Sucking louse

{{short description|Parvorder of insects}} {{good article}} {{Automatic taxobox | name = Sucking louse | image = Hundelaus.jpg | image_caption = ''Linognathus setosus'' (Linognathidae) | display_parents = 3 | taxon = Anoplura | authority = Leach, 1815 | subdivision_ranks = Families | subdivision = * Echinophthiriidae * Enderleinellidae * Haematopinidae * Hamophthiriidae * Hoplopleuridae * Hybophthiridae * Linognathidae * Microthoraciidae * Neolinognathidae * Pecaroecidae * Pedicinidae * Pediculidae * Polyplacidae * Pthiridae * Ratemiidae | synonyms = Siphunculata<ref>{{cite book|last1=Ibarra|first1=J.|date=1993|chapter=Lice (Anoplura)|editor-last1=Lane|editor-first1=R.P.|editor-last2=Crosskey|editor-first2=R.W.|title=Medical Insects and Arachnids|pages=517–528 |publisher=Springer|location=Dordrecht|doi=10.1007/978-94-011-1554-4_15|isbn=978-94-010-4679-4 }}</ref> }}

'''Sucking lice''' (known scientifically as '''Anoplura''') are a parvorder<ref>{{Cite web |title=Psocodea Species File - Anoplura Leach, 1815 |url=https://psocodea.speciesfile.org/otus/878997/overview |access-date=2025-05-10 |website=psocodea.speciesfile.org}}</ref> of around 550 species of lice. All sucking lice are blood-feeding ectoparasites of mammals. They can cause localized skin irritations and are vectors of several blood-borne diseases.

At least three species or subspecies of Anoplura are parasites of humans; the human condition of being infested with sucking lice is called pediculosis. ''Pediculus humanus'' is divided into two subspecies, ''Pediculus humanus humanus'', or the human body louse, sometimes nicknamed "the seam squirrel" for its habit of laying of eggs in the seams of clothing, and ''Pediculus humanus capitis'', or the human head louse. ''Pthirus pubis'' (the human pubic louse) is the cause of the condition known as crabs.

== Classification == Sucking lice are classified as a parvorder called Anoplura, named by Leach in 1815. Anoplura belongs to the infraorder Phthiraptera, which contains all lice, and is part of the larger order Psocodea, which also contains booklice, barklice and barkflies.

=== External phylogeny === A cladogram showing the position of Anoplura within Phthiraptera and Psocodea is shown below:<ref name="deMoya2021">{{Cite journal|last1=de Moya|first1=Robert S|last2=Yoshizawa|first2=Kazunori|last3=Walden|first3=Kimberly K O|last4=Sweet|first4=Andrew D|last5=Dietrich|first5=Christopher H|last6=Kevin P|first6=Johnson|date=2021-06-16|editor-last=Buckley|editor-first=Thomas|title=Phylogenomics of Parasitic and Nonparasitic Lice (Insecta: Psocodea): Combining Sequence Data and Exploring Compositional Bias Solutions in Next Generation Data Sets|url=https://academic.oup.com/sysbio/article/70/4/719/5912026|journal=Systematic Biology|language=en|volume=70|issue=4|pages=719–738|doi=10.1093/sysbio/syaa075|pmid=32979270|issn=1063-5157|doi-access=free|url-access=subscription}}</ref> {{clade| style=font-size:85%; line-height:100% |label1='''Psocodea''' |1={{clade |1={{clade |label1=Troctomorpha |1={{clade |1={{clade |1={{clade |label1='''Phthiraptera''' |1={{clade |1={{clade |1=Philopteridae |2={{clade |1={{clade |1='''Anoplura''' |2=Rhynchophthirina }} |2=Trichodectidae }} }} |2=Amblycera }} |2=Liposcelididae }} |2={{clade |1=Pachytroctidae |2=Sphaeropsocidae }} }} |2=Amphientometae }} |label2=Psocomorpha |2={{clade |1={{clade |1={{clade |1=Homilopsocidea |2=Caeciliusetae }} |2={{clade |1={{clade |1=Psocetae |2=Epipsocetae }} |2=Philotarsetae }} }} |2=Archipsocetae }} }} |label2=Trogiomorpha |2={{clade |1={{clade |1=Atropetae |2=Psyllipsocetae }} |2=Prionoglaridetae (paraphyletic) }} }} }}

