June 2005, Volume 27, No. 6
Original Articles

Scabies in an elderly nursing home

Xiao-Ling Sun 孫曉玲, Tak-Shing Au 區德成, Stephen K S Foo 傅鑑蘇

HK Pract 2005;27:230-234

Summary

Objective: To investigate the prevalence and atypical clinical presentations of scabies in an elderly nursing home in Hong Kong. Furthermore, a clinical decision-making process to prevent scabies outbreaks is suggested.

Design: Retrospective, quantitative and descriptive analyses.

Subjects: 241 residents of a nursing home in Hong Kong.

Main outcome measures: (1) Scabies was visually and clinically diagnosed using dermatological techniques and guidelines. (2) Clinical categories of scabies were: diagnosed scabies, likely scabies and suspected scabies. (3) Therapeutical effectiveness of scabicide (benzyl benzoate 25%) was observed.

Results: (1) The 95% confidence interval for the overall prevalence of scabies in the elderly nursing home is 5.8% + 2.95%. The scabies prevalence acquired while in residence in other elderly nursing homes, acquired from a hospital, and as a pre-existing condition is respectively 10.9%, 2.6% and 1.4%. The relative risks in elderly nursing homes and hospital, using pre-existing condition rate as the base-rate, are 7.8 and 1.8 respectively. (2) The most commonly involved sites of infection were the abdomen (86%), the buttocks (57%) and the upper arms (50%). Typical scabies burrows were not seen. Papular, vesicular and erythema lesions are respectively 86%, 43% and 36%. Only half of the scabies cases presented with an itchiness-degree over 5/10.

Conclusion: To prevent scabies outbreaks in elderly institutions, special clinical management is required for those who have recently resided in other elderly nursing homes or hospitals. Initiation of scabies control should predominantly rely on clinical judgment, especially paying attention to atypical presentations.

Keywords: Nursing home, elderly, scabies, prevalence

摘要

目的： 本文旨在探討和研究在安老護養院的疥瘡發病率及其非典型臨床表現。此外，亦提出預防疥瘡傳播及爆發的建議。

設計： 回顧性、描述性及定量性分析。

研究對象： 241名居於香港一所護養院院友。

主要測量內容： (1)依據標準及指引診斷疥瘡。 (2)臨床分類為：確診疥瘡、可能性疥瘡和懷疑疥瘡。 (3)觀察病人對疥瘡藥物的療效。

結果： 此護老院的疥瘡整體發病率是5.8 + 2.95%（置信度為95%）。 來自其他老人院或醫院的老人，其疥瘡發病率分別是10.9%和2.6%，相對風險系數為7.8及1.8。 而作為先存疾病的比率是1.4%。常見的疥瘡發生部位是：腹部(86%)，骰部(55%)和上肢(50%)。 所有病例末見典型的疥瘡侵噬皮膚隧道，而丘疹、小水泡及紅斑分別是86%，43%和36%。只有一半病人呈現嚴重皮膚搔癢(>5/10)。

結論： 為防止疥瘡在老人院舍傳播及爆發，需要對從其他老人院或醫院轉介入住的老人進行皮膚情況觀察。要特別留意疥瘡的非典型臨床表現，並對有關老人進行適時處理以防疥瘡蔓延。

詞彙： 護養院，老年，疥瘡，普遍度。

Introduction

Human scabies is a highly contagious skin disease that occurs in all ages and social groups throughout the world. In developed countries, there has been a surge in scabies in elderly nursing homes (ENH).1

The prevalence of scabies varies in different populations. A report shows that the overall prevalence rate of scabies in an Egyptian village is 5.4%.2 Another study suggests that in a large Aboriginal community in the Northern Territory, it is 35%.3 Sato revealed that in outpatient settings with a large proportion of elderly, the incident rate was 1.96% across an 11-year period.4 In epidemics, it can vary widely from 91.5% to 4%.5-8 In Asia, Derek found that the prevalence of scabies was 3.3% in a nursing home in southern Taiwan.9 In Hong Kong, a report revealed scabies infestation to be 4% of new attendees of Social Hygiene Service clinics in 1979 and 0.52% in 2002.10,11 However, since scabies is not a notifiable disease, there is little information on its prevalence in ENH.11 The figures may underestimate the actual prevalence rate in ENH. Although general guidelines for control of institutional outbreaks of scabies have been published and recognized, there are still many reports of persistent epidemics of scabies.12-15

We retrospectively investigated the prevalence of scabies and atypical presentations of elders with scabies in the ENH setting in this study. Finally, we propose a process of formulating clinical decision in preventing scabies outbreaks.

