Scabies
Encyclopedia
Scabies known colloquially as the seven-year itch, is a contagious skin infection
that occurs among humans and other 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 infection in animals (caused by different but related mite species) is called sarcoptic mange.
The disease may be transmitted from objects but is most often transmitted by direct skin-to-skin contact, with a higher risk with prolonged contact. Initial infections require four to six weeks to become symptomatic. Reinfection, however, may manifest symptoms within as little as 24 hours. Because the symptoms are allergic, their delay in onset is often mirrored by a significant delay in relief after the parasites have been eradicated. Crusted scabies, formerly known as Norwegian scabies, is a more severe form of the infection often associated with immunosuppression
.
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. Ivermectin may be used orally and topically. Treatment with lindane
preparations has fallen out of favor due to high toxicity and parasite resistance. In order to prevent re-infection, the host's contacts are also often treated.
In most people, the trails of the burrowing mites show as linear or s-shaped tracks in the skin, often accompanied by what appear as rows of small pimple-like mosquito, or insect bites. These signs are often found in crevices of the body, such as on the webs of fingers and toes, around the genital area, and under the breasts of women.
Symptoms typically appear 2–6 weeks after infestation for individuals never before exposed to scabies. For those having been previously exposed, the symptoms can appear within several days after infestation. However, it is not unknown for symptoms to appear after several months or years.Acropustulosis
, or blisters and pustules on the palms and soles of the feet, are characteristic symptoms of scabies in infants.
The elderly and people with an impaired immune system
, such as HIV
, cancer
or those on immunosuppressive medications, are susceptible to crusted scabies (formerly called "Norwegian scabies"). On those with a weaker immune system, the host becomes a more fertile breeding ground for the mites, which spread over the host's body, except the face. Sufferers of crusted scabies exhibit scaly rashes, slight itching, and thick crusts of skin that contain thousands of mites. Such areas make eradication of mites particularly difficult, as the crusts protect the mites from topical miticides, necessitating prolonged treatment of these areas.
, variety hominis, as the cause of
scabies. Sarcoptes is a genus of skin parasites and part of the larger family of mites collectively known as "scab mites". These organisms have 8 legs as adults, and are placed in the same phylogenetic class (Arachnida) as spiders and ticks.
Sarcoptes scabiei are microscopic, but sometimes are visible as pinpoints of white. Pregnant females tunnel into the dead, outermost layer (stratum corneum
) of a host's skin and deposit eggs
in the shallow burrows. The eggs hatch into larva
e in 3–10 days. These young mites move about on the skin and molt
into a "nymphal
" stage, before maturing as adults, which live 3–4 weeks in the host's skin. Males roam on top of the skin, occasionally burrowing into the skin. In general, there are usually few mites on a healthy hygienic person infested with non-crusted scabies; approximately 11 females in burrows can be found on such a person.
The movement of mites within and on the skin produces an intense itch, which has the characteristics of a delayed cell-mediated inflammatory response to allergens. IgE
antibodies are present in the serum and the site of infection, which react to multiple protein allergens the body of the mite. Some of these cross-react to allergens from house-dust mites. Immediate antibody-mediated allergic reactions (wheals) have been elicited in infected persons, but not in healthy persons; immediate hypersensitivity of this type is thought to explain the observed far more rapid allergic skin response to reinfection seen in persons having been previously infected (especially having been infected within the previous year or two). Because the host develops the symptoms as a reaction to the mites' presence over time, there is usually a 4– to 6-week incubation period after the onset of infestation. As noted, those previously infected with scabies and cured may exhibit the symptoms of a new infection in a much shorter period, as little as 1–4 days.
Scabies is contagious, and can be spread by scratching an infected area, thereby picking up the mites under the fingernails, or through physical contact with a scabies-infected person for a prolonged period of time. Scabies is usually transmitted by direct skin-to-skin physical contact. It can also be spread through contact with other objects, such as clothing, bedding, furniture, or surfaces with which a person infected with scabies might have come in contact. Scabies mites can survive without a human host for 24 to 36 hours. As with lice, scabies can be transmitted through sexual intercourse even if a latex condom is used, because it is transmitted from skin-to-skin at sites other than sex organs.
