Editing Flea (section)

== Relationship with host ==
[[File:Fleabite.JPG|thumb|Flea bites in humans.]]

Fleas feed on a wide variety of [[warm-blooded]] [[vertebrate]]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]]'' affects poultry as well as wild birds.<ref name=Krasnov72/> 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.<ref name=Poulin>{{cite book |last=Poulin |first=Robert |author-link=Robert Poulin (zoologist) |title=Evolutionary Ecology of Parasites |edition=Second |url=https://books.google.com/books?id=eegdgaR81k0C&pg=PA68 |year=2011 |publisher=Princeton University Press |isbn=978-1-4008-4080-9 |page=68}}</ref>

Although there are species named dog fleas ([[Dog flea|''Ctenocephalides canis'']] Curtis, 1826) and cat fleas ([[Cat flea|''Ctenocephalides felis'']]), fleas are not always strictly species-specific. A study in [[Virginia]] 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 in the United States is likely a cat flea (''Ctenocephalides felis'').<ref>{{Cite journal|last=Eckerlin|first=Ralph P.|date=2011|title=WHAT KIND OF FLEAS DOES YOUR DOG HAVE?|url=http://virginianaturalhistorysociety.com/banisteria/pdf-files/ban37/Banisteria37_Fleas.pdf|journal=Banisteria|volume=37|pages=42–43|access-date=7 September 2020|archive-date=5 July 2021|archive-url=https://web.archive.org/web/20210705093120/http://virginianaturalhistorysociety.com/banisteria/pdf-files/ban37/Banisteria37_Fleas.pdf|url-status=dead}}</ref><ref>{{Cite journal |last1=Marchiondo|first1=A. A. |last2=Holdsworth |first2=P. A. |last3=Green |first3=P. |last4=Blagburn |first4=B. L. |last5=Jacobs |first5=D. E. |date=2007-04-30 |title=World Association for the Advancement of Veterinary Parasitology guidelines for evaluating the efficacy of parasiticides for the treatment, prevention and control of flea and tick infestation on dogs and cats |url=http://www.sciencedirect.com/science/article/pii/S0304401706006236 |journal=Veterinary Parasitology |volume=145 |issue=3 |pages=332–344 |doi=10.1016/j.vetpar.2006.10.028 |pmid=17140735 |issn=0304-4017}}</ref>

One theory of human hairlessness is that the loss of hair helped humans to reduce their burden of fleas and other ectoparasites.<ref>{{cite journal |author=Rantala, M.J. |year=2006 |title=Evolution of nakedness in ''Homo sapiens'' |journal=Journal of Zoology |volume= 273 |pages= 1–7 |doi=10.1111/j.1469-7998.2007.00295.x |issn=0952-8369 |url=https://wiki.bio.purdue.edu/MultidiscPhysioLab/images/b/b3/Evolution_of_nakedness.pdf }}</ref>

=== Direct effects of bites ===
{{Main|Pulicosis}}
[[File:Jigger infested foot (2).jpg|thumb|Human foot infested with jigger fleas, ''[[Tunga penetrans]]'']]

In many species, fleas are principally a nuisance to their hosts, causing an [[itch]]ing 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.<ref name="Mullen">{{cite book |title=Medical and Veterinary Entomology |last=Mullen |first=Gary R. |author2=Mullen, Gary|author3=Durden, Lance |year=2009 |publisher=Academic Press |isbn=978-0-12-372500-4 |page=637 |url=https://books.google.com/books?id=6R1v9o-uaI4C }}</ref>{{rp|126}} This can lead to an [[eczema]]tous itchy skin disease called [[flea allergy dermatitis]], which is common in many host species, including dogs and cats.<ref name=Krasnov72>{{cite book|author=Krasnov, Boris R. |title=Functional and Evolutionary Ecology of Fleas: A Model for Ecological Parasitology |url=https://books.google.com/books?id=tkvr8h8zxFwC&pg=PA72 |year=2008 |publisher=Cambridge University Press |isbn=978-1-139-47266-1 |pages=72–74}}</ref> 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]] in extreme cases.<ref name="Mullen"/>{{rp|126}}

=== As a vector ===
Fleas are [[Vector (epidemiology)|vectors]] for [[virus|viral]], [[bacteria]]l and [[rickettsia]]l [[disease]]s of humans and other animals, as well as of [[protozoa]]n and [[helminth]] parasites.<ref name="Krasnov">{{cite book |title=Functional and evolutionary ecology of fleas: a model for ecological parasitology |last=Krasnov |first=Boris R.|year=2008 |publisher=Cambridge University Press |isbn=978-0-521-88277-4 |page=593 |url=https://books.google.com/books?id=tkvr8h8zxFwC}}</ref> Bacterial diseases carried by fleas include [[Murine typhus|murine or endemic typhus]]<ref name="Mullen" />{{rp|124}} and [[bubonic plague]].<ref>{{cite book |title=Tending animals in the global village: a guide to international veterinary medicine |last=Sherman |first=David M. |year=2002 |publisher=Wiley-Blackwell |isbn=978-0-683-18051-0 |page=209 |url=https://books.google.com/books?id=ax_lLPG634AC}}</ref> Fleas can transmit ''[[Rickettsia typhi]]'', ''[[Rickettsia felis]]'', ''[[Bartonella henselae]]'', and the [[myxomatosis]] virus.<ref name="Krasnov"/>{{rp|73}} They can carry ''[[Hymenolepiasis]]'' [[tapeworms]]<ref>{{cite book |title=Anorectal and colon diseases: textbook and color atlas of proctology |last=Stein |first=Ernst |year=2003 |publisher=Springer |isbn=978-3-540-43039-1 |page=478 |url=https://books.google.com/books?id=yrlD7i4A68IC}}</ref> and [[Trypanosoma|Trypanosome]] protozoans.<ref name="Krasnov"/>{{rp|74}} The chigoe flea or jigger (''[[Tunga penetrans]]'') causes the disease [[tungiasis]], a major public health problem around the world.<ref name="Gibbs">{{cite web |url=http://emedicine.medscape.com/article/231037 |title=Tungiasis |author=Smith, Darvin Scott |publisher=Medscape |access-date=11 November 2016}}</ref> Fleas that specialize as parasites on specific mammals may use other mammals as hosts; thus, humans may be bitten by cat and dog fleas.<ref>{{cite book |title=Diseases and Human Evolution |last=Barnes |first=Ethne |year=2007 |publisher=UNM Press |isbn=978-0-8263-3066-6 |page=253 |url=https://books.google.com/books?id=wnlB7EMtqFYC}}</ref>