| Dermatophytosis | |
|---|---|
| Other names | Ringworm, tinea |
 | |
| Ringworm on a human leg | |
| Specialty | Dermatology,Internal Medicine |
| Symptoms | Red, itchy, scaly, circular skin rash[1] |
| Causes | Fungal infection[2] |
| Risk factors | Using public showers, contact sports, excessive sweating, contact with animals,obesity,poor immune function[3][4] |
| Diagnostic method | Based on symptoms,microbial culture, microscopic examination[5] |
| Differential diagnosis | Dermatitis,psoriasis,pityriasis rosea,tinea versicolor[6] |
| Prevention | Keep the skin dry, not walking barefoot in public, not sharing personal items[3] |
| Treatment | Antifungal creams (clotrimazole,miconazole)[7] |
| Frequency | 20% of the population[8] |
Dermatophytosis, also known astinea andringworm, is afungal infection of theskin[2] (adermatomycosis), that may affect skin, hair, and nails.[1] Typically it results in a red, itchy, scaly, circular rash.[1] Hair loss may occur in the area affected.[1] Symptoms begin four to fourteen days after exposure.[1] Thetypes of dermatophytosis are typically named for area of the body that they affect.[2] Multiple areas can be affected at a given time.[4]
About 40 types of fungus can cause dermatophytosis.[2] They are typically of theTrichophyton,Microsporum, orEpidermophyton type.[2] Risk factors include using public showers, contact sports such aswrestling, excessive sweating, contact with animals,obesity, andpoor immune function.[3][4] Ringworm can spread from other animals or between people.[3] Diagnosis is often based on the appearance and symptoms.[5] It may be confirmed by eitherculturing or looking at a skin scraping under amicroscope.[5]
Prevention is by keeping the skin dry, not walking barefoot in public, and not sharing personal items.[3] Treatment is typically withantifungal creams such asclotrimazole ormiconazole.[7] If the scalp is involved, antifungals by mouth such asfluconazole may be needed.[7]
Dermatophytosis has spread globally, and up to 20% of the world's population may be infected by it at any given time.[8] Infections of the groin are more common in males, while infections of the scalp and body occur equally in both sexes.[4] Infections of the scalp are most common in children while infections of the groin are most common in the elderly.[4] Descriptions of ringworm date back toancient history.[9]
A number of different species of fungus are involved in dermatophytosis.Dermatophytes of the generaTrichophyton andMicrosporum are the most common causative agents. These fungi attack various parts of the body and lead to the conditions listed below. The Latin names are for the conditions (disease patterns), not the agents that cause them. The disease patterns below identify the type of fungus that causes them only in the cases listed:
Infections on the body may give rise to typical enlarging raised red rings of ringworm. Infection on the skin of the feet may causeathlete's foot and in the groin,jock itch. Involvement of the nails is termedonychomycosis.
Animals including dogs and cats can also be affected by ringworm, and the disease can be transmitted between animals and humans, making it azoonotic disease.
Specific signs can be:
Fungi thrive in moist, warm areas, such aslocker rooms,tanning beds,swimming pools, andskin folds; accordingly, those that cause dermatophytosis may be spread by usingexercise machines that have not been disinfected after use, or by sharing towels, clothing, footwear, or hairbrushes.
