Scabies Handbook

SSCCAABBIIEESS HHAANNDDBBOOOOKK Georgia Scabies Manual Table of Contents 1. Introduction 2. Biology i) Life Cycle ii) Habits and Habitat iii) Transmission 3. Identification, Diagnosis, and Treatment of Scabies i) Identification ii) Diagnosis iii) Differential Diagnoses iv) Treatment v) Prevention 4. Crusted (Norwegian) Scabies i) Identification ii) Diagnosis iii) Treatment iv) Prevention 5. References 6. Appendices 2 revised: 6/21/12 Georgia Scabies Manual Introduction Scabies is a common communicable skin infestation caused by a mite. This mite, Sarcoptes scabiei, is sometimes known as the human itch or mange mite due to the intense itching caused when the pregnant female mite burrows into the top layer of skin and lays eggs. Based on archeological evidence, including Egyptian drawings depicting people afflicted with signs of scabies, scabies is estimated to have been an infestation of humans for at least 2,500 years. There are many controversial accounts of the history of discovery of the infectious agent. Prior to the 17th century, the condition of scabies was known by many names and widely believed to be a humoral disease, possibly associated with a mite. Humoral diseases were part of an ancient theory that held that health came from balance between the bodily liquids. These liquids were termed humors. Disease arose when imbalance occurred between the humors. The term scabies is believed to be derived from the Latin term scabere, which means to scratch, or possibly from the term scabs, which are secondary to bacterial infection. It is estimated that more than 300 million cases of scabies occur worldwide every year. Anyone who has had contact with the mite can catch scabies. Scabies infestations can affect people from all socioeconomic levels without regard to age, sex, race or standards of personal hygiene. Scabies spreads rapidly under crowded conditions where there is frequent skin-to-skin contact between people, such as hospitals, institutions, child-care facilities, and nursing homes. In young, healthy persons scabies is generally considered to be more of a nuisance than a disease. In elderly persons, or those who are immunocompromised, scabies is generally not diagnosed until cutaneous (skin) lesions and symptoms are apparent. Because of the long incubation period, many people can be exposed to scabies before the infested person is diagnosed. The purpose of this manual is to provide schools, local health departments, 3 revised: 6/21/12 Georgia Scabies Manual Healthcare facilities, and other group settings a comprehensive guide to identify, treat, manage, and prevent scabies infestations. This handbook was designed to serve as a universal guide, providing technical information about scabies as well as a quick reference. Biology Life Cycle The Sarcoptes scabiei mite (Figure 1) is an obligate parasite that lives in the skin. The adults are small (females 0.3 to 0.4 mm, males 0.25 to 0.35 mm in length) and rounded in shape, with tiny pointed spines on their dorsal surface that assist them in burrowing. Sarcoptes scabiei undergoes 4 stages in its life cycle; egg, larva, nymph and adult. The adult mites can crawl rapidly on the surface of the skin, with females traveling up to 2.5 cm/min (~1 in/min). Upon finding a suitable site, the female mite burrows into the skin, completely disappearing beneath the surface in about an hour. A saliva-like substance is secreted by the mite to aid in burrowing by dissolving the skin. Male and female mites mate within these burrows, after which the impregnated Figure 1: Scabies mite (D.S. Kettle) female emerges and excavates a permanent burrow in which to lay her eggs; the male mite dies. The female mite will spend the rest of her life (commonly 30-60 days) in this permanent burrow and will continue to extend the length of the burrow, usually burrowing a total length of 1 cm (~½ inch) or more. Shortly after digging her permanent burrow, the female mite begins laying eggs, producing 2 or 3 each day. The eggs hatch in 3-4 days, and within one day of hatching, the larvae begin actively crawling out of the burrow towards the surface of the skin. They then excavate shallow burrows in which they feed and molt to nymphs 4 revised: 6/21/12 Georgia Scabies Manual about 3 days later. The nymphs return to the skin surface or dig just beneath the surface, where they molt to adults in 3-4 days. The developmental time from egg to adult typically takes about 10 days for males and 14 days for females (Figure 2, top). Male mites live only 1-2 days and spend this time seeking out unmated females. Although a female mite can lay as many as 180 eggs in her life time, fewer than 10% of her offspring live long enough to hatch and reach the adult stage. Most eggs are removed from the skin by bathing, scratching, or rubbing of the skin. Once away from the human body, mites do not survive more than 48-72 hours. Sarcoptes scabiei infestation is specific