SCABIES Medical Author: Melissa Conrad Stöppler, MD Medical Editor: William C. Shiel Jr., MD, FACP, FACR 1) Scabies Facts Scabies is an itchy, highly contagious skin condition caused by an infestation by the itch mite Sarcoptes scabiei. Direct skin-to-skin contact is the mode of transmission. A severe and relentless itch is the predominant symptom of scabies. Sexual contact is the most common form of transmission among sexually active young people, and scabies has been considered by many to be a sexually transmitted disease (STD). Scabies produces a skin rash composed of small red bumps and blisters and affects specific areas of the body. Treatment includes oral or topical scabicidal drugs. TREN.net Editor s note: Treatment can be accomplished with a non-chemical, non-drug alternative such as cedar oil and inert carriers.
2) What is Scabies? What Causes a Scabies Infestation? Scabies is an itchy, highly contagious skin disease caused by an infestation by the itch mite Sarcoptes scabiei. Mites are small eight-legged parasites (in contrast to insects, which have six legs). They are tiny, just 1/3 millimeter long, and burrow into the skin to produce intense itching, which tends to be worse at night. The mites that infest humans are female and are 0.3 mm-0.4 mm long; the males are about half this size. Scabies mites can be seen with a magnifying glass or microscope. The scabies mites crawl but are unable to fly or jump. They are immobile at temperatures below 20 C, although they may survive for prolonged periods at these temperatures. Scabies infestation occurs worldwide and is very common. It has been estimated that worldwide, about 300 million cases occur each year. Human scabies has been reported for over 2,500 years. Scabies has been reported to occur in epidemics in nursing homes, hospitals, long-term care facilities, and other institutions. In the U.S., it is seen frequently in the homeless population but occurs episodically in other populations of all socioeconomic groups as well. 3) How do You Get Scabies? Direct skin-to-skin contact is the mode of transmission. Scabies mites are very sensitive to their environment. They can only live off of a host body for 24-36 hours under most conditions. Transmission of the mites involves close person-toperson contact of the skin-to-skin variety. It is hard, if not impossible, to catch scabies by shaking hands, hanging your coat next to someone who has it, or even sharing bedclothes that had mites in them the night before. Sexual physical contact, however, can transmit the disease. In fact, sexual contact is the most common form of transmission among sexually active young people, and scabies has been considered by many to be a sexually transmitted disease (STD). However, other forms of physical contact, such as mothers hugging their children, are sufficient to spread the mites. Over time, close friends and relatives can
contract it this way, too. School settings typically do not provide the level of prolonged personal contact necessary for transmission of the mites. How Long Does Scabies Last? The mite cannot lie more than 3 days without a human host, but it can survive up to a month when living on a human. The mite also lays eggs in human skin, which hatch and grow into adult mites. This means that symptoms of the condition can last for months or even years if left untreated. (4) Can You Catch Scabies from a Dog or Cat? Dogs and cats are infected by different types of mites than those which infect humans. Animals are not a source of spread of human scabies. Scabies on dogs is called mange. When canine or feline mites land on human skin, they fail to thrive and produce only a mild itch that goes away on its own. This is unlike human scabies which gets worse and worse unless the condition is treated. 5) What are Risk Factors for Scabies? Scabies can infest any human who comes in contact with the mites. The only known risk factor is direct skin contact with someone who is infested. The contact one experiences in social or school settings is not likely to be sufficient to transmit the mites. Sexual or other close contact (such as hugging) is required to spread the condition. The condition does appear in clusters, so outbreaks may occur within a given community. 6) What does Scabies Look Like? What are Scabies Symptoms and Signs? Scabies produces a skin rash composed of small red bumps and blisters and affects specific areas of the body. Scabies may involve the webs between the fingers, the wrists and the backs of the elbows, the knees, around the waist and umbilicus, the axillary folds, the areas around the nipples, the sides and backs of the feet, the genital area, and the buttocks. The bumps (medically termed papules) may contain blood crusts. It is helpful to know that not every bump is a bug. In most cases of scabies affecting otherwise healthy adults, there are no
more than 10-15 live mites even if there are hundreds of bumps and pimples on the skin. The scabies rash is often apparent on the head, face, neck, palms, and soles of the feet in infants and very young children, but usually not in adults and older children. Textbook descriptions of scabies always mention "burrows" or "tunnels." These are tiny threadlike projections, ranging from 2 mm-15 mm long, which appear as thin gray, brown, or red lines in affected areas. The burrows can be very difficult to see. Often mistaken for burrows are linear scratch marks that are large and dramatic and appear in people with any itchy skin condition. Scratching actually destroys burrows as shown on this slide to the right. The scaly patch at the left is due to scratching of the original papule. The mite traveled from there to the upper right, where it can be seen as a dark spot at the end of the burrow. 7) What does Scabies Feel Like?
