The Cryptococcus gattii species complex can also cause the disease. Symptoms alone cannot distinguish which species is responsible in a cat. Although cryptococcosis is among the most common systemic fungal diseases in cats, it is rare overall or occurs only sporadically.
When to see a vet urgently
Go to an emergency vet immediately if your cat has any of the following symptoms:
- Breathing is difficult or your cat breathes with its mouth open.
- Your cat has seizures, collapses or has an altered level of consciousness.
- Vision suddenly deteriorates or your cat starts bumping into objects.
- Your cat cannot walk normally or its coordination deteriorates rapidly.
You can find a vet near you. A persistent nasal discharge or a skin lump that does not heal also needs investigation, even without emergency signs.
Overview
Cryptococcosis is caused by the yeast-like fungus Cryptococcus neoformans, which lives in the environment, particularly in enriched soil containing bird droppings, especially those of pigeons. Cats become infected by breathing in fungal spores. The initial lesion is usually in the nasal cavity and respiratory tract, but infection can spread to the brain, eyes, skin and internal organs. The disease can often be chronic and hidden behind symptoms resembling other respiratory or neurological diseases.
Environmental sources of the fungus also include decaying vegetation and wood. Exposure therefore does not require direct contact with a bird. Small infectious particles carried in the air can enter the respiratory tract unnoticed, and the exact place where an affected cat became infected is not always found.
The disease may remain in the nasal cavity or occur as a skin, nervous system or systemic disease. Not every cat develops these forms in the same order. Nasal disease is common, but the absence of neurological or skin findings does not establish that the infection is definitely localised.
Causes
The main factors involved in infection include:
- Inhaling fungal spores from the environment, particularly where bird droppings are present.
- A weakened immune system due to chronic disease, stress or immunosuppressive medicines.
- Living in endemic areas where the fungus is common in soil and air.
- Contact with soil and places contaminated by bird droppings, especially pigeon droppings.
It is important to distinguish infection from factors affecting resistance to disease. The fungus must be acquired from the environment; stress or chronic disease alone does not cause cryptococcosis. Some fungi reaching the respiratory tract may also remain as superficial colonisation without tissue-invasive disease. Disease itself develops when the fungus starts damaging tissues.
Risk factors
- Cats with outdoor access.
- Animals with viral infections, such as feline immunodeficiency virus or feline leukaemia virus.
- Young and old cats with weakened immune systems.
- Living in areas with large numbers of pigeons.
Research in cats on risk factors is partly conflicting. The disease has also been found in indoor cats, and outdoor access alone does not explain why a cat becomes ill. Studies have reached differing conclusions about the effects of FIV and FeLV infection on disease development and prognosis. Cryptococcosis therefore does not automatically indicate immune deficiency, and normal immune function does not rule it out.
Main symptoms
Symptoms depend on the location of the disease:
- Respiratory signs: sneezing, nasal discharge, often bloody or containing pus, and difficulty breathing.
- Neurological signs: seizures, behavioural changes, impaired coordination and blindness.
- Skin signs: lumps, sores and draining tracts around the head and neck.
- General condition: lethargy, reduced appetite and weight loss.
In the nasal form, swelling of the muzzle or bridge of the nose can be a prominent finding. A polyp-like mass may be visible in a nostril, and discharge may come from one or both nostrils. However, such a change is not specific to fungal disease, so samples are needed for diagnosis.
Skin lumps may be painless and not itchy before they ulcerate. Eye changes can include a poor pupillary response to light, inflammation of the choroid and retina, or retinal detachment. Enlarged lymph nodes, joint symptoms or bone changes can also be associated with disseminated disease. Tell your vet about every change you have noticed, rather than only the nasal discharge.
Complications and consequences
Without treatment, cryptococcosis can lead to:
- chronic rhinitis and sinusitis
- central nervous system damage, including meningoencephalitis
- severe neurological disorders and paralysis
- blindness when the eyes are damaged
- disseminated infection, which often ends in death
Central nervous system inflammation can damage the function of both the brain and its surrounding membranes. Sight loss may be associated with damage to eye tissues or a problem with the optic nerve. Although the neurological form is serious, it does not always mean treatment cannot succeed. Treatment options are assessed in the context of the cat's overall situation.
Diagnosis at the vet
Diagnosis is based on:
- cytological examination of discharge from nasal and skin lesions
- serological tests detecting Cryptococcus antigen in blood or cerebrospinal fluid
- culturing samples on fungal growth media
- X-rays or CT scans of the chest and skull to assess the spread of infection
- brain MRI when neurological symptoms are present
Cytology examines cells and any yeast cells in a sample under a microscope. A sample may be obtained from a skin lump or nasal lesion, for example. If the organism is not detected in a surface sample, a tissue sample may provide further information. Investigating a visible lump helps distinguish infection from a tumour, for example.
The antigen test looks for a substance associated with the fungal capsule. This is different from measuring antibodies. The test can support diagnosis, and changes in the level can help monitor treatment response. However, the blood test can be negative in localised nasal or skin disease even when infection is present. Tissue samples then become particularly important.
