Ringworm

Ringworm is one of the most common skin infections that cats get. It is highly transmissible through physical contact, and often spreads in settings where cats are overcrowded, ill, stressed, or have poor nutrition. Fortunately, while it can be unsightly and difficult to treat, ringworm isn't usually itchy or painful, though it can be in rare cases.

Ringworm actually has nothing to do with worms. It is a fungal infection of the skin, hair, and nails caused by a group of fungi known as dermatophytes. The species of fungus that is responsible for the majority of cases of ringworm is Microsporum canis, which belongs to the same family as the fungus that causes athlete’s foot.

Ringworm is zoonotic, which means that it can be transmitted between species, including from cats to humans and dogs. In healthy cats and humans ringworm is self-limiting. It will typically resolve within 3-5 months, but it is extremely important to treat ringworm in order to prevent environmental contamination and the infection to other cats and humans.

Ringworm Appearance

A typical ringworm lesion appears as a round, red, raised 'ring' marking the boundary of inflammation and is often found on the face, ears, chest, groin, paws, and tail. The appearance of ringworm lesions can vary and may be mild or even undetectable. They can appear as bald patches or flaky areas similar to dandruff. In our experience ringworm is often first detected as very small patches of missing fur on the chin and neck and toes. See additional resources below for more images.

Photo credit: Past VOKRA fosters

What do I do if I Suspect My Foster Kitty has Ringworm?

First, immediately separate the affected cat from the rest of the household (e.g. put kitty in the bathroom) and then:

Contact your Foster Coordinator. It is very helpful to send clear photos of the affected area.
If your foster coordinator suspects it is ringworm, they will ask you to submit a Medical Concern form.

Kittens often have patches of scabby skin and hair loss, especially around the muzzle. This can be caused by crusted food and poor grooming habits and is not necessarily an indicator of ringworm, but it is good to be on the safe side and rule out ringworm.

Risk Factors

Ringworm can affect all cats, but cats with weakened immune systems, living in high-stress environments, with poor overall health or nutrition, and/or the inability to groom properly are generally more susceptible:

Kittens less than a year old (especially if they don’t have a mamma to groom them),
Senior cats,
Longhaired cats,
Immunocompromised cats, and
Cats that have been living outdoors.

Healthy adult cats and humans are usually quite resistant to infection unless the fungus comes into contact with broken skin. Warm and humid conditions tend to promote ringworm, so we often see cases of infection during the spring and summer.

The incubation period for ringworm is 2-4 weeks. Since ringworm can’t be transmitted until after birth, you usually won’t see kittens under 4 weeks old with ringworm.

Diagnosis

Photo credit: reddit/u/pythonidae_love

A Wood’s Lamp (a special ultraviolet light) is often used as a quick screen for ringworm. The Wood’s Lamp may glow bright lime green in the presence of fungal metabolites. However, using a black light is not a conclusive test for ringworm, as only about 50% of Microsporum canis will fluoresce and some other species that cause ringworm will not glow at all. It is also possible that other things, such as creams, will glow under a black light leading to a false positive.

A laboratory culture of the fungus is the most reliable method of diagnosing ringworm. Hairs and skin scrapings from the lesions are embedded in a DTM (dermatophyte test medium) which is observed for colony growth over 2-3 weeks. If colony growth is observed, the growth will be identified microscopically to determine whether it is indeed ringworm.

If there is a strong suspicion that the kitty has ringworm, it is best to start topical treatment as soon as possible! Waiting 2+ weeks for the results of the fungal culture to return will lead to an exponential amount of spores being released into the environment, making it much more difficult to disinfect the environment and prolonging the amount of time that the cat will need to be treated.

Treatment

The most effective treatment for ringworm involves a combination of topical treatment (2x/day), oral medication (1x/day), and environmental cleaning (2x/week). Most cats can be ringworm free in 3 weeks if this is followed.

Note: It is extremely important that you continue treating the cat for ringworm until 2 consecutive negative culture tests have been obtained, even if there is no longer any sign of skin lesions. If this is not done, new lesions will likely develop requiring another full round of treatment.

Topical Treatment

Preferred VOKRA Treatment

Lime-Sulfur is the most effective at sterilizing the coat to prevent further growth of ringworm.

Lime-Sulfur solution: use 8% concentration (8oz per gallon of warm water). DO NOT pre-wet the cat. Apply solution using a garden sprayer to entire body avoiding only the face. Keep the sprayer end close to the skin while applying. Use a small rag or sponge to apply solution to face, nose, and ears. If solution gets in eyes rinse thoroughly with water or flush generously with saline. DO NOT RINSE lime-sulfur off after application; wrap the cat in a warm towel for 10 minutes and leave to dry.

