Cat Health

Ringworm In Cats (Dermatophytosis)

What Is Ringworm?

Despite the name, ringworm is not literally a worm. In fact, it is an infection of the skin and hair by fungi known as dermatophytes, thus the medical name dermatophytosis. The word ‘ring’ comes from the round, red, circular marking of the inflamed skin. However, the affected areas are not necessarily ring in shape. So the title is somewhat misleading.

Although found in soil and thrive in humid and warm environments, this fungal organism can live anywhere and is not restricted to ground. The spores can easily get on fur, clothing and blankets, which transport them indoors, where they are able to flourish just fine.

Ringworm is one of feline diseases that humans can contract. During an outbreak, cat guardians are often affected along with their pets. The good news is, although contagious, this disease is not life-threatening. In fact, it is treatable and avoidable if you know what to do.

Species Of Ringworm

Skin fungi vary in category based on their natural habitat, namely anthrophilic (on people), geophilic (in soil), and zoophilic (on animals). Some species of dermatophytes are species-specific, meaning that they will only infect one species, whereas others can spread between different species of animals or from animals to humans.

The type of ringworm that most commonly affects cats is Microsporum canis, a zoophilic fungus that has adapted greatly to cats that it may live on their skin and hair without causing any signs of disease. This species is infectious to dogs and humans. Other species such as Trichophyton mentagrophytes and Microsporum gypseum are less common, but can also cause ringworm in felines. These species are also zoonotic, meaning that it can also infect humans.

How Does Ringworm Develop?

Ringworm fungus are tiny. They may be carried on dust particles and air currents. Once they reach the coat, if the spores survive kittie’s natural defense mechanisms (e.g. grooming and sunbathing), they cling to keratinocytes, the cells on the skin and hair shaft (sometimes on the nails too). 

The fungus exploits keratin protein as its main source of nutrition. It produces enzymes that consume dead, keratinized tissue, reproducing millions of spores that develop into new microorganisms as it consumes. The fungi then penetrate the hair. Then, hair shafts turn brittle and readily broken. Skin scales and hair fragments are shed into the air, along with hundreds of spores. They can linger for months to years in the environment that serves as an infected container for cats and humans stepping into it.

How Does Ringworm Infect Cats? 

The sole presence of a ringworm spore on the coat isn’t enough to render infection and ailments. Kitties (and hoomans) must be in contact with a number of spores before an infection happens. Depending on the circumstances of exposure and each individual, the minimum number varies. Having said that, they become infected with ringworm when exposed to infectious spores. This happens through contact with a contaminated object, an infected animal, or a contaminated environment.

Cats in catteries and animal shelters are much more likely to acquire ringworm than pet cats. Isolation of this fungus from just one kitten or cat in the surrounding necessitates treatment of the entire place. This is because they may catch ringworm indirectly by merely touching the toys, bedding, water and food dishes, as well as other items that infected cat has come in contact with.

Which Cats Are More Likely To Suffer From Ringworm?


One way cats remove ringworm spores from their coat is by grooming. Himalayans and Persians tend to groom less, making them more prone to getting ringworm infection. However, long-haired cats are more susceptible because the long hairs make removing the spores tricky when grooming. Furthemore, matted hairs that commonly happen with long hair increase infection from ringworm. Grooming is important to help cats limit ringworm infection. This may be why older and sick cats are more likely to develop the condition as they have lost the flexibility to groom. 

Generally, kittens are the most vulnerable, with the forelimbs, face, ears, head primarily involved. Experts speculate that the ears and face of a kitten are commonly affected spots,. Although groomed well by mother cat, these areas tend to not be very well groomed by kittens themselves. Interestingly, kittens often have lesions around the time of weaning, which supports this theory.

Concurrent disease can also make infection occur easier. For example, cats affected with feline immunodeficiency virus (FIV) are 3 times more likely to contract ringworm than healthy cats. Genetics may also play a role in a cat’s vulnerability to ringworm. Studies have shown that extreme ringworm infections are prevalent in catteries where cats were genetically related. This happens when breeders unintentionally select susceptible cats when breeding for certain coat characteristics.

