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DR5.1,DR6.1 | Ectoparasitic Infestations — PBL Case

CLINICAL SETTING

Dr Meera, the newly posted medical officer at a 120-bed district hospital in rural Maharashtra, is called urgently by the nursing superintendent. Over the past 10 days, 14 patients from Ward 7 (a general medicine ward) and 3 nursing staff have developed a pruritic rash. The pruritus is worst at night. A 58-year-old male patient with poorly-controlled type 2 diabetes, who has been an inpatient for 3 weeks, is identified as the probable index case. He has extensive hyperkeratotic, scaly plaques over the hands, forearms, and dorsal feet, and his skin scraping shows an extremely high mite count on microscopy. Several patients in adjacent beds have typical burrows in finger web spaces and wrist flexures. The three affected nurses work different day and night shifts and share a common rest room.

Trigger 1: Identifying the Index Case and Making the Diagnosis

Dr Meera examines the index patient, Mr Ramesh, aged 58. He has been inpatient for 3 weeks for diabetic foot management. His examination reveals extensive, thick, silvery-grey hyperkeratotic plaques over both hands, forearms, and dorsal feet. He has been on systemic corticosteroids for 2 weeks for an unrelated inflammatory condition. His pruritus is relatively mild despite the extensive cutaneous involvement. Scraping from the plaques shows hundreds of mites on microscopy. A junior nurse documents this as 'psoriasis with secondary infection'. Dr Meera disagrees. **Available data:** The corticosteroid treatment history; diabetes (immunosuppression); the low level of itch relative to the enormous mite burden; the location of lesions; the hyperkeratotic, crusted morphology.

DISCUSSION POINTS

  • What is the specific diagnosis for Mr Ramesh, and how does it differ from classical scabies? Name the condition and its causative organism.
  • Why does the level of pruritus appear disproportionately low relative to the extensive infestation? What is the immunological explanation?
  • What factors in Mr Ramesh's history predisposed him to this severe presentation? How does each factor contribute?
  • The junior nurse documented 'psoriasis'. What clinical features would help distinguish Mr Ramesh's condition from psoriasis? What single bedside test provides a definitive answer?
  • Why is Mr Ramesh likely to be a highly efficient source for infesting other patients and staff, compared with a patient with classical scabies?
Click to reveal Trigger 2: Managing the Index Case and Choosing the Treatment Strategy (discuss previous trigger first!)

Trigger 2: Managing the Index Case and Choosing the Treatment Strategy

Dr Meera confirms the diagnosis and now faces the challenge of treating Mr Ramesh effectively. The ward pharmacist informs her that permethrin 5% cream, malathion lotion, and oral ivermectin (200 mcg/kg tablets) are available. The infection control team asks her to propose a treatment plan for Mr Ramesh specifically, before they address the ward-wide outbreak. **Available data:** Mr Ramesh is on metformin, glipizide, and prednisolone 30 mg/day. His eGFR is 52 mL/min/1.73m². He weighs 64 kg. He is not on any neurological medications. No known drug allergies.

DISCUSSION POINTS

  • Would topical permethrin 5% alone be adequate for Mr Ramesh? Justify your answer by explaining the pharmacological limitation of topical-only treatment in this specific case.
  • Propose a combined treatment regimen (topical + oral) for Mr Ramesh. Specify the dose of oral ivermectin, the number and timing of doses, and any dietary instruction for optimal absorption.
  • Are there any contraindications to oral ivermectin in Mr Ramesh? Review his drug history and renal function — do any of his concurrent medications interact with ivermectin?
  • The ward pharmacist suggests lindane 1% as it is 'highly effective and cheap'. Should Dr Meera agree? List the contraindications to lindane that apply to Mr Ramesh.
  • How would you modify the treatment plan if Mr Ramesh's case were a woman in the first trimester of pregnancy?
Click to reveal Trigger 3: Outbreak Control — The Affected Patients and Staff (discuss previous trigger first!)

Trigger 3: Outbreak Control — The Affected Patients and Staff

After addressing the index case, Dr Meera must manage the 14 affected ward patients and the 3 nursing staff. The ward nurses have typical burrows and nocturnal itch. All 14 patients have varying severity of classical scabies. Two patients are elderly (>80 years, frail). One patient is a 22-year-old woman who is 28 weeks pregnant. **Additional problem:** Five patients who share the ward but currently have NO symptoms are asking if they need treatment. The hospital administrator says treating asymptomatic patients is 'wasteful and unnecessary'.

DISCUSSION POINTS

  • How would you respond to the hospital administrator's concern? What is the scientific rationale for treating asymptomatic close contacts in a scabies outbreak?
  • Construct the treatment plan for the pregnant patient in Ward 7. Which scabicide is preferred and why? Which agents are contraindicated and why?
  • What specific precautions would you take when prescribing permethrin 5% for the two frail elderly patients? Are there any modifications to the standard application instructions?
  • Outline the environmental decontamination and infection control measures required for Ward 7. Include bedlinen, patient clothing, common equipment (blood pressure cuffs, wheelchairs), and nursing staff uniforms.
  • Design a communication strategy for the nursing staff who are affected. What are their treatment needs? What return-to-work criteria would you apply? How would you address their concerns about the stigma of having scabies?
Click to reveal Trigger 4: Two-Week Follow-Up and Policy Implications (discuss previous trigger first!)

Trigger 4: Two-Week Follow-Up and Policy Implications

Two weeks after the outbreak response, Dr Meera reviews the ward. Mr Ramesh has completed combination treatment (oral ivermectin + permethrin 5% × 3 applications) and his hyperkeratotic plaques have substantially reduced; skin scraping now shows very few mites. However, 6 of the 14 initially affected patients still report intense pruritus, although only 2 of them have new burrows on clinical examination. Dr Meera is also asked by the Medical Superintendent to draft a post-outbreak policy for preventing future institutional scabies outbreaks in the hospital.

DISCUSSION POINTS

  • For the 4 patients with persistent pruritus but NO new burrows: what is the most likely explanation? How would you manage them — specifically, is re-treatment with scabicide indicated?
  • For the 2 patients with new burrows: what does this finding indicate? What is the most likely cause, and how would you investigate and manage this?
  • Identify one key lesson from this outbreak regarding the timing and completeness of contact treatment. How would an earlier intervention have altered the outbreak's trajectory?
  • Draft five evidence-based policy points for the hospital's post-outbreak prevention protocol, addressing: (a) early case detection and screening triggers; (b) admission screening for high-risk patients; (c) staff education; (d) environmental protocols; (e) outbreak response thresholds.
  • Reflect on the role of the corticosteroid prescription in this outbreak. What prescribing practice should be reconsidered when admitting at-risk patients (homeless, immunocompromised, institutionalised) to a ward?