Fungal Infection (Aspergillosis) in Cats

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Last updated on
5 min read

Key takeaways

Aspergillosis is a type of fungal infection in cats caused by the organism Aspergillus, a species of fungus. 

  • Two types of aspergillosis occur in cats: nasal (affects the nose) and systemic (affects internal organs)
  • Clinical signs depend on the type and location of the infection
  • Nasal aspergillosis often presents with signs of chronic nasal infection such as sneezing and nasal - discharge
  • Systemic aspergillosis might present with coughing, disorientation, and diarrhea depending on the organs affected
  • Diagnosis is challenging and often includes physical evaluation, bloodwork, and urinalysis, diagnostic imaging, and biopsies
  • Treatment often lasts months and involves numerous rounds of antifungal medications
  • Surgical removal of affected tissue might also be necessary
  • The prognosis of nasal aspergillosis is fair, with many cases recurring
  • Systemic aspergillosis has a poor prognosis due to difficulty in treatment, and many cats are euthanized
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A closer look: Fungal Infection (Aspergillosis) in Cats

Aspergillosis is a rare type of infection in cats caused by species of Aspergillus fungi. Species of Aspergillus are found commonly in the environment, especially in foods or materials that have gone visibly moldy. Aspergillosis is more common in dogs and birds than it is in cats.

Aspergillosis infection in cats is usually categorized as nasal or systemic. Nasal infections are less severe and stay localized to the nasal passage and sinus cavities. Systemic or disseminated infections affect the internal organs, including the lungs, nervous system, or gastrointestinal tract. Disseminated forms of aspergillosis infection are life-threatening and prognosis is poor.

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Risk factors

It is unknown why some cats develop nasal aspergillosis and some systemic aspergillosis. Systemic infections are seen more often in cats with weakened immune systems which do not allow the body to control the initial fungal infection.

Aspergillosis is a rare condition in cats, compared to dogs, and is often only seen in cats who already have a compromised immune system.

Possible causes

Aspergillosis is caused by inhaling or ingesting Aspergillus spores, which are the reproductive cells of the fungus. Fungi then start to grow inside the nasal cavity and sinuses. In some cases, the infection spreads throughout the body, causing a systemic infection.

Main symptoms

Symptoms vary according to the form and location of the infection.

Symptoms of disseminated aspergillosis vary depending on the organ affected.

Testing and diagnosis

Diagnosing aspergillosis might prove a difficult task as its symptoms are similar to many other infections, especially infections of the upper respiratory system. The diagnostic process consists of many tests, including a complete physical evaluation, bloodwork, and urinalysis. In some cases, blood tests that identify antibodies against the fungus can be used to confirm a diagnosis. Sampling the tissue or nasal discharge for fungal culture or microscopic examination can definitively diagnose the infection. Diagnostic imaging such as ultrasound, CT, rhinoscopy, and X-rays are used to determine how far the infection has spread through the body.

For cats it is also important to test for diseases that might be affecting the immune system such as FeLV (Feline Leukemia Virus) or FIV (Feline immunodeficiency virus).

Steps to Recovery

Treatment also proves difficult. Antifungal medications may be effective but the therapy often lasts months. Surgical removal of affected tissues might also be needed. Recurrence or reinfection is common. In cases of nasal aspergillosis, topical antifungal medication infused into the nasal sinuses may be effective, and reduce potential side effects of the medication. Treatment for systemic aspergillosis is typically more complicated due to the extensive nature of the infection.

Aspergillosis is a serious condition and often proves fatal. Nasal aspergillosis has a better prognosis and may be cured with treatment. Recurrence is common and treatment often takes months of repeated antifungal medications.

Disseminated aspergillosis is more difficult to treat and often cats are euthanized due to a poor prognosis. Cats receiving systemic antifungal medications require routine bloodwork to monitor for side effects of the antifungal medications.


There are no notable prevention measures for aspergillosis. If aspergillosis is suspected, an early diagnosis often leads to more effective treatment and a better prognosis. Cats diagnosed with immunosuppressive conditions such as FeLV or FIV require particularly close monitoring for any signs of infection.

Is Fungal Infection (Aspergillosis) in Cats common?

Aspergillosis is rare in cats, compared to dogs. Cats with a compromised immune system may be more prone to infection.

Typical Treatment

  • Antifungal medications
  • Surgical removal of affected tissues


Tamara Gull , DVM, PhD, DACVM, DACVIM (LA), DACVPM - Writing for Merck Veterinary Manual
Katrin Hartmann et al. - Writing for European Advisory Board on Cat Diseases
Jacqueline Brister, DVM - Writing for Veterinary Partner
No Author - Writing for Cornell University College of Veterinary Medicine

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