What is Scabies? 

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Scabies is a parasitic infestation of the skin by a microscopic eight legged mite Sarcoptes scabiei. Only 300 micron in length, it burrows into the skin and causes an intense itchy skin reaction. Itching occurs more commonly at night.

An early scabies rash will show up on the skin as a line of tiny blisters or little red bumps. In more serious cases, the skin might be crusty or scaly. The full life cycle takes place in the skin where it lives and lays eggs.

 

 

 

SCABIES

Credit to Johnson County Health Department

 

Who is at risk?

Scabies can affect anyone. Mites are transferred through direct skin-to- skin contact. This usually occurs through sexual contact, children playing, or in settings where people have to live in close proximity to one another. Very rarely are the mites transferred via clothing or bedding and never via animals (Sarcoptes scabiei is human specific).

Contact must be prolonged (a quick handshake or hug will usually not spread infestation). Infestation is also easily spread to household members. Anyone can get scabies regardless of age, sex, race or standards of personal hygiene.

Immunocompromised people and the elderly are at risk for a more severe form of scabies, called crusted or Norwegian scabies.

 

Symptoms 

A severely itchy rash with red patches, usually between the fingers, around the wrists, and on the elbows, armpits, navel, nipples, lower abdomen, and genitals may occur. Itching may also present under your rings, bracelet, and watchband, where scabies mites like to hide. Generally the face is not affected since scabies mites rarely venture above the neck (except in babies). Itching is usually most intense after a hot bath or at night and may keep you awake. Curvy white or thin red lines where the mites have burrowed under your skin (these are visible in only about 25 percent of people with scabies) might occur. Nasty-looking scabs might also form over the scratched areas where a bacterial infection may develop.

Four to six weeks may pass from the time the bugs latch onto you until itching starts. If you've had scabies before, the wait will last only one to three days.

Crusted or Norwegian scabies, a more severe and highly infectious form of the illness, may also develop. If so, hands, feet, and trunk will be scaly and crusted, with innumerable live mites hiding under the crusts. Often there will be little or no itching. Crusted scabies is most often found among the elderly and among people with AIDS.

 

Treatment

Over the years many different pharmacological products have been used in the treatment of scabies. These include sulphur ointment, monosulfiram, benzyl benzoate and GBHC (lindane). Permethrin 5% skin application is the treatment of choice for scabies. In the developed world this has been used as first line treatment for a number of years.

Paediatric Use

Unlike other treatments, Permethrin 5% lotion is safe and effective in paediatric patients two months of age and older. Safety and effectiveness in paediatric patients less than two months of age have not been established. Two week old babies have however been treated successfully.

Use in breast feeding and lactation

Permethrin 5 % has a category B risk factor. For lactating women with scabies, permethrin is considered the treatment of choice in the United States and the United Kingdom.

The risk of foetal toxicity following maternal application of permethrin is likely to be no greater than that for the general population

Cochrane review:

Cochrane Infectious Diseases Group Specialized Register, CENTRAL (The Cochrane Library 2006, Issue 1), MEDLINE, EMBASE, LILACS, and INDMED, March 2007:

Interventions for treating scabies

Scabies is a parasitic infection of the skin. It occurs throughout the world, but is particularly problematic in areas of poor sanitation, overcrowding, and social disruption, and is endemic in many resource-poor countries. The global prevalence of scabies is estimated at 300 million cases, but the level of infection varies between countries and communities. The female mite burrows into the skin to lay eggs which then hatch out and multiply. The infection can spread from person to person via direct skin contact, including sexual contact. It causes intense itching with eruptions on the skin. Various drugs have been developed to treat scabies, and herbal and traditional medicines are also used. The review of trials attempted to cover all these. The authors identified 20 small trials involving 2392 people, with 17 of the trials taking place in resource-poor countries. Permethrin appeared to be the most effective topical treatment for scabies and ivermectin appeared to be an effective oral treatment. However, ivermectin is unlicensed for this indication in many countries. Adverse events such as rash, vomiting, and abdominal pain were reported, but the trials were too small to properly assess serious but rare potential adverse effects. No trials of herbal or traditional medicines were identified for inclusion.
Treatment of contacts (people in the same household or living space) whether they show symptoms or not, should be treated simultaneously. Re-infestation is a common occurrence and should be prevented at all cost. Treatment guidelines are the same as with a real infestation.

 

From Dermnetnz, Dr Jessica Rachel Maguire, IMT, Barts Health NHS Trust, London, United Kingdom www.dermentnz.org, March 2022:

Topical therapies

• Topical 5% permethrin (acaricidal and ovicidal) cream or lotion remains first-line therapy.
• Applied from the jawline downwards, and left overnight for 8–12 hours. Reapplication is needed if hands are washed during the treatment period. Infants, the elderly, and the immunosuppressed should also treat the face and scalp.
• Application should include under the nails and between the toes.
• Treatment should be repeated after 7–10 days.
• If the case is permethrin-resistant, or permethrin is not available, alternative insecticides, include 25% benzyl benzoate or 0.5% malathion aqueous lotion.

 

Other treatments

• Benzyl Benzoate Lotion
  Despite its side effect profile, BBL has been used for scabies for more than 50 years. It is effective in treating scabies but needs more than one application and possibly a second treatment within two weeks. This compromises compliance and ultimately the outcome. It's important to note that benzyl benzoate is not commercially available in the U.S. and Canada for the treatment of scabies due to toxicity.
• Lindane
  Lindane (gamma benzene hexachloride) is an a chlorinated hydrocarbon and banned by the MCC for the treatment of scabies in South Africa due to toxicity on the nervous system.
• Monosulfiram
  Mostly used in the form of a soap but not effective on its own. Not allowed by the FDA due to toxicity.
• Ivermectin (Not readily available in RSA)
  This oral medication is an alternative scabicide that does not require creams to be applied. The CDC recommends taking this drug at a dosage of 200 micrograms per kilogram body weight as a single dose, followed by a repeat dose two weeks later. Although taking a drug by mouth is more convenient than application of the cream, ivermectin has a greater risk of toxic side effects than permethrin and has not been shown to be superior to permethrin in eradicating scabies.

 

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