Aspergillosis (fungal disease)

Fungal disease is most commonly seen in young to middle-aged (6.5 years old) cats, but can occur at any age. The fungal spores are widely found in the soil and are sniffed into the nose and airways. Most cats are able to remove the spores from their respiratory tract but in some cats this does not happen and the spores are able to develop into fungal plaques in the upper respiratory tract, lungs or elsewhere in the body.

A number of forms of fungal disease are seen in the cat. Infection may develop in the upper respiratory tract (sinonasal aspergillosis; SNA) only, or be more aggressive and extend into the area around the eye (sino-orbital aspergillosis; SOA). In some cats the fungal spores can spread throughout the entire body and cause disseminated disease (disseminated-invasive aspergillosis; DIA). 

©Ian Ramsey

The most common fungal species causing infection in cats are Aspergillus fellis, Aspergillus fumigatus and Aspergillus niger. This type of fungus is found worldwide in the environment and is usually associated with decaying vegetation, compost, moldy hay etc.

It is not clear why some cats develop disease when most cats must be exposed to the fungus in their environment. Cats with the SNA or SOA are generally healthy cats, with brachycephalic pure-bred cats such as Persian and Himalayan cats accounting for 1/3 of cases reported. Occasionally disease may be seen together with nasal cancers or foreign bodies.

Cats with DIA are often identified as being immunosuppressed due to concurrent disease, or various viral infections (FeLV, FIV, FIP, panleukopenia virus) or secondary to immunosuppressive drug administration.

Cats with upper respiratory tract forms (SNA, SOA) can have a range of clinical signs that most commonly include a watery to cream nasal discharge and sneezing. In some cases increased respiratory noise and nose bleeds may be observed. The SOA form of disease is associated with extension of disease around the eye and protrusion of the globe of the eye, or swelling of the tissues alongside the nose and eye may be reported. Blindness or seizures may also be identified or reported if there is involvement of the eye or brain.

Cats with disseminated disease can also have a range of clinical signs that can be vague and non-specific. This can include coughing or breathing difficulties, signs of depression or altered mentation, blood in the urine, vomiting, diarrhea or changes in appetite.

Your veterinarian may suspect what is wrong with your pet from the signs they are showing. However they will need to do further tests to confirm the diagnosis and rule out other possible causes. These tests are likely to include blood and urine tests, X-rays (or an MRI or CT scan) of your cat’s head and possibly putting an endoscope (camera examination) into your cat’s nose or lungs to take some samples to look and try and grow the fungus. These procedures will require a general anesthetic.

A blood test is available but it is important to remember that this test is not 100% accurate and some unaffected cats may be diagnosed as positive and some infected cats may test negative. This test is not very sensitive for cats with DIA.

The treatment for fungal infection in cats is not straightforward and depends upon the form of disease diagnosed (SNA versus SOA versus DIA).

For cats with SNA treatment strategies are aimed at removing as much of the infection as possible under anesthetic (debridement) before applying liquid or cream anti-fungal agents directly to the site of infection. Oral tablets may also be prescribed depending upon the extent of disease and the exact Aspergillus spp organism that has been identified. Multiple topical treatments may be needed to cure infection and this would require multiple anesthetics. Hospitalization following the procedure may be needed overnight or for a more prolonged period depending upon the presentation and recovery.

Cats with SOA or DIA are more likely to be treated with oral anti-fungal medications either alone, or in combination with injections of anti-fungal agents under the skin or intravenously. These medications are generally very well tolerated, but side effects may be seen with treatment and therefore monitoring with regular clinical assessments and blood tests to check liver function are usually recommended depending upon the combination of tablets prescribed.

For all forms of disease, additional supportive care such as fluid therapy, nutritional support, pain relief or seizure control may be required depending upon the signs seen and how the individual cat tolerates procedures.

Cats with disease confined to the nose (SNA) have the best chance of a recovery, although this can still be difficult to achieve and the prognosis remains guarded.

Resolution of clinical signs is one of the best indicators of response to treatment. Nasal discharge may be worse immediately after topical treatment, but often improves within a few weeks. It may be necessary to examine the nose again using a combination of endoscopy and imaging (CT or MRI) approximately 2 weeks after therapy to check that the fungus has been treated successfully. If discharge persists, or where there is any suspicion of ongoing infection with reassessment, a second treatment is likely to be recommended.

Where the fungal disease has spread around the eye (SOA) or into the brain, or is in a disseminated form (DIA) then treatment options may be more limited and the outlook is considered very poor.

The fungal spores that cause Aspergillus infection are present throughout the environment so every person and all pets will normally be exposed to them. Importantly, most people and animals do not become infected and nasal aspergillosis is not considered contagious.

Standard hygiene measures, washing your hands after contact with your pet and cleaning up nasal discharge, will reduce contamination of the environment. It would be wise to take special precautions with an infected animal, and consult your doctor if there are individuals in the household that have a compromised immune system due to disease, certain medications and very old or very young age.

Since the spores are present throughout the environment there is really no way to prevent your cat coming into contact with them. It is important to remember that the vast majority of cats exposed to environmental aspergillosis never develop a problem. Prompt consultation with your veterinarian if there are signs of a persistent nose discharge, sneezing, nose bleeds or swelling around the nose or eyes can help identify disease early and may improve the success of treatment.