Cats get fungal infections through three main routes: direct contact with an infected animal, inhaling spores from contaminated soil or droppings, and penetration through wounds or broken skin. The specific route depends on the type of fungus involved, but environmental exposure is the most common thread. Even strictly indoor cats can be at risk.
Direct Contact With Infected Animals
Ringworm is the most familiar example of a contact-transmitted fungal infection in cats. The fungus lives on the skin and hair of infected animals, and cats pick it up by touching or grooming an infected cat, dog, or rodent. Shared bedding, brushes, and furniture can also harbor fungal spores for months, making shelters and multi-cat households particularly high-risk environments. A cat doesn’t need to have visible skin lesions to spread the infection, which is why outbreaks in catteries can be difficult to contain.
Ringworm is also one of the most common fungal infections that cats pass to people. If your cat has patchy hair loss, scaly skin, or crusty lesions, especially around the ears, face, or paws, those are classic signs. Treatment typically combines oral medication with topical antifungal washes, and it takes a long time: at least 10 weeks in most cases, continuing until fungal cultures come back negative on two consecutive tests spaced one to three weeks apart.
Inhaling Spores From Soil and Droppings
Several of the more serious fungal infections in cats start in the lungs. Cats breathe in microscopic spores from contaminated environments, and the infection can then spread to other organs. The fungi responsible live in soil, and their growth is often fueled by bird or bat droppings.
Cryptococcosis is a good example. The fungus thrives in soil enriched with pigeon droppings, where it produces spores small enough to reach deep into the lungs when inhaled. It’s the most common systemic fungal infection in cats and often shows up as nasal swelling, chronic sneezing, or skin nodules on the face.
Histoplasmosis follows a similar pattern. Cats inhale spores from soil contaminated with bat and bird feces. It’s most common in humid regions, particularly the Midwest and South-Central United States, though cases have been reported much more widely than scientists originally expected. Cornell University’s Feline Health Center notes that even indoor cats can be exposed through potted plants or unfinished basements where spores may accumulate.
Blastomycosis, another inhaled fungal disease, clusters in specific geographic hotspots. Northern Minnesota and Wisconsin have notably high rates, as does western Ontario in Canada. Valley fever, caused by a different soil fungus, is concentrated in the arid Southwest: southern Arizona, the San Joaquin Valley in California, and parts of New Mexico, Nevada, Utah, and West Texas along the Rio Grande.
Wounds and Skin Breaks
Some fungi enter through cuts, scratches, or puncture wounds rather than through the lungs. Sporotrichosis is the classic wound-entry infection. The fungus lives on soil, decaying plant matter, sphagnum moss, rose bushes, and hay. Cats typically pick it up when a thorn prick or scratch exposes tissue to contaminated material.
What makes sporotrichosis unusual is how aggressively cats can then spread it. Infected cats carry high levels of the fungus in their skin lesions and can transmit it to other cats, other animals, and humans through bites, scratches, and even sneezes. In Brazil, a particularly virulent strain has become a significant public health concern, causing more severe disease in both cats and people than other forms of the fungus. The CDC recommends that any unexplained skin lesion following a cat scratch or bite be evaluated, especially if the cat has ties to South America.
How a Weakened Immune System Changes the Picture
A healthy immune system keeps many fungi in check. Cats carry small amounts of yeast on their skin all the time without any problems. When the immune system is compromised, those normally harmless organisms can multiply and cause disease.
Feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) are two of the biggest risk factors. Cats with these retroviruses don’t typically get sick from the virus itself. Instead, the immune suppression it causes opens the door to secondary infections, including fungal ones. Yeast overgrowth on the skin, chronic ringworm that won’t clear, and systemic fungal infections that a healthy cat would fight off can all be consequences of retroviral infection.
Diabetes is another predisposing condition. Cats with diabetes or other metabolic diseases are more prone to yeast overgrowth on the skin and in the ear canals. Certain breeds also carry higher baseline risk: Sphynx and Devon Rex cats tend to harbor more yeast on their skin naturally and often develop a greasy buildup around their claws and claw folds, even without an underlying illness.
Why Indoor Cats Aren’t Fully Protected
Living indoors reduces a cat’s exposure to contaminated soil, but it doesn’t eliminate fungal risk. Spores are microscopic and travel easily. You can carry them inside on shoes and clothing. Potted plants may contain contaminated soil. Basements, crawl spaces, and areas where bats or birds have roosted can harbor spores for years.
Indoor cats can also pick up ringworm from a new cat entering the household, from visiting a groomer or boarding facility, or even from contact with contaminated objects brought into the home. If your indoor cat develops unexplained skin changes, hair loss, or chronic nasal symptoms, a fungal infection is worth considering regardless of lifestyle.
Recognizing the Signs Early
Fungal infections in cats don’t always look the same because different fungi target different parts of the body. Skin infections like ringworm cause hair loss, scaling, and crusty patches. Yeast overgrowth tends to produce greasy, itchy skin, often in the ears or around the nails. Respiratory fungal infections may start with sneezing, nasal discharge, or labored breathing before spreading to the skin, eyes, or nervous system.
Systemic infections like cryptococcosis and histoplasmosis can be subtle at first, with vague signs like weight loss, lethargy, and poor appetite. By the time more obvious symptoms appear, such as facial swelling or draining skin nodules, the infection may be well established. Cats with FIV, FeLV, diabetes, or other chronic conditions deserve extra attention to these early, nonspecific changes.