Pediculosis

Pediculosis

Definition

• Humans are parasitized by three species of Anoplura:
  1. Pediculus humanus capitis or head louse.
  2. Pediculus humanus corporis or body louse.
  3. Phthirus pubis or pubic louse.

Clinical types

1. Pediculosis Capitis
2. Pediculosis Corporis
3. Pediculosis Pubis

1) Pediculosis Capitis

Synonym: Head lice. Cause: Pediculus humanus capitis. Epidemiology:

• Common in children & homeless people
• Spread from person to person by head- to-head contact, and by shared combs or hats.
• Often seen in epidemics amng kindergarten and school children

Morphology and biology

• Female lifespan is approximately 40 days
• Lays about 300 eggs, at the rate of 7-10 daily
• Eggs are cemented to hair shafts with a material secreted by female’s accessory glands
• Eggs hatch in about 8 days.

Pathogenesis

• Lice live on the scalp and suck blood
• They firmly attach their eggs (nits) to the hair shaft just at the skin surface
• The head louse measures some 3-4 mm in length and is greyish, and often rather hard to find

Clinical features

• Pruritic eruption on back of scalp and nape
• Excoriations & secondary infections (lice drmt)
• Hairs may become matted due repeated scratch
• Lice identified especially when combing hair
• Nits may be present throughout the scalp, but most common in the retroauricular region (ova close to scalp are viable)

Diagnostic approach:

Look for: – Nits on the hair shafts (retro-auricular), – Lice on the scalp.

Therapy

Effective therapeutic agents must kill/remove both lice and ova.

1. Pyrethrins and the synthetic permethrin:

• 1% and 5% cream
• Must be applied (10 min) after shampooing and drying hair completely
• No hair washing for 24 hours

1. Malathion 0.5% lotion.

• Has the extra value of sticking to the hair, so protecting against re-infection for 6 weeks.

1. Lindane (gama benzene hexachloride)

• Has potential neurotoxicity if abused

1. Crotamiton (Eurax)10% cream or lotion

Nits treatment: Nits are always a problem

• No treatment is available
• Re-treatment in a week is advsable for all pnts
• Combing with a metal or plastic nit comb (fine-toothed) is an important adjunctive measure

Other therapy methods: Oral treatment Ivermectin

• Has no ovicidal activity
• Two doses separated by an interval of 10 days would be more effective.

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2) Pediculosis Corporis

Synonym: Body lice. Cause: Pediculus humanus corporis. Epidemiology:

• Is primarily a disease of the unwashed “Vagabond’s disease”

Morphology and biology

• Identical in developmnt & appearance to head louse
• Its natural habitat is the clothing of its host, it only visits the skin to feed.
• Eggs are cemented to clothing fibres
• With a preference for clothing close to the skin.
• Seams are a favoured site

Pathogenesis

• The lice feed on the body, but live in the clothing
• The parasite obtains its nourishment by descending to the skin and taking a blood meal.
• Lay their eggs in the seams of clothing

Clinical features

• Pruritus,
• Itching is accompanied by erythematous and copper-colored macules, wheals
• Excoriations and secondary infections (lice dermatitis) on trunk (vagabond skin) are common.

Diagnostic Approach

• Look for the lice and nits on the clothing, not on the skin.
• Is differentiated from scabies by the lack of involvement of the hands and feet 19

Therapy

• Same pediculicides as for Pediculus humanus capitis can be used • Lice may live in clothing for 1 month without a blood meal. • Disinfection of clothing and bedding (boiling, hot ironing). • Attempt to change living conditions.

1. Pyrethrins and the synthetic permethrin:
   • 1% and 5% cream
2. Malathion 0.5% lotion. – Has the extra value of sticking to the hair, so protecting against re-infection for 6 weeks.
3. Lindane (gama benzene hexachloride)
   • Has potential neurotoxicity if abused
4. Crotamiton (Eurax)10% cream or lotion

3- Pediculosis Pubis

Synonym: Pubic lice. Cause:Phthirus pubis Epidemiology:

• Is found in the pubic region, as well as hairy areas of legs, abdomen, chest, axillae, arms
• Spread through close physical contact
• Usually transmitted by sexual contacts

Clinical features

• Lice and nits present in the hair of pubic area • The signs and symptoms are similar to those of body louse infestation.

Therapy

1. Pyrethrins and the synthetic permethrin:

   • 1% and 5% cream

2. Malathion 0.5% lotion.

   • Has the extra value of sticking to the hair, so protecting against re-infection for 6 weeks.

3. Lindane (gama benzene hexachloride)

   • Has potential neurotoxicity if abused

4. Crotamiton (Eurax)10% cream or lotion Numerous eggs (nits) seen