Scabies, Head lice & Thread Worms

Introduction to OSCE Topics

• Focus on infestations: scabies, head lice, threadworms.

• Importance of eradicating infestations to prevent spreading within families.

Learning Objectives

• Describe prevalence and etiology of:

  • Scabies

  • Head Lice

  • Threadworms

• Discuss symptoms associated with these conditions.

• Recommend evidence-based treatments for each condition.

• Recognize when to refer patients to a doctor.

• Counselling on appropriate treatment usage and lifestyle recommendations.

Skin Anatomy Overview

• Skin Functions: Protects from external injury, UV overexposure, microorganisms, and harmful chemicals.

• Sensory Organ: Contains receptors for touch, pressure, temperature, pain, and vibration.

• Homeostasis: Maintains body temperature.

• Skin Structure: Composed of epidermis and dermis.

• Epidermis: Top layer with four distinct layers, five in palms/soles:

  • Stratum Corneum: Dead, keratin-rich cells, flat appearance.

  • Stratum Lucidum: Present only in palms/soles, appears bright.

  • Stratum Granulosum: Contains granular cells.

  • Stratum Spinosum: Spiky appearance.

  • Stratum Basale: Bottom layer, where new cells are generated.

• Cell Turnover: Normal skin takes 35 days; accelerated in certain conditions like psoriasis (10 days).

Scabies

• Etiology: Caused by Sarcoptes scabiei (scabies mite).

• Prevalence:

  • No specific age or gender; more common in elderly.

  • Higher rates in Aboriginal and Torres Strait Islander communities; up to 50% in children.

• Transmission: Direct physical contact or from contaminated bed linen (mite survives 24-36 hours outside skin).

• Effect on Skin: Female mites burrow into the stratum corneum, causing hypersensitivity and allergic reactions, leading to itching.

• Symptoms:

  • Severe pruritus (itching) especially at night; rash typically occurs between fingers and wrists.

  • Small red papules developing into vesicles; mites burrowing leaves blue-grey threadlike markings.

• At-Risk Populations: Immunocompromised individuals might experience thickened, crusted scabies (Norwegian scabies).

Diagnostic Considerations for Scabies

• Questions for suspected cases:

  • Are there visible signs of the mite?

  • Location and history of rash?

  • Presence of similar rashes in family?

• Eliminate differential diagnoses like:

  • Allergic contact dermatitis (not straight line rashes).

  • Dermatitis herpetiformis (itchy clusters).

  • Dyshidrotic eczema (intensely itchy blisters).

  • Insect bites (asymmetrical, grouped).

Treatment for Scabies

• Household Treatment: Treat all household members simultaneously.

• First-line Treatment: Permethrin (Lyclear).

  • Application guidelines: neck down, repeat in 7 days.

  • Special considerations for children and immunocompromised patients.

• Second-line Treatment: Benzyl benzoate (apply diluted in children).

• Third-line Treatment: Croton Miton for post-treatment itch.

• Post-Treatment Care: Expect itch from dead mites; management with antihistamines is recommended.

Head Lice

• Characteristics: Ectoparasites; size 1-3 mm, feed on human blood.

• Transmission: Head-to-head contact or through fomites (hats, pillows).

• Diagnosis: Confirm with visual checks, ideally using wet combing technique.

• Symptoms:

  • Itchy scalp due to saliva reaction, presence of live lice or nits, typically at temples/ears.

• Prevalence:

  • Common in school-aged children (up to 30% in some areas); misconception leads to stigma.

Treatment for Head Lice

• Insecticidal Treatments: Varied effectiveness; resistance is an issue.

• Alternative Treatments:

  • Dimethicone and wet combing.

  • Essential oils may also help.

• Application Guidelines: Follow up treatments are critical; repeat in 7 days, especially for unhatched eggs.

Threadworms (Pinworms)

• Etiology: Caused by Enterobius vermicularis; widespread in children.

• Transmission: Fecal-oral route, particularly through scratching and finger sucking.

• Symptoms: Typically involves discomfort in the anal region, especially at night.

• Preferred Treatment: Mebendazole for all family members; repeat dose in 14 days.

• Alternative: Pyrantel, particularly suitable in children.

Lifestyle Recommendations for Infestations

• Ensure all family members receive treatment to prevent reinfection.

• Maintain good hygiene practices (hand washing, nail care).

• Frequent washing of bed linen and personal items.

• Monitor for any signs of secondary infections; refer to a doctor if necessary.