We report a case of a 71-year-old man infected at a nursing home who developed a bullous pemphigoid-like eruption with nail involvement. He was diagnosed by his family doctor as suffering from eczema and was treated with topical corticosteroids, then blisters started appearing. He was next diagnosed as suffering from bullous pemphigoid and treated with oral prednisolone, which worsened his condition. He was finally diagnosed as having crusted scabies with bullous pemphigoid-like eruptions and nail involvement at our clinic. He was then prescribed oral ivermectin (two doses of 12 mg ivermectin with a 1-week interval) and topical lindane (1%gamma-BHC in petrolatum) for scabies with 5% salicylic acid in plastibase as an additional treatment for the crusted lesions on his soles. He showed remarkable improvement in 2 weeks, and his nails showed complete recovery after 7 weeks of occlusive dressing treatment with 1%gamma-BHC. One and a half years later, the patient showed no sign of a recurrence of scabies. The histology of a blister taken from this patient was similar to that of bullous pemphigoid. Direct immunofluorescence showed immunoglobulin (Ig)G and C3 deposition at the dermoepidermal junction similar to that of bullous pemphigoid, but indirect immunofluorescence was negative. The bullous symptoms of this patient were considered to be due to the scabies, because the patient recovered completely after receiving treatment for scabies. Indirect immunofluorescent study is important to distinguish between scabies with blister formation and true bullous pemphigoid.

To evaluate the mechanism of mosquito bite reaction in man, the reaction to Aedes albopictus was observed in 162 subjects ranging in age between 1 to 68 years old. Bite reactions were found to consist of both an immediate and a delayed reaction. The eruption and time course of the immediate reaction were consistent with type I hypersensitivity. The eruption and time course of the delayed reaction were consistent with cutaneous basophil hypersensitivity. Positive rates of immediate reaction increased from early childhood to adolescence and decreased with age from adulthood. The appearance and intensity of the delayed reaction decreased with age. Mosquito bite reactions in human beings exposed continuously and regularly are known to change from stage 1 to stage 5 (stage 1; no reaction, 2; delayed reaction only, 3; immediate and delayed reaction, 4; immediate reaction only, 5; no reaction). Analysis of the relationship between age and bite reaction in this study indicated that the principle held true even when the exposures were irregular or at random.

A considerable number of patients suffer recurrence of scabies. To elucidate risk factors for recurrence of scabies, we compared patients who experienced scabies recurrence and those who suffered scabies only once. We conducted a retrospective review of medical records of all scabies patients in a long-term care hospital for the elderly (300 beds; six wards) for a period of 42 months to determine frequency of scabies onsets, underlying diseases, history of treatment, and demographic data such as age and sex. One hundred and forty-eight patients and five hospital staff members suffered scabies during the 42-month study period. All staff members and 98 patients had no recurrence, while 50 patients experienced at least one recurrence of scabies. The cumulative number of scabies diagnoses was 228. The rates of scabies onset and recurrence were considerably different among wards. The dementia unit showed the highest rate of onset and recurrence. In addition to frequent exposure to infectious sources, problematic behavior, such as lying in other patients beds, might cause the high recurrence rate in dementia units. Higher serum total lymphocyte count and topical use of γ-benzene hexachloride were associated with lower risk of scabies recurrence. Recurrence of scabies is not uncommon among elderly patients in institutional settings. Impaired immunity may be a risk factor for recurrence of scabies. Groups with a high onset rate of scabies pose a high likelihood of recurrence. Problematic behavior of demented patients may increase the risk of recurrence. Use of effective topical treatment may effectively prevent recurrence.

We report two cases of scabies treated with oral ivermectin (200 micro g/kg). Case 1, a 72-year-old man, developed crusted scabies with the use of oral corticosteroids due to a misdiagnosis by an earlier physician. The patient was successfully treated with two doses of oral ivermectin at a 7 day interval with concomitant topical use of crotamiton and keratolytic agents. However, the nail scabies in this patient failed to respond to these treatments. Live mites were detected from all his toenails two weeks after the second dose of ivermectin. A complete cure of the nail scabies was achieved by occlusive dressing of 1% gamma-BHC on all toenails for one month. Case 2, a 52-year-old woman, had been treated with oral corticosteroid for mesangial nephritis. She developed common scabies, but a topical scabicide, crotamiton, was not effective. Two weeks after treatment with a single dose of oral ivermectin, eggs were still detected from a burrow on her trunk. Her treatment was completed after a further two doses of oral ivermectin were administered at 7 day intervals. In both patients, the administration of oral ivermectin did not induce any clinical or laboratory side effects. Oral ivermectin is effective for crusted scabies, but not effective for nail scabies. Two doses of oral ivermectin, administered with a one-week interval, is an appropriate treatment regimen.

Despite the commonness of scabies in Japanese institutional settings, the nationwide prevalence of scabies has not been elucidated. This study was conducted to assess the prevalence of scabies and control measures in Japanese hospitals. A questionnaire on scabies epidemiology (e.g. number of patients and onsets of outbreak) and preventive measures were sent to psychiatric hospitals and long-term care hospitals nationwide (n = 1795) in January 2005. Seven hundred and forty-one hospitals responded (41.3%). Three hundred and thirty-three (44.9%) respondent hospitals had one or more scabies cases in 2004. Among 159 hospitals that had experienced scabies outbreak, only 32 of them reported cases of crusted scabies. Multivariate regression analysis showed that hospitals had a greater number of beds, and that acute- and long-term care wards were more likely to experience scabies onsets. Hospitals that compiled their infection control manuals on scabies, treated suspicious patients with scabicides without confirmed diagnosis, and performed skin checkup of inpatients were more likely to experience scabies cases. Infection control personnel should be aware that unrecognized crusted scabies can cause outbreaks. Higher patient turnover is a risk factor for scabies introduction into a hospital. Preventive measures against scabies, such as patient screening at admission and treating all suspicious patients without confirmed diagnosis, were not effective to avoid scabies introduction.