Sat, 07/01/2023 - 17:03
Episode 337: Scabies (schurft; la gale): Back from never gone.
Dear colleagues,
My colleagues GP in this small and quiet town are confronted with rising numbers of scabies in several communities, including the “autochones”. In addition, they get the impression that the standard treatment with pyremethrin often doesn’t really help. Obviously, scabies is generally not a dangerous infection, but it is often recalcitrant and comes with shame and stigma. All good reasons to leave my comfort zone (of immunovirology) and see what we can learn from the literature about recent epidemiology, on pseudo- or real drug resistance and therapeutic options.
PAR 1 General knowledge
Most info from Ep 337-1 Critina Thomas Ectoparadsites 2020;
also Ep 337-2 Chante Karamkhani Lancet Infect Dis 2017
Ep 337-3 Jacob Al-Dabbagh Medicine 2023.
Ep 337-4 WHO Scabies May 2023
Life cycle
Female mites burrow into the stratum corneum, inducing a cutaneous hypersensitivity reaction to the mite and its products, producing pruritus (itch)
Epidemiology
- Scabies affects around 200 million people worldwide: highest in low- and middle-income tropical countries.
- Population crowding and skin-to-skin contact promotes transmission among children, homeless individuals, and displaced groups
- Outbreaks of scabies can occur in either closed, institutional settings (such as hospitals, boarding schools or long-term care facilities) or open community settings.
- Refugee or internally displaced person camps are at particularly high risk due to overcrowding which increases skin to skin contact.
Ep 337-2 Most affected areas (with highest Disability-Adjusted Life Years or DALYs) in 2015
= East, South-East and South ASIA; OCEANIA and Tropical South-America;
with most affected countries: Indonesia; China; Timor; Vanatui and Fijhi
Clinical features
- Classic scabies presents with pruritus and multiple skin lesion morphologies involving finger webspaces, hands, the volar surfaces of the wrists, axillae, buttocks, the areola in women, and genitalia in men.
- Disease patterns may differ in infants, children, elderly, and the immunocompromised.
- Crusted scabies most frequently occurs in immunocompromised patients, manifesting as hyperkeratosis with or without pruritus.
A, Papules and scaling on the fingers and webspaces; B, Erythematous papules and nodules on the penile shaft and glans penis. C, Acral crusted papules and scaling in an infant. D, Red-brown nodules on the trunk of an infant.
E, Hyperkeratosis on the sole and interdigital webspaces in crusted scabies.
F, Pustules and papules with overlying honey-colored crust on the dorsal surface of the hand in impetiginized scabies.
- Complications include secondary impetigo, cellulitis, abscesses, poststreptococcal glomerulonephritis, rheumatic fever, and sepsis.
Systemic complications of scabies are mainly caused by secondary bacterial infection
- S pyogenes infection may lead to acute poststreptococcal glomerulonephritis (APSGN): long-term effects, particularly chronic kidney disease, have substantial morbidity.
- Streptococcal skin infection may result in acute rheumatic fever and subsequent rheumatic heart disease.
- Risk on sepsis: Untreated crusted scabies carries a high risk of mortality from secondary sepsis.
Diagnostic criteria
Clinical scabies At least one of:
1: Scabies burrows
2: Typical lesions affecting male genitalia
3: Typical lesions in a typical distribution and 2 history features
History features
H1: Itch
H2: Close contact with an individual who has itch or typical lesions in a typical distribution
Confirmed scabies: At least one of:
1: Mites, eggs, or feces on light microscopy of skin samples
2: Mites, eggs, or feces visualized on individual using high-powered imaging device
3: Mite visualized on individual using dermoscopy
Noninvasive scabies diagnostic techniques.
A, Dermoscopy showing the ‘‘delta-wing jet’’ sign composed of a burrow ending in a mite.
B, Videodermoscopy demonstrating burrows ending in mites.
C, Reflectance confocal microscopy showing a mite with feces.
Therapeutic options
Advice WHO (Ep 337-4) : Scabies can be treated with topical creams or oral medication in more severe cases.
Itchiness often gets worse for 1–2 weeks after treatment starts.
Topical treatments that are applied to the whole body include:
5% permethrin cream
0.5% malathion in aqueous base
10–25% benzyl benzoate emulsion
5–10% sulphur ointment.
