Nasal Aspergillosis in Dogs: Fungal Nasal Infection

Nasal aspergillosis is a fungal infection of the nasal cavity and sometimes the frontal sinuses. In dogs, it is usually caused by Aspergillus fumigatus, a mold found widely in the environment. Most dogs breathe in fungal spores without any problem, but in some dogs the fungus settles in the nose and forms plaques on the lining of the nasal passages.

As the infection continues, it can damage the delicate turbinate bones inside the nose. That damage helps explain why affected dogs often have chronic discharge, sneezing, pain, and intermittent bleeding. The disease is usually localized to the nose, which is different from disseminated aspergillosis, a much less common form that spreads through the body.

This condition is seen most often in medium to large dogs with longer noses. It can look a lot like other causes of chronic nasal disease, including nasal tumors, foreign material in the nose, chronic rhinitis, or severe dental disease. That is why a careful workup matters before treatment decisions are made.

Nasal aspergillosis is caused by inhaled fungal spores, most often from Aspergillus fumigatus. These spores are common in soil, compost, hay, straw, grass clippings, and other decaying plant material. Exposure alone does not mean a dog will get sick. Healthy dogs inhale spores regularly and clear them without developing infection.

Researchers believe the disease develops when local defenses inside the nose are not able to remove the fungus effectively. That may involve changes in the nasal lining, prior inflammation, foreign material, or other local factors. Unlike disseminated aspergillosis, the nasal form is not usually linked to whole-body immune suppression.

Breed pattern matters. Long-nosed dogs are overrepresented, including Collies, Greyhounds, Dachshunds, German Shepherds, Retrievers, and Rottweilers. Short-nosed breeds are affected less often. Nasal aspergillosis is generally considered an opportunistic environmental infection, not a contagious disease passed from dog to dog in normal household settings.

Diagnosis usually takes more than one test. Your vet may start with bloodwork, nasal exam findings, and sometimes skull imaging, but advanced testing is often needed because fungal infection can mimic cancer, chronic inflammation, tooth-root disease, or a nasal foreign body.

CT is commonly the most useful imaging test because it can show turbinate destruction, sinus involvement, and whether there are changes that make another diagnosis more likely. Rhinoscopy lets your vet or a specialist look directly inside the nose under anesthesia, remove fungal plaques, and collect samples. Biopsy or histopathology can confirm fungal hyphae in affected tissue, while culture or blood antibody testing may support the diagnosis but are not strong enough alone.

In many dogs, diagnosis and treatment planning happen during the same anesthetic event. That can help reduce repeated procedures and may allow plaque removal and topical antifungal treatment once the disease pattern is confirmed.

There is no reliable way to fully prevent nasal aspergillosis because the fungus is common in the environment. Avoiding heavy exposure to compost, moldy hay, and decaying plant material may be reasonable for dogs with chronic nasal disease, but it does not guarantee prevention.

After treatment, many dogs have more discharge for a short time as dead fungal material and inflamed debris clear from the nose. Improvement is often gradual over the next two to four weeks. Your vet may recommend a recheck exam, repeat rhinoscopy, or additional imaging if discharge, bleeding, or pain continues.

Some dogs need more than one treatment. Also, dogs with severe turbinate destruction may keep a mild chronic discharge even after the infection is controlled because the nasal structures do not fully regenerate. That does not always mean the fungus is still active, so follow-up with your vet is important.

See your vet promptly if your dog develops renewed nosebleeds, worsening facial pain, swelling, reduced appetite, or any breathing difficulty. Chronic nasal signs deserve a full workup rather than repeated empiric antibiotics alone.