Saturday, December 18, 2010

Pediculosis & Phthiriasis  

Pediculosis is an eyelid infestation by either Pediculus humanus corporis (body) or Pediculus humanus capitus (head). Phthiriasis, which is actually the most common eyelid infestation, is caused by Phthirus pubis (pubic lice, sometimes referred to as crab lice).

Pediculus are 2 to 4 mm long, and typically infest the hair of the patient. Infestation of the cilia is rare and only occurs in the worst cases. Phthirus are 2mm long, and have a broad-shaped, crab-like body. Its thick, clawed legs make it less mobile than the Pediculus species and lend it to infesting areas where the adjacent hairs are within its grasp (eyelashes, beard, chest, axillary region, pubic region). They rarely infest the scalp.

Ocular signs and symptoms include visible organisms on the scalp, hair, eyelashes or beard; visible blue skin lesions (louse bites); reddish brown deposits (louse feces); secondary blepharitis with preauricular adenopathy; follicular conjunctivitis; and, in severe cases, marginal keratitis. The patient often complains of bilateral ocular itching and irritation.

The Pediculus and Phthirus organisms look similar the each other and interbreed freely. Both types lay eggs on the hair shafts and remain firmly adherent, resisting both mechanical and chemical removal. The Pediculus organism moves well and can be passed from person to person by either close contact or by contact with contaminated bedding. Conversely, Phthiriasis are slow moving, and cannot typically be passed unless cilia is brought into close proximity with infested cilia. Both species are associated with crowded conditions or poor personal hygiene.

Begin management by removing all visible organisms and nits (eggs) with forceps. Place the removed debris in an alcohol wipe and discard it promptly. Instruct the patient to use a pediculocidic-medicated shampoo such as Rid (a safe, effective, non-prescription pediculoside), Lidane 1% (gamma benzene hexachloride), Permethrin 1%, A-200 Pyrinate (pyrethrins, piperonyl butoxide, kerosene), Kwell or Nix.

Topical ocular therapy may include any of the following:

smothering the lice and nits with petroleum jelly or other bland ointments, TID
mercuric oxide 1% or ammoniated mercuric oxide 3%, BID
cholinesterase inhibitors such as physostigmine

Typically, the nits will survive a single application of these agents.


Daily follow up is required for seven to ten days, as nits hatch every seven to ten days.
Instruct patients to thoroughly wash all clothing and linens that may have been exposed to the organism, and educate patients about the transmission of the disease, advising them to refrain from interpersonal contact until the disease is 100 percent resolved. Also counsel patients to educate their recent sexual partners about possible exposure.
Due to ocular toxicity, pediculocide shampoos cannot be used to remove organisms from the eyelid.

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