(antibodies, it is presumed, mediate the very rapid symptoms on re-infection). The allergy-type symptoms (itching) continue for some days, and even several weeks, after all mites are killed. New lesions may appear for a few days after mites are eradicated. Nodular lesions from scabies may continue to be symptomatic for weeks after the mites have been killed.
Scabies may be diagnosed clinically in geographical areas where it is common when diffuse itching presents along with either lesions in two typical spots or there is itchiness of another household member. The classical sign of scabies is the burrows made by the mites within the skin. To detect the burrow the suspected area is rubbed with ink from a fountain pen or a topical tetracycline solution, which glows under a special light. The skin is then wiped with an alcohol pad. If the person is infected with scabies, the characteristic zigzag or "S" pattern of the burrow will appear across the skin; however, interpreting this test may be difficult, as the burrows are scarce and may be obscured by scratch marks. A definitive diagnosis is made by finding either the scabies mites or their eggs and fecal pellets. Searches for these signs involve either scraping a suspected area, mounting the sample in potassium hydroxide
, and examining it under a microscope, or using dermoscopy to examine the skin directly.
, syphilis
, various urticaria
-related syndromes, allergic reactions, and other ectoparasites such as lice and fleas.
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. Objects in the environment
pose little risk of transmission except in the case of crusted scabies, thus cleaning is of little importance. Rooms used by those with crusted scabies require thorough cleaning.
s.
is the most effective treatment for scabies, and the treatment of choice. It is applied from the neck down usually before bedtime and left on for about 8 to 14 hours, then showered off in the morning. One application is normally sufficient for mild infections. For moderate to severe cases, another dose is applied 7–14 days later. Permethrin causes slight irritation of the skin, but the sensation is tolerable. The medication, however, is the most costly of topical treatments.
Topical
ivermectin preparations have been found to be effective for scabies in adults, and are attractive due to their low cost, ease of preparation, and low toxicity. It has also been useful for sarcoptic mange (the veterinary analog of human scabies).
, benzyl benzoate
, crotamiton
, malathion
, and sulfur
preparations. Lindane is effective; however, concerns over potential neurotoxicity has limited its availability in many countries. It is approved in the United States for use as a second-line treatment. Sulfur ointments or benzyl benzoate are often used in the developing world due to their low cost; 10% sulfur solutions have been shown to be effective, and sulfur ointments are typically used for at least a week. Crotamiton in limited studies has been found to be less effective than permethrin. Crotamiton or a sulfur
preparation is often recommended instead of permethrin for children, due to concerns over dermal absorption
of permethrin.
and pyoderma
. The mites are distributed around the world and equally infect all ages, races, and socioeconomic classes in different climates. Scabies is more often seen in crowded areas with unhygienic living conditions. Globally as of 2009, it is estimated that 300 million cases of scabies occur each year, although various parties claim the figure is either over- or underestimated. About 1–10% of the global population is estimated to be infected with scabies, but in certain populations, the infection rate may be as high as 50–80%. Scabies is one of the three most common dermatological disorders in children.
(Leviticus
, the third book of Moses) ca. 1200 BC. Later in fourth century BC, the ancient Greek philosopher Aristotle
reported on "lice" that "escape from little pimples if they are pricked"; scholars believe this was actually a reference to scabies.
Nevertheless, it was Roman physician Celsus
who is credited with naming the disease "scabies" and describing its characteristic features. The parasitic etiology of scabies was later documented by the Italian physician Giovanni Cosimo Bonomo (1663–99 AD) in his famous 1687 letter, "Observations concerning the fleshworms of the human body." With this (disputed) discovery, scabies became one of the first diseases with a known cause.
Scabies may occur in a number of domestic and wild animals; the mites that cause these infestations are of different scabies subspecies. These subspecies can infest animals or humans that are not their usual hosts, but such infections do not last long. Scabies-infected animals suffer severe itching and secondary skin infections. They often lose weight and become frail.
The most frequently diagnosed form of scabies in domestic animals is sarcoptic mange
, which is found on dogs. The scab mite Psoroptes is the mite responsible for mange. Scabies-infected domestic fowl suffer what is known as "scabies leg". Domestic animals that have gone feral and have no veterinary care are frequently afflicted with scabies and a host of other ailments. Non-domestic animals have also been observed to suffer from scabies. Gorillas, for instance, are known to be susceptible to infection via contact with items used by humans.
