pairs of long and stout jointed appendages; among them, the hind pair is especially well adapted for [[kinesis|kinetic]] jumping&mdash;vertically up to 18 centimeters (cm) and horizontally 33 cm, about 200 times their own body length (Lyon 2007). The abdomen of the parasite is made of ten segments.  
  
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==Breaking an infestation==
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The flea body is hard, polished, and covered with many hairs and short spines (bristles) directed backward, allowing the flea a smooth passage through the hairs of its host (Koehler and Oi 2003). Its tough body is able to withstand great pressure, likely an adaptation to survive scratching, and so forth. Even hard squeezing between the fingers is often insufficient to kill the flea; it may be necessary to crush them between the fingernails.
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[[Image:Flea Larva.jpg|thumb|Flea larva]]
 
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Different people have varying sensitivities to the movement of fleas and to their bites.   Some can detect the flea and nab it on the skin; unlucky compatriots only learn of the infestation after a series of rashes erupt the next day.  Some people attract fleas while others never learn about them.
 
  
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<!--- I posted this on the help forum and CnPing here so forgive if it needs fixed a bit user:fabartus 7 April 06 ----->
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==Life Cycle and Habitat==
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If an animal lives in the home, one should treat it monthly with one of the long duration products as recommended by your [[veterinarian]]. In general, at least in the [[United States]], one should avoid grocery store or pet shop products which are less effective than the prescription strength products from a licensed veterinarian (or the equivalent in [[Commonwealth Nation]]s [[veterinary surgeon]]). These products will keep the fleas off the pets, not off the owners or out of the [[furnishing]]s. More drastic measures are required to protect the owners or unlucky non-pet owner with these ''unwelcome house guests''.
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Fleas are [[metamorphosis|holometabolous]] (complete metamorphosis) insects, going through all the four stages of the [[life cycle]]; namely the [[embryo]] (egg), [[larva]], [[pupa]], and [[imago]] (adult). Adult fleas must feed on blood before they can become capable of [[reproduction]] (Koehler and Oi 2003). Thus, after a blood meal, breeding starts. The female begins laying a total of about 300 to 400 tiny white oval eggs soon after copulation. Eggs are laid in batches of up to 20 or so, usually on the host itself, which then easily roll onto the ground. As such, areas where the host rests and sleeps become one of the primary [[habitat]]s of eggs and developing fleas. The eggs take around two days to two weeks to hatch depending on temperature and humidity (Lyon 2007).
  
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To deal with an home infestation one needs to break the [[life cycle]] of the fleas and kill off the breeding age individuals which will otherwise produce a new generation within about 10-18 days, so repeat this technique about every two weeks, ''at least three times''.  
+
[[Image:Flea Larva.jpg|left|thumb|Micrograph of a flea larva.]]
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<!--- Source is advice given to many over the years by veterinarian father. user:fabartus --->
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Flea larvae are small, cylindrical, and [[maggot]]-like in appearance, with neither legs nor eyes. The head is small but equipped with chewing mouthparts, while the body is made of 13 visible segments and a hidden terminal segment, all provided with rather sparse bristles to aid in crawling. They show negative phototaxis and avoid sunlight, keeping to dark places like sand, cracks, and crevices, as well as bedding. While the adult flea's diet consists solely of blood, the larvae feed on various available organic matter, such as dead [[insect]]s, feces (including the feces of mature fleas), and vegetable matter (Bartlett et al. 2006).
  
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=== Area or room treatment ===
+
Given an adequate supply of food, larvae should pupate within 1-2 weeks. When ready to pupate, the larvae spin little [[silk]]en cocoons that are viscid, so that particles of sand, dust, or lint readily adhere to them.  
−
The goal with this method is to create a vapor cloud of a common inexpensive household pest-control ([[poison]]) above which the breeding population cannot avoid by jumping. This method uses the ubiquitous anti-moth products available at many retail stores, especially [[hardware store]]s (certain) and perhaps grocery stores.
 