Methods

 
A. Setting and residents
  There were 216 beds distributed across four floors in this nursing home. During the study period (01/01/2004 _ 30/09/2004), there was a total of 241 residents of scabies. All residents were assessed by the Minimum Data System. Dementia, cerebrovascular accidents, diabetes mellitus and hypertension were highly prevalent. Polypharmacy was common, and the majority of residents were completely dependent.16
   
B. Diagnosis of scabies based on clinical presentations
  The residents' medical files contained data on involved sites, degree of pruritus and lesions of the skin. Scabies was visually and clinically diagnosed using dermatological techniques and according to guidelines.17-18 Three clinical categories of scabies were observed: diagnosed scabies, likely scabies and suspected scabies.18 Therapeutical effectiveness of scabicide (benzyl benzoate 25%) was regarded as evaluation criteria, e.g. if skin lesion/rash improved significantly within two weeks after using scabicide, it was regarded as successful scabicide treatment. Those cases were considered clinically diagnosed scabies. On the contrary, the cases in which the skin condition did not improve within two weeks of using scabicide were regarded as non-scabies.
   
C. Clinical management process
 

Initial assessment: Residents with skin problems were initially assessed and divided into a scabies group and a non-scabies group. The former was subdivided into diagnosed scabies, likely scabies and suspected scabies. Subsequently, benzyl benzoate 25% was applied. Assessment of therapeutical effectiveness and confirmation of clinical diagnosis: If skin lesions disappeared within two weeks after scabicide treatment, the diagnosed scabies would be clinically confirmed. The patients were further observed for another six weeks. On the contrary, if the symptoms worsened or stayed the same after the first two weeks, the possibility of other skin diseases, such as eczema, xerosis, bacteria/fungal infection, psoriasis, pemphigoid or erythrasma, etc. were considered.

Scabies surveillance for two months: The scabies surveillance included communicating with infectious control personnel; considering epidemiologic variables, such as differentiation of conventional and Norwegian scabies; monitoring high risk cases like immunocompromised dementia and tracing contacts two months before. It also included isolation of skin care workers, nursing staff or personal care workers; hygienic practices such as wearing plastic disposable gloves and gowns, and separately treating clothes and bedding while going through a normal washing procedure at a high temperature (Temperature: >50oC).19

Results

 
A. Prevalence of scabies
 

During the study period, there was a total of 241 residents with scabies: 70 residents, 55 from other ENHs and 116 from hospitals. Twenty-four cases were treated with benzyl benzoate 25%. Fourteen out of the 24 cases (58%) were clinically diagnosed as scabies following treatment. The remaining 10 cases (42%) were finally diagnosed as non-scabies cases because their skin conditions did not improve after an average period of 7.2 weeks had passed, during which other non-scabies treatments were used.

As a result, the overall prevalence of scabies was 5.8% with CI range of 5.8% 2.98. The prevalence of scabies cases from other ENHs, the hospitals and our setting is respectively 10.9% (6/55), 2.6% (3/116) and 1.4% (1/70). In addition, it was confirmed that 4 of the cases that we studied were due to cross infection. The relative risks (RR) of scabies cases from other ENHs, the hospitals and cross-infection cases that were found in the nursing home were 7.6, 1.8 and 1.2 respectively. The prevalence of the three different origins and RR to the setting is presented in Table 1.
   
B. Clinical features

 

Itchiness: Among the 14 scabies cases, 7 cases (50%) were accompanied with severe itchiness (> 5/10). The other 7 cases (50%) were not presented with itchiness due to dementia.

Cutaneous lesions: Typical scabies burrows were not found. 12 cases of papular lesion (86%), 6 cases of vesicular lesion (43%) and 5 cases of erythematious lesion (36%) were noted.

Cutaneous lesion sites: Among the 14 scabies cases, the common lesion sites were the abdomen (12 cases, 86%), followed by the buttocks (8 cases, 57%), the upper arms (7 cases, 50%), the back, the thigh and the lower leg (6 cases, 43%). Axilla and hand lesion occurred in 5 cases (36%), while the most common sites among the non-scabies cases were the back (4 cases, 40%), followed by the chest, the abdomen and the thigh (3 cases, 30%). The detailed information is shown in Table 2.

Discussion and conclusions

Geriatric population can be presented with certain challenges in the diagnosis of skin diseases. Geriatric dermatology is a specialty that has been receiving more attention recently.20
 
A. Prevalence of scabies
  The study reveals that the residents from ENHs, hospitals and the studied setting have different scabies prevalence, respectively 10.9%, 2.6% and 1.4%. The RR of scabies infestation in ENHs and hospitals is 1.8 and 1.2. The cross-infection cases in the studied setting is 7.6. The overall prevalence of the studied setting is 5.8%, with a CI range of 5.8% 2.98. Compared to Taiwan's data,7 the scabies prevalence is higher. Special attention should be paid to recent admissions with skin problems from other ENHs and hospitals and have follow ups to prevent scabies outbreaks.
 
