Scabies: 20 minutes of hand holding for a Seven Year Itch

I need a scientific name….

Female-human-scabies-mite-Sarcoptes-scabiei-var-humanus-The-mite-is-approximately-03
Sarcoptes Mite uploaded at Researchgate

Sarcoptes scabiei var homiinis. Known as ‘mange’ in animals this mite has been irritating humans since the dawn of time.  Hieroglyphics from Ancient Egypt demonstrate the symptoms of scabies and there is a description of a skin irritation which is thought to be scabies in Aristotle’s writing from the 4th century BC, describing “lice” escaping from pricked pimples.  Somehow even in the 21st century this mite rears its ugly head.

Isn’t that a dog thing?

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Scabies has just been reported in Koalas

This bug is 0.4×0.3mm size and ais a mite- a member of the Arachnida class alongside scorpions.   It is thought that 100 million people across the globe have this infection and the highest numbers of patients are found in the Pacific region (us!) as well as Latin America.  It is spread person to person. It is thought that 20 minutes of skin to skin contact eg hand holding will cause transmission.

Scabies are not spread from pets to humans so are not a zoonosis. Most mammals have their own various versions of a Sarcoptes mite but these critters cannot survive away from their particular animal host for a long time and definitely cannot breed or spread.

How do they cause a problem?

Infection occurs when the pregnant female scabies mite digs into the your skin, laying eggs in a ‘burrow’, with the offspring emerging 48-72 hours later. These new bugs go on to form new burrows and continue to grow. 2 weeks later they are considered adult mites and the cycle of mite life continues. Adult mites will be transmitted by skin to skin contact.  Mites can survive away from a host in the environment for 24-36hrs which means blankets and mattresses are infective for a day or two after contact.

If I had scabies, how would I know?

Clinically a patient will develop very itchy skin between the fingers, toes, wrists, or under the arms. There is usually a low number of scabies present, 10-15 mites initially, and then 5-10 in reinfection cases.  The itch is mainly due to the patients immune system becoming sensitized; which can take a prolonged period to complete. As such, symptoms can occur up to 6 weeks after infestation.  This itch is usually worse at night and can reduce the quality of a patients sleep.

I’m itching just reading this article- how would my doctor know?

Diagnosing scabies can be difficult and is mainly based on the clinical picture.  Symptoms in the areas discussed above, consisting of nodules or thin lines may be able to be seen when looking at the skin with the naked eye.  ‘Jet plane with contrail’ is the best way to describe a mite in the skin with its burrow behind it, although it is not going as fast.  If the mite can be seen ie the plane at the start of the contrail, then a scraping of the skin may useful to identify the bug microscopically. Otherwise, there is no good workable test to 100% identify the presence of this bug.

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Contrail over Main Beach looking a lot like a Scabies mite burrow.

As gross as a scabies infection sounds it’s only 10 mites- how much damage can they do?

Complications associated with scabies infection include impetigo or school sores.  Scratching the skin can lead to bacterial infection, especially as some mites and their faecal pellets carry staphylococcus and streptococcus. There is also an increased risk of developing psoriasis following scabies infection.

Treatment options?

There are a number of treatments for scabies which are very effective.  A treatment can take up to 6 weeks to work after one application due to the patients body being sensitive to the mites which are still present even when dead, within the skin.

img_5428We use topical permethrin lotion or cream.  This will kill adult mites and eggs so can be very powerful, requiring in theory only one application.  However, in my experience often two applications are required.

Benzyl benzoate emulsion can sometimes work better than permethrin but is also associated with increased risk of skin irritation following application.  Treatment should be reapplied 7 days later.   Your doctor will also consider treating you for impetigo due to the bacteria being carried by the mites. Itch relief should be considered with use of a steroid cream.  Oral Ivermectin may be required if infection continues after these treatments.

Clothes and towels can be treated with heat- hot clothes dryer or hot iron.  But storing the infested material would also work to kill bugs as mites will die away from a host host after 36hrs.

You mentioned seven year itch?

It is thought that this saying originated due to the itch of scabies, not the itch of greener pastures!

GPearls on the GC

  • look for the contrail
  • treat with permethrin once identified
  • really want to see the ancient egyptian tomb painting of scabies

Read more at

A Review of Scabies: An Infestation More than Skin Deep.   Chandler DJ, Fuller LC.  Dermatology. 2018 Dec 13:1-12. doi: 10.1159/000495290. [Epub ahead of print] Review.

 

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