=== Internal phylogeny === A cladogram showing the internal phylogeny of Anoplura is shown below, with paraphyletic groupings noted:<ref name="Light2010" /> {{clade| style=font-size:85%; line-height:85% |label1='''Anoplura''' |1={{clade |1={{clade |1=Echinophthiriidae |2={{clade |1={{clade |1=Linognathidae |2={{clade |label1=Hoplopleuridae |sublabel1=(paraphyletic) |1={{clade |1=''Hoplopleura trispinosa'' |2={{clade |1={{clade |1={{clade |1=''Hoplopleura arizonensis'' |2=''Hoplopleura hirsuta'' }} |2={{clade |1={{clade |1=''Hoplopleura ferrisi'' 1 (paraphyletic) |2=''Hoplopleura ferrisi'' 3 (paraphyletic) |3={{clade |1=''Hoplopleura ferrisi'' 2 (paraphyletic) |2=''Hoplopleura reithrodontomydis'' }} |4=''Hoplopleura hesperomydis'' }} |2=''Hoplopleura onychomydis'' }} |3=''Hoplopleura sicata'' |4={{clade |1=''Hoplopleura aitkeni'' |2=''Pterophthirus imitans'' }} |5={{clade |1={{clade |1={{clade |1=''Hoplopleura fonsecai'' |2=''Hoplopleura travassosi'' }} |2=''Hoplopleura'' new sp. }} |2=''Hoplopleura rimae'' |3=''Hoplopleura tiptoni'' }} |6=''Hoplopleura quadridentata'' }} |2=''Pterophthirus splendica'' }} }} |2=''Hoplopleura erratica'' (Hoplopleuridae) |label3=Polyplacidae |sublabel3=(paraphyletic) |3=''Linognathoides'' }} }} |label2=Polyplacidae |sublabel2=(paraphyletic) |2={{clade |1={{clade |1=''Neohaematopinus sciuri'' |2=''Neohaematopinus neotomae'' }} |2=''Neohaematopinus sciuropteri'' |3=''Haemodipsus'' |4=''Sathrax'' }} }} }} |2={{clade |1=Haematopinidae |label2=Polyplacidae |sublabel2=(paraphyletic) |2=''Lemurpediculus'' }} |3={{clade |label1=Hoplopleuridae |sublabel1=(paraphyletic) |1=''Ancistroplax'' |2={{clade |label1=Polyplacidae |sublabel1=(paraphyletic) |1=''Polyplax'' |2={{clade |1={{clade |1=Pediculidae |2=Pthiridae }} |2=Pedicinidae }} }} }} |label4=Polyplacidae |sublabel4=(paraphyletic) |4=''Fahrenhalzia'' }} }}

== Characteristics == Sucking lice are typically flattened and wingless, with sharp claws on their legs that are used to attach themselves to hair or human clothing. All sucking lice suck blood through a small proboscis that is usually kept inside of their head. Their color typically ranges between a mixture of yellow and white.<ref>{{Cite web |title=Sucking louse {{!}} Parasite, Blood-Feeding, Pest {{!}} Britannica |url=https://www.britannica.com/animal/sucking-louse |access-date=2025-05-09 |website=www.britannica.com |language=en}}</ref> There are around 540 different species of Anoplura, and unlike the closely related Mallophaga, sucking lice only parasitize mammals.<ref name="Light2010" />

Sucking lice bodies are typically oblong, with a flattened body and a head that is rounded in the front and smaller than the thorax.<ref name="bulletin-1883">{{Cite book |title=Bulletin |publisher=U.S. Government Printing Office |year=1883 |publication-date=December 12, 2011 |page=187 |language=en |oclc=365228942 }}</ref> The lice have anywhere from three to five separate thread{{ndash}}like antennae on top of the end of the head that is used to help navigate their surroundings.<ref name="bulletin-1883" /> The head tends to slightly widen next to the antennae.<ref name="bulletin-1883" /> The antennae are composed of three to five equal sized joints that are used to aid in sensing their surrounding.<ref>{{Cite web |date=2022-02-15 |title=Lice (Phthiraptera) - Factsheet for health professionals |url=https://www.ecdc.europa.eu/en/all-topics-z/disease-vectors/facts/factsheet-lice-phthiraptera#:~:text=Sucking%20lice%20are%20less%20biodiverse,their%20relevance%20to%20public%20health |access-date=2025-05-09 |website=www.ecdc.europa.eu |language=en}}</ref> The thorax contains two irregularly shaped triangular plates that help defend the insect's interior. Most sucking lice are no more than two millimeters in length.<ref name="bulletin-1883" />

