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Sucking louse

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Sucking louse
Linognathus setosus (Linognathidae)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Psocodea
Suborder: Troctomorpha
Infraorder: Phthiraptera
Parvorder: Anoplura
Leach, 1815
Families
Synonyms

Siphunculata[1]

Sucking lice (known scientifically as Anoplura) are a parvorder[2] 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

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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. A cladogram showing the position of Anoplura within Phthiraptera and Psocodea is shown below:[3]

Psocodea

Characteristics

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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.[4] There are around 540 different species of Anoplura, and unlike the closely related Mallophaga, sucking lice only parasitize mammals.[5]

Sucking lice bodies are typically oblong, with a flattened body and a head that is rounded in the front and smaller than the thorax.[6] The lice have anywhere from three to five separate thread–like antennae on top of the end of the head that is used to help navigate their surroundings.[6] The head tends to slightly widen next to the antennae.[6] The antennae are composed of three to five equal sized joints that are used to aid in sensing their surrounding.[7] 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.[6]

Life cycle

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All sucking lice undergo a process of slow metamorphosis, with three life stages of egg, nymph and adult.[8] 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.[9] Once a female louse matures, they will lay large amounts of small eggs (also known as nits) on the individual hairs of hosts.[9] Nits are usually between 0.3 to 0.8 millimeters long, and are often pale in color or nearly transparent.[10]

Feeding method

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Sucking lice live exclusively on the outside of their hosts, making them considered ectoparasites.[11] The louse's proboscis consists of two distinct tubes, with the upper being called a rostrum, and the lower being called a stylet.[11] The lice will use their upper mouth piece to latch onto the skin with teeth–like structures, maintaining a firm hold during their feeding. The lower mouth piece consists of two stylets, also known as "stabbers".[11] After the rostrum obtains a firm hold, the stylets will penetrate the skin with the serrated edges in a saw–like fashion. The louse will then regurgitate saliva through the proboscis inside of the body, before proceeding to suck the host's blood[12] in what has been described as a "pumping action".[11] Different species of sucking louse have specialised anatomy to help parasitize on different mammals and to help survive various climates.[12]

Effects

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In humans

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Anoplura contains three species of lice that parasitize humans.[13] Anoplura body lice (Pediculus humanus humanus) typically carry the potential of causing skin irritation, and are vectors of multiple blood-born diseases.[14] Common symptoms of Anoplura body lice include relapsing fever, trench fever and epidemic typhus.[14][15] Due to increased societal standards for hygiene, body lice in general is significantly less prevalent in developed regions.[15] 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.[16] 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.[17] Cases of head lice are most common in children between the ages of 3 and 11.[18] 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.[18] Public 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.[19]

In other animals

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Dogs can be affected by three individual species of Anoplura lice: Linognathus setosus, Heterodoxus spiniger and Trichodectes canis.[20] Dogs infested by lice show symptoms of discomfort such as rubbing, scratching and biting areas affected.[20] Coats of affected animals are often rough to the tough, and can become matted over time if left untreated.[21] Severe infestations of sucking lice can lead to anemia from the loss of blood as well.[21] Lice in dogs can only be contracted through either direct or indirect contact with another infested dog, and cannot be transferred across different species.[22]

Cats are not affected by Anoplura lice, rather they can only contract the species Felicola subrostrata, a type of chewing lice.[23][24]

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.[25] Anoplura lice can only live off of the animal for a few days.[26] Female lice specialized to cattle tend to lay a single egg every day for around 2 to 3 weeks.[26] Similar to sucking lice in dogs, severe infestations can cause cattle to experience anemia, with newborn calves being particularly vulnerable.[25]

Families

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These 15 families are generally recognized in the Anoplura:[5]

