Sexually Transmitted Infections: Parasites

Introduction

• Description: Phthirus pubis (pubic or crab lice) and Sarcoptes scabiei (scabies or itch mite) are parasitic insects that may be transferred through sexual activity or contact with contaminated clothing or bedding.

• Prevalence: Three million cases per year in the United States.

• Predominant Age: Reproductive age.

Etiology and Pathogenesis

• Causes: Parasitic insects P. pubis (pubic or crab lice) and S. scabiei (scabies or itch mite). P. pubis is a 0.8–1.2 mm long, translucent parasite, with four of its six legs terminating in prominent claws, which are used to grasp pubic hairs. S. scabiei var. hominis is a whitish-brown, eight-legged mite, measuring approximately 0.4 × 0.3 mm (female).

• Risk Factors: Contact (skin-to-skin) with infected person or fomites.

• Genetics: No genetic pattern.

Signs and Symptoms

• Intense itching (greatest at night), most frequently in the area of the pubic hair.

• Infestations most frequently occur in the area of the pubic hair. Spread to other hairy areas can and does occur. Scabies infections are not confined to hairy area but may be found in any area of the body, notably the periareolar skin (especially in women).

• Pale, bluish, 0.5–1 cm macules may develop with prolonged louse infestation, resulting from louse anticoagulant saliva introduced during feeding.

Diagnostic Approach