Infectious Disease Compendium

Lice

Microbiology

Bugs. Pediculus humanus var. corporis, the body louse; Pediculus humanus var. capitis, the head louse; and Phthirus pubis, the pubic louse (or crabs).

Epidemiologic Risks

Being human, going to school (to judge from what keeps happening at my kids school). Living in filth and squalor, which is a suburb. I still think that if the can be seen without a gram stain and a microscope, they are not in my field.

Because of shaving pubic hair, lice are becoming less common and Pthirus pubis, the pubic lice, may be at risk for becoming extinct (Pubic lice: an endangered species?).

But. The more aggressive the patient is at pubic hair grooming and shaving, the greater the risk of other STI's (PubMed).

Syndromes

Itch and itch and itch. Boy do I itch just writing this.

Treatment

1% lindane, gamma benzene hexachloride shampoo (Kwell) OR pyrethrins with piperonyl butoxide solution (RID, A-200 pyrinate liquid) OR 1% permethrin cream rinse (Nix. Resistance to Nix is increasing).

A single application of 0.5% ivermectin leads to 94.9% louse-free on day 2, 85.2% louse-free on day 8 (vs. 20.8%), and day 73.8 % free on day (PubMed); much better than placebo.

Also, one 30-minute application of hot air can eradicate head lice (eggs and hatched lice) infestations and may be superior to the creams (PubMed) so best option is to place the patient near a presidential candidate.

Spinosad (Natroba Topical Suspension 0.9%, > 4 years old; new as of 2011): apply to dry scalp and hair, using the minimal amount needed to cover both. After 10 minutes, thoroughly rinse the head and hair with warm water, being careful to avoid contact with the eyes. Repeat a week later if lice persist.

For difficult-to-treat head-lice infestation, ivermectin 400 micrograms/kg po, given twice at a 7-day interval, was superior to topical 0.5% malathion lotion (PubMed).

Notes

They can be an important vector for diseases including epidemic typhus (Rickettsia prowazekii), trench fever (Bartonella quintana), and relapsing fever (Borrelia recurrentis).

It may be best to comb through wet hair to find the organism, but I am just nit picking (PubMed).