Common Fungal Infections in Cats: What You Need to Know
Fungal infections can be a serious concern for cat owners. These infections are caused by spore-producing organisms called fungi. While not as prevalent as bacterial or viral diseases, fungal pathogens can cause a wide range of illnesses in cats—sometimes affecting only the skin and other times spreading throughout the body. Understanding the most common types of fungal infections and their symptoms helps you keep your feline companion healthy.
How Do Cats Get Fungal Infections?
Cats typically pick up fungal infections from their environment. Soil is the most common source, but fungi also thrive on decaying organic matter and in animal feces. Cats may become infected by inhaling spores, ingesting contaminated material, or through wounds in their skin. Spores are incredibly resilient and can linger for years where conditions allow.
Most healthy adult cats have robust immune systems that fend off these invaders. However, stress, illness, immune suppression (from disease or medications), or prolonged antibiotic use can increase susceptibility.
Types of Fungal Infections in Cats
- Dermatophytosis (Ringworm): This is the most frequent skin fungal infection in cats. It's mainly caused by Microsporum canis, but other species like M. gypseum and Trichophyton mentagrophytes can also be culprits. Lesions often show ring-shaped hair loss and scaling; however, some cats carry the fungus without showing any signs.
- Cryptococcosis: Caused by Cryptococcus neoformans and C. gattii, this infection is often acquired from soil or pigeon droppings. It usually starts with chronic nasal discharge and sneezing but can progress to facial swelling or even neurological issues if it spreads to the brain.
- Coccidioidomycosis (Valley Fever): This disease is caused by Coccidioides immitis, especially common in arid regions like the southwestern United States. Signs include skin lesions, fever, weight loss, respiratory distress, lameness, and eye problems.
- Histoplasmosis: Infection with Histoplasma capsulatum, often found in soil rich with bird or bat guano (especially in humid river valleys). It can cause respiratory distress or spread to organs like lymph nodes and bone marrow.
- Blastomycosis: Caused by Blastomyces dermatitidis, this fungus thrives near waterways and moist soils. Symptoms include skin nodules, coughing, breathing difficulty, fever, eye involvement, and sometimes urinary or reproductive tract issues.
- Aspergillosis: Usually from Aspergillus fumigatus or A. felis, this infection targets the nasal cavities but may extend to facial tissues or even the brain—especially risky for certain breeds or immunocompromised cats.
- Sporotrichosis: Outdoor male cats are at higher risk for this infection caused by Sporothrix schenckii. It enters through wounds and causes ulcers or nodules on the face and limbs; it can also spread internally.
- Phaeohyphomycosis: Pigmented fungi like Alternaria, Cladophialophora, and others produce cutaneous nodules or draining wounds—often on ears or digits—and may invade deeper tissues if unchecked.
- Candidiasis: Most often a superficial issue caused by Candida albicans. Oral thrush is typical; invasive disease is rare but more likely in immunosuppressed cats.
- Mycetomas & Dermatophytic Pseudomycetoma: Mycetomas create granules within tissues (usually as subcutaneous nodules). Dermatophytic pseudomycetomas are rare deep-seated infections seen mostly in Persian cats with underlying ringworm.
- Rhinosporidiosis: Caused by Rhinosporidium seeberi, this rare infection produces polyp-like growths inside the nose (more often reported outside North America).
- Malassezia Yeast Overgrowth: This yeast lives on cat skin naturally but can overgrow—especially in Rex breeds or those with allergies—causing ear infections or dermatitis.
Main Symptoms of Fungal Infections in Cats
The symptoms vary depending on which fungus is involved and what part of the body it affects. Some general signs to watch for include:
- Patches of hair loss with redness or scaling
- Nodules under the skin; non-healing wounds; draining tracts
- Persistent fever; lethargy; poor appetite; weight loss
- Nasal discharge; sneezing; cough; trouble breathing
- Nervous system changes: seizures; blindness; odd behavior
- Lameness; swollen joints; bone pain
- Eyelid swelling; uveitis; retinal detachment; blindness
- Lymph node enlargement or organ swelling (organomegaly)
Zoonotic Risk: Can People Catch These Fungi?
A number of these infections—especially ringworm and sporotrichosis—are zoonotic (they can pass from cats to humans). Sometimes a cat shows no symptoms yet still spreads spores around your home. Good hygiene practices are crucial when handling infected animals.
Treatment Options for Fungal Infections in Cats
Treating fungal diseases requires patience because therapy often lasts for months. The approach depends on which fungus is involved and how far the infection has spread:
- Systemic antifungals: Drugs like fluconazole, itraconazole, posaconazole, ketoconazole, amphotericin B, terbinafine, and flucytosine are used based on organism sensitivity.
- Topical/oral treatments: For superficial cases such as ringworm or yeast overgrowth.
- Surgery: May be needed to remove masses or drain abscesses if present.
- Treat secondary issues: Supportive care for dehydration/nutrition plus treatment for any secondary bacterial infections.
- Avoid reinfection: Thorough cleaning of bedding/toys/environment is essential—especially where zoonotic risk exists.
- Zoonotic precautions: Isolation of affected pets when necessary to protect people at home (particularly those who are immunocompromised).
The Prognosis: What’s Ahead?
The outlook depends on both the type of fungus involved and how widespread the infection has become before treatment begins. Superficial infections like ringworm usually respond well to therapy if caught early. Systemic cases involving internal organs—or especially the brain—carry a much more guarded outlook. Prompt diagnosis combined with appropriate antifungal medication gives your cat its best chance at recovery.
