Pediculus humanus var capitis AKA head louse | Centers for Disease Control and Prevention’s Public Health Image Library (PHIL) #377 Public Domain, https://commons.wikimedia.org/w/index.php?curid=482602
Pediculosis corporis (Pediculosis vestimenti, Vagabond’s disease):
Image of body lice. CDC image – public domain https://www.cdc.gov/parasites/lice/body/index.html
Pediculosis pubis (Crabs):
Adult pubic lice are 1.1–1.8 mm in length. Pubic lice typically are found attached to hair in the pubic area but sometimes are found on coarse hair elsewhere on the body (for example, eyebrows, eyelashes, beard, mustache, chest, armpits, etc.). Pubic lice infestations (pthiriasis) are usually spread through sexual contact. Dogs, cats, and other pets do not play a role in the transmission of human lice. | Centers for Disease Control and Prevention: https://www.cdc.gov/parasites/lice/pubic/index.html, Public Domain, https://commons.wikimedia.org/w/index.php?curid=64588209
Clinical features
Pubic lice in genital area. | SOA-AIDS Amsterdam, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=45747
Pubic lice on the abdomen | KostaMumcuoglu CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=7737851
Pubic lice on the eyelashes | KostaMumcuoglu CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=16506825
Diagnosis
Pediculosis in the head of a 6-year-old boy caused by the crab louse, as confirmed by optical (c) and electron microscopy (d) | a. There were some small pieces of erythema (in the circle) and a brown dot-like substance on the scalp (arrow). b. The dermoscopy revealed a brown parasite (0.9 mm in horizontal axes and 1.2 mm in vertical axes) with two crab-like feet adhered to the scalp. c. Under the microscope, the parasite was characterized by a flat body like a crab and three pairs of feet in different sizes. There was an area (red box) full of blood in the middle part of the parasite. A large number of short setae (arrow) were noted at the edge of the parasite abdomen. d. The SEM showed a vivid three-dimensional ultrastructure of the parasite: the whole body was composed of three parts including spherical head, chest, and elliptical abdomen; a pair of feelers was noted on the head; the three pairs of feet were in shaped section and curved serrated claws were noted at the end of foot; short setae in different length were not only at the edge of the abdomen but also on the feet. | Ran Yuping et al. – , CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=52253615
Differential diagnosis:
Dandruff (pityriasis sicca)
Impetigo
Seborrhoeic dermatitis
White piedra, black piedra
Monilethrix, pseudomonilethrix
Pili torti
Psocids (book lice)
Management
Non-pharmacological management:
A few historical methods to get rid of lice. (a) Detecting lice or nits by direct visual examination; (b) wooden comb found at Ein Rachel (Negev Desert) (100 BC–200 AD) containing 10 head lice and 5 nits; (c) modern fine plastic comb. | Sangaré, A. K., Doumbo, O. K., & Raoult, D. (2016). Management and Treatment of Human Lice. BioMed Research International, 2016, 8962685. https://doi.org/10.1155/2016/8962685
Pharmacological management (ovicides):
Local treatment suffices for all but exceptional cases of head lice infestation. Many head lice are resistant to pyrethroids. Good results without the development of resistance are achieved with dimethicones.
> 95% ovicidal:
Long contact (overnight application):
Malathion 0.5% lotion
Occlusive agents:
Crotamiton 10%
Dimethicone 4%
Short term (10-30 mins):
Malathion 0.5% gel
Spinosad 0.9% suspension
70% ovicidal:
Short contact (10 mins):
Permethrin 1% lotion
Benzyl alcohol 5%
Treatment for head lice Course over time of therapeutic interventions in the life cycle of the head louse: Unless an ovicide is used, the treatment must be repeated on day 8 (day 1 = first day of treatment) so as to eliminate the nymphs that were protected inside eggs at the time of the first treatment before they are sexually mature and can lay new eggs. Studies have shown that after egg lay some nymphs may hatch later, after 13 days. In the worst case, therefore, nymphs that survived the first repeat treatment undamaged inside the egg may not hatch until the 13th day. The only way to eliminate these would be a third treatment on day 15. Ovicides, on the other hand, only need to be applied once. | Meister, L., & Ochsendorf, F. (2016). Head Lice. Deutsches Arzteblatt International, 113(45), 763–772. https://doi.org/10.3238/arztebl.2016.0763