  
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#The best area method would be to place [[moth crystal]]s (flakes) and [[moth ball]]s in the infested areas periodically for several hours at a time; this needs to be done thoroughly, placing moth balls about the floor and on couches, beds, and wherever there are fabrics within a foot or so from the floor. In particular, large area items like couches, and beds need to be individually sprinked across more than 50% of their surface area. Moth flakes are more volatile and would be the better product on these furnishings. Exact placement of the material is not necessary (e.g., some flakes fall into cracks), as the [[vapor]]s spread both outwards and down.
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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&mdash;vibrations (including sound), heat, and [[carbon dioxide]] are all stimuli indicating the probable presence of a host (Lyon 2007). Fleas are known to overwinter or [[diapause]] in the larval or pupal stages.
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#One should block off the area's (or room's) egress with towels under doors or sheets (bedding or plastic types) taped across the doorways. All ventilation (forced hot air [[furnace]]s and [[air conditioner]]s) should be shut off until after the treatment.
 
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#The area should be vacated by humans and pets and the area allowed to 'soak' for two to three hours.
 
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#Before use, the vacuum cleaner should be cleaned. Then, the vacuum cleaner should be used to vacuum up the flakes or balls and transfer them into a plastic bag or container for reuse for the next treatment in two weeks. Leaving moth balls or flakes under beds in closets, behind dressers, etc. is recommended, as any leftover fleas may be sickened or killed. As the vapors stay low, this should be safe if performed in moderation. Anything that is likely to inhibit the growth of hatchlings will aid the eradication effort.
 
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#This cleaning process should be repeated two to three times, with each cleaning two weeks apart. If the home being treated is in a sub-tropical clime subject to a higher humidity like the American south (say below the [[Mason-Dixon line]]), then the number of treatments should be increased up to five or six times overall. If a flea bite occurs anytime afterwards, the treatment process should be performed again.
 
  
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===Whole home treatment===
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Once the flea reaches adulthood, its primary goal is to find blood. Adult fleas only have around a week to find food once they emerge, though they can survive two months to a year between meals. Thus, the life expectancy of adult fleas depends largely on food supply, temperature, and humidity. At low temperatures (60° F), well-fed fleas may live for several years. In the absence of a host, they have less endurance than ticks. Unlike most blood-sucking insects, fleas usually feed at frequent intervals, generally at least once a day. A flea population is unevenly distributed, with 50 percent eggs, 35 percent larvae, 10 percent pupae and 5 percent adults (Lyon 2007). Their total life cycle can take as little as two weeks, but may be lengthened to many months if conditions are unfavorable. Female fleas can lay 500 or more eggs over their life, allowing for phenomenal growth rates.
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For a particularly widespread infestation, one should follow the above strategy with [[insecticide bomb]]s. Chain home stores sell four packs at a cheap price compared to singletons purchased from hardware stores. The objective is to kill the immature hatchlings before they mature and lay more eggs. The first downside to this method is that it requires vacating the premises for several hours. However, the main downside to this method is the need to protect foodstuffs; therefore, the user is strongly urged to read all directions carefully. This method is generally practiced in commercial restaurants once or twice monthly, so some due caution is warranted, but managable with appropriate safeguards.
 
  
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If the home is carpeted throughout, whole home treatment would generally be preferred, as there is no way of knowing where the fleas may be at any moment. However, if the home contains mostly hard flooring, the using mothflakes/mothballs would be the better method, as problem areas that need to be treated can be specifically targeted, although it is possible that some infested areas could be missed with the targeted method.
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==Evolution==
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Based on genetic and morphological evidences, it is supposed that fleas are related to, or even descendants, of the [[scorpionfly]] family [[Boreidae]], which have good eyesight and either reduced or no wings (Grimaldi and Engel 2005). With their rudimentary wings, these flightless ''snow scorpions'', also known as ''snow fleas'', do resemble the fleas and seem to be close to the common ancestor of the 2000 or so currently known varieties of fleas. It is considered that they split off in many directions about 160 million years ago (Grimaldi and Engel 2005). Their [[evolution#theory of descent with modification|descent with modification]] continued to produce adaptations for their specialized [[parasite|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 niche]]s to which to adapt.
  
