Crusted scabies; a 2-year prospective study from the Northern Territory of Australia

Abstract

Background Scabies is listed as a neglected tropical disease by the World Health Organization. Crusted scabies affects vulnerable and immunosuppressed individuals and is highly contagious because of the enormous number of Sarcoptes scabiei mites present in the hyperkeratotic skin. Undiagnosed and untreated crusted scabies cases can result in outbreaks of scabies in residential facilities and can also undermine the success of scabies mass drug administration programs. Methods and principal findings Crusted scabies became a formally notifiable disease in the Northern Territory of Australia in 2016. We conducted a 2-year prospective study of crusted scabies cases notified between March 2016 and February 2018, with subsequent follow up for 22 months. Demographics, clinical and laboratory data, treatment and outcomes were analysed, with cases classified by severity of disease. Over the 2-year study period, 80 patients had 92 episodes of crusted scabies; 35 (38%) were Grade 1 crusted scabies, 36 (39%) Grade 2 and 21 (23%) Grade 3. Median age was 47 years, 47 (59%) were female, 76 (95%) Indigenous Australians and 57 (71%) from remote Indigenous communities. Half the patients were diabetic and 18 (23%) were on dialysis for end-stage kidney failure. Thirteen (16%) patients had no comorbidities, and these were more likely to have Grade 3 disease. Eosinophilia was present in 60% and high immunoglobulin E in 94%. Bacteremia occurred in 11 episodes resulting in one fatality with methicillin-susceptible Staphylococcus aureus bacteremia. Two other deaths occurred during admission and 10 others died subsequent to discharge consequent to comorbidities. Treatment generally followed the recommended guidelines, with 3, 5 or 7 doses of oral ivermectin depending on the documented grade of crusted scabies, together with daily alternating topical scabicides and topical keratolytic cream. While response to this therapy was usually excellent, there were 33 episodes of recurrent crusted scabies with the majority attributed to new infection subsequent to return to a scabies-endemic community. Conclusions Crusted scabies can be successfully treated with aggressive guideline-based therapy, but high mortality remains from underlying comorbidities. Reinfection on return to community is common while scabies remains endemic.

Active case detection methods for crusted scabies and leprosy: A systematic review

“…The use of historical disease records for identifying index cases may also be of value for ACD in crusted scabies. Similarly to review studies finding historic index cases with active leprosy, crusted scabies cases are often reported as recurrences or on-going due to incomplete treatment [ 3 , 10 ]. Drawing index cases from historical disease records may be a useful starting point for crusted scabies ACD campaign targeting.…”

“…Caused by Sarcoptes scabiei , the same mite that causes simple scabies, crusted scabies is a severe, progressive and debilitating form of scabies that occurs in individuals with reduced immune competence to control mite replication [ 1 ]. In immunosuppressed individuals, exposure to simple scabies can lead to crusting of the skin due to mite loads of up to a million or more [ 2 , 3 ]. Secondary bacterial skin infections associated with scratching, can lead to bacteremia with sepsis and death, chronic lymphadenopathy, post-streptococcal glomerulonephritis and rheumatic heart disease, [ 4 ].…”

“…Historically crusted scabies had a 5-year mortality rate of up to 50% [ 5 ]. People with crusted scabies are highly infectious core transmitters of scabies, known to cause scabies outbreaks and contribute to scabies endemicity [ 3 , 6 ], making early detection of crusted scabies an important component of scabies control. This is particularly so given the increasing use of Mass Drug Administration (MDA) programs for scabies control in scabies endemic communities globally [ 6 ], as even a single crusted scabies case risks reducing MDA program efficacy and subsequently, acceptability [ 7 ].…”

First Description of the Composition and the Functional Capabilities of the Skin Microbial Community Accompanying Severe Scabies Infestation in Humans

“…Both patients presented with clinical grade 3 crusted scabies at the time of sampling [ 2 , 36 ]. Neither patient had an identified immunosuppressive comorbidity although both had high serum IgE levels as seen almost universally in crusted scabies [ 18 ]. Prior to sampling, the skin was not washed, disinfected or otherwise treated, and no topical or oral antibiotics were administered.…”

“…In 2015, rheumatic heart disease was estimated to be responsible for 319,400 deaths [ 15 , 16 ]. Additionally, patients with severe forms of scabies (i.e., crusted scabies) often present with S. aureus bacteraemia [ 11 ], leading to potentially life-threatening sepsis [ 17 , 18 ].…”