=== Life cycle === All sucking lice undergo a process of slow metamorphosis, with three life stages of egg, nymph and adult.<ref>{{Cite web |title=Anoplura |url=https://entomology.k-state.edu/outreach-and-services/4-h/Guide-to-Insect-Orders/anoplura.html |access-date=2025-05-09 |website=entomology.k-state.edu}}</ref> The entire process of Anoplura's growth occurs whilst on their host; however, they are able to survive for small periods of time in outside environments.<ref name=":0">{{Cite web |title=Lice Dogs and Cats: chewing (Mallophaga), and sucking (Anoplura) - Learn About Parasites - Western College of Veterinary Medicine |url=https://wcvm.usask.ca/learnaboutparasites/parasites/lice-chewing-mallophaga,-and-sucking-anoplura.php |access-date=2025-05-09 |website=wcvm-learnaboutparasites |language=en}}</ref> Once a female louse matures, they will lay large amounts of small eggs (also known as nits) on the individual hairs of hosts.<ref name=":0" /> Nits are usually between 0.3 and 0.8 millimeters long, and are often pale in color or nearly transparent.<ref>{{Cite web |date=2022-05-31 |title=Life cycle of lice: Stages, how they spread, and more |url=https://www.medicalnewstoday.com/articles/life-cycle-of-lice#life-cycle-of-head-lice |access-date=2025-05-09 |website=www.medicalnewstoday.com |language=en}}</ref>

== Feeding method == Sucking lice live exclusively on the outside of their hosts, making them considered ectoparasites.<ref name="lapage-1951">{{Cite book |last=Lapage |first=Geoffrey |title=Parasitic Animals |publisher=Cambridge University Press |year=1951 |isbn=978-1-107-49661-3 |pages=115–116 |language=en}}</ref> The louse's proboscis consists of two distinct tubes, with the upper being called a rostrum, and the lower being called a stylet.<ref name="lapage-1951" /> The lice will use their upper mouth piece to latch onto the skin with teeth{{ndash}}like structures, maintaining a firm hold during their feeding. The lower mouth piece consists of two stylets, also known as stabbers.<ref name="lapage-1951" /> After the rostrum obtains a firm hold, the stylets will penetrate the skin with the serrated edges in a saw{{ndash}}like fashion. The louse will then regurgitate saliva through the proboscis inside of the body, before proceeding to suck the host's blood<ref name="aspinall-2006">{{Cite book |last=Aspinall |first=Victoria |title=The Complete Textbook of Veterinary Nursing |publisher=Saunders/Elsevier |isbn=978-0-7020-4050-4 |edition=2nd |publication-date=May 25, 2006 |pages=504 |language=en}}</ref> in what has been described as a "pumping action".<ref name="lapage-1951" /> Different species of sucking louse have specialised anatomy to help parasitize on different mammals and to help survive various climates.<ref name="aspinall-2006" />