Skin infection
A skin infection is an infection of the skin. Infection of the skin is distinguished from dermatitis, which is inflammation of the skin, but a skin infection can result in skin inflammation...
that occurs among humans and other animals. It is caused by a tiny and usually not directly visible parasite
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
, the mite Sarcoptes scabiei
Sarcoptes scabiei
Sarcoptes scabiei or the itch mite is a parasitic arthropod that burrows into skin and causes scabies. Animals affected include not only human but also wild and domesticated dogs and cats in which it is one cause of mange...
, which burrows under the host's skin, causing intense allergic itching. The infection in animals (caused by different but related mite species) is called sarcoptic mange.
The disease may be transmitted from objects but is most often transmitted by direct skin-to-skin contact, with a higher risk with prolonged contact. Initial infections require four to six weeks to become symptomatic. Reinfection, however, may manifest symptoms within as little as 24 hours. Because the symptoms are allergic, their delay in onset is often mirrored by a significant delay in relief after the parasites have been eradicated. Crusted scabies, formerly known as Norwegian scabies, is a more severe form of the infection often associated with immunosuppression
Immunosuppression
Immunosuppression involves an act that reduces the activation or efficacy of the immune system. Some portions of the immune system itself have immuno-suppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other...
.
The disease can be effectively treated with a number of medications. Permethrin
Permethrin
Permethrin is a common synthetic chemical, widely used as an insecticide, acaricide, and insect repellent. It belongs to the family of synthetic chemicals called pyrethroids and functions as a neurotoxin, affecting neuron membranes by prolonging sodium channel activation. It is not known to...
cream is the most effective, but expensive compared to other treatments. Crotamiton
Crotamiton
Crotamiton is a drug that is used both as a scabicidal and as a general antipruritic . It is a prescription and OTC lotion based medicine that is applied to the whole body to get rid of the scabies parasite that burrows under the skin and causes itching.-Use:For treating scabies, crotamiton should...
is less effective, but also nontoxic and soothing. Ivermectin may be used orally and topically. Treatment with lindane
Lindane
Lindane, also known as gamma-hexachlorocyclohexane, , gammaxene, Gammallin and erroneously known as benzene hexachloride , is an organochlorine chemical variant of hexachlorocyclohexane that has been used both as an agricultural insecticide and as a pharmaceutical treatment for lice and...
preparations has fallen out of favor due to high toxicity and parasite resistance. In order to prevent re-infection, the host's contacts are also often treated.
Signs and symptoms
The characteristic symptoms of a scabies infection include intense itching and superficial burrows. The burrow tracks are often linear, to the point that a neat "line" of four or more closely placed and equally developed mosquito-like "bites," is almost diagnostic of the disease.Itching
In the classic scenario, the itch is made worse by warmth and is usually experienced as being worse at night, possibly because there are fewer distractions. As a symptom it is less common in the elderly.Rash
The superficial burrows of scabies usually occur in the area of the hands, feet, wrists, elbows, back, buttocks, and external genitals. The burrows are created by excavation of the adult mite in the epidermis.In most people, the trails of the burrowing mites show as linear or s-shaped tracks in the skin, often accompanied by what appear as rows of small pimple-like mosquito, or insect bites. These signs are often found in crevices of the body, such as on the webs of fingers and toes, around the genital area, and under the breasts of women.
Symptoms typically appear 2–6 weeks after infestation for individuals never before exposed to scabies. For those having been previously exposed, the symptoms can appear within several days after infestation. However, it is not unknown for symptoms to appear after several months or years.Acropustulosis
Acropustulosis
Acropustulosis refers to Acrodermatitis with pustular involvement.Types include:* Pustulosis palmaris et plantaris* Infantile acropustulosis...
, or blisters and pustules on the palms and soles of the feet, are characteristic symptoms of scabies in infants.
Crusted scabies
Immunodeficiency
Immunodeficiency is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Immunodeficiency may also decrease cancer immunosurveillance. Most cases of immunodeficiency are acquired but some people are born with defects in their immune system,...