Oral: Ivermectin taken orally is also highly effective, but it should not be taken by pregnant women or children who weigh less than 15 kg.
Treatments do not kill the parasite’s eggs, and treatment should be repeated to kill newly hatched mites.
People do not experience symptoms in the early stages of infestation. To reduce spread, all people in the household should be treated, even if they do not have symptoms.
Other treatments may be needed to treat the complications of scabies. Antiseptics or antibioticsare used to treat bacterial skin infections or impetigo.
Prevent scabies from spreading with these steps:
- Avoid skin-to-skin contact with an infested person, especially if they have an itchy rash;
- Treat all members of the household if someone has scabies to prevent the mites from spreading to others;
- Wash and dry bedding and clothing that has been in contact with the infested person, using hot (> 60°C) water and drying in direct sunlight, a hot dryer cycle or dry cleaning;
- Seal items that can’t be washed in a plastic bag for a week to help eliminate the mites;
- Clean and vacuum or sweep rooms after an infested person has been treated.
Par 2 Recent evolution on epidemiology
There is quite some evidence for a rising trend in Europe and North America:
Ep 337-5: M D Aždaji Life MDPI: shows clearly increasing trends in various neighboring European countries e.g.
- NL: 3-fold during 2011–2020,
- Germany: 9-fold during 2009-2018;
I did not find a recent scientific publication from Belgium:
Ep 337-6: Lapeere Epidemiol. Infect. 2008, with data from prospective study in 2004
- Crude incidence rate of 28/100 000 inhabitants.
- Higher in the very young elderly
- Higher incidence also in immigrants (88/100 000).
Alarming reports in the general press (Dutch) in Feb 2022
Ep 337-7 Schurft duikt op in Antwerpse studentenwijk, apotheker verwonderd_ “Nog nooit meegemaakt” Gazet van Antwerpen
Ep 337-8 Vijf vragen over schurft na uitbraak in Leuven_ VRT NWS_ nieuws
Par 3: Recent evolution on (pseudo-) resistance
Ep 337-9: Stefano Veraldi J Infect Dis Dev Cties Jan 2023 observed a lot of pseudo-resistance to permethrin in his African patients in Milano. The most frequent reasons were:
- Incorrect treatment, because of inadequate counselling by physicians, insufficient quantity of permethrin; too short length of treatment and poor adherence and compliance by patients.
→ a) leave permethrin for 12 hours, b) to apply permethrin 7 to 10 days after the first application, c) to treat the nails carefully,
- Irritant contact dermatitis: → distinguish nodular scabies from post-scabies prurigo.
Ep 337-10: Riebenbauer Eur J Dermatol Venerol 23 June 2023 shows that resistance to permethrin can be real and is based on a knockdown mutation in the voltage-sensitive sodium channel
Ep 337-11: Nannan Liu Annu Rev Entomol 2015: this type of lockdown mutation is well known in Aedes mosquitoes:
The activity of permethrin is by binding to a voltage-sensitive sodium channel in the central nervous system, leading to death by overactivation and paralysis.
The term knockdown resistance (kdr) is used to describe cases of resistance to DDT and pyrethroid insecticides in insects and other arthropods due to the reduced target-site sensitivity of sodium channels
Ep 337-12: Andrea Bassi in Trop Med Infect Dis May 2023 proposes a combined therapy with oral ivermectin and local benzyl benzoate to overcome permethrin resistance
Par 4 : Interesting websites
With country-adapted info
US: https://www.cdc.gov/parasites/scabies/index.html
Netherlands: https://www.rivm.nl/scabies very nice site with patient-oriented information in multiple languages
France: https://www.alpes-maritimes.gouv.fr/content/download/5538/33309/file/Conduite_Gale.pdf
Belgium:
https://www.cm.be/ziekte-en-behandeling/klachten-en-ziekten/schurft
Finally, some practical guidelines to manage the scabies epidemics in Antwerp (Ep 337-13) and Gent (Ep 335-14).
CONCLUSION
- Scabies is spreading and it is not a shame: people should be encouraged to not hide, but take action to get rid of it and stop further dissemination to household members and friends.
- Resistance to the most popular Permethrin treatment is real, but there are other options.
- Correct treatment requires good understanding and execution of all needed measures: health professionals should explain the different requirements extensively, patients should show discipline and health workers should check until success is obtained.