- Alopecia (hair loss), antifungal, clotrimazole, dermatitis, dermatophytes, dermatophytic pseudomycetoma, dermatophytosis, FeloVax MC-K, fluconazole(Diflucan®), fungal culture, fungal infections, griseofulvin (Fulvicin®), hyphae, itraconazole (Sporonix®), kerion, ketoconazole (Nizoral®, Ketosidin®, Panfungol®), lesions, lime-sulfur dips, lufenuron (Program®), Malassezia
furfur, Malassezia globosa, Malassezia nana, Malassezia pachydermatis, Malassezia slooffiae, Malassezia sympodialis, Malassezia, miconazole, microscopic exam, Microsporum audouinii, Microsporum canis, Microsporum gypseum, Microsporum, papular, pathogen score (p-score), ringworm, spores, terbinafine (Lamisil®), thiabendazole, Trichophyton, Wood's lamp.
- Ringworm (or ring worm) is the common name for dermatophytosis, an infection of the skin that is highly contagious (easily spread). Ringworm may also affect hair and nails (or claws in cats). Although the common name suggests that this condition is caused by worms, it is actually caused by certain types of fungi (including yeasts) known as dermatophytes. A dermatophyte is any type of fungus that can grow on animal or human skin. Dermatophytosis became known as ringworm, because on human skin, fungal infections often have a ring-like appearance that looks like a worm.
- In animals, ringworm usually looks like a dry, scaly patch on the skin. Ringworm is quite common in domestic animals, including farm animals, dogs, and cats. Many experts estimate that about 20% of pet dogs and 30% of pet cats have ringworm at some point. Pets with ringworm may be otherwise healthy and have mild or no symptoms. Very often, ringworm will go away without treatment. However, even if they have no symptoms, pets with ringworm can easily transmit the condition to humans and other animals.
- Ringworm is one of the most common pet-associated human conditions, causing about half of all pet-related infections. Each year in the United States, an estimated two million cases of ringworm in humans can be traced to pets. Experts believe that ringworm can spread more easily from cats than from dogs. Because there are around 70 million pet cats (outnumbering dogs by about 10%) and 70 million more stray cats in the United States alone, it is important to control ringworm infections in cats.
Types of the Disease and Causes
General: Cats can get ringworm from direct contact with any animal or human that is infected with any fungus that causes ringworm. Fungi reproduce by shedding spores, which can survive for months or even years in the environment. Therefore, cats can also get ringworm from any surface (such as floors, furniture, or bedding) that has been contaminated with a fungus that causes ringworm.
- There are about 30 different known kinds of fungi that can cause ringworm in animals and humans. However, most cases of feline ringworm are caused by a few types of fungi: Microsporum, Trichophyton, or Malassezia.
: The fungus Microsporum causes most cases of ringworm in cats, dogs, and humans worldwide. The species Microsporum canis grows especially well on cats, even if they are healthy. Other Microsporum species that are less common in ringworm infections include Microsporum gypseum and Microsporum audouinii.
: Fungi in the genus Trichophyton may also cause ringworm in cats, dogs, and humans. This group of fungi often causes ringworm in birds, cattle, and horses.
: The Malassezia genus of yeasts also grows on the skin of cats. Species of Malassezia that have been found in ringworm infections include Malassezia pachydermatis, Malassezia sympodialis, Malassezia globosa, Malassezia
furfur, Malassezia nana, and Malassezia slooffiae.
General: Ringworm is very contagious, and humans and animals are at risk of becoming infected. However, cats are especially prone to catching ringworm, and certain cats have a greater risk of becoming infected.
Age: Kittens and younger cats are more likely to develop ringworm than older cats. This may be because the immune systems in young cats have not had time to develop fully. Furthermore, younger cats tend to have smaller amounts of skin oils (sebaceous lipids) that help protect the skin from infections. Older cats may also be at greater risk for contracting ringworm, because their immune systems tend to be weaker. Older cats may also have lower quantities of protective sebaceous lipids on their skin and fur.
