, a small case series suggests.
What remains a matter of debate is how widely to use prophylaxis, according to authors of a study of two approaches published in Infection, Disease & Health.
The case series, coauthored by Dr. Nikki R. Adler and her colleagues at Alfred Hospital in Melbourne, compares and contrasts two approaches to a scabies outbreak in a tertiary care setting (Infect Dis Health. 2017. doi: 10.1016/j.idh.2017.01.001).
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One scenario involved an elderly woman who had been transferred from a rehabilitation facility for hip replacement surgery. Although upon admission the patient reported a pruritic truncal rash of 2 weeks’ duration, it was associated by the care team with either a cutaneous adverse drug reaction or with paraneoplastic syndrome, as she had recently been diagnosed with multiple myeloma. As a result, it wasn’t until after the patient’s emergent care needs were met 4 weeks later that she was given a formal dermatology consult, at which time several punch biopsies confirmed crusted scabies; she was treated with 5% permethrin cream for a week, weekly oral ivermectin 200 mcg/kg for 1 month, as well as with topical keratolytics.
Meanwhile, because the delayed diagnosis meant the patient – who had been treated across several wards – had potentially exposed multiple health care workers and patients to Sarcoptes scabiei, the hospital immediately instituted contact precautions and implemented its outbreak protocols: communication statements, prophylactic treatment of asymptomatic staff and close patients, and treatment and quarantine for those with clinical symptoms.
The second case involved an elderly man admitted through the emergency department after presenting with fever, hypotension, and a 3-week history of a progressive, hyperkeratotic, pruritic rash on his trunk and arms. A recent heart transplant recipient, he was taking cyclosporine, mycophenolate, and prednisolone, and he had hemodialysis-dependent end-stage kidney disease. After an ED dermatologic review, he was diagnosed with S. scabiei, immediately triggering contact precautions in the ED and elsewhere. He was treated with ivermectin, 5% permethrin, and topical keratolytics. All staff thought to have been exposed to the patient were treated prophylactically with 5% permethrin single-dose therapy.
Because thickened skin flakes that slough off in crusted scabies may house hundreds of mites for longer than 48 hours, environmental cleaning was enhanced in both cases.
The latter case did not feature a prolonged outbreak thanks to early diagnosis and quick preventive action. The outbreak in the first case lasted 7 weeks and 5 days. The hospital in that case opted not to employ a mass prophylaxis strategy, instead treating 306 persons identified to have been in contact with the patient. In all, 54 symptomatic patients and health care workers were identified.
The authors cited data that, across 19 nosocomial outbreaks between 1990 and 2003, the mean number of infested patients was 18; the mean number for health care workers was 39. The attack rate, defined as the number of new cases divided by the total number of persons at risk, was 13% for patients and 35% in health care workers. The median duration of outbreak was 14.5 weeks (range, 4-52 weeks).
“The variation of outbreak size and duration in the reported literature suggests that there may be important differences in the efficacy of various infection control strategies,” Dr. Adler and her colleagues wrote, noting that while some institutions might prefer simultaneous mass prophylaxis to rapidly and efficiently control a scabies outbreak, the cost of doing so can be prohibitive, and might not be more effective than the information-centered management model used in Case 1 that relied on close tracking of all patient contacts, and use of the hospital intranet and internal memos.
This strategy does run the risk of overreaction, however: “The communication strategy may have contributed to heightened levels of concern among staff and arguably, excessive prophylaxis and/or overdiagnosis,” the authors wrote.
To help diagnose potential cases of crusted scabies quickly, Dr. Adler and her colleagues suggested clinicians consider that various dermatoses can mimic a scabies infestation and that care teams have a high index of suspicion in patients most at risk for scabies: the elderly and those who are immunocompromised, such as the heart transplant patient in Case 2, and also those with altered T-cell function.
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