to humans and is different from the mite infestations that affect dogs and other animals, which are more commonly known as mange. Mites from mange-infested animals can burrow into human skin but cannot reproduce, so they die within a few days. Habits and Habitat The most frequent S. scabiei burrow sites are in the folds of skin around the wrists and in the webbing between the fingers. Other common sites are the elbows, feet, and ankles; axillae; buttocks; genital regions; and for women, breasts (Figure 2, bottom). The location of burrows in infants and young children differs somewhat from that of adults, commonly involving the palms, sides, soles of the feet, and the head and neck region. Rashes may also occur on other parts of the body and are often caused by the burrowing of immature stages and unfertilized female mites. Unlike adults, children often develop rashes on the face, chest and back. Feeding activity and host immune system response to mite secretions and fecal matter are the sources of irritation that lead to scratching, scabbing, and subsequent secondary infections. 5 revised: 6/21/12 Georgia Scabies Manual The severity of scabies infestation is directly related to the number of mites residing on the skin and the length of time between initial infestation and subsequent diagnosis and treatment. Fewer than 10-15 mites may be present on an infested person who is otherwise healthy. If diagnosis and treatment are delayed, the number of live mites multiplies resulting in heavier or atypical Figure 2: Scabies Life Cycle & Transmission (CDC) infestations. Keratotic or crusted scabies, sometimes referred to as Norwegian scabies, was first described in persons diagnosed with leprosy in Norway. This severe form of scabies occurs when treatment for infestation has been delayed for many months or when a person is immunocompromised, and is characterized by thick, crusted lesions. Imbedded within these crusts are thousands to millions of live mites. 6 revised: 6/21/12 Georgia Scabies Manual There are several physiological and immunological factors that influence the progression of infestation. Persons diagnosed with renal failure, insulin dependent diabetes, or severe mental retardation may progress from typical to atypical scabies in a shorter period of time than healthy persons. Crusted scabies is more commonly associated with persons diagnosed with acquired immunodeficiency syndrome (AIDS), T cell leukemia and those who are receiving steroids or immunosuppressive therapy. Transmission The most common means of scabies transmission is by direct contact between individuals when the mites are crawling on the skin surface. This contact needs to be direct, prolonged skin-to-skin contact for scabies to be transmitted (a quick handshake or hug will not usually spread the infestation). Because scabies often spreads during the close physical contact of sexual activity, it is sometimes classified as a sexually transmitted disease. However, scabies is more usually passed from person to person in settings where people live in close quarters, including hospitals, nursing homes, prisons, child care facilities, and institutions. Scabies transmission can also occur via prolonged contact with bed linen, clothing, and other fabrics from infested hosts. The mites are able to survive 2-3 days at room temperatures when the relative humidity is more than 30%; the higher the relative humidity, the higher the survival rate. Larvae of S. scabiei can hatch from eggs deposited off the host and infest fomites (inanimate objects that may be contaminated with infectious organisms and serve in their transmission) for up to 7 days. Indirect transfer from fomites is not common and usually only occurs if fomites are contaminated by infested hosts immediately beforehand. The role of any inanimate objects will play little, if any, role in the transmission of scabies if the infestation is typical. However, if the infestation is atypical or has progressed to the crusted stage, the environment may harbor mites and contribute to transmission. 7 revised: 6/21/12 Georgia Scabies Manual A person is considered infectious from the time he/she becomes infested until treatment is successfully completed. Linens and clothing are considered infectious until treatment is completed or until 2 weeks after the last known exposure. Reinfestation does occur, and after treatment a person may unknowingly become reinfested through exposure to the primary source of infestation or contact with a different infested source. Identification, Diagnosis, and Treatment of Scabies Identification When a person is infested with scabies mites for the first time, there is usually little evidence of infestation for the first month (range 2 to 6 weeks). After this time, and in subsequent infestations, people can become sensitized to mites and noticeable symptoms generally occur within 1 to 4 days.

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