Chlorhexidine + Miconazole shampoo: Wet coat thoroughly. Apply and lather shampoo over entire body, use a small rag or sponge for the face, nose, and ears. Allow for 10 minutes of contact time. Rinse thoroughly. Dry the cat thoroughly and provide a heating disc or wrap in a warm towel until completely dry.

Additional Treatments

Antifungal Creams (active ingredients: Tolnaftate or Clotrimazole): Apply to lesions 2x/day. While these creams are not a very effective means of controlling ringworm when used on their own, they can be used in addition to lime-sulfur or antifungal shampoo. The creams are usually rich in Lanolin, giving them both anti-fungal and moisturizing properties. This may soothe the skin.

Tips for Bathing

When bathing: the solution has to stay on for a minimum of 10 minutes. During this time it can be a challenge to keep the kitten from licking it off. You can wrap the kitty in a blanket “purrito” and hold them while you’re waiting for the 10 minutes to pass. This will also help keep them warm. Treats can make bath time more bearable for the kitty!
After bathing or treating: be sure to wash your hands and sanitize any surfaces that your cat has been in contact with. It is best to have a separate set of clothes or a smock to use when treating the cats. You may also want to get a box of plastic gloves or a pair of rubber dish gloves to have on hand.

Clipping fur is unnecessary in short and medium haired cats and may worsen lesions through micro-abrasions on the skin and mechanical spread of spores. Reserve clipping for very long haired cats and those that may be unable to groom or have a matted coat. Nail trimming should be done throughout treatment as the fungus can hang out around the nails/nailbeds.

Oral Treatment

Sporanox (active ingredient: Itraconazole): The typical dose is 10 mg/kg once a day for 21 days. The treatment must be adjusted carefully according to weight and the dose must be increased regularly as the kittens gain weight. Sporanox is generally well-tolerated by most cats, but it's always good to watch closely for signs of possible side effects including vomiting, diarrhea, and or lack of appetite.

Environmental Cleaning

When you first identify ringworm, you will have to clean every area of the house where the cat has spent time. Dispose of any hard-to-clean items like cardboard scratching posts. Wash all of the cat’s other supplies like bedding, dishes, and toys in hot water and bleach. Vacuum all carpets and dispose of the bag after, or sanitize the inside of the vacuum with hot water and bleach. Carpets can be steam cleaned, but note that the steam from household steam cleaners usually doesn’t get hot enough to kill the spores. Spray Peroxigard on every possible surface.

It is important to quarantine the infected cat to an easily cleaned area to minimize the spread of fungal spores to other animals and the environment. Spores can survive in the environment for up to 18 months if not properly cleaned. We prefer using a large wire kennel that can be easily disinfected. The kennel should be disinfected daily and the bedding should be washed with hot water and bleach. Cats can be placed in the bathtub (kittens) or travel carrier while their kennel is being cleaned.

Clean surfaces thoroughly with a detergent. Follow by disinfecting with either Peroxigard or bleach:

Peroxigard: This is our preferred product for disinfection as it is less harsh than bleach. Instructions for Peroxigard as a fungicide: Dilute 1 part Peroxigard Plus concentrate to 40 parts water. Place this diluted solution into a spray bottle. Apply. Let sit for 5 minutes. Rinse with a damp cloth. If you have a 1000ml spray bottle, a 1:40 concentration will be 25ml of Peroxigard in 975ml of water.
Bleach: a 1:10 dilution of bleach can be used

What if I get ringworm?

For the most part, ringworm is little more than a minor annoyance for humans. It will usually start as a small itchy spot that may seem like a flea bite.

At first sign of a ringworm lesion, start applying over-the-counter antifungal cream 2x/day to any suspected spots. Apply well beyond the border of the lesion and continue to apply cream for 2 weeks after there is no longer evidence of lesions (putting a band aid over the spot can help prevent you from scratching the area and potentially spreading the ringworm). A prescription for anti-fungal cream can also be obtained from your doctor or a walk in clinic.

It is important to wash bedding and towels frequently, especially during the first few weeks. You can also use a tea tree oil shampoo. Fungal infections tend to happen after spores come into contact with injured or vulnerable skin: if you have cuts, scrapes, acne, or dry skin, keep these areas protected when handling cats with ringworm and wash well afterwards.