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With the first method, one can leave the barriers in place for a few weeks if necessary, and naturally, the two methods can be used simultaneously.
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Previously, based on the similarities of the larvae, it had been believed that fleas had evolved from the [[fly|flies]] ([[Diptera]]).
  
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===Individual treatment===
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==Relationship with Host==
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Consumption of aged [[garlic]] is purported to be a natural flea repellant, as the fleas do not like the different taste of blood it creates.  This consumption based prophylatic treatment may take far longer than conventional methods. Un-aged garlic can cause a toxic fatal reaction in some household pets, so caution should be used in choosing the correct product.
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[[Image:Fleabite.JPG|thumb|left|Flea bites on the back of a human]]
 +
Fleas attack a wide variety of [[warm-blooded]] [[vertebrate]]s, including [[dog]]s, [[human]]s, [[chicken]]s, [[rabbit]]s, [[squirrel]]s, [[rat]]s, and [[mice]].  
  
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Apply [[Frontline (medicine)|Frontline]] or [[lufenuron]] (Program) on pets as directed.
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Fleas are a nuisance to their hosts, causing an [[itch]]ing sensation, which in turn may result in the host attempting to remove the parasite by biting, pecking, scratching, and so forth in the vicinity of the parasite. However, fleas are not simply a source of annoyance. Some people and animals suffer [[allergy|allergic reaction]]s to flea [[saliva]], resulting in [[rash]]es. 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 self scratching and biting by the animal. In extreme cases, they can lead to [[anemia]].
  
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[[Baking soda]] mixed with equal amount of salt kills fleas. It is rubbed into a pet's fur, pet's bedding, and the carpet. It can kill adult fleas by irritating their chitinous exoskeletons and causing dessication. Wash/rinse pet after treatment to avoid a skin problem. Do not dust the carpet on a rainy day, as the salt will absorb moisture from the air, causing the carpet to become wet. [http://frugalliving.about.com/cs/tips/a/blbakingsoda1.htm]
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Besides the problems posed by their sucking of blood, fleas can also act as a vector for many [[disease]]s. For example, oriental rat fleas (''Xenopsylla cheopsis'') are the chief transmitter of the [[bubonic plague]] between rodents and humans by carrying the bacteria ''[[Yersinia pestis]]''. Murine typhus (endemic typhus) fever, caused by ''Rickettsia typhi'', and in some cases [[tapeworm]]s (''Hymenolepis'' sp.), can also be transmitted by fleas.
  
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While killing live fleas is a noble proposition, the true threat comes from their scattered eggs that resist even machine washing, Those with an energy intensive kitchen can freeze their sheets and clothing to guarantee that the adults and the eggs perish.  This has been 100% effective when combined with a cleansing shower.
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== Flea Treatment and Control ==
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[[Image:Fleadirt.jpg|thumb|right|Flea "dirt" in the fur of a cat, is actually excess blood (from host) consumed by the adult flea, passed as feces.]]
  
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[[Category:Pest insects]]
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Flea [[bite]]s can be treated with calamine lotion or 0.5-1 percent concentrated [[hydrocortisone]] cream. Itching can be lessened by applying menthol, camphor, or ice as well.
  