== Effects ==

=== In humans === Anoplura contains three species of lice that parasitize humans.<ref>{{Cite journal |last1=Akhoundi |first1=Mohammad |last2=Heriniaina |first2=Hantatiana Juliana |last3=Brun |first3=Sophie |last4=Benamari |first4=Emma |last5=Izri |first5=Arezki |date=2024-11-03 |title=Morphological discrimination of human lice (Anoplura: Pediculidae) by eggs' cap-like operculum |journal=Scientific Reports |language=en |volume=14 |issue=1 |page=26506 |doi=10.1038/s41598-024-78292-8 |pmid=39489815 |issn=2045-2322|pmc=11532422 |bibcode=2024NatSR..1426506A }}</ref> Anoplura body lice (''Pediculus humanus humanus'') typically carry the potential of causing skin irritation, and are vectors of multiple blood-born diseases.<ref name=":1">{{Cite journal |last1=Johnston |first1=J. Spencer |last2=Yoon |first2=Kyong Sup |last3=Strycharz |first3=Joseph P. |last4=Pittendrigh |first4=Barry R. |last5=Clark |first5=J. Marshall |date=2007-11-01 |title=Body Lice and Head Lice (Anoplura: Pediculidae) Have the Smallest Genomes of Any Hemimetabolous Insect Reported to Date |url=https://academic.oup.com/jme/article/44/6/1009/1088303?login=false |journal=Journal of Medical Entomology |volume=44 |issue=6 |pages=1009–1012 |doi=10.1093/jmedent/44.6.1009 |issn=0022-2585|doi-access=free |pmid=18047199 }}</ref> Common symptoms of Anoplura body lice include relapsing fever, trench fever and epidemic typhus.<ref name=":1" /><ref name=":2">{{Cite journal |last1=Bonilla |first1=Denise L. |last2=Durden |first2=Lance A. |last3=Eremeeva |first3=Marina E. |last4=Dasch |first4=Gregory A. |date=2013 |title=The biology and taxonomy of head and body lice--implications for louse-borne disease prevention |journal=PLOS Pathogens |volume=9 |issue=11 |article-number=e1003724 |doi=10.1371/journal.ppat.1003724 |issn=1553-7374 |pmc=3828170 |pmid=24244157 |doi-access=free}}</ref> Due to increased societal standards for hygiene, body lice in general is significantly less prevalent in developed regions.<ref name=":2" /> During the American Civil War, body lice were colloquially known as "seam squirrels" due to their tendency to lay eggs within the seams of soldier's clothes.<ref>{{Cite web |last=Parsons |first=Susan |title=The Civil War and Body Lice |url=https://www.cayugacounty.us/DocumentCenter/View/1775/Civil-War-and-Body-Lice-PDF#:~:text=Body%20lice%2C%20Pediculus%20Vestimenti%2C%20had,bit%20larger%20than%20head%20lice |access-date=May 11, 2025 |website=cayugacounty.us |format=PDF}}</ref><ref>{{Cite book |title=The Oxford Dictionary of Modern Slang |date=2013 |publisher=Oxford University Press |isbn=978-0-19-172771-9 |editor-last=Ayto |editor-first=John |edition=2nd |chapter=seam-squirrel |doi=10.1093/acref/9780199543700.001.0001 |orig-date=2010 |editor-last2=Simpson |editor-first2=John}}</ref> Anoplura head lice (''Pediculus humanus capitis)'' is significantly more common than pubic or body lice, with studies reporting an infestation rate between 3.6% and 61.4% from countries in North and South America.<ref>{{Cite journal |last1=Falagas |first1=Matthew E. |last2=Matthaiou |first2=Dimitrios K. |last3=Rafailidis |first3=Petros I. |last4=Panos |first4=George |last5=Pappas |first5=Georgios |date=2008 |title=Worldwide prevalence of head lice |journal=Emerging Infectious Diseases |volume=14 |issue=9 |pages=1493–1494 |doi=10.3201/eid1409.080368 |issn=1080-6059 |pmc=2603110 |pmid=18760032}}</ref> Cases of head lice are most common in children between the ages of 3 and 11.<ref name=":3">{{Cite web |date=2022-02-15 |title=Lice (Phthiraptera) - Factsheet for health professionals |url=https://www.ecdc.europa.eu/en/all-topics-z/disease-vectors/facts/factsheet-lice-phthiraptera#:~:text=Due%20to%20their%20blood%20feeding,mechanical%20transmission%20of%20opportunistic%20bacteria. |access-date=2025-05-10 |website=www.ecdc.europa.eu |language=en}}</ref> ''Pthirus pubis'' (also known as pubic lice or crabs) is a species of sucking lice that affects the genitals of humans, and is the cause of ''Pediculosis pubis''.<ref name=":3" /> Pubic lice are often mistaken as sexually transmitted infections due to frequently being contracted through sexual contact; however, they are only considered parasites as they can be spread through non-sexual methods such as sharing blankets or towels.<ref>{{Cite web |title=Pubic Lice (Crabs) |url=https://my.clevelandclinic.org/health/diseases/4522-pubic-lice-crabs |access-date=May 10, 2025 |website=clevelandclinic.org}}</ref>

=== In other animals === Dogs can be affected by three individual species of Anoplura lice: ''Linognathus setosus, Heterodoxus spiniger'' and ''Trichodectes canis''.<ref name=":4">{{Cite web |title=Lice of Dogs - Dog Owners |url=https://www.merckvetmanual.com/dog-owners/skin-disorders-of-dogs/lice-of-dogs |access-date=2025-05-10 |website=Merck Veterinary Manual |language=en-US}}</ref> Dogs infested by lice show symptoms of discomfort such as rubbing, scratching and biting areas affected.<ref name=":4" /> Coats of affected animals are often rough to the touch, and can become matted over time if left untreated.<ref name=":5">{{Cite web |title=Overview of Lice in Animals - Integumentary System |url=https://www.merckvetmanual.com/integumentary-system/lice/overview-of-lice-in-animals |access-date=2025-05-10 |website=Merck Veterinary Manual |language=en-US}}</ref> Severe infestations of sucking lice can lead to anemia from the loss of blood as well.<ref name=":5" /> Lice in dogs can only be contracted through either direct or indirect contact with another infested dog, and cannot be transferred across different species.<ref>{{Cite web |title=Lice |url=https://capcvet.org/guidelines/lice/#:~:text=Lice%20of%20dogs%20and%20cats,combs,%20or%20similar%20grooming%20equipment. |access-date=2025-05-10 |website=Companion Animal Parasite Council |language=en}}</ref>

