Scabies
Scabies is a contagious skin infestation caused by a mite called Sarcoptes scabiei. These mites burrow into the skin where they live and reproduce.
Symptoms
The most common symptom of scabies is intensely itchy skin. The itch is typically worse at night. It may also be worse after a hot shower or exercise.
The infestations can be found in the:
- armpits
- thighs
- genitalia
- nipples
- lower abdomen
- buttocks
- webs between the fingers.
In infants, the head, neck, palms and soles of the feet may also be affected.
The burrows may be seen on the webs between the fingers, around the waist (under the belt line) and in the creases of the wrists and elbows. The burrows are not always easily visible.
In some cases there is a raised lumpy rash. Scratching the lumps may cause open sores, which can then become infected.
Symptoms usually develop 2–6 weeks after exposure. However, people who have had a scabies infestation in the past may develop symptoms only 1-4 days after re-exposure.
How scabies is spread
Scabies is passed from person-to-person through direct prolonged contact with infested skin. It can be spread easily within households or residential care settings such as aged care facilities.
Infectious period
A person remains infectious with scabies until they are treated with an anti-scabie medication.
It is important to exclude or isolate infested individuals from school or work until they are no longer infectious. In general, a person is considered no longer infectious 24 hours after commencing treatment.
Longer isolation or exclusion periods may be recommended in institutional settings or outbreak situations or for people with heavy infestation.
If not treated, scabies causes ongoing irritation, sores may become infected, and may become more transmissible to other people due to the heavy infestation of mites.
Who is at risk of infection
Although scabies can affect anyone, people with a weakened immune system and older people are susceptible to heavy infestation of scabies with extensive scaling and crusted lesions of the skin (known as crusted or Norwegian scabies).
If you have contact with someone with scabies
People who have had prolonged skin-to-skin contact with a person diagnosed with scabies should also be treated for scabies (whether they have symptoms or not). The person diagnosed with scabies and any household and sexual contacts should all be treated for scabies at the same time to avoid reinfesting each other.
Diagnosis
Scabies is diagnosed by a doctor based on observing the signs and symptoms or identifying the burrows on the skin. Scabies can be confirmed by taking a skin scraping for testing. However, a negative result does not rule scabies out.
Treatment
Person
Treatment usually requires application of a cream or lotion which may need to be repeated after 7 days. It is important to follow the instructions carefully to make sure the treatment is effective. Other household members and sexual contacts should be treated at the same time to prevent possible reinfestation.
Norwegian or crusted scabies requires more complex treatment. Treatment may also be different for some groups of people, including babies and children less than 2 years of age, pregnant women, the elderly and people with certain skin conditions. Your doctor can recommend which treatment to use.
Do not over-treat as the skin may become irritated. It is common for the itch to persist for 1- 2 weeks even after effective treatment. Antihistamines can help to reduce the itch and prevent scratching. See your doctor if symptoms persist for longer than 2-3 weeks following treatment.
Environment
As mites can live on clothing, bed linen and towels, any of these items that have been worn or used in the 72 hours before treatment should be washed on the day of treatment. Items should be washed in hot water (>50°C) and a hot dryer cycle is also beneficial.
If the treatment is going to be left on overnight, put clean sheets on the bed before going to bed and remove and wash them again in the morning.
Blankets and other items that cannot be laundered can be put in a sealed bag for 3 days, after which time any mites will have died.
More information
For more information on scabies contact your doctor or call the Health Protection Service, Communicable Disease Control Information Line during business hours on 02 5124 9213.
Acknowledgements
- Heymann DL. Control of Communicable Diseases Manual. 20th edn. Washington: American Public Health Association, USA; 2015.
- Queensland Health.
- Communicable Diseases Section Department of Human Services (2005). The blue book - guidelines for the control of infectious diseases. Melbourne: Victorian Government Department of Human Services.