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| Fig. 3.7 Microscopic examination of a hair shaft demonstrates an empty hair louse egg that is glued to the hair shaft. (Courtesy of James E. Fitzpatrick, MD.) |
Lice infestation is caused by
Pediculus humanus capitis (head louse),
P. humanus corporis (body louse), or
Phthirus pubis (pubic louse). Lice can be identified by eye or by using a hand lens, but they can be very difficult to locate. If body lice infestation is suspected, examination of the seams of clothing is more likely to be diagnostic than is examining the skin. Lice will appear as brownish-gray specks. Head and pubic lice are more often seen in hairy areas and are often found with their mouth parts embedded in the skin with outstretched claws grasping hairs on either side. Usually more numerous are nits (eggs), which are white-gray oval structures smaller than 1 mm in size and are firmly attached to the hair shaft. Eggs that are near the junction of the hair shaft and the skin are indicative of active or recent infection. Since hair casts are white and may resemble nits, it is sometimes necessary to examine possible nits under the microscope to prove their identity (Fig. 3-7).
