Section G: Infestations

Lice

PATIENT STORY

A 64-year-old homeless woman with schizophrenia presented to a homeless clinic for itching all over her body. She stated that she could see creatures feed on her and move in and out of her skin. The physical examination revealed that she was unwashed and had multiple excoriations over her body (Figure 148-1). Body lice and their progeny were visible along the seams of her pants (Figure 148-2). Treatment of this lousy infestation required giving her new clothes and a shower.¹

INTRODUCTION

Lice are ectoparasites that live on or near the body. They will die of starvation within 10 days of removal from their human host. Lice have coexisted with humans for at least 10,000 years.² Lice are ubiquitous and remain a major problem throughout the world.³

SYNONYMS

Pediculosis, crabs (pubic lice).

EPIDEMIOLOGY

• Human lice (pediculosis corporis, pediculosis pubis, and pediculosis capitis) are found in all countries and climates.³

• Head lice are most common among school-age children. Each year, approximately 6 to 12 million children, ages 3 to 12 years, are infested.⁴

• Head lice infestation is seen across all socioeconomic groups and is not a sign of poor hygiene.⁵

• In the United States, black children are affected less often as a result of their oval-shaped hair shafts that are difficult for lice to grasp.⁴

• Body lice infest the seams of clothing (see Figure 148-2) and bed linen. Infestations are associated with poor hygiene and conditions of crowding.

• Pubic lice are most common in sexually active adolescents and adults. Young children with pubic lice typically have infestations of the eyelashes. Although infestations in this age group may be an indication of sexual abuse, children generally acquire the crab lice from their parents.⁶

ETIOLOGY AND PATHOPHYSIOLOGY

• Lice are parasites that have six legs with terminal claws that enable them to attach to hair and clothing. There are three types of lice responsible for human infestation. All three kinds of lice must feed daily on human blood and can only survive 1 to 2 days away from the host. The three types of lice are as follows:

  • Head lice (Pediculus humanus capitis...