Sexually Transmitted Infections: Parasites

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Chapter 55 Sexually Transmitted Infections: Parasites

INTRODUCTION

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

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

Predominant Age: Reproductive.

ETIOLOGY AND PATHOGENESIS

Causes: Parasitic insects (P. humanus [pubic or crab lice] and S. scabiei [scabies or itch mite]).

Risk Factors: Contact with infected person or fomites.

Genetics: No genetic pattern.

CLINICAL CHARACTERISTICS

Signs and Symptoms

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

• Infestations occur most frequently in the area of the pubic hair. Spread to other hairy areas can and does take place. Scabies infections are not confined to hairy area but may be found in any area of the body.

MANAGEMENT AND THERAPY

Nonpharmacologic

General Measures: Local cleansing, soothing creams, or lotions may be used.

Specific Measures: Topical applications of insecticide. Other family members should be treated and the home disinfected at the same time. Scabies—bedding and clothing should be decontaminated (i.e., either machine washed, machine dried using the hot cycle, or dry cleaned) or removed from body contact for at least 72 hours. Fumigation of living areas is unnecessary.

Diet: No specific dietary changes indicated.

Activity: No restriction.

Patient Education: American College of Obstetricians and Gynecologists Patient Education Pamphlet AP009 (How to Prevent Sexually Transmitted Diseases). Patients should be advised to have all sexual partners seen for diagnosis and treatment.

Drug(s) of Choice

Permethrin cream (5%) applied to all areas of the body from the neck down and washed off 8 to 14 hours later. Topical applications of lindane 1% (Kwell) lotion and shampoo applied for 4 minutes, then washed off. Malathion 0.5% lotion applied for 8 to 12 hours and washed off or Ivermectin 250 μg/kg repeated in 2 weeks

Contraindications: Lindane is contraindicated in premature neonates, pregnant or lactating patients, children younger than 2 years of age, or patients with Norwegian (crusted) scabies. Patients with seizure disorders or known or suspected hypersensitivity should not use the product.

Precautions: Care must be taken to avoid the eyes. The dose of lindane should be reduced in elderly patients because of increased skin absorption. Lindane should not be used immediately after a bath or shower, and it should not be used by persons who have extensive dermatitis. (Seizures have occurred when lindane was applied after a bath or used by patients who had extensive dermatitis. Aplastic anemia after lindane use also has been reported.) Lindane is not recommended as first-line therapy because of toxicity. It should only be used as an alternative if the patient cannot tolerate other therapies or if other therapies have failed.

Interactions: Oils and ointments may increase the rate of absorption and should not be used.

Alternative Drugs

Crotamiton (Eurax) (10%) applied to all areas of the body from the neck down for two nights; on the third night, wash off the medication. Repeat the cycle beginning the fourth night.

FOLLOW-UP

Patient Monitoring: Normal health maintenance. Patients should be warned that the rash and pruritus of scabies might persist for up to 2 weeks after treatment.

Prevention/Avoidance: Sexual monogamy.

Possible Complications: Secondary skin infection from scratching.

Expected Outcome: Generally good response to insecticide therapy. Reinfection is possible if each partner, family members, and fomites are not all treated simultaneously.

MISCELLANEOUS

Pregnancy Considerations: No direct effect on pregnancy. Lindane is contraindicated during pregnancy.

ICD-9-CM Codes: 132.2 (Phthirus pubis), 131.0 (Scabies).

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