Fungal culture, antigen detection and drug susceptibility testing answer different questions. Culture can provide the fungus itself for investigation, while susceptibility testing helps assess medicine options. Not every patient needs every method. The combination of investigations is selected according to the samples available and the information needed for treatment decisions.
Imaging helps establish the location and extent of changes, but an image alone does not confirm cryptococcosis. Cerebrospinal fluid is not sampled automatically in every cat with neurological signs. The need and safety are assessed separately, after brain imaging where necessary.
Treatment and monitoring
Treatment is based on a prolonged course of antifungal medication. The choice of medicine depends on the infection's location and extent, other illnesses and how treatment can be managed in practice. Infection in the nervous system or eyes needs a medicine that reaches those tissues. Severe disease may require a combination of medicines and initial treatment in hospital.
Removing some nasal or skin masses can complement medication. However, removing a visible lump alone does not address treatment of the whole disease, as other sites of infection may remain. The treatment plan also takes account of problems with breathing, eating and general wellbeing.
During treatment, changes in antigen results and possible medicine side effects are monitored alongside symptoms. Blood tests can monitor liver function, for example. Kidney health can also affect the choice of medicine and how treatment is given. Tell the treating vet about new loss of appetite, vomiting or any other change in your cat's condition.
The decision to end treatment is made from test results and the clinical situation. Nasal discharge or skin changes may improve before the prolonged treatment programme is complete. Do not stop medication on your own initiative at the first visible improvement. Follow-up may also be needed after treatment ends.
Prognosis and relapse
Many cats can be treated successfully, but the prognosis varies. Nervous system involvement can reduce the chances of recovery compared with localised disease. Long-term follow-up of patients has also found relapses, sometimes even after blood antigen results have become negative.
A negative follow-up result is therefore useful, but it does not guarantee that symptoms cannot return. If nasal discharge, lumps, eye symptoms or neurological changes recur, a fresh assessment is needed. Treatment outcome studies describe groups of patients; they cannot promise a definite cure for an individual cat.
Prevention
- Minimise contact with areas containing pigeons and their droppings.
- There is no vaccine against cryptococcosis: avoiding pigeon droppings and promptly treating diseases that weaken immunity, such as FIV and FeLV, can reduce risk.
- Keep the places where pets are housed clean.
- Avoid uncontrolled outdoor access in affected areas.
No reliably effective prevention methods have been demonstrated. Environmental cleanliness and avoiding accumulations of droppings therefore do not guarantee complete protection, and it is impossible to make all outdoor air or soil free of the fungus. No vaccine is available.
What it means for owners
Cryptococcosis in cats is a serious disease requiring early diagnosis and prolonged antifungal medication. Cryptococcus fungi, C. neoformans and C. gattii, are also dangerous to people with weakened immune systems, but transmission from cats to people effectively does not occur: both cats and people acquire infection from the environment. If your cat shows signs of cryptococcosis, take it to a vet immediately.
Human disease is usually associated with inhaling the fungus from the environment. Risk is higher in people with weakened immune systems. A cat's diagnosis may therefore indicate shared environmental exposure, but illness in a cat living in the same home does not itself mean transmission from the cat. Discuss concerns about your own health with a healthcare professional.
Note: this material provides general information and does not replace treatment advice. Contact a vet if you notice the first symptoms.
Frequently asked questions
Can an indoor cat get cryptococcosis?
Yes. The fungus can be carried from the environment into the air a cat breathes, and the disease has also been described in indoor cats. A lack of outdoor access alone does not rule it out.
Does a negative blood test rule out cryptococcosis?
Not in every situation. Localised nasal or skin disease may go undetected by a blood antigen test. Your vet may then need a sample taken directly from the lesion.
Can I stop the medicine when the nasal discharge disappears?
Not on your own initiative. Treatment is prolonged, and stopping it also depends on investigations and your vet's assessment. Symptoms may improve before the infection is sufficiently controlled.
Can cryptococcosis spread from an infected cat to a person?
The disease is not considered transmissible from cats to people. Both cats and people can acquire the fungus from the same environment. People with weakened immune systems should discuss concerns about their own exposure with a healthcare professional.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- GUIDELINE for Cryptococcosis in Cats, European Advisory Board on Cat Diseases, accessed 2026-11-03.
- Cryptococcosis in Animals, Merck Veterinary Manual, accessed 2026-11-03.
- Cryptococcosis, Cornell Feline Health Centre, accessed 2026-11-03.
- Long-term outcome of therapy for 59 cats and 11 dogs with cryptococcosis, Australian Veterinary Journal / PubMed, accessed 2026-11-03.
- Clinical Overview of Cryptococcosis, Centres for Disease Control and Prevention, accessed 2026-11-03.
- Laboratory Testing, University of California, Davis, Centre for Companion Animal Health, accessed 2026-11-03.