Breed: Long-haired cats (such as Persians and Himalayans) seem to be at greater risk of getting ringworm than other cats. Some experts believe that there is a genetic (inheritable) factor that makes certain breeds at a higher risk of getting ringworm. It is also possible that long fur creates an environment that promotes fungal growth, or the long fur helps to spread fungal spores on the cat and its surroundings.
- Persians and Himalayans are often bred in catteries, where they are in close contact with many other cats. Catteries, therefore, create situations where ringworm can spread very easily. For this same reason, purebred (pedigreed) cats in general are at greater risk of having ringworm.
Habitat and environment: Because ringworm is spread easily between animals, cats that live in close contact with other cats or animals are at greater risk of contracting ringworm. Cats from farms, shelters, and breeding or boarding catteries have more chances of having ringworm. Because fungal spores are abundant in the environment, outdoor or stray cats (especially those living in warm and humid climates) also have an increased risk of getting ringworm. Cats may be more prone to catching and spreading ringworm simply because there are many more cats (both pets and strays) than dogs in the United States. It is estimated that there are 70 million pet cats (outnumbering dogs by about 10%) and 70 million more stray cats in the United States alone.
Health: Cats with injuries or other health problems tend to have weaker immune systems and may not be able to fight off infections very well. Therefore, if a cat is sick, has poor nutrition, or is on medications that affect immune responses, it may be at an increased risk of getting ringworm. Fungi that cause ringworm are also more likely to infect skin that is injured. Cats with feline immunodeficiency virus (FIV, or feline AIDS) have very weak immune systems and are especially at risk of getting ringworm.
Signs and Symptoms
- The signs and symptoms of ringworm may depend on where the infection occurs or how severe the infection is. Ringworm can affect any part of a cat's body, such as the claws, paws, skin, and hair. However, it occurs most often on the face, ears, legs, and feet, because these are the parts of the body where the skin is most likely to come into contact with fungi that cause ringworm.
- The classic signs of ringworm in cats are small bald patches of skin. These patches (lesions) may be inflamed, crusty, flaky, scaly, or covered with small pustules or pus-filled blisters. Lesions are often red with itchy skin (dermatitis). Very often, the first sign of ringworm is excessive scratching and shedding of fur. However, fungi that cause ringworm can grow on the skin, hair, or claws of a cat that shows no sign of disease.
- Ringworm usually starts out as small, round lesions on the skin. If the infection spreads, the patches may cover large areas of the body and may become bloody from scratching. Deep infections may result in kerion, a condition in which the infected skin becomes inflamed and raised or bumpy.
- If the infection occurs in the toes or affects the claws, the claws may become misshapen or discolored (often opaque).
- Dermatophytosis (ringworm) is not always easy to diagnose in cats, especially because not all infected cats show the classic signs and symptoms of infection. Moreover, feline ringworm infections seldom have the characteristic ring-like shape of human ringworm infections. Therefore, simply looking at the lesion is not a reliable way to diagnose ringworm. Several testing methods may be used to diagnose ringworm. Very often, a veterinarian may use more than one method to confirm a diagnosis of ringworm.
- Because cats can easily spread ringworm to other animals and humans, it is important to get an accurate diagnosis as quickly as possible if ringworm is suspected. Pet owners should keep cats with suspected ringworm separate from other animals and humans, and wash their hands after handing an animal that might have ringworm.
Wood's lamp: One of the simplest methods of diagnosing ringworm is using a Wood's lamp. This is a lamp that shines ultraviolet light (black light). Some types of fungi that cause ringworm will fluoresce (glow) bright green under a Wood's lamp. Only about half of all fungi that cause ringworm will fluoresce under a Wood's lamp, so veterinarians cannot rule out ringworm if a suspected lesion does not test positive by this method. However, because the Wood's lamp method is fast, easy, and inexpensive, it is often the first test used to determine if a suspected skin legion could be a ringworm infection.
