Case #162 – August, 2005

A 6-year-old girl complained to her parents that her head was itchy after returning from a 4-week summer camp in the southeastern United States. Her parents took her to the doctor where she was examined. The doctor observed small, whitish objects located near the base of hair shafts on the scalp. Although the physician was able to make a diagnosis based on what he observed on the patient’s scalp, he did collect a few hairs to examine under the microscope. Figure A shows the objects that were found on the girl’s head and Figure B shows a close up of the objects that were found on the girl’s hair shafts. What is your diagnosis? Based on what criteria?

Figure A

Figure B

This was a case of pediculosis caused by Pediculus humanus. Diagnostic features were:

the presence of eggs (nits) attached to the hair shaft.
location on the host, which was consistent with head lice.
the presence of wingless insects demonstrating one pair of eyes, a pair of antennae, and six legs. The presence of six legs and antennae rules-out ticks and mites.

Head and body lice (and their eggs) often cannot be reliably distinguished by the naked eye. The variability of lice populations is substantial, particularly internationally.