Scabies

Scabies is a condition where the skin is infested by a mite called Sarcoptes scabei. Scabies occurs worldwide and is endemic in some tropical countries. The mite is very small and cannot be seen with the naked eye. It is highly contagious and can be spread easily to others living in the same house or in close contact. Scabies can affect anybody of any age, social class, country or demographic.

Pathogenesis

The scabies mite has a life span of 30 days. It spends the majority of its life cycle in the epidermis. The pregnant female burrows through the superficial layers of the skin, breaking down parts of the tissue with special enzymes, before laying its eggs within the epidermis. Infestation with scabies is incredibly itchy. This is the result of an allergic response to the proteins of the mite, its faeces and eggs. Scabies can be extensive and affect many parts of the body. The mites often burrow within folds of the skin, such as the hands, wrists, armpits, genital region, the front of the elbow and the backs of the knees.

Risk Factors

Some of the risk factors for scabies include:

• Close contact with an infected person – contact sports, school/kindergarten
• Sharing towels and clothes with an infected person
• Sharing a bed/linen with an infected person
• Living in the same house as an infected person
• Age: scabies is most common children under the age of 15
• Having a partner infected with scabies (amongst adults, most cases of scabies are transmitted sexually)
• Poor hygiene
• Prison environment
• Living in a nursing home
• Attending childcare
• Overcrowding in homes
• Homelessness
• Caring for a child with scabies

Signs and Symptoms

The signs and symptoms of scabies can take 4-6 weeks to develop after first coming in contact with an infested person. However, if you have been infected with scabies in the past, the symptoms may start within 1-4 days. The most common symptoms of scabies are:

• Itching
• Rash – characterised by small red bumps which might look like tiny pimples or bites
• Sores – scratching the rash can lead to sores on the skin. Sores break the skin and leave the person prone to secondary infections
• In a more severe type of scabies, called Norwegian scabies, thick crusts develop on the skin
• In most cases, there is some symmetry across both left and right sides of the body

The lesions most commonly appear first on the hands, especially on the folds of skin between the fingers. People who have poor hygiene or a weakened immune system (such as people with cancer, HIV/AIDS and diabetes) are at an increased risk of developing the more severe form, Norwegian scabies. Most normal scabies infections involve a maximum of around 20 mites; in Norwegian scabies, there can be 1000s of mites. It is also important to note that you cannot catch scabies from dogs. This is because the mite that infects dogs is unable to infect humans.

Diagnosis

Scabies is sometimes diagnosed by looking at the skin, the rash and lesions alone. A scraping of the infected skin can also be preformed and analysed under the microscope to look for the mite itself, its eggs or faeces.

Treatment of Scabies

Scabies is commonly treated with a topical cream called Permethrin. Permethrin should be applied to all areas of skin from the neck down (not the face or eyes) for at least 8 hours. The easiest time to apply the cream is before bed and to sleep with the cream on overnight. One application is usually sufficient to kill the mites. In the case of an allergy to permethrin cream, a solution of benzyl benzoate can be applied for 24 hours. If the first round of treatment does not clear the scabies, another treatment may be advised one to two weeks later. However, it is important to make sure that there is still actually a scabies infection because sometimes the itch may remain for a few weeks, even if the mites have all died following the treatment. This is because the immune system still reacts to the dead mites. If the itching is severe and keeping you awake at night, anti-histamine medications may be recommended to help reduce the itchiness.

For Norwegian scabies and other cases of scabies that do not respond to topical agents, an oral treatment called ivermectin is given. This is usually as a single oral dose, which may be repeated 1 week later.

When treating scabies, everyone who is in close contact with the affected person also needs to be treated. This includes everyone living in the same household, close contacts (such as friends at school) and sexual contacts in sexually transmitted cases.

Preventing the spread of Scabies

In addition to treating all household contacts, a number of other measures need to be taken to kill any mites remaining in the household. Washing all linen, clothing and towels on a hot machine cycle is important. Ideally, these items should also be tumble-dried or hung out to dry under direct sunlight in hot weather. If for some reason these items cannot be washed, placing them in a sealed plastic bag for up to a week can also help. This is because the mites causing scabies cannot survive away from a human host for more than 72 hours. Avoiding contact with an infected person and sharing towels, clothing and bedding is also advised to limit the spread of the infection.

Complications of Scabies

The main complications of scabies are related to scratching and breaking of the skin. When the surface of the skin is broken, it is easier for bacteria and other infectious agents to get through the skin’s surface and cause infection. A common secondary infection to scabies is impetigo; a skin infection that is commonly caused by Streptococcus pyogenes or Staphylococcus aureus. In some people, scabies may also cause eczema to flare.

If you have any questions or concerns about scabies, you may contact our clinic. Contact Us Today.