Lice

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The page below is a sample from the LabCE course Arthropods and the Clinical Laboratory. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Lice

Lice belongs to the order Phthiraptera. Lice infestation is called pediculosis.
  • Lice are wingless, small (0.4–10mm in length), sucking, with claws.
  • One pair of five-segmented antennae is present.
  • The head, thorax, and abdomen are all distinctly visible.
  • Nits are eggs approximately 1mm long, having operculum; head nits are deposited on hair shafts. Operculum may be present. Be aware that hair casts, dander, hair spray, and fungal infections can mimic nits (McPherson & Pincus, 2011). Body lice nits are deposited on clothing.
  • Spread of lice occurs through close contact/shared clothing.
The three types of lice in humans:
Head: Pediculus humanus capitis
Body: Pediculus humanus corporis
Pubic: Phthiris pubis
  • Head and body lice are longer than wide, approximately 3mm long. Head and body are indistinguishable from each other to the nonspecialist.
  • Pubic lice may measure up to 2mm in diameter. They are crab-like in appearance.
  • "Crabs" may be passed from human to human during sexual or non-sexual transmission. Transmission occurs from close contact, sleeping on an infested bed, or using infested towels.
  • Note: Pubic lice found on children may be a sign of sexual abuse.
Lice species are animal-specific. Animals do not get lice from humans or spread lice from humans.
19. CDC. Image# 15870 (cropped). (1963). "... a head louse, Pediculus humanus capitis, a pubic louse, Phthirius pubis." PHIL public domain. https://phil.cdc.gov/Details.aspx?pid=15870
20. CDC. Image# 17328. (1975). "This 1975 photomicrograph, originally provided by Reed & Carnrick Pharmaceuticals, depicted an enlarged view of a louse egg, laid upon a hair shaft, by a female Pediculus humanus var. capitis, prior to any pharmaceutical treatment implementation." PHIL public domain. https://phil.cdc.gov/Details.aspx?pid=17328

Lice. (19)
Nit (louse egg, laid upon a hair shaft, by a female Pediculus humanus capitis). (20)