Transmission of scabies in a newborn nursery

Retrospective analysis of institutional scabies outbreaks from 1984 to 2013: lessons learned and moving forward

Scabies outbreaks can be disruptive in institutional settings, and are associated with considerable but under-researched morbidity, especially in vulnerable populations. In this paper, we describe key findings from a retrospective review of scabies outbreaks reported in the literature over the past 30 years. We undertook this review to gain insights into the impact of institutional outbreaks, the burden in terms of attack rates, economic costs, treatment trends, the types of index cases and outbreak progression. We found 84 reports over 30 years, with outbreaks most frequently reported in aged care facilities (n = 40) and hospitals (n = 33). On average, scabies outbreaks persisted for 3 months, and the median attack rate was 38%. While 1% lindane was once the most commonly employed acaricide, 5% permethrin and oral ivermectin are increasingly used. Crusted scabies represented the index case for 83% of outbreaks, and scabies was misdiagnosed in 43% outbreaks. The frequency of reported scabies outbreaks has not declined consistently over time suggesting the disease is still highly problematic. We contend that more research and practice emphasis must be paid to improve diagnostic methods, surveillance and control, health staff education and management of crusted scabies to prevent the development of scabies outbreaks in institutional settings.

The Potential for a Blood Test for Scabies

Background

Scabies afflicts millions of people worldwide, but it is very difficult to diagnose by the usual skin scrape test, and a presumptive diagnosis is often made based on clinical signs such as rash and intense itch. A sensitive and specific blood test to detect scabies would allow a physician to quickly make a correct diagnosis.

Objective

Our objective was to profile the mite-specific antibodies present in the sera of patients with ordinary scabies.

Methods

Sera of 91 patients were screened for Ig, IgD, IgE, IgG and IgM antibodies to S. scabiei, as well as to the house dust mites Dermatophagoides farinae, D. pteronyssinus and Euroglyphus maynei.

Results

45%, 27% and 2.2% of the patients had measurable amounts of mixed Ig, IgG and IgE that recognized scabies mite antigens. However, 73.6% of the scabies patients had serum IgM that recognized scabies proteins, and all except two of them also had IgM that recognized all of the three species of dust mites. No patient had serum antibody exclusively reactive to scabies mite antigens.

Conclusions

Co-sensitization or cross-reactivity between antigens from scabies and house dust mites confounds developing a blood test for scabies.

Scabies, caused by the mite S. scabiei that burrows in the skin of humans, is a contagious skin disease that affects millions of people worldwide. It is a significant public health burden in economically disadvantaged populations, and outbreaks are common in nursing homes, daycare facilities, schools and workplaces in developed countries. It causes significant morbidity, and in chronic cases, associated bacterial infections can lead to renal and cardiac diseases. Scabies is very difficult to diagnose by the usual skin scrape test, and a presumptive diagnosis is often made based on clinical signs such as rash and itch that can mimic other skin disease. A sensitive and specific blood test to detect scabies-specific antibodies would allow a physician to quickly make a correct diagnosis. Our manuscript reports the antibody isotype profiles of the sera of two groups of patients with ordinary scabies (17 from the US and 74 from Brazil) and concludes that such a blood test should be based on circulating IgM type antibodies that do not also recognize antigens of the related and ubiquitous house dust mites. Both are important considerations for research for developing a blood test for the diagnosis of scabies.

Control of large institutional scabies outbreaks

BACKGROUND

Scabies outbreaks in community facilities may reach large dimensions and take a protracted course. Highly contagious crusted scabies is a major cause of nosocomial outbreaks.

PATIENTS AND METHODS

On the occasion of an extensive scabies outbreak in a north Bavarian sheltered workshop and its associated residential homes with over 500 exposed individuals, a multifaceted control strategy was developed and pursued. Knowledge from a comprehensive review of the literature was utilized.

RESULTS

Our successful scabies elimination concept includes: 1) Careful organization (formation of an outbreak management team, registration and information of all exposed individuals, prospective time management, financial calculation); 2) simultaneous clinical examination of all individuals at risk; 3) synchronous topical treatment of all exposed individuals with permethrin 5 % cream on day 0, repeated treatment of proven and doubtful cases on days 1 and 14; systemic treatment of selected cases with oral ivermectin; 4) decontamination and quarantine measures; 5) follow-up investigations and repeated treatment if indicated.

CONCLUSIONS

Management of large institutional scabies outbreaks requires a high degree of motivation, communication skills and perseverance.