, such as HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
, cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
or those on immunosuppressive medications, are susceptible to crusted scabies (formerly called "Norwegian scabies"). On those with a weaker immune system, the host becomes a more fertile breeding ground for the mites, which spread over the host's body, except the face. Sufferers of crusted scabies exhibit scaly rashes, slight itching, and thick crusts of skin that contain thousands of mites. Such areas make eradication of mites particularly difficult, as the crusts protect the mites from topical miticides, necessitating prolonged treatment of these areas.
Cause
In the 18th century, Italian biologist Diacinto Cestoni (1637–1718) described the mite now called Sarcoptes scabieiSarcoptes scabiei
Sarcoptes scabiei or the itch mite is a parasitic arthropod that burrows into skin and causes scabies. Animals affected include not only human but also wild and domesticated dogs and cats in which it is one cause of mange...
, variety hominis, as the cause of
Etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
scabies. Sarcoptes is a genus of skin parasites and part of the larger family of mites collectively known as "scab mites". These organisms have 8 legs as adults, and are placed in the same phylogenetic class (Arachnida) as spiders and ticks.
Sarcoptes scabiei are microscopic, but sometimes are visible as pinpoints of white. Pregnant females tunnel into the dead, outermost layer (stratum corneum
Stratum corneum
The stratum corneum is the outermost layer of the epidermis, consisting of dead cells that lack nuclei and organelles. The purpose of the stratum corneum is to form a barrier to protect underlying tissue from infection, dehydration, chemicals and mechanical stress...
) of a host's skin and deposit eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
in the shallow burrows. The eggs hatch into larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e in 3–10 days. These young mites move about on the skin and molt
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...
into a "nymphal
Nymph (biology)
In biology, a nymph is the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis before reaching its adult stage. Unlike a typical larva, a nymph's overall form already resembles that of the adult. In addition, while a nymph moults it never enters a...
" stage, before maturing as adults, which live 3–4 weeks in the host's skin. Males roam on top of the skin, occasionally burrowing into the skin. In general, there are usually few mites on a healthy hygienic person infested with non-crusted scabies; approximately 11 females in burrows can be found on such a person.
The movement of mites within and on the skin produces an intense itch, which has the characteristics of a delayed cell-mediated inflammatory response to allergens. IgE
IGE
IGE was one of the largest services company buying and selling virtual currencies and accounts for MMORPG. During its peak time, it had offices in Los Angeles, China , and headquarters & customer service centre in Hong Kong. IGE was one of the main monopoly in virtual economy services, also known...
antibodies are present in the serum and the site of infection, which react to multiple protein allergens the body of the mite. Some of these cross-react to allergens from house-dust mites. Immediate antibody-mediated allergic reactions (wheals) have been elicited in infected persons, but not in healthy persons; immediate hypersensitivity of this type is thought to explain the observed far more rapid allergic skin response to reinfection seen in persons having been previously infected (especially having been infected within the previous year or two). Because the host develops the symptoms as a reaction to the mites' presence over time, there is usually a 4– to 6-week incubation period after the onset of infestation. As noted, those previously infected with scabies and cured may exhibit the symptoms of a new infection in a much shorter period, as little as 1–4 days.
Scabies is contagious, and can be spread by scratching an infected area, thereby picking up the mites under the fingernails, or through physical contact with a scabies-infected person for a prolonged period of time. Scabies is usually transmitted by direct skin-to-skin physical contact. It can also be spread through contact with other objects, such as clothing, bedding, furniture, or surfaces with which a person infected with scabies might have come in contact. Scabies mites can survive without a human host for 24 to 36 hours. As with lice, scabies can be transmitted through sexual intercourse even if a latex condom is used, because it is transmitted from skin-to-skin at sites other than sex organs.
Pathophysiology
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. The allergic reaction is both of the delayed (cell-mediated) and immediate (antibody-mediated) type, and involves IgEIGE
IGE was one of the largest services company buying and selling virtual currencies and accounts for MMORPG. During its peak time, it had offices in Los Angeles, China , and headquarters & customer service centre in Hong Kong. IGE was one of the main monopoly in virtual economy services, also known...
(antibodies, it is presumed, mediate the very rapid symptoms on re-infection). The allergy-type symptoms (itching) continue for some days, and even several weeks, after all mites are killed. New lesions may appear for a few days after mites are eradicated. Nodular lesions from scabies may continue to be symptomatic for weeks after the mites have been killed.