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== External links ==
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Immediate bites from the adult flea can be prevented by the use of insect repellents like N,N-Diethyl-meta-toluamide ([[DEET]]) over the exposed skin and the outer clothing (Lyon 2007).
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* [http://parents.berkeley.edu/advice/health/fleas.html Advice about fleas] from the Berkeley Parents Network
 
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* [http://www.lib.uiowa.edu/hardin/md/fleabites.html Links to flea bite pictures (Hardin MD/Univ of Iowa)]
 
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* [http://www.primalnature.org/wildlife.html Good Neighbors] An essay on the natural history of the flea
 
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*[http://ohioline.osu.edu/hyg-fact/2000/2081.html Ohio State University Fact Sheet] Life cycle and control methods for fleas
 
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*[http://www.petloveshack.com/flea.html Breaking the Flea Cycle]
 
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*[http://eastvillagepodcasts.com/2006/06/13/my-foot-and-sand-flea-bites/ Sand Flea Bite Picture]
 
  
 +
Long term control of fleas can be achieved with a simultaneous and integrated efforts involving strict sanitation, pet treatments, and premises treatments (both indoors and outdoors).
  
 +
The medicines to control fleas need to be used with care. [[Phenothrin]] (85.7%) in combination with [[Methoprene]] was a popular topical flea/tick therapy for [[cat|feline]]s. Phenothrin kills adult fleas and ticks. Methoprene is an insect growth regulator (IGR) that interrupts the insect's life cycle by killing the eggs. However, the United States Environmental Protection Agency ([[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.  The Phenothrin was believed to be the cause of the adverse reactions (EPA 2006).
  
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{{credit|67159531}}
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[[Lufenuron]] is veterinary medicine that attacks the larval flea's ability to produce [[chitin]], thus breaking the life cycle. A combination of etofenprox (55.0%) and [[pyriproxyfen]] (2.2%) is another formulation used in Sergeant's Gold treatment for cats.
  
 +
Fleas can be controlled in dwellings by application of [[borax]], [[diatomaceous earth]], and other [[insecticides]] to floors, furniture, and carpeting.
  
 +
== References ==
 +
* Bartlett, T., P. Coin, and R. McLeod. 2006. [http://bugguide.net/node/view/7040 "Order Siphonaptera: Fleas."] ''BugGuide''. Iowa State University Entomology. Retrieved May 6, 2007.
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* Grimaldi, D., and M. S. Engel. 2005. ''Evolution of the Insects''. Cambridge University Press. ISBN 0521821495.
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* Kirby, R. 2005. [http://www.wood.army.mil/chmdsd/Army_Chemical_Review/pdfs/Jul-Dec%202005/Kirby.pdf  "Using the Flea as Weapon."] ''Army Chemical Review''. July-December (2005): 30-35. Retrieved May 6, 2007.
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* Koehler, P. G., and F. M. Oi. 2003. [http://edis.ifas.ufl.edu/IG087 ''Fleas'']. ''University of Florida,  Institute of Food and Agricultural Sciences''. Retrieved May 6, 2007.
 +
* Lyon, W. F. 2007. [http://ohioline.osu.edu/hyg-fact/2000/2081.html ''Fleas''. HYG-2081-97]. ''Ohio State University Extension Fact Sheet''. Retrieved May 6, 2007.
 +
* U. S. Environmental Protection Agency (EPA). 2006. [http://www.epa.gov/pesticides/factsheets/flea-tick-drops.htm Hartz Flea and Tick Drops for Cats and Kittens to be Cancelled]. ''EPA. Pesticides: Topical & Chemical Fact Sheets''. Retrieved May 6, 2007.
  
  
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{{credit|113534721}}
 
[[Category:Life sciences]]
 
[[Category:Life sciences]]
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[[Category:Animals]]
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[[Category:Invertebrates]]
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[[Category:Arthropods]]
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[[Category:Insects]]

Latest revision as of 13:57, 29 August 2008

Fleas
SEM of a flea
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 – rat and mouse 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, and laterally compressed insects belonging to the order Siphonaptera (or Aphaniptera). Fleas thrive in dark and damp (not wet) places and live as ecto-parasites of warm blooded animals like birds and mammals, feeding on their blood (hematophagy).

The intimate association that human beings often have with their pets, such as household cats and dogs, is sometimes compromised by the infestation of fleas on such pets. In a way, the persistent presence of fleas in pets serves as an indicator for the need for greater care of the pets by the pet owners.

