Sarcoptes scabiei, a microscopic mite, is the cause of an intensely itchy skin condition known as scabies in humans. This burrowing parasite creates tunnels within the upper layers of the skin. A related condition, sarcoptic mange, affects animals and is also caused by different varieties of the Sarcoptes scabiei mite.
Understanding Sarcoptes Scabiei
The Sarcoptes scabiei mite is a minuscule organism, measuring between 0.1 to 0.5 millimeters long and 0.15 to 0.25 millimeters wide. It has a round, flattened body with eight short, stubby legs, giving it a tortoise-like appearance. The female mite burrows into the stratum corneum, the outermost layer of human skin, secreting a saliva-like fluid that dissolves skin tissue to create tunnels.
Inside these burrows, the female mite lays two to three eggs per day. These eggs hatch into larvae, which develop into nymphs, and then mature into adult mites over about two weeks. The intense itching and rash associated with scabies are a result of the body’s allergic reaction to the mites, their eggs, and their fecal matter.
Recognizing and Confirming an Infestation
An infestation with Sarcoptes scabiei in humans presents with intense itching, which often worsens at night or after a hot bath or shower. This itching is accompanied by a rash that can appear as small red bumps, blisters, or tiny, irregular lines, which are the characteristic burrows made by the mites. These burrows are grayish or skin-colored and can be a centimeter or more in length.
Common areas for these signs in adults and older children include the skin folds, such as between the fingers and toes, wrists, elbows, armpits, around the waist, genitals, and buttocks. In infants and young children, scabies can also appear on the face, scalp, neck, palms of the hands, and soles of the feet. A healthcare professional confirms a diagnosis by examining the skin for these characteristic signs and symptoms. Confirmation involves a skin scraping, where a small sample of skin from an affected area is examined under a microscope to identify mites, eggs, or fecal pellets.
Transmission and Prevention
Sarcoptes scabiei mites are primarily transmitted through direct, prolonged skin-to-skin contact with an infested person, such as through intimate contact or sharing a bed. Brief contact, like a quick handshake, does not spread scabies. Less commonly, transmission can occur through shared personal items like bedding, clothing, or towels. Individuals can spread scabies even if they have not yet developed symptoms, as it can take four to six weeks for symptoms to appear after initial infestation.
Avoiding direct, prolonged skin-to-skin contact with infested individuals is important. Also avoid sharing personal items such as clothing, bedding, or towels with someone who has scabies. Prompt treatment of an infested person and all close contacts, including household members, is important to prevent further spread within a family or community.
Treatment Approaches
Treating Sarcoptes infestations requires specific medications, as scabies will not resolve on its own. For humans, common prescription treatments include topical creams like permethrin 5%, which is applied to the entire body from the neck down and washed off after 8 to 14 hours. A second application about a week later is necessary to eliminate newly hatched mites, as the initial treatment may not kill eggs. Oral medications like ivermectin tablets are also prescribed. Ivermectin is taken as a single dose, repeated after 7 to 14 days.
For animals affected by sarcoptic mange, veterinarians prescribe treatments such as topical spot-ons, oral medications, or dips. Environmental decontamination is also a part of treatment for both humans and animals. All clothing, bedding, and towels used by an infested individual or animal during the three days prior to treatment should be machine-washed in hot water and dried on a hot cycle for at least 10 minutes to kill mites and eggs. Non-washable items can be sealed in plastic bags for several days to a week to effectively kill any remaining mites.