Scabies is a contagious skin infection that occurs among humans and animals. It is caused by a tiny and usually not directly visible parasite—the mite Sarcoptes scabiei—which burrows under the host's skin, causing intense allergic itching. The word scabies is derived from the Latin word scabere, which means scratch. The disease in humans may be transmitted from objects or bedding (like mattresses,etc.), but is most often transmitted by direct skin-to-skin contact, with prolonged contact being more efficient. Initial infections of scabies require four to six weeks to become symptomatic. Scabies mites prefer thin hairless skin, and for this reason concentrate on intertriginous parts of the body below the neck (e.g., between fingers and in skin folds), avoiding callused areas. Infants may be infected over any part of the body, as may also immunosuppressed persons. Otherwise healthy persons with good hygiene may be infected with only an average of 11 mites. Crusted scabies, formerly known as "Norwegian scabies," is a more severe form of the infection often associated with immunosuppressed hosts. In crusted scabies, the mites, numbering thousands in such cases, cause scaly rashes and thick crusts of skin.
In both humans and animals, the disease can be effectively treated with a number of medications. Permethrin cream is the most effective, but expensive compared to other treatments. Crotamiton is less effective, but also nontoxic and soothing, allowing it to be used more often. Ivermectin is also used orally and topically, subject to restrictions involving treatment toxicity differences between hosts. Treatment with lindane preparations have fallen out of favor due to high toxicity and parasitSigns and symptoms
The characteristic symptoms of a scabies infection include intense itching and rashes.The symptoms are caused by an allergic reaction of the host's body to mite proteins, though exactly which proteins remains a topic of study. The mite proteins are also present from the gut, in mite feces, which are deposited under the skin.
Mass treatment programs that use topical permethrin or oral ivermectin have been effective in reducing the prevalence of scabies in a number of populations. There is no vaccine available for scabies. The simultaneous treatment of all close contacts is recommended, even if they show no symptoms of infection (asymptomatic), to reduce rates of recurrence. Asymptomatic infection is relatively common. Fomites pose little risk of transmission except in the case of crusted scabies thus cleaning of the environment is of little importance.[clarification needed] In hospitals, rooms used by a patient who was diagnosed with crusted scabies are often thoroughly cleaned because an outbreak is hard to control.
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