Fleas can be vectors for serious diseases, notably bubonic plague. In the twentieth century, this led to the fleas being a focus for biological warfare. Kirby (2005), who notes that "plague fleas have a rich military heritage as vectors of disease," records efforts by Japan during World War II to develop a weapon using plague fleas. One such weapon was designed to be used against the United States in the Pacific theater in 1944, but apparently was foiled by the sinking of a submarine. Fortunately, after considering to use such weapons of devastating destructiveness against the continental United States, the Chief of Staff of the Imperial Japanese Army canceled the mission in March of 1945, considering it to be ethically unacceptable. Other nations, such as Canada on behalf of the Allies in World War II (as well as the USSR and Germany beginning in the 1930s) were active in this endeavor, and the United States became active after the Korean War, but eventually such programs subsided (Kirby 2005).

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).

Siphonaptera also is the name of a genus of foraminiferan protozoa.

Morphology and Behavior

Hooke's drawing of a flea in Micrographia

Fleas are small (1.5 to five mm long), agile, usually dark colored (e.g. the cat flea is reddish-brown), wingless insects. Their bodies are oval and laterally compressed, (i.e., flattened side to side) permitting easy movement through the hairs (or feathers, etc.) on the host's body.

The head and thorax are relatively small compared to the enlarged abdomen. Fleas have short and thick antennae, only a pair of simple eyes or ocelli, and piercing and sucking type of mouthparts adapted to feeding on the blood of their hosts.The thorax consists of three pairs of long and stout jointed appendages; among them, the hind pair is especially well adapted for kinetic jumping—vertically up to 18 centimeters (cm) and horizontally 33 cm, about 200 times their own body length (Lyon 2007). The abdomen of the parasite is made of ten segments.

The flea body is hard, polished, and covered with many hairs and short spines (bristles) directed backward, allowing the flea a smooth passage through the hairs of its host (Koehler and Oi 2003). Its tough body is able to withstand great pressure, likely an adaptation to survive scratching, and so forth. Even hard squeezing between the fingers is often insufficient to kill the flea; it may be necessary to crush them between the fingernails.

Life Cycle and Habitat

Fleas are holometabolous (complete metamorphosis) insects, going through all the four stages of the life cycle; namely the embryo (egg), larva, pupa, and imago (adult). Adult fleas must feed on blood before they can become capable of reproduction (Koehler and Oi 2003). Thus, after a blood meal, breeding starts. The female begins laying a total of about 300 to 400 tiny white oval eggs soon after copulation. Eggs are laid in batches of up to 20 or so, usually on the host itself, which then easily roll onto the ground. As such, 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 depending on temperature and humidity (Lyon 2007).

Micrograph of a flea larva.

Flea larvae are small, cylindrical, and maggot-like in appearance, with neither legs nor eyes. The head is small but equipped with chewing mouthparts, while the body is made of 13 visible segments and a hidden terminal segment, all provided with rather sparse bristles to aid in crawling. They show negative phototaxis and avoid sunlight, keeping to dark places like sand, cracks, and crevices, as well as bedding. While the adult flea's diet consists solely of blood, the larvae feed on various available organic matter, such as dead insects, feces (including the feces of mature fleas), and vegetable matter (Bartlett et al. 2006).

Given an adequate supply of food, larvae should pupate within 1-2 weeks. When ready to pupate, the larvae spin little silken cocoons that are viscid, so that particles of sand, dust, or lint readily adhere to them.

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 (Lyon 2007). Fleas are known to overwinter or diapause in the larval or pupal stages.

Once the flea reaches adulthood, its primary goal is to find blood. Adult fleas only have around a week to find food once they emerge, though they can survive two months to a year between meals. Thus, the life expectancy of adult fleas depends largely on food supply, temperature, and humidity. At low temperatures (60° F), well-fed fleas may live for several years. In the absence of a host, they have less endurance than ticks. Unlike most blood-sucking insects, fleas usually feed at frequent intervals, generally at least once a day. A flea population is unevenly distributed, with 50 percent eggs, 35 percent larvae, 10 percent pupae and 5 percent adults (Lyon 2007). Their total life cycle can take as little as two weeks, but may be lengthened to many months if conditions are unfavorable. Female fleas can lay 500 or more eggs over their life, allowing for phenomenal growth rates.

