Introduction
Cat fungus refers to several types of fungal infections that can affect cats. It is caused by various species of fungi, including Microsporum canis, Trichophyton mentagrophytes, and Microsporum gypseum [1]. These fungi live on the skin, hair, and nails of cats and can spread between cats through direct contact. Fungal spores can also be picked up from contaminated environments. Cat fungus manifests as skin lesions, nail deformities, and hair loss. If left untreated, the infection can spread and become quite severe. However, with prompt diagnosis and treatment, the prognosis is good.
Types of Fungal Infections in Cats
Some of the most common fungal infections in cats include:
Ringworm
Ringworm is the most common fungal infection in cats, caused by dermatophyte fungi like Microsporum canis. Ringworm manifests as circular patches of hair loss and crusty, scaling skin. It is highly contagious between cats and other animals (Merck Veterinary Manual).
Aspergillosis
Aspergillosis is caused by Aspergillus mold spores that cats inhale. It often affects the nasal cavity and sinuses, causing sneezing, nasal discharge, or nosebleeds. The infection can spread to the eyes, brain, and lungs in severe cases (VMSG).
Cryptococcosis
Cryptococcosis is caused by Cryptococcus neoformans fungi found in soil or bird droppings. Cats are infected by inhaling the spores, which then spread through the body. It often causes skin lesions and swelling of the eyes or central nervous system (PetMD).
Histoplasmosis
Histoplasmosis is caused by Histoplasma capsulatum fungus and affects the lungs after cats inhale spores from contaminated soil. It causes respiratory symptoms like coughing, fever, and shortness of breath (Merck Veterinary Manual).
Transmission Between Cats
Fungal infections can spread between cats through direct contact or sharing of items and spaces. Some key ways transmission occurs between cats include:
Grooming/Biting: Cats regularly groom themselves and each other. Fungal spores on fur can be ingested during grooming. Biting during play can also spread infection if one cat has an open lesion. [1]
Shared Litter Boxes: Fungal spores can be present in litter and get transferred between cats using the same litter box. Maintaining clean litter boxes is important to reduce transmission. [2]
Shared Food/Water Bowls: Saliva and nasal discharge can transfer fungal spores to shared food and water bowls. Using separate bowls can limit spread between cats. [1]
Scratching/Biting: If one cat has a skin lesion from a fungal infection, scratches or bites can transfer fungal spores to another cat. Keeping claws trimmed reduces scratching risk. [2]
Transmission from Environment
Soil and other parts of the environment can be a source of fungal infection for cats. Fungus is commonly found in soil, especially soil containing decaying organic matter like leaves, grass clippings, and manure. Birds and rodents can also spread fungal spores in their droppings. Cats who go outside and dig in the dirt or explore areas with lots of decaying matter are at higher risk of coming into contact with fungal spores. Some specific fungi found in soil that can infect cats include Blastomyces, Histoplasma, Coccidioides, and Cryptococcus.
According to the CDC, cat-associated sporotrichosis is a type of fungal infection that can spread from cats to humans. The fungus responsible is called Sporothrix brasiliensis.
Transmission to Humans
There are a few ways humans can contract sporotrichosis from infected cats:
Handling Infected Cats: The fungus can enter the skin through scratches or bites from infected cats. Even handling an infected cat without getting scratched or bitten can potentially lead to transmission if there is skin-to-skin contact where the cat’s fur touches broken skin or mucous membranes on the human. Direct contact with discharge from the cat’s lesions can also cause infection in humans (1).
Inhaling Spores: In rare cases, humans can develop lung infections by inhaling spores from contaminated environments. This is more likely in settings where there are many infected cats in a confined space (2).
Immune Compromised Higher Risk: People with weakened immune systems, such as those with HIV/AIDS, cancer, or on immunosuppressive medications, are at higher risk of developing sporotrichosis. The infection can disseminate more widely in the body in immunocompromised individuals (1).
(1) https://www.cdc.gov/fungal/diseases/sporotrichosis/pdf/Sporothrix-brasiliensis-HCP-508.pdf
(2) https://www.cdc.gov/fungal/diseases/sporotrichosis/brasiliensis.html
Symptoms in Cats
Some common symptoms of fungal infections in cats include:
Hair loss: Patchy hair loss or bald spots can occur due to skin fungal infections like ringworm. The hair loss is usually localized to one or a few areas on the body.