Who Is More Likely To Contract Ringworm?

People who are immunocompromised have a higher risk of acquiring ringworm from an infected cat. These are organ transplant recipients, people with HIV infection or receiving chemotherapy, the very young, or the very old.

Signs Of Ringworm On Cats


Signs of ringworm infection have an array of presentations. Generally, ringworm is not an especially itchy disease, although some cats have mild itchiness (pruritus), while others are severely itchy and will scratch to the point of mutilating. Itchiness of one or both ears is a less common sign of ringworm, but has been seen every now and then.

A few cats with ringworm disease develop rough or crusty only claw infections (onychomycosis ) as their clinical sign of ringworm. Otherwise, ringworm causes hair loss (alopecia), and the areas often have redness when first develop. This may be mild or chronic, and may be in a symmetrical pattern or be completely asymmetrical. Ringworm lesions also tend to be crusty. Usually, the scaling is subtle, but in some it’s quite extreme. Then, ringworm infection can cause darkening skin (hyperpigmentation). For young cats, ringworm occasionally causes blackheads on the chin of young cats.

Cats with hair loss from overgrooming are sometimes the result of ringworm infection. So check with your vet to determine the actual cause. Long-haired cats may have ringworm without any sign of hair loss. They are called asymptomatic carriers as they may infect others without anyone knowing they are carrying the fungus. 

Ringworm Is A Lot Like Other Diseases

Cats can experience itching and hair loss from mange and fleas. They may also lick their fur excessively due to stress, anxiety or allergies. Due to its close similarities to other issues, ask your veterinarian to do other tests as misdiagnosis can have your cat consuming the wrong kind of medication.

Diagnosing Cats With Ringworm

Veterinarians commonly diagnose ringworm infection through fungal culture. This is done by plucking hairs from affected cats with a sterile hemostat and placing them on a designated fungal culture medium. Most practices use “dermatophyte test medium” as it has a color indicator that will turn medium red when a ringworm begins growing on it. However, this method takes over a week for result.

To better sample the fungal culture, shining a fluorescent light (Wood’s lamp) on the coat might help. Half of Microsporum canis will glow “yellow-green” or “apple-green” under the lamp, the fluorescence being a metabolite that growing fungi secrete onto the hair. The Wood’s lamp is merely a screening tool. Therefore, you shouldn’t use it to definitively diagnose ringworm. But if the cat with fluorescent hair is confirmed to have ringworms via fungal culture, you may use Wood’s lamp to monitor the response to treatment. Depending on the stage of infection, fluorescent hairs will show various patterns. During an early or active infection, the entire hair length will glow. As the infection diminishes, only the tip of the hair will glow, most likely because the hairs are healing, so the base of the hair shaft no longer has ringworm. The number of fluorescent hairs should also lessen during treatment.

Next, by using a microscope, your vet can scrutinize for Microsporum which are fungal spores. They will place a piece of clear tape on the lesion, which then picks up cells that they later stain. The special purple stain will make small ellipses with lines faintly visible.Those are ringworm spores!

Although invasive, skin biopsy is also accurate for diagnosing ringworm. Your vet will cut out a piece of skin and send it for microscopic analysis, which can take several days for results. If you prefer a non-invasive test, there is a new method called PCR, that’s similar to culture test, uses hair and skin but can detect ringworm in a matter of few days.

How To Treat Ringworm On Cats

Veterinarians should set two goals when forming a treatment plan for ringworm: cat treatment, and environment disinfection. Both are compulsory to prevent reinfection in felines, and people contracting this disease.

Treatment plans may vary somewhat for each individual cat that are ringworm positive. But all of them involve a combination of trimming the hair coat, systemic (oral) antifungal medication, topical therapy, and suggestions for sanitization of contaminated environment. To achieve a great success in treatment, feline practitioners suggest an aggressive therapy, which is trimming the coat, using oral medications and bathing with antifungal shampoos.

The treatment plan must include other furry friends in the household. Therefore, veterinarians should also perform fungal culture on all other animals in contact with or living with the infected cat. While waiting for the test results, you should bathe other pets twice a week.