See also

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References

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  1. ^ Ibarra, J. (1993). "Lice (Anoplura)". In Lane, R.P.; Crosskey, R.W. (eds.). Medical Insects and Arachnids. Dordrecht: Springer. pp. 517–528. doi:10.1007/978-94-011-1554-4_15. ISBN 978-94-010-4679-4.
  2. ^ "Psocodea Species File - Anoplura Leach, 1815". psocodea.speciesfile.org. Retrieved 2025-05-10.
  3. ^ de Moya, Robert S; Yoshizawa, Kazunori; Walden, Kimberly K O; Sweet, Andrew D; Dietrich, Christopher H; Kevin P, Johnson (2021-06-16). Buckley, Thomas (ed.). "Phylogenomics of Parasitic and Nonparasitic Lice (Insecta: Psocodea): Combining Sequence Data and Exploring Compositional Bias Solutions in Next Generation Data Sets". Systematic Biology. 70 (4): 719–738. doi:10.1093/sysbio/syaa075. ISSN 1063-5157. PMID 32979270.
  4. ^ "Sucking louse | Parasite, Blood-Feeding, Pest | Britannica". www.britannica.com. Retrieved 2025-05-09.
  5. ^ a b Light, Jessica E.; Smith, Vincent S.; Allen, Julie M.; Durden, Lance A.; Reed, David L. (2010-09-22). "Evolutionary history of mammalian sucking lice (Phthiraptera: Anoplura)". BMC Evolutionary Biology. 10 (1): 292. Bibcode:2010BMCEE..10..292L. doi:10.1186/1471-2148-10-292. ISSN 1471-2148. PMC 2949877. PMID 20860811.
  6. ^ a b c d Bulletin. U.S. Government Printing Office (published December 12, 2011). 1883. p. 187. OCLC 365228942.
  7. ^ "Lice (Phthiraptera) - Factsheet for health professionals". www.ecdc.europa.eu. 2022-02-15. Retrieved 2025-05-09.
  8. ^ "Anoplura". entomology.k-state.edu. Retrieved 2025-05-09.
  9. ^ a b "Lice Dogs and Cats: chewing (Mallophaga), and sucking (Anoplura) - Learn About Parasites - Western College of Veterinary Medicine". wcvm-learnaboutparasites. Retrieved 2025-05-09.
  10. ^ "Life cycle of lice: Stages, how they spread, and more". www.medicalnewstoday.com. 2022-05-31. Retrieved 2025-05-09.
  11. ^ a b c d Lapage, Geoffrey (1951). Parasitic Animals. Cambridge University Press. pp. 115–116. ISBN 9781107496613. {{cite book}}: ISBN / Date incompatibility (help)
  12. ^ a b Aspinall, Victoria (May 25, 2006). The Complete Textbook of Veterinary Nursing (2nd ed.). Saunders/Elsevier. p. 504. ISBN 9780702040504.
  13. ^ Akhoundi, Mohammad; Heriniaina, Hantatiana Juliana; Brun, Sophie; Benamari, Emma; Izri, Arezki (2024-11-03). "Morphological discrimination of human lice (Anoplura: Pediculidae) by eggs' cap-like operculum". Scientific Reports. 14 (1): 26506. Bibcode:2024NatSR..1426506A. doi:10.1038/s41598-024-78292-8. ISSN 2045-2322. PMC 11532422. PMID 39489815.
  14. ^ a b Johnston, J. Spencer; Yoon, Kyong Sup; Strycharz, Joseph P.; Pittendrigh, Barry R.; Clark, J. Marshall (2007-11-01). "Body Lice and Head Lice (Anoplura: Pediculidae) Have the Smallest Genomes of Any Hemimetabolous Insect Reported to Date". Journal of Medical Entomology. 44 (6): 1009–1012. doi:10.1093/jmedent/44.6.1009. ISSN 0022-2585. PMID 18047199.
  15. ^ a b Bonilla, Denise L.; Durden, Lance A.; Eremeeva, Marina E.; Dasch, Gregory A. (2013). "The biology and taxonomy of head and body lice--implications for louse-borne disease prevention". PLOS Pathogens. 9 (11): e1003724. doi:10.1371/journal.ppat.1003724. ISSN 1553-7374. PMC 3828170. PMID 24244157.
  16. ^ Parsons, Susan. "The Civil War and Body Lice" (PDF). cayugacounty.us. Retrieved May 11, 2025.
  17. ^ Falagas, Matthew E.; Matthaiou, Dimitrios K.; Rafailidis, Petros I.; Panos, George; Pappas, Georgios (2008). "Worldwide prevalence of head lice". Emerging Infectious Diseases. 14 (9): 1493–1494. doi:10.3201/eid1409.080368. ISSN 1080-6059. PMC 2603110. PMID 18760032.
  18. ^ a b "Lice (Phthiraptera) - Factsheet for health professionals". www.ecdc.europa.eu. 2022-02-15. Retrieved 2025-05-10.
  19. ^ "Pubic Lice (Crabs)". clevelandclinic.org. Retrieved May 10, 2025.
  20. ^ a b "Lice of Dogs - Dog Owners". Merck Veterinary Manual. Retrieved 2025-05-10.
  21. ^ a b "Overview of Lice in Animals - Integumentary System". Merck Veterinary Manual. Retrieved 2025-05-10.
  22. ^ "Lice". Companion Animal Parasite Council. Retrieved 2025-05-10.
  23. ^ "Lice of Cats - Cat Owners". Merck Veterinary Manual. Retrieved 2025-05-10.
  24. ^ Paul Pion, D. V. M.; Spadafori, Gina (2017-08-08). "Veterinary Partner". VIN.com.
  25. ^ a b "Lice: A Wintertime Threat - Oklahoma State University". news.okstate.edu. 2021-02-03. Retrieved 2025-05-10.
  26. ^ a b Schlesser, Heather. "Lice Management For Cattle". Livestock. Retrieved 2025-05-10.
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