PARASITIC INFESTATIONS

Pediculosis capitis (head lice) is the commonest parasitic skin infestation in Indian children, while other types, e.g. P. corporis (body lice) and P. pubis (groin lice) is uncommon.

Etiologically P. capitis is ~2-4 mm in length, transmitted by head-to-head contact or through shared comb or towels. Female lice lives for about 1 month and lays 3-10 eggs/ day. Eggs glue to the proximal part of hair shaft and hatch to form larvae that feeds on human blood along with adult lice—injecting their salivary juices into host and depositing fecal matter over skin (responsible for itching). Nits are empty sacs of chitin left behind on hair shaft after hatching and migration of larvae.

Clinically, pruritus is the hallmark of infestation, though secondary pyoderma over scalp are common in children. On examination, nits are easily visible than the lice and may be differentiated from dandruff by its firm attachment with hair shaft.

Treatment of choice for killing adult lice/larvae is the single application of Permethrin 1% cream on wet hair for 10 minutes followed by head wash and repeated after 7 days. Other options include similar application of Gamma benzene hexachloride 1% for overnight or Malathion 0.5% for 6 hours, both on dry hair, which may also be repeated after 7-10 days.

Nits may be removed by fine-tooth combing after rinsing the hair with 1:1 vinegar. Other important steps include treatment of all family members sharing common bed, hot-water washing of cloths/bed linens and regular shampooing of hair.

Scabies is the second commonest parasitic infestation of skin after pediculosis, mostly seen in slum children living in overcrowded and unhygienic slums.

Etiologically, it is caused by burrowing and release of toxic or antigenic substances by the female mite Sarcoptes scabiei. Infestation is transmitted by close physical contact with an infested family member, and rarely by fomites.

Clinically lesions appear after about one month of infestation, presenting with pruritus, particularly at night, and tiny (1-2 mm) red papules over the burrowed site that may crust, excoriate or get infected to form Vesiculopustular lesions (Fig. 25.6). While any part of body may be affected in infants/toddlers, lesions are more common oVer inter-digital spaces, wrist and flexural regions in older children sparing head, neck, palm and soles.

Complications include: (a) eczematous dermatitis, (b) superimposed pyoderma, folliculitis, cellulitis, and (c) regional lymphadenopathy.

Diagnosis may be made clinically on history and visualization of burrows with a magnifying lens, while confirmation requires microscopic examination of scraping from these burrows or papules to demonstrate adult mite, ova or scybala. Other family members are frequently co-infected.

Treatment includes application of a scabicidal agent from neck to toe (also on face, neck and scalp in infants) after a scrub bath. Treatment should be repeated after a gap of 7-10 days in severe cases.

While Benzyl benzoate 25% (for 3 days) or Gamma benzene hexachloride 1% (single application) are

Fig. 25.6: Scabies: (A) Hand; (B) Inter-digital region.

(Courtesy: Dr Uday Khopkar)

commonly used for this purpose, a single application of Permethrin 5% is the preferred choice in children gt;2 months, to avoid burning sensation on benzyl benzoate application and potential neurotoxicity of gamma benzene hexachloride. Scabies in infants lt; 2 months may be treated with Crotamiton 10% two applications daily for 14 days.

Oral Ivermectin 0.2 mg/kg is an effective alternative for infected scabies in older children gt; 3 years.

Other important components of scabies treatment are simultaneous treatment of all family members (even if asymptomatic) and washing of patient's clothing and bed-linens with hot water. Antihistaminics may be used for symptomatic relief from pruritus. Despite effective treatment scabies tend to be recurrent in susceptible population, unless proper hygiene is maintained.

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