Microscopic exam: A veterinarian may also pluck hairs or scrape skin cells from around a suspected lesion and inspect them under a microscope. The veterinarian will look for hyphae (threadlike fungal structures) or spores. A microscopic exam may also distinguish fungal infections from other skin parasites, such as mites. This is also a rapid and inexpensive testing method for ringworm and is accurate in about half of cases. However, spores are very small and easy to miss, so veterinarians will often perform additional tests.
Fungal culture: The most accurate way to diagnose ringworm is to perform a fungal culture. In this test, samples of skin or hair from a suspected lesion are placed on agar (a jellylike substance) containing nutrients that support fungal growth. This method not only confirms a fungal infection but can reveal the specific type of fungus.
- Veterinarians may assign a pathogen score, or p- score, based on the number of fungal colonies growing on the contact plate. This is done to determine the severity of the infection and to guide treatment. P-scores are assigned as follows: 1 (<4 colonies), 2 (5-9 colonies), and 3 (the plate is completely covered with fungal growth).
- Fungal colonies must be examined under a microscope to confirm diagnosis of ringworm. However, colonies can take up to a week or even longer to grow in a culture. Therefore, more rapid tests such as Wood's lamp and microscopic exams are usually performed first and confirmed with a fungal culture if necessary.
Biopsy: If the ringworm infection is deep in the skin or if other tests cannot reliably diagnose or rule out ringworm, a skin biopsy may be necessary. A sample of skin is taken from a suspected lesion, and a fungal culture may be performed. The biopsy can also be cut into thin sections and examined under a microscope. The veterinarian may apply a stain that makes the fungal hyphae or spores easier to see.
- Fungi that cause ringworm often grown on the skin, fur, and claws of cats without causing any symptoms. If the skin becomes infected, it may result in dermatitis (itching skin). Infected patches of skin may become papular (raised and bumpy) with crusty, acne-like eruptions. Although ringworm generally clears on its own within four months, more serious infections may require treatment and cause complications. Certain antifungal medications used to treat ringworm have also been associated with serious side effects.
- If ringworm is not treated properly, widespread lesions and alopecia (hair loss) may result. Cats with uncontrolled ringworm are also at a greater risk of bacterial and viral infections.
- Deep (subcutaneous) ringworm infection is known as dermatophytic pseudomycetoma. The lesions may become large ulcers with thick discharge. Severe dermatophytic pseudomycetoma can be fatal.
General: Ringworm may be treated with medications applied to the skin (such as creams, ointments, or shampoos) or with medications taken by mouth. The type of treatment usually depends on the cat's age, other health conditions, fur length, and how serious the ringworm infection is. Sometimes it is necessary to use a combination of treatments applied to the skin and those taken by mouth to cure ringworm. Some treatments may be performed at home, while others treatments require visits to a veterinarian. All treatments should be continued until the cat tests negative for ringworm (usually 1-2 months), even if symptoms have disappeared.
- For treatments applied to the skin, veterinarians may remove the cat's hair by clipping or shaving to help the treatment reach the infection. Hair removal may be useful for long-haired cats or for treatments that may disrupt the cat's fur (such as lime-sulfur treatments). However, some veterinarians discourage shaving, as it may spread isolated ringworm infections to other parts of a cat's body. If hair removal is performed, it should be done carefully to avoid spreading ringworm (especially to other animals or people), and the veterinarian should thoroughly clean any instruments (such as clippers) with an antifungal disinfectant.
- Veterinarians often use a pathogen score, or p-score, based on the number of fungal colonies growing on the contact plate to determine the severity of the infection and to guide treatment. P-scores are assigned as follows: 1 (<4 colonies), 2 (5-9 colonies), and 3 (the plate is completely covered with fungal growth). If there is a p-score of 1 or 2 with no skin lesions, the cat will be treated with a lime-sulfur dip and retested. If there are skin lesions present (regardless of p-score), or if there is a p-score of 3, veterinarians may recommend treating the cat both with medications applied to the skin and systemically with oral medications.