Diagnosis
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
, and examining it under a microscope, or using dermoscopy to examine the skin directly.
Differential diagnosis
Symptoms of early scabies infestation mirror other skin diseases, including dermatitisDermatitis
-Etymology:Dermatitis derives from Greek derma "skin" + -itis "inflammation" and genetic disorder.-Terminology:There are several different types of dermatitis. The different kinds usually have in common an allergic reaction to specific allergens. The term may describe eczema, which is also called...
, syphilis
Syphilis
Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...
, various urticaria
Urticaria
Urticaria is a kind of skin rash notable for pale red, raised, itchy bumps. Hives is frequently caused by allergic reactions; however, there are many non-allergic causes...
-related syndromes, allergic reactions, and other ectoparasites such as lice and fleas.
Prevention
Mass treatment programs that use topical permethrinPermethrin
Permethrin is a common synthetic chemical, widely used as an insecticide, acaricide, and insect repellent. It belongs to the family of synthetic chemicals called pyrethroids and functions as a neurotoxin, affecting neuron membranes by prolonging sodium channel activation. It is not known to...
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
Asymptomatic
In medicine, a disease is considered asymptomatic if a patient is a carrier for a disease or infection but experiences no symptoms. A condition might be asymptomatic if it fails to show the noticeable symptoms with which it is usually associated. Asymptomatic infections are also called subclinical...
), to reduce rates of recurrence. Asymptomatic infection is relatively common. Objects in the environment
Fomite
A fomite is any inanimate object or substance capable of carrying infectious organisms and hence transferring them from one individual to another. A fomite can be anything...
pose little risk of transmission except in the case of crusted scabies, thus cleaning is of little importance. Rooms used by those with crusted scabies require thorough cleaning.
Management
A number of medications are effective in treating scabies, however treatment must often involve the entire household or community to prevent re-infection. Options to improve itchiness include antihistamineAntihistamine
An H1 antagonist is a histamine antagonist of the H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions...
s.
Permethrin
PermethrinPermethrin
Permethrin is a common synthetic chemical, widely used as an insecticide, acaricide, and insect repellent. It belongs to the family of synthetic chemicals called pyrethroids and functions as a neurotoxin, affecting neuron membranes by prolonging sodium channel activation. It is not known to...
is the most effective treatment for scabies, and the treatment of choice. It is applied from the neck down usually before bedtime and left on for about 8 to 14 hours, then showered off in the morning. One application is normally sufficient for mild infections. For moderate to severe cases, another dose is applied 7–14 days later. Permethrin causes slight irritation of the skin, but the sensation is tolerable. The medication, however, is the most costly of topical treatments.
Ivermectin
Ivermectin is an oral medication shown by many clinical studies to be effective in eradicating scabies, often in a single dose. It is the treatment of choice for crusted scabies, and is often used in combination with a topical agent. It has not been tested on infants and is not recommended for children under six years of age.Topical
Topical
In medicine, a topical medication is applied to body surfaces such as the skin or mucous membranes such as the vagina, anus, throat, eyes and ears.Many topical medications are epicutaneous, meaning that they are applied directly to the skin...
ivermectin preparations have been found to be effective for scabies in adults, and are attractive due to their low cost, ease of preparation, and low toxicity. It has also been useful for sarcoptic mange (the veterinary analog of human scabies).
Others
Other treatments include lindaneLindane
Lindane, also known as gamma-hexachlorocyclohexane, , gammaxene, Gammallin and erroneously known as benzene hexachloride , is an organochlorine chemical variant of hexachlorocyclohexane that has been used both as an agricultural insecticide and as a pharmaceutical treatment for lice and...
, benzyl benzoate
Benzyl benzoate
Benzyl benzoate is the ester of benzyl alcohol and benzoic acid, with the formula C6H5CH2O2CC6H5. This easily prepared compound has a variety of uses.-Synthesis:This colorless liquid is formally the condensation product of benzoic acid and benzyl alcohol...
, crotamiton
Crotamiton
Crotamiton is a drug that is used both as a scabicidal and as a general antipruritic . It is a prescription and OTC lotion based medicine that is applied to the whole body to get rid of the scabies parasite that burrows under the skin and causes itching.-Use:For treating scabies, crotamiton should...