Evolution

Based on genetic and morphological evidences, it is supposed that fleas are related to, or even descendants, of the scorpionfly family Boreidae, which have good eyesight and either reduced or no wings (Grimaldi and Engel 2005). With their rudimentary wings, these flightless snow scorpions, also known as snow fleas, do resemble the fleas and seem to be close to the common ancestor of the 2000 or so currently known varieties of fleas. It is considered that they split off in many directions about 160 million years ago (Grimaldi and Engel 2005). Their descent with modification 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 which to adapt.

Previously, based on the similarities of the larvae, it had been believed that fleas had evolved from the flies (Diptera).

Relationship with Host

Flea bites on the back of a human

Fleas attack a wide variety of warm-blooded vertebrates, including dogs, humans, chickens, rabbits, squirrels, rats, and mice.

Fleas are a nuisance to their hosts, causing an itching sensation, which in turn may result in the host attempting to remove the parasite by biting, pecking, scratching, and so forth in the vicinity of the parasite. However, fleas are not simply a source of annoyance. 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. 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 self scratching and biting by the animal. In extreme cases, they can lead to anemia.

Besides the problems posed by their sucking of blood, fleas can also act as a vector for many diseases. For example, oriental rat fleas (Xenopsylla cheopsis) are the chief transmitter of the bubonic plague between rodents and humans by carrying the bacteria Yersinia pestis. Murine typhus (endemic typhus) fever, caused by Rickettsia typhi, and in some cases tapeworms (Hymenolepis sp.), can also be transmitted by fleas.

Flea Treatment and Control

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

Flea bites can be treated with calamine lotion or 0.5-1 percent concentrated hydrocortisone cream. Itching can be lessened by applying menthol, camphor, or ice as well.

Immediate bites from the adult flea can be prevented by the use of insect repellents like N,N-Diethyl-meta-toluamide (DEET) over the exposed skin and the outer clothing (Lyon 2007).

Long term control of fleas can be achieved with a simultaneous and integrated efforts involving strict sanitation, pet treatments, and premises treatments (both indoors and outdoors).

The medicines to control fleas 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 (IGR) that interrupts the insect's life cycle by killing the eggs. However, the United States Environmental Protection Agency (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. The Phenothrin was believed to be the cause of the adverse reactions (EPA 2006).

Lufenuron is veterinary medicine that attacks the larval flea's ability to produce chitin, thus breaking the life cycle. A combination of etofenprox (55.0%) and pyriproxyfen (2.2%) is another formulation used in Sergeant's Gold treatment for cats.

Fleas can be controlled in dwellings by application of borax, diatomaceous earth, and other insecticides to floors, furniture, and carpeting.

References
ISBN links support NWE through referral fees

  • Bartlett, T., P. Coin, and R. McLeod. 2006. "Order Siphonaptera: Fleas." BugGuide. Iowa State University Entomology. Retrieved May 6, 2007.
  • Grimaldi, D., and M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press. ISBN 0521821495.
  • Kirby, R. 2005. "Using the Flea as Weapon." Army Chemical Review. July-December (2005): 30-35. Retrieved May 6, 2007.
  • Koehler, P. G., and F. M. Oi. 2003. Fleas. University of Florida, Institute of Food and Agricultural Sciences. Retrieved May 6, 2007.
  • Lyon, W. F. 2007. Fleas. HYG-2081-97. Ohio State University Extension Fact Sheet. Retrieved May 6, 2007.
  • U. S. Environmental Protection Agency (EPA). 2006. Hartz Flea and Tick Drops for Cats and Kittens to be Cancelled. EPA. Pesticides: Topical & Chemical Fact Sheets. Retrieved May 6, 2007.


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