Lime-sulfur dips: Veterinarians consider topical lime-sulfur treatments (or lime-sulfur dips) to be relatively safe and recommend this treatment for kittens over three weeks old and cats that are nursing or pregnant. In this treatment, a warm-water solution containing 8% lime-sulfur is sprayed on the cat or applied with a sponge. The solution should not be rinsed or shampooed off, but the cat should be dried with a towel. It is usually recommended that this treatment be repeated 1-2 times weekly until the cat tests negative for ringworm with fungal culture.
- When the lime-sulfur solution is applied, care should be taken to avoid getting the solution in the cat's eyes. If the solution gets into the cat's eyes, saline solution should be used to flush the lime-sulfur out of the cat's eyes. After each treatment is applied, the cat should be prevented from grooming by a protective cone worn around the neck.
- This treatment may be performed at home using commercially available lime-sulfur concentrated solutions and following the manufacturer's instructions closely. Alternatively, most veterinarians can also perform this treatment. Lime-sulfur treatments are relatively inexpensive, generally safe, and usually effective. However, they can leave an unpleasant odor and yellow or green stains on clothing, furniture, or the cat's fur.
Antifungals applied to the skin: In short-haired cats and kittens that are otherwise healthy, ringworm infections that are localized (not widespread) may usually be treated with an antifungal cream, lotion, ointment, or solution. Common antifungal medications used to treat ringworm in cats include clotrimazole, miconazole (MicaVed®, Miconosol®, or Conofite®), or thiabendazole (Tresaderm®). Clotrimazole cream (1%) is available over the counter (OTC) in most pharmacies without a prescription and is commonly used to treat athlete's foot (a fungal infection of the foot, or tinea pedis) in humans. However, miconazole (usually a solution containing 1.15% miconazole nitrate) and thiabendazole (usually a solution containing 40 milligrams of thiabendazole per milliliter) are available by prescription only. The medication is applied to the affected area as directed by the veterinarian (usually once or twice daily for 2-4 weeks). If the infection does not clear up by the end of the treatment, or if side effects occur, the veterinarian should be contacted immediately.
Antifungals taken by mouth: Oral treatment (or combined treatments taken by mouth and those applied to the skin) with an antifungal medication is usually recommended for cats with lesions or widespread ringworm infections. Veterinarians may also recommend oral antifungal medications if a cat with ringworm does not response to treatment to the skin.
- Itraconazole (Sporonox®) and griseofulvin (Fulvicin®) are approved by the U.S. Food and Drug Administration (FDA) for treating ringworm in animals. Itraconazole is usually the preferred treatment. Other antifungals that are intended for human use, such as terbinafine (Lamisil®), may also be prescribed by veterinarians to treat ringworm. However, use is considered "off-label" because they are not FDA-approved for treating ringworm in animals.
Griseofulvin (Fulvicin®): Griseofulvin is a prescription-only antifungal medication that prevents fungal cells from dividing and multiplying. Once the fungus stops growing, the cat's own immune system can clear the infection. Griseofulvin is given at a dose of 25 milligrams per pound of body weight (about 50 milligrams per kilogram). It must be given with a fatty meal (such as tuna packed in oil) for the medication to be effective.
- Griseofulvin was the standard treatment for ringworm for decades and is somewhat less expensive than itraconazole (Sporonix®). However, its use is becoming less common, due to its known side effects, which may be fatal. Gastrointestinal side effects, such as nausea, diarrhea, and vomiting are very common, especially in kittens. Griseofulvin should not be given with phenobarbital, a seizure medication, which makes griseofulvin harder to absorb and less effective.