Redness/inflammation: Fungal skin infections often cause red, inflamed skin in the affected areas. The skin may become scaly and thickened as well.
Nasal discharge: Upper respiratory infections from fungi like Cryptococcus can lead to chronic nasal discharge that contains mucus, pus or even blood (https://www.merckvetmanual.com/cat-owners/disorders-affecting-multiple-body-systems-of-cats/fungal-infections-in-cats).
Sneezing/coughing: Fungal respiratory infections can cause sneezing, coughing, and wheezing as the fungi irritate the nasal passages and lungs.
Lethargy: Systemic fungal infections that spread throughout the body can result in fever, appetite loss, and lethargy. Cats may seem depressed and lack energy.
Diagnosis
Diagnosing fungal infections in cats begins with a thorough physical exam by the veterinarian. They will check for skin lesions, ear discharge, nasal discharge, or other visible signs that may indicate a fungal infection. The vet will also ask about the cat’s symptoms and medical history.
If a fungal infection is suspected, the vet will often take samples for a fungal culture. This involves taking small skin scrapings, hair samples, or fluid samples from infected areas and sending them to a lab to be cultured. Any fungal growth in the culture can help identify the specific fungal organism causing infection. Fungal cultures provide a definitive diagnosis.
In some cases a biopsy may be done, particularly for infections affecting internal organs. This involves surgically removing a small sample of infected tissue and examining it under a microscope. The visual presence of fungal hyphae in the biopsy can confirm a fungal infection diagnosis.
According to one source, “Deep skin scrapes and cytology: While fungal structures are not commonly found during these procedures, they may provide supportive information such as the presence of inflammation and structural changes.” (Source)
Treatment
The primary treatment for fungal infections in cats is antifungal medication. Common antifungal medications prescribed by vets include itraconazole, fluconazole, terbinafine, and ketoconazole. These are usually given orally and the course of treatment can last 1-2 months or longer to fully clear the infection. Antifungal medication works by stopping the growth and reproduction of fungal organisms. Vets will typically start with a broad spectrum antifungal drug until lab results determine the specific type of fungus infecting the cat.
In addition to oral medication, topical antifungal creams, ointments, or shampoos may be prescribed to treat skin lesions directly. These can include miconazole, clotrimazole, or ketoconazole creams. For generalized skin infections, lime sulfur dips may be recommended 1-2 times per week. This helps remove scales and crusting and allows the topical antifungal to better penetrate the skin.
Keeping the cat’s environment clean is also important to limit reinfection. All bedding should be washed frequently in hot water and disinfectants can be used to clean hard surfaces. Other cats should be checked for infection and treated as well since fungi can spread between cohabiting pets. With appropriate antifungal treatment and environmental control, most fungal infections in cats can be cured within a few weeks.[1]
Prevention
There are several ways to help prevent fungal infections in cats:
Routine grooming – Regularly brushing and combing your cat’s fur can help remove dirt, debris, and excess hair that fungal spores can get trapped in. Be gentle, especially around any irritated areas of the skin.
Separate food and water bowls – Give each cat their own food and water dishes to prevent sharing that could spread infection. Wash all dishes regularly with hot, soapy water.
Clean the litter box daily – Scoop waste out of litter boxes daily and change the litter completely every 1-2 weeks. Disinfect the litter box with a gentle cleaner. This helps remove feces that could harbor fungal spores.
Limit outdoor access – Keeping your cat indoors avoids exposure to fungus in the soil and environment. If they go outside, check their coat and paws for debris when they come back in.
When to See a Vet
Cat owners should consult a vet if their cat is exhibiting persistent symptoms of a fungal infection that are not improving with over-the-counter treatment. Here are some key signs it’s time to see a vet:
- Skin lesions, scabs, or hair loss persists for more than 1-2 weeks despite OTC antifungal treatment
- Cat is excessively licking, scratching, or biting at infected areas
- Appetite loss, lethargy, or other signs of illness not improving
- OTC antifungal shampoos, creams, or medication do not seem effective
- Multiple cats in the home have similar fungal infections
- Infection seems to be spreading or getting worse
- Cat has a history of reoccurring fungal infections
- Immunocompromised cat with a fungal infection
A vet can properly diagnose the type of fungal infection through skin scrapings or fungal culture. Prescription oral antifungal medication may be necessary for stubborn infections. For cats with weakened immune systems, vets can provide guidance on ways to boost immune health and prevent reinfection.
