Aspergillosis

Aspergillosis is a fungal infection triggered by moulds of the genus Aspergillus. In dogs, various organs can be affected – most commonly the nose and nasal sinuses (nasal aspergillosis), less frequently the lungs or other internal organs (systemic aspergillosis). The fungus is literally everywhere in the environment: in rotting organic materials such as compost, old hay, or damp soil. Dogs simply inhale the spores – this is hardly avoidable.

Causes of Aspergillosis

Aspergillus fungi are so ubiquitous that healthy dogs encounter them daily without falling ill. Only when the immune system is weakened or simply overwhelmed can inhaled spores take hold in the respiratory tract and trigger an infection. Notably, dogs with longer snouts – so-called dolichocephalic breeds – fall ill more frequently because their extensive nasal sinuses literally catch spores.

Some risk factors additionally increase susceptibility:

• Weakened immune system: Dogs with cancer, autoimmune diseases, or long-term corticosteroid treatment are significantly more vulnerable than healthy animals.
• Breed susceptibility: Particularly German Shepherds seem – for reasons not yet fully understood – to carry an increased risk for the systemic form.

Forms of Aspergillosis

In dogs, two fundamentally different course forms are distinguished:

1. Nasal aspergillosis: By far the most common form. It remains confined to the nasal cavities and nasal sinuses and arises from directly inhaling fungal spores.
2. Systemic or disseminated aspergillosis: The significantly more dangerous variant. The fungus enters the entire body via the bloodstream and attacks internal organs – including the lungs, spine, liver, and kidneys. This form is rarer, but primarily affects immunocompromised dogs and is considerably more difficult to treat.

Symptoms of