- Griseofulvin is known to cause birth defects, so it should not be given to female cats that are pregnant or lactating, that is, producing milk to feed their young. It should also not be used in male cats that are used for breeding purposes. Griseofulvin may cause serious liver damage, so it should not be given to cats that have liver problems. Griseofulvin is also dangerous to use in ill cats, especially those with feline immunodeficiency virus (FIV, or feline AIDS), because it can further weaken a cat's immune system.
Itraconazole (Sporonox®): Itraconazole is a prescription-only antifungal medication that weakens fungal cell walls, causing the fungus to die. It is usually given at a dose of 5-10milligrams per kilogram by mouth once daily (about 25 milligrams daily for an adult cat). Itraconazole can be expensive, but it has fewer known adverse effects than ketoconazole or letoconazole. Thus, it is the preferred oral antifungal medication for treating ringworm in cats.
- Although oral itraconazole is generally safer than the alternative (griseofulvin), it still carries a risk of adverse effects. Like griseofulvin, itraconazole should be given with food and should not be used in female cats that are pregnant or lactating. It should also not be used in male cats that are used for breeding purposes. Itraconazole may cause serious liver damage, so it should be used cautiously in pets with liver problems. Itraconazole can interact with many drugs, including antacids and anticoagulants, so the veterinarian should be informed of all of the other medications (if any) the cat is taking.
Fluconazole (Diflucan®) or ketoconazole (Nizoral®, Ketosidin®, Panfungol®): Fluconazole and ketoconazole are related prescription-only antifungal medications that stop fungal growth by preventing the outer layer (wall) of fungal cells from forming. These drugs are not approved by the FDA for use in animals, but they are often prescribed by veterinarians to treat ringworm and other fungal infections. They are generally prescribed at a dose of 2.2-13 milligrams per pound of body weight and given once or twice daily for up to several months.
- Fluconazole and ketoconazole can interact with many drugs, including antacids and anticoagulants, so the veterinarian should be informed of all the other medications (if any) the cat is taking. Fluconazole and ketoconazole should not be given to pregnant or nursing cats. Ketoconazole does not seem to be very effective against Microsporum canis, the most common cause of ringworm in cats. It may also harm the cat's liver. Therefore, many veterinarians discourage the use of ketoconazole in cats despite its widespread use. Fluconazole appears to be more effective than ketoconazole for some forms of ringworm, but this is not entirely clear.
Lufenuron (Program®): Program® is a medication that is given once monthly to control fleas, and some veterinarians have used higher doses to treat ringworm. However, most veterinarians now believe that the drug is not effective for treating ringworm. Thus, Program® is generally not recommended as a treatment for ringworm.
Surgery: Complicated cases of ringworm, such as deep (subcutaneous) infections, may develop into a condition known as dermatophytic pseudomycetoma. The lesions may become large ulcers or open sores with thick discharge. Severe lesions may need to be removed with surgery.
Vaccination: A vaccine, FeloVax MC-K, has been introduced for the treatment or prevention of ringworm in cats. However, the effectiveness of this vaccine is not certain. Veterinary experts believe that the vaccine only prevents symptoms from worsening and does not prevent the infection itself. Therefore, vaccinated cats may still be carriers of ringworm and transmit the disease to humans or other animals. Use of this vaccine by itself is generally discouraged.
Note: Some of the integrative therapies below may have been used or studied in humans. A qualified veterinarian should be consulted before making decisions about the medical treatment of animals.
Apple cider vinegar: Apple cider vinegar has purported antifungal effects. Many secondary sources recommend diluting one teaspoonful of apple cider vinegar in one cup of warm water and using the solution topically on ringworm infections. However, it is not clear if this treatment is effective. It is possibly not safe for cats to take apple cider vinegar orally or to use undiluted vinegar topically.
Grapefruit: One home remedy for treating ringworm in cats involves diluted grapefruit seed extract on infected skin. It is not clear if this treatment is safe or effective.
Papaya: One home remedy for treating ringworm in cats involves rubbing raw papaya on infected skin. It is not clear if this treatment is safe or effective.
