Sir,

Phthiriasis palpebrarum is the most common eyelid infestation caused by Phthirus pubis (pubic lice), sometimes referred to as crab lice

Case report

Two brothers, aged 8 and 3 years, presented to the casualty with a 3-week history of itchy red eyes. They had no previous ocular history and were generally fit and healthy. They lived with their parents and one other brother, who had no ocular complaints.

The visual acuity of the older boy was 6/6 and that of the younger boy was not recordable.

On examination, lice and nits were noted on the eyelashes of both patients, and microscopic examination subsequently confirmed these as pubic lice (Figure 1).

Figure 1
figure 1

Lice and nits noted on the eyelashes.

Full size image

The children were managed with Oc. Pilogel 4% applied twice daily to the lashes, leading to elimination of the lice.

Comment

Phthiriasis palpebrarum, is the most common cause of eyelid infestation, and is caused by Phthirus pubis (pubic lice). Phthirus are 2 mm long and have a broad-shaped, crab-like body. Their thick, clawed legs make them less mobile than the Pediculus species, but enable them to infest areas where the adjacent hairs are within their grasp (eyelashes, beard, chest, axillary region, pubic region).1 They rarely infest the scalp.

Pediculosis palpebrarum is an eyelid infestation caused by Pediculus humanus corporis (body lice) or Pediculus humanus capitus (head lice). Pediculus species are 2–4 mm long and typically infest the hair. Infestation of the cilia, however, is rare.

Ocular signs and symptoms include the following: bilateral ocular itching, irritation, visible lice and nits, visible erythematous lesions resulting from louse bites, reddish-brown deposits on the lashes (louse faeces) secondary blepharitis, follicular conjunctivitis, and marginal keratitis.

Adult females lay eggs on the hair shafts, which are resistant to mechanical and chemical removal. They lay as many as 26 eggs (up to 3 eggs a day),1 which hatch every 7–10 days. The average lifespan of adult lice is less than a month, and they die within 24–48 h if removed from their hosts. They interbreed freely within different species. Crowded conditions and poor personal hygiene may be reasons for infestation.

A number of treatment options are available. These include trimming or plucking of eye lashes,2,3 traumatic amputation, cryotherapy,4 argon laser photocoagulation,5 fluorescein 20%,5 physostigmine 0.25%,6 Q1lindane 1%,7 petroleum jelly,8 yellow mercuric oxide ointment 1%,8 malathion drops 1% or malathion shampoo 1%,9 and pilogel 4%.

The exact mechanism of action of pilocarpine 4% gel is not yet known. It could be attributed to its direct cholinergic action of depolarising the effector cell, causing paralysis of the lice, or because of direct pediculocidal action or even the smothering effect of the gel.

Pilocarpine 4% gel is cheap and easily available and has much less side effects than indirectly acting cholinergic agonists like physostigmine or organophosphorous compounds, as they have a longer duration of action than pilocarpine.

These patients require follow-up for 7–10 days, and education regarding transmission to avoid interpersonal contact until completely cured.

Laundering of potential fomites (eg towels, pillow covers, sheets, hats) at a temperature exceeding 131°F for more than 5 min kills the eggs, nymphs, and mature lice. Since adult lice cannot survive more than 48hrs if separated from the host, and nits hatch in 7–10 days, careful sealing of fomites in plastic bags for 2 weeks can also be effective.

Lastly, pubic lice in children may be an indication of sexual abuse, and it is of interest that the patients discussed herein were reported to have shared a bed with an uncle on several occasions. There has been a resurgence of pubic louse infestation from increased sexual activity in the adolescent population, and associated venereal diseases have been detected in a large percentage of involved subjects.7