Dermatophyte infections can be readily diagnosed based on the history, physical examination, and potassium hydroxide (KOH) microscopy.[10]
Advice often given includes:
As of 2016,[update] no approved human vaccine exist against dermatophytosis. Forhorses,dogs andcats there is available an approved inactivated vaccine calledInsol Dermatophyton (Boehringer Ingelheim) which provides time-limited protection against severaltrichophyton andmicrosporum fungal strains.[14] With cattle, systemic vaccination has achieved effective control of ringworm. Since 1979 a Russian live vaccine (LFT 130) and later on a Czechoslovakian live vaccine against bovine ringworm has been used. In Scandinavian countries vaccination programmes against ringworm are used as apreventive measure to improve the hide quality. In Russia, fur-bearing animals (silver fox, foxes, polar foxes) and rabbits have also been treated with vaccines.[15]
Antifungal treatments includetopical agents such asmiconazole,terbinafine,clotrimazole,ketoconazole, ortolnaftate applied twice daily until symptoms resolve — usually within one or two weeks.[16] Topical treatments should then be continued for a further 7 days after resolution of visible symptoms to prevent recurrence.[16][17] The total duration of treatment is therefore generally two weeks,[18][19] but may be as long as three.[20]
In more severe cases or scalp ringworm,systemic treatment with oral medications (such asitraconazole,terbinafine, andketoconazole) may be given.[21]
To prevent spreading the infection, lesions should not be touched, and good hygiene maintained with washing of hands and the body.[22]
Misdiagnosis and treatment of ringworm with atopical steroid, a standard treatment of the superficially similarpityriasis rosea, can result intinea incognito, a condition where ringworm fungus grows without typical features, such as a distinctive raised border.[citation needed]
Dermatophytosis has been prevalent since before 1906, at which time ringworm was treated with compounds ofmercury or sometimessulfur oriodine. Hairy areas of skin were considered too difficult to treat, so thescalp was treated withX-rays and followed up withantifungal medication.[23] Another treatment from around the same time was application ofAraroba powder.[24]
The most common term for the infection, "ringworm", is amisnomer, since the condition is caused byfungi of several differentspecies and not byparasitic worms.
Ringworm caused byTrichophyton verrucosum is a frequent clinical condition incattle. Young animals are more frequently affected. The lesions are located on the head, neck, tail, andperineum.[25] The typical lesion is a round, whitish crust. Multiple lesions may coalesce in "map-like" appearance.
Clinical dermatophytosis is also diagnosed insheep,dogs,cats, andhorses. Causative agents, besidesTrichophyton verrucosum, areT. mentagrophytes,T. equinum,Microsporum gypseum,M. canis, andM. nanum.[26]
Dermatophytosis may also be present in theholotype of theCretaceouseutriconodont mammalSpinolestes, suggesting aMesozoic origin for this disease.
Ringworm in pets may often be asymptomatic, resulting in acarrier condition which infects other pets. In some cases, the disease only appears when the animal develops animmunodeficiency condition. Circular bare patches on the skin suggest the diagnosis, but no lesion is truly specific to the fungus. Similar patches may result fromallergies,sarcoptic mange, and other conditions. Three species of fungi cause 95% of dermatophytosis in pets:[citation needed] these areMicrosporum canis,Microsporum gypseum, andTrichophyton mentagrophytes.
Veterinarians have several tests to identify ringworm infection and identify the fungal species that cause it:
Woods test: This is anultraviolet light with a magnifying lens. Only 50% ofM. canis will show up as an apple-green fluorescence on hair shafts, under the UV light. The other fungi do not show. The fluorescent material is not the fungus itself (which does not fluoresce), but rather an excretory product of the fungus which sticks to hairs. Infected skin does not fluoresce.
Microscopic test: The veterinarian takes hairs from around the infected area and places them in a staining solution to view under the microscope. Fungal spores may be viewed directly on hair shafts. This technique identifies a fungal infection in about 40%–70% of the infections, but cannot identify the species of dermatophyte.
