Answer to Case 43

Answer: Pthirus pubis, the crab louse.

Little known facts about the crab louse:
1. It's an obligate parasite, living and feeding only on humans.
2. It takes 4 to 5 blood meals a day.
3. The closely related body louse feeds even more frequently and can cause anemia in heavily infected individuals. Historically, children with louse-induced anemia looked pale and unwell - this is where the term "lousy" came from.
4. The crab louse most commonly inhabits the genital area but can also inhabit the hair under the arm pits, eye brows, and eye lashes. The latter may be seen in children and does not necessarily indicate sexual abuse; infection can be passed from one child to another through casual contact.