Tea tree oil: Tea tree oil is a popular home remedy for fungal infections of the skin, such as tinea pedis (athlete's foot) in humans. Products applied to the skin containing tea tree oil are commercially available for treating ringworm in cats, and there are anecdotal reports that this treatment is effective. However, essential oils (including tea tree oil) can be extremely toxic to cats, especially those with other health problems (such as nerve disorders). There have been several reports of fatal poisonings with undiluted tea tree oil in otherwise healthy cats. Some manufacturers claim that topical treatments, such as shampoos, are safe for use in cats if they contain no more than 1% tea tree oil. Some experts warn that even this concentration may be toxic to cats. Therefore, pet products containing tea tree oil (or any herbal extracts) should be used cautiously in cats. A veterinarian should be contacted immediately if the cat shows signs of unusual behavior or poor health.
- Because cats can easily spread ringworm to other animals and humans, it is important for pet owners to keep cats with suspected ringworm separate from other animals and humans and to wash their hands after handling a cat that might have ringworm. It is important to get an accurate diagnosis as quickly as possible and to start treatment promptly if ringworm is confirmed. Pet owners should have new pets evaluated before bringing them home and get regular checkups for their pets.
- Many cases of ringworm can be traced to an area where there are many animals. This includes catteries, farms, kennels, shelters, pet stores, and even veterinary clinics. To avoid bringing ringworm into a home with cats, pet owners should only work with reputable breeders, kennels, and other animal organizations. Owners should also use caution when bringing home a new pet. Many shelters and pet stores treat their cats for ringworm before sending them home with new owners.
- Fungi, including those that cause ringworm, reproduce by shedding spores. These spores can survive for months on surfaces and can be easily spread in the air. It is important to immediately treat pets that have been infected with ringworm. If a pet has a suspected ringworm infection, it should be quarantined until it has been thoroughly checked and treated if necessary.
- Clothing, furniture, and surfaces should be thoroughly cleaned and disinfected to prevent ringworm from recurring. Furniture and carpets may be steam cleaned. Surfaces may be disinfected using diluted bleach (one part bleach, 10 parts water).
- A vaccine, FeloVax MC-K, has been introduced for the treatment or prevention of ringworm in cats. However, the effectiveness of this vaccine is not certain. Veterinary experts believe that the vaccine only prevents symptoms from worsening and does not prevent the infection itself. Therefore, vaccinated cats may still be carriers of ringworm and transmit the disease to humans or other animals. Use of this vaccine by itself is generally discouraged.
- This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).
Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.
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- Bond R. Superficial veterinary mycoses. Clin Dermatol. 2010 Mar 4;28(2):226-36. View Abstract
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- Centers for Disease Control and Prevention. www.cdc.gov
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- National Association of State Public Health Veterinarians, Inc. (NASPHV); Centers for Disease Control and Prevention (CDC); Council of State and Territorial Epidemiologists; American Veterinary Medical Association. Compendium of measures to prevent disease associated with animals in public settings, 2007: National Association of State Public Health Veterinarians, Inc. (NASPHV). MMWR Recomm Rep. 2007 Jul 6;56(RR-5):1-14. View Abstract
- Natural Standard: The Authority on Integrative Medicine. www.naturalstandard.com
- Nobre Mde O, Negri Mueller E, Teixeira Tillmann M, et al. Disease progression of dermatophytic pseudomycetoma in a Persian cat. Rev Iberoam Micol. 2010 Jun 30;27(2):98-100. View Abstract
- Rabinowitz PM, Gordon Z, Odofin L. Pet-related infections. Am Fam Physician. 2007 Nov 1;76(9):1314-22. View Abstract
- Scott FW, LaHunta A, Schultz RD, et al. Teratogenesis in cats associated with griseofulvin therapy. Teratology. 1975 Feb;11(1):79-86. View Abstract
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interpreted as specific medical advice. Users should consult with a
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diagnosis and/or health conditions, prior to making therapeutic decisions.