Culture test: This is the most effective, but also the most time-consuming, way to determine if ringworm is on a pet. In this test, the veterinarian collects hairs from the pet, or else collects fungal spores from the pet's hair with a toothbrush, or other instrument, and inoculates fungal media for culture. These cultures can be brushed with transparent tape and then read by the veterinarian using a microscope, or can be sent to a pathological lab. The three common types of fungi which commonly cause pet ringworm can be identified by their characteristic spores. These are different-appearingmacroconidia in the two common species ofMicrospora, and typicalmicroconidia inTrichophyton infections.[26]
Identifying the species of fungi involved in pet infections can be helpful in controlling the source of infection.M. canis, despite its name, occurs more commonly in domestic cats, and 98% of cat infections are with this organism.[citation needed] It can also infect dogs and humans, however.T. mentagrophytes has a major reservoir inrodents, but can also infect petrabbits, dogs, and horses.M. gypseum is a soil organism and is often contracted from gardens and other such places. Besides humans, it may infect rodents, dogs, cats, horses, cattle, andswine.[27]
Treatment requires both systemic oral treatment with most of the same drugs used in humans—terbinafine, fluconazole, or itraconazole—as well as a topical "dip" therapy.[28]
Because of the usually longer hair shafts in pets compared to those of humans, the area of infection and possibly all of the longer hair of the pet must be clipped to decrease the load of fungal spores clinging to the pet's hair shafts. However, close shaving is usually not done because nicking the skin facilitates further skin infection.
Twice-weekly bathing of the pet with dilutedlime sulfur dip solution is effective in eradicating fungal spores. This must continue for 3 to 8 weeks.[29]
Washing of household hard surfaces with 1:10 householdsodium hypochloritebleach solution is effective in killing spores, but it is too irritating to be used directly on hair and skin.
Pet hair must be rigorously removed from all household surfaces, and then thevacuum cleaner bag, and perhaps even the vacuum cleaner itself, discarded when this has been done repeatedly. Removal of all hair is important, since spores may survive 12 months or even as long as two years on hair clinging to surfaces.[30]
Inbovines, an infestation is difficult to cure, assystemic treatment is uneconomical. Local treatment withiodine compounds is time-consuming, as it needs scraping of crusty lesions. Moreover, it must be carefully conducted usinggloves, lest the worker become infested.
Worldwide, superficial fungal infections caused by dermatophytes are estimated to infect around 20-25% of the population and it is thought that dermatophytes infect 10-15% of the population during their lifetime.[31][32] The highestincidence of superficial mycoses result from dermatophytoses which are most prevalent in tropical regions.[31][33] Onychomycosis, a common infection caused by dermatophytes, is found with varying prevalence rates in many countries.[34]Tinea pedis + onychomycosis,Tinea corporis,Tinea capitis are the most common dermatophytosis found in humans across the world.[34]Tinea capitis has a greater prevalence in children.[31] The increasing prevalence of dermatophytes resulting inTinea capitis has been causingepidemics throughout Europe and America.[34] In pets, cats are the most affected by dermatophytosis.[35] Pets are susceptible to dermatophytoses caused byMicrosporum canis,Microsporum gypseum, andTrichophyton.[35] For dermatophytosis in animals, risk factors depend on age, species, breed, underlying conditions, stress, grooming, and injuries.[35]
Numerous studies have foundTinea capitis to be the most prevalent dermatophyte to infect children across the continent of Africa.[32] Dermatophytosis has been found to be most prevalent in children ages 4 to 11, infecting more males than females.[32] Lowsocioeconomic status was found to be a risk factor forTinea capitis.[32] Throughout Africa, dermatophytoses are common in hot- humid climates and with areas of overpopulation.[32]
Chronicity is a common outcome for dermatophytosis in India.[33] The prevalence of dermatophytosis in India is between 36.6 and 78.4% depending on the area, clinical subtype, and dermatophyte isolate.[33] Individuals ages 21–40 years are most commonly affected.[33]
A 2002 study looking at 445 samples of dermatophytes in patients in Goiânia, Brazil found the most prevalent type to beTrichophyton rubrum (49.4%), followed byTrichophyton mentagrophytes (30.8%), andMicrosporum canis (12.6%).[36]
A 2013 study looking at 5,175 samples ofTinea in patients in Tehran, Iran found the most prevalent type to beTinea pedis (43.4%), followed byTinea unguium. (21.3%), andTinea cruris (20.7%).[37]
Authority control databases: National |
|---|
