What is ringworm in cats and how do you treat it?

Ringworm Trusted Source Centers for Disease Control and Prevention (CDC) Federal agency. Go to source — dermatophytosis in medical terms — is a fungal infection on the top layers of the skin, hair, and nails that affects both humans and household animals like cats and dogs. Unlike its name may suggest, ringworm isn’t caused by worms but by a specialized group of fungi known as dermatophytes.

While there are different species of ringworm, cats, dogs, and humans tend to catch and transfer the same species: Microsporum canis (M. canis). The other two most common ringworm species include Microsporum gypseum and Trichophyton mentagrophytes, which are also contagious to cats, dogs, and humans.

Ringworm is spread by direct contact or touching an object or surface that an infected person or animal touched. It often causes a round, red, raised ring-like rash that’ll appear on your cat’s face, ear tips, tail, and feet, but this isn’t always the case.

Sometimes there are no symptoms at all, especially with long-haired cats. Unfortunately, it can be challenging to detect in cats since the lesions may be very mild or undetectable. Besides the tell-tale ring-like rash, several other symptoms may indicate ringworm:

• Scaling. This is often described as a “cigarette ash” scaling that appears on your cat’s cat. You may also notice round, thickened patches of skin with hair loss.
• Hair loss. Also called alopecia, it includes fur loss on your cat’s coat, including bald spots, patchiness, or thinning. Ringworm causes hair loss in cats by infecting their hair shafts, making the infected hairs frail.
• Solid bumps. Itchy small, solid bumps called miliary dermatitis may appear on your cat’s skin. As the ringworm progresses, these bumps can become larger and open sores.
• Claw infection. Ringworm can cause a condition in a cat’s nails called onychomycosis, which causes their claws to become rough, pitted, and potentially deformed.
• Excessive grooming and scratching. You may notice your cat vigilantly cleaning themselves if they have ringworm. It can also cause your cat to obsessively itch, though this isn’t always the case.
• No symptoms. Some cats, especially long-haired breeds, may have ringworm without any clinical signs or hair loss. These cats are called asymptomatic carriers.

Ringworm is transmitted by direct contact with an infected animal or person, or by handling or touching a contaminated object or surface. But just because you came into direct contact with the infection doesn’t mean your cat will get it.

Age plays a significant role in whether you may be more prone to contracting ringworm. In humans, older adults, young children, and individuals with weakened immune systems are more prone to becoming infected after contact with ringworm.

Similarly, kittens and immune-compromised and elderly cats are more prone to infection after contact. On average, the incubation period for ringworm is seven to 14 days. After that, symptoms and ringworm lesions may occur. However, it can sometimes take up to 21 days for your cat to start showing symptoms, if at all.

The most accurate way for your veterinarian to detect ringworm is by taking a fungal culture using plucked hairs from your cat. Results for traditional fungal cultures take up to three weeks, but IDEXX (a common diagnostic lab company used by many vets) has a fungal PCR test that produces results in two to three days.

Vets may also use a Wood’s lamp, which is an ultraviolet light that causes your cat’s ringworm to glow yellow-green. While this lamp is less than 50% accurate in M. canis cases, it can be used to look for hairs your vet may want to test.

In addition, if your cat is experiencing hair loss, especially without other ringworm symptoms, your vet may want to run tests to check for and rule out additional causes. Sick visits and diagnostic tests may be covered by pet insurance.

While ringworm may clear up on its own, treatment is highly recommended to minimize and stop the infection. Treating ringworm is a long process that can last up to three to five months. The most common way to treat ringworm in cats is to use a combination of topical therapies and systemic oral therapy and thoroughly clean the cat’s home. Here’s a closer look at each method:

• Topical treatments. You can apply various topical ointments and creams to localized areas of the skin that ringworm affects. Shaving your cat’s hair in small areas may be necessary if the infection is severe enough and concentrated in one or two areas.
• Medicated dips or baths. If your cat has ringworm in multiple places on their skin or they’re a long-haired breed, your veterinarian may recommend clipping all of your cat’s hair, along with bathing your cat with a medicated shampoo.
• Oral treatment. The most widely used oral treatments are itraconazole or terbinafine (Lamisil). Treatment usually lasts for a minimum of six weeks.
• Environmental cleaning. Infected hairs contain numerous microscopic fungal spores that your cat can shed into the environment. The spores can live on surfaces like bedding and carpets for up to 18 months. It’s important to thoroughly clean your home after a ringworm diagnosis to prevent infecting other animals or humans. Keeping the home environment as clean as possible is as important as minimizing direct contact with your cat.