It is important to note that symptoms may not appear for up to two months after being infested with the scabies mite. Even though symptoms do not occur, the infested person is still able to spread scabies during this time. When symptoms develop, itching is the most common symptom of scabies. The itch of scabies is insidious and relentless and often worsens over a period of weeks. The itch is typically worse at night. For the first weeks, the itch is subtle. It then gradually becomes more intense until, after a month or two, sleep becomes almost impossible. What makes the itch of scabies distinctive is its relentless quality, at least after several weeks. Other itchy skin conditions -- eczema, hives, and so forth -- tend to produce symptoms that wax and wane. These types of itch may keep people from falling asleep at night for a little while, but they rarely prevent sleep or awaken the sufferer in the middle of the night. 8) How is a Scabies Infestation Diagnosed? Scabies is suggested by the presence of the typical rash and symptoms of unrelenting and worsening itch, particularly at night. Ultimately, the definitive diagnosis is made when evidence of mites is found from a skin scraping test. By scraping the skin (covered with a drop of mineral oil) sideways with a scalpel blade over an area of a burrow and examining the scrapings microscopically, it is possible to identify mites, eggs, or pellets. This process can be difficult, however, since burrows can be hard to identify. Sometimes scratch marks are mistaken for burrows, and even the examination of scrapings from 15 or more burrows may only reveal one or two mites or eggs. If the characteristic physical findings are present, scabies can often be treated without performing the skin scrapings necessary to identify the mites. 9) What is the Treatment for a Scabies Infestation? Curing scabies is rather easy with the administration of prescription scabicide drugs. There are no approved over-the-counter preparations that have been proved to be effective in eliminating scabies. The following steps should be included in the treatment of scabies:
1. Apply a mite-killer like permethrin (Elimite). These creams are applied from the neck down, left on overnight, then washed off. This application is usually repeated in seven days. Permethrin is approved for use in people 2 months of age and older. TREN.net Editor s note: permethrins are neuro toxins that end up in the bloodstream. Cedar oil and hydrated silica is non-toxic. An alternative treatment is 1 ounce of a 1% lotion or 30 grams of cream of lindane, applied from the neck down and washed off after approximately eight hours. Since lindane can cause seizures when it is absorbed through the skin, it should not be used if skin is significantly irritated or wet, such as with extensive skin disease, rash, or after a bath. As an additional precaution, lindane should not be used in pregnant or nursing women, the elderly, people with skin sores at the site of the application, children younger than 2 years of age, or people who weigh less than 110 pounds. Lindane is not a first-line treatment and is only recommended if patients cannot tolerate other therapies or if other therapies have not been effective. TREN.net Editor s note: There is no place for the use of Lindane under any circumstances, according to the National Pediculosis Association, citing a growing body of evidence that the product can cause serious and sometimes fatal conditions. 2. Ivermectin, an oral medication, is an antiparasitic medication that has also been shown to be an effective scabicide, although it is not FDA-approved for this use. The CDC recommends taking this drug at a dosage of 200 micrograms per kilogram body weight as a single dose, followed by a repeat dose two weeks later. Although taking a drug by mouth is more convenient than application of the cream, ivermectin has a greater risk of toxic side effects than permethrin and has not been shown to be superior to permethrin in eradicating scabies. It is typically used only when topical medications have failed or when the patient cannot tolerate them. TREN.net Editor s note: Very scary stuff. 3. Crotamiton lotion 10% and cream 10% (Eurax, Crotan) is another drug that has been approved for the treatment of scabies in adults, but it is not approved for use in children. However, treatment failures have been documented with the use of crotamiton. 4. Sulfur in petrolatum applied as a cream or ointment is one of the earliest known treatments for scabies. It has not been approved by the FDA for this use,
