Aspergillosis in dogs is an infection caused by species of a fungus called Aspergillus. This fungus is commonly found in soil, compost and decaying vegetation, and is usually a harmless part of the ecosystem. However, it does have the potential to infect animals. Aspergillus fungi produce tiny airborne spores. And if a susceptible animal inhales these tiny spores it can set up an infection, usually in their respiratory tract. 

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Snuffling through an old pile of mouldy leaves to find a lost ball is the classic way dogs can pick up aspergillosis. Dogs with long noses (e.g. Retrievers, Collies) seem to be most susceptible to infections. Thankfully in reality, aspergillosis is rare and typically will only affect dogs who already have a compromised immune system. (e.g. if they are otherwise poorly, have had their spleen removed, or are on medication which suppresses their immune system). However, if your dog is unfortunate enough to pick it up, aspergillosis can be very serious.  

What does Aspergillosis do?

Inhaled Aspergillus spores will typically set up a local infection in the upper respiratory tract, particularly in the nasal cavity or nasal sinuses. Local aspergillosis infections can spread to the lungs (pulmonary aspergillosis) or other organs of the body (disseminated aspergillosis) which is even more serious, but this is even rarer than the local form. Once established, the infection can be very destructive. It can seriously damage lung tissue, affected organs, and bone; eroding through the bones inside the nasal cavities or sinuses, even through the skull and into the brain.

What are the signs of canine Aspergillosis?

Signs will vary depending on the site of infection, but they can include:

  • Nasal discharge or bleeding (often just from one nostril)
  • Nose / sinus pain
  • Sneezing 
  • Loss of pigment on the area of nose under the nostril(s) 
  • Coughing 
  • Breathing difficulties 
  • Neurological signs
  • Lethargy
  • Loss of appetite
  • Fever 

How can aspergillosis be diagnosed?

Accurate diagnosis of aspergillosis relies on a combination of a clinical exam, imaging, and sampling of the lesions. First, your vet will take a thorough history of the signs you have noticed at home and conduct a full physical exam of your dog. The next steps will then likely be an X-ray or CT scan; these will show up any damage to the bones inside the nose / sinuses / skull, and can check for lesions in the lungs. A CT scan will give much greater detail than an X-ray, and may be advised if the bone erosion is severe or brain involvement is suspected. A small endoscopic camera can also be inserted into the nose or sinuses to directly visualise the damage, and can be used to collect samples for a definitive diagnosis. Samples taken can then be tested at the lab to confirm the diagnosis, and guide treatment. 

Can aspergillosis be treated?

The short answer is yes, but it needs to be aggressive, usually spans several months, and isn’t always successful. Treatment can encompass both antifungal medicine and surgical interventions, tailored to the site and severity of infection. Because of how destructive aspergillosis can be, the sooner the treatment is started, the better. 

If the infection is isolated to the nasal cavity or frontal sinus, a topical antifungal solution can be placed directly to the site via a nasal catheter whilst the dog is under anaesthetic. The solution must be left for an hour before being flushed out. Infection in a sinus is sometimes treated with a procedure called trephination, where a hole is drilled through the skull bone in order to access the sinus and instil the antifungal solution. Treatment of an isolated infection has around an 86% success rate, but some patients need repeat treatments if the infection is not clear after a few weeks. 

If the infection has got into the lungs, brain or other parts of the body (disseminated infections), it is much more serious, harder to treat, and will require long-term oral anti-fungal medications which can be costly and have unpleasant side-effects. The success rate for disseminated infection is lower than for a local infection in the nose or sinuses – only around 60-70%. 

Conclusion

Canine aspergillosis is a relatively rare disease, at least in the UK’s climate, but can be very serious when it is contracted. The prognosis is variable and depends on the site and extent of infection, the immune status of the dog, and the speed of diagnosis and treatment. Local aspergillosis (in the nose or sinuses) generally carries a more favourable prognosis compared to pulmonary or disseminated forms, given the accessibility of affected tissues and response to therapy. However, relapse or persistence of infection may occur, and long-term prognosis for canine aspergillosis remains guarded. It will take time and patience to treat, so working closely with your vet is key to giving your dog the best chance to recover from this challenging infection.

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