Cats are not affected by Anoplura lice, rather they can only contract the species ''Felicola subrostrata,'' a type of chewing lice.<ref>{{Cite web |title=Lice of Cats - Cat Owners |url=https://www.merckvetmanual.com/cat-owners/skin-disorders-of-cats/lice-of-cats |access-date=2025-05-10 |website=Merck Veterinary Manual |language=en-US}}</ref><ref>{{Cite journal |last1=Paul Pion |first1=D. V. M. |last2=Spadafori |first2=Gina |date=2017-08-08 |title=Veterinary Partner |url=https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4952773#:~:text=There%20is%20one%20kind%20of,chewing%20louse)%20that%20affects%20cats.&text=What%20you%20will%20notice%20with,areas%20will%20be%20most%20affected. |website=VIN.com}}</ref>

Most cattle species can be affected by sucking lice, with certain lice species being specially adapted to their preferred cattle and unable to be transferred across any other species.<ref name=":6">{{Cite web |last= |first= |last2= |last3= |first3= |date=2021-02-03 |title=Lice: A Wintertime Threat - Oklahoma State University |url=https://news.okstate.edu/articles/veterinary-medicine/2021/lice_a_wintertime_threat.html#:~:text=Lice%20that%20affect%20cattle%20cannot,or%20chewing)%20and%20sucking%20lice. |access-date=2025-05-10 |website=news.okstate.edu |language=en}}</ref> Anoplura lice can only live off of the animal for a few days.<ref name=":7">{{Cite web |last=Schlesser |first=Heather |title=Lice Management For Cattle |url=https://livestock.extension.wisc.edu/articles/lice-management-for-cattle/#:~:text=It%20takes%20the%20nymphs%20about,weight%20gain,%20and%20general%20thriftiness. |access-date=2025-05-10 |website=Livestock |language=en-US}}</ref> Female lice specialized to cattle tend to lay a single egg every day for around 2 to 3 weeks.<ref name=":7" /> Similar to sucking lice in dogs, severe infestations can cause cattle to experience anemia, with newborn calves being particularly vulnerable.<ref name=":6" />

==Families== These 15 families are generally recognized in the Anoplura:<ref name="Light2010">{{Cite journal |last1=Light |first1=Jessica E. |last2=Smith |first2=Vincent S. |last3=Allen |first3=Julie M. |last4=Durden |first4=Lance A. |last5=Reed |first5=David L. |date=2010-09-22 |title=Evolutionary history of mammalian sucking lice (Phthiraptera: Anoplura) |journal=BMC Evolutionary Biology |volume=10 |issue=1 |page=292 |doi=10.1186/1471-2148-10-292 |issn=1471-2148 |pmc=2949877 |pmid=20860811 |doi-access=free|bibcode=2010BMCEE..10..292L }}</ref>

{| class="wikitable" |- !Family!! Authority !! Host |- |Echinophthiriidae |Enderlein, 1904 |Seals/Sea Lions & Otters |- |Enderleinellidae |Ewing, 1929 |Squirrels |- |Haematopinidae |Enderlein, 1904 |Ungulates (Artiodactyls & Equids) |- |Hamophthiriidae |Johnson, 1969 |Colugos |- |Hoplopleuridae |Ewing, 1929 |Shrews & Moles (Soricomorpha), Pikas, Rodents |- |Hybophthiridae |Ewing, 1929 |Aardvarks |- |Linognathidae |Webb, 1946 |Artiodactyls, Canids, Hyraxes |- |Microthoraciidae |Kim & Lugwig, 1978 |Camels & Llamas |- |Neolinognathidae |Fahrenholz, 1936 |Elephant Shrews (Macroscelidea) |- |Pecaroecidae |von Kéler, 1963 |Peccaries |- |Pedicinidae |Enderlein, 1904 |New World Primates |- |Pediculidae |Leach, 1817 |Old World Primates |- |Polyplacidae |Fahrenholz, 1912 |Rodents, Rabbits, Shrews, Tree Shrews, Primates (Lemurs & Bush Babies) |- |Pthiridae |Ewing, 1929 |Old World Primates |- |Ratemiidae |Kim & Lugwig, 1978 |Equids |}

== See also ==

* Mallophaga

==References== {{Reflist}}

== External links == {{commons category|Anoplura}} {{Wikispecies|Anoplura}} * [http://entomology.ifas.ufl.edu/creatures/livestock/little_blue_cattle_louse.htm ''Solenopotes capillatus'', little blue cattle louse] on the UF / IFAS Featured Creatures Web site * [https://web.archive.org/web/20100821222458/http://phumanus.vectorbase.org/ VectorBase homepage for ''Pediculus humanus''] (genome browser, downloads and more)

Category:Lice