and sulfur should only be used when permethrin, lindane, or ivermectin cannot be tolerated. However, sulfur is safe for use in pregnant women and infants. 5. Antihistamines, such as Benadryl (diphenhydramine), can be useful in helping provide relief from itching. Sometimes, a short course of topical or oral steroids is prescribed to help control the itching. 6. Wash linens and bedclothes in hot water. Because mites don't live long away from the body, it is not necessary to dry-clean the whole wardrobe, spray furniture and rugs, and so forth. 10) Scabies Treatment: Additional Tips Treat sexual contacts or relevant family members (who either have either symptoms or have the kind of relationship that makes transmission likely). Cut your nails, and clean under them thoroughly to remove any mites or eggs that may be present. Thoroughly vacuum your rugs, furniture, bedding, and car interior and throw the vacuum cleaner bag away when finished. Try to avoid scratching. Keep any open sores clean. Just as the itch of scabies takes a while to reach a crescendo, it takes a few days to subside after treatment. After a week or two, relief is dramatic. If that doesn't happen, the diagnosis of scabies must be questioned. 11) Are Cases of Scabies Often Misdiagnosed? Scabies is very easy to misdiagnose because early subtle infestation may look like small pimples or mosquito bites. Those affected may believe they have another condition, such as bedbug bites or other kinds of rashes. Over a few weeks, however, mistakes like this become evident as patients feel worse and worse with
symptoms they can't ignore. 12) What are Possible Complications of Scabies? The intense itching of scabies leads to prolonged and often intense scratching of the skin. When the skin is broken or injured due to scratching, secondary bacterial infections of the skin can develop from bacteria normally present on the skin, such as Staphylococcus aureus or beta-hemolytic streptococci. 13) Can a Scabies Infestation be Prevented? Scabies can be prevented by avoiding close personal contact with infested people. Sexual contacts and household members of people who develop scabies can be treated as soon as the condition is identified so that they will not develop the signs or symptoms of the condition. The treatment for these exposed people is the same as the treatment of the infested individual. 14) In what Special Situations Can Scabies be More Easily Spread? Elderly and weakened people in nursing homes and similar institutional settings may harbor scabies without showing significant itching or visible signs. In such cases, there can be widespread epidemics among patients and health care workers. Such cases are dramatic but, fortunately, uncommon. 15) What is Norwegian or Crusted Scabies? Norwegian scabies, or crusted scabies, is a severe form of scabies first described in Norway. Crusted scabies almost always affects people with a compromised immune system and is observed most frequently in the elderly, those who are mentally or physically disabled, and in patients with AIDS, lymphoma, or other conditions that decrease the effectiveness of the immune response. Due to the poor function of the immune system, an individual may become infested with hundreds of thousands of the mites. The lesions of this distinctive form of scabies are extensive and may spread all over the body. The elbows, knees, palms, scalp, and soles of the feet are most commonly the original sites of involvement, and the scaly areas eventually take on a wart-like appearance. The fingernails can be thickened and discolored. Interestingly, itching may be minimal or absent in this
form of scabies. A particular danger of crusted scabies is that these lesions often predispose to the development of secondary infections, as with staphylococcus or streptococcus bacteria. 16) What is the Prognosis (outlook) for Scabies? Scabies is curable with scabicide medications. Treatment failures are not common but are possible, and people with Norwegian scabies may require a combination of different treatment methods. Previous contributing author: Alan Rockoff, MD REFERENCES: Chosidow, O. "Clinical Practices. Scabies." N Engl J Med 354.16 Apr. 2006: 1718-1727. Cordoro, Kelly M. "Dermatologic Manifestations of Scabies." Medscape. Dec. 9, 2009. <http://emedicine.medscape.com/article/1109204- overview>. Dourmishev, A.L., L.A. Dourmishev, and R.A. Schwartz. "Ivermectin: Pharmacology and Application in Dermatology." Int J Dermatol 44.12 Dec. 2005: 981-988. McCroskey, Amy L. "Scabies in emergency medicine." Medscape.com. Oct. 6, 2010. <http://emedicine.medscape.com/article/785873-overview>. McCroskey, Amy L., and Adam J. Rosh. "Scabies." emedicine.com. Apr. 5, 2010. <http://emedicine.medscape.com/article/785873-overview>. United States. Centers for Disease Control and Prevention. "Scabies." Nov. 10, 2008. <http://www.cdc.gov/scabies/index.html>.