B. Atypical clinical features of scabies
  Half of the scabies cases did not demonstrate any sign of itchiness due to dementia. Typical burrows were not found in all cases, and cutaneous lesions were atypical presentations of scabies. The predominant cutaneous lesion sites were in the trunk, the abdomen, the buttocks and the upper limb instead of the classic sites on the hand and foot. These results are similar to other reports.6,7,13
   
C. Control of scabies infestation in nursing homes is a long battle
 

Since the dermatological investigation is not yet satisfactory, the clinical history of a patient becomes crucial in making a proper diagnosis. Application of scabicide should rely on the patient's clinical history.15-18 Delayed diagnosis and treatment could cause scabies to spread and persist.21 Factors contributing to the persistence of an epidemic of scabies in a nursing home are as follows:

  1. Admission of a new resident with unrecognized Norwegian scabies.12,15
  2. High prevalence disability, dementia, neurological disorders, malnutrition, malignancy, and compromised immune system in elderly setting.12, 20
  3. Resistance and failure of scabicide.8, 12, 15
  4. Atypical clinical presentations result in delayed diagnosis and treatment.6, 8, 17, 20
  5. Even most experienced clinicians will fail to diagnose scabies at least once, resulting in undiagnosed scabies cases.18
  6. Nursing home staff will often become infected, playing the role of carriers. It was reported that the prevalence of scabies among nursing home workers was 10.7% in southern Taiwan.9
  7. Failure to coordinate, educate, and disinfect the environment can cause the treatment for scabies to fail.8
   
D. Efficient scabies control in elderly institution
 

It was noted that 4 of the scabies cases were due to cross infection within the setting. In theory, eradication of scabies can only be achieved if the treatment is completed.8,14 However, the entire treatment is difficult and time consuming, so this makes good clinical decisions more important than ever. In addition, identification of risk factors and appropriate follow ups are crucial for eradicating scabies. The following three suggestions might help in clinical decision making:

  1. Differentiate early between conventional and Norwegian scabies, and identify cases that are highly contagious, resistant to treatment, complicated by malignancy or immuno-suppressive status.14
  2. Ascertain the epidemic level, namely, the proportion of residents/employees affected by scabies. A suspected case of scabies among the employees could be a sign of an outbreak.7, 9
  3. Monitor efficacy of isolation care to check for any new cases contracted by cross-infection.

One of the limitations of this study is that it is a small scale retrospective study on scabies prevalence in one particular ENH in Hong Kong. Another is that two weeks review after applying scabicide may not be sufficient to see the improvement and thus some scabies may have been underdiagnosed. Therefore, the results cannot be used to calculate the prevalence of scabies in other nursing homes. However, the findings of this study are useful in giving some insight in scabies control in nursing homes. General practitioners should be aware of this infectious skin disease and its possible atypical presentations among the institutionalized elderly. The diagnosis of scabies should be considered and it could be empirically treated in nursing home residents with unexplained itch. Looking for contacts may be a better clue than classical burrows in making the diagnosis.

Acknowledgement

The authors would like to thank Associate Professor, Dr. Xinping Shi in Hong Kong Baptist University and Mr. NH Fu who have contributed their invaluable time and opinions.

Key messages

  1. Institutionalized elderly is at risk of scabies infestation.
  2. Be aware of this infectious skin disease and its possible atypical presentations.
  3. Elderly residents who are newly admitted from other ENHs or hospital should be especially paid attention to.
  4. To look for contacts may be a better clue than classical burrows in making the diagnosis.
  5. The diagnosis of scabies should be considered and it could be empirically treated among nursing home residents in unexplained itch.

Xiao-Ling Sun LMCHK, Pdip Community Geriatrics (Hong Kong), DFM (HKCFP)
Medical Officer,
Pok Oi Hospital, Tuen Mun Nursing Home.

Tak-Shing Au, MBBS (HK), FRCP (Edin), FHKAM (Medicine)
Specialist in Dermatology and Venereology,
Hong Kong Dermatology Centre.

Stephen KS Foo, MBBS (HK), FHKCFP, FHKAM (Family Medicine), FRACGP (Hon)
Family Physician in Private Practice,

Correspondence to : Dr Xiao-Ling Sun, 2 Siu Lun Street, Tuen Mun, N.T., Hong Kong.

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