Coat Trimming

First step in therapy for an infected cat is to determine whether to trim the coat or not. When ringworms invade the hairs, these fungi make them easily broken. When the hair shafts snap, damaged hair particles and spores are shed into the air and onto the cat’s fur. Shedding intensifies the risk of spreading the ringworm, also increasing the possibility of re-exposing the spores in the environment to said cat. This will cause kitty to continuously test positive for ringworm. Trimming the coat removes affected hairs and minimizes continued shedding of hair particles and spores. It also allows for better penetration of topical medicated shampoos. 

As the general rule, if a short-haired cat has five or more subtle spots of ringworm, trim their entire coat. If a short-haired cat has less than five subtle spots, trim only the hair around each spot. If the cat is long-haired, trim the entire coat regardless of how many subtle ringworm spots are palpable on the coat.

Topical Treatment

All cats that are ringworm positive should receive topical therapy as it minimizes the spread of infectious spores into the surroundings. Moreover, it helps remove infectious crusts and spores from the fur. Without topical therapy, treatment can take longer, even more costly.

Topical products like Miconazole is effective by itself, or in combination with chlorhexidine. Malaseb shampoo, which is a combination of chlorhexidine and miconazole, is also very effective against ringworm. For the shampoo to be effective, bathe your cats twice weekly, and leave the shampoo on them for 10 minutes before rinsing. Dipping them in lime-sulphur or enilconazole are helpful in treating ringworm too.

Generally,  veterinarians will not recommend local topical therapy with creams and ointments, because they are messy, easily licked off when grooming, and tempt cat guardians to try spot treatment instead of aggressive treatment with oral medications and shampoo. However, feline practitioners asserted that miconazole lotion can be helpful when applied to affected areas on non-bathing days.

Oral Medication

The key to curing ringworm is systemic treatment with an oral medication. Ideally, you should not use these drugs in kittens younger than 8 weeks (instead, resort to topical treatment). Effective drugs that veterinarians recommend include griseofulvin, ketoconazole, terbinafine and itraconazole. When given 10 mg/kg once daily, everyday, for 6 weeks, itraconazole is very effective. But due to the capsule size, it should only be prepared by a compounding pharmacy, as they will custom it into a form that allows proper dosing. They may also prepare a flavored liquid that makes dosing more preferable to cats. If side effects occur, they tend to only be decreased in appetite and vomiting.

Decontamination Of Objects And Environment

Finding out your cat is ringworm positive naturally means disinfecting the living spaces they had accessed. This is to kill the remaining spores, as they can lie dormant for up to 18 months in the environment, which presents risk of re-infection. 

Physically Removing Particles And Objects


Firstly, sanitize or dispose of any object such as grooming tools, baskets, collars and bedding with diluted bleach solution. You can use cardboard boxes as make-shift beds and dispose of each at least once a week. Secondly, thoroughly vacuum clean contaminated areas everyday, and burn the vacuum bags to completely destroy the spores. You can also vacuum fabrics in your home if you can’t wash them. Under suitable circumstances, you may use a blow-lamp to burn hairs off cages and wire runs.

Chemical Disinfection

ringworm in cats

Make sure you dilute the bleach solutions using the correct ratio (1:20) and spray it on every area, nook and cranny. After that, wait for a full 10 minutes contact of the beach solution and the surface to ensure thorough disinfection, before wiping it dry.

How To Prevent Ringworm Infection


Ringworm is undoubtedly contagious. But it’s preventable if you take the appropriate steps. The easiest way to decrease the risk of anyone or any cat getting ringworm is to wash your hands before and after touching cats. In addition, keep your indoor cat(s) away from other cats that are not within the same household. 


When handling infected cats, it is crucial to wear gloves during contact, and thoroughly wash your hands afterwards. On the other hand, if you are the one with ringworm, avoid handling your cat until the doctor declares you no longer have the infection.

I Adopt A Cat!

Before introducing a new cat into your household, first isolate the new cat. Then, brush all over their coat, and perform a fungal culture using the hair on the brush. With the condition that the result is negative, you may safely introduce the new cat.

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