, malathion
Malathion
Malathion is an organophosphate parasympathomimetic which binds irreversibly to cholinesterase. Malathion is an insecticide of relatively low human toxicity, however one recent study has shown that children with higher levels of organophosphate pesticide metabolites in their urine are more likely...
, and sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
preparations. Lindane is effective; however, concerns over potential neurotoxicity has limited its availability in many countries. It is approved in the United States for use as a second-line treatment. Sulfur ointments or benzyl benzoate are often used in the developing world due to their low cost; 10% sulfur solutions have been shown to be effective, and sulfur ointments are typically used for at least a week. Crotamiton in limited studies has been found to be less effective than permethrin. Crotamiton or a sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
preparation is often recommended instead of permethrin for children, due to concerns over dermal absorption
Absorption (skin)
Skin absorption is a route by which substances can enter the body through the skin. Along with inhalation, ingestion and injection, dermal absorption is a route of exposure for toxic substances and route of administration for medication...
of permethrin.
Epidemiology
Scabies is one of the three most common skin disorders in children, along with tineaTinea
Tinea is a general term used to describe skin mycoses. The term ringworm is even less precise, but is usually considered a synonym.It is sometimes equated with dermatophytosis, and it is true that most conditions identified as "tinea" are members of the imperfect fungi that make up the dermatophytes...
and pyoderma
Pyoderma
Pyoderma means any skin disease that is pyogenic. These include superficial bacterial infections such as impetigo, impetigo contagiosa, ecthyma, folliculitis, Bockhart impetigo, furuncle, carbuncle, tropical ulcer, etc. Autoimmune conditions include pyoderma gangrenosum...
. The mites are distributed around the world and equally infect all ages, races, and socioeconomic classes in different climates. Scabies is more often seen in crowded areas with unhygienic living conditions. Globally as of 2009, it is estimated that 300 million cases of scabies occur each year, although various parties claim the figure is either over- or underestimated. About 1–10% of the global population is estimated to be infected with scabies, but in certain populations, the infection rate may be as high as 50–80%. Scabies is one of the three most common dermatological disorders in children.
History
Scabies is an ancient disease. Archeological evidence from Egypt and the Middle East suggests that scabies was present as early as 494 BC. The first recorded reference to scabies is believed to be from the BibleBible
The Bible refers to any one of the collections of the primary religious texts of Judaism and Christianity. There is no common version of the Bible, as the individual books , their contents and their order vary among denominations...
(Leviticus
Leviticus
The Book of Leviticus is the third book of the Hebrew Bible, and the third of five books of the Torah ....
, the third book of Moses) ca. 1200 BC. Later in fourth century BC, the ancient Greek philosopher Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
reported on "lice" that "escape from little pimples if they are pricked"; scholars believe this was actually a reference to scabies.
Nevertheless, it was Roman physician Celsus
Celsus
Celsus was a 2nd century Greek philosopher and opponent of Early Christianity. He is known for his literary work, The True Word , written about by Origen. This work, c. 177 is the earliest known comprehensive attack on Christianity.According to Origen, Celsus was the author of an...
who is credited with naming the disease "scabies" and describing its characteristic features. The parasitic etiology of scabies was later documented by the Italian physician Giovanni Cosimo Bonomo (1663–99 AD) in his famous 1687 letter, "Observations concerning the fleshworms of the human body." With this (disputed) discovery, scabies became one of the first diseases with a known cause.
In other animals
The most frequently diagnosed form of scabies in domestic animals is sarcoptic mange
Mange
Mange is the common name for a class of persistent contagious skin diseases caused by parasitic mites. Since mites also infect plants, birds, and reptiles, the term "mange," suggesting poor condition of the hairy coat due to the infection, is sometimes reserved only for pathological...
, which is found on dogs. The scab mite Psoroptes is the mite responsible for mange. Scabies-infected domestic fowl suffer what is known as "scabies leg". Domestic animals that have gone feral and have no veterinary care are frequently afflicted with scabies and a host of other ailments. Non-domestic animals have also been observed to suffer from scabies. Gorillas, for instance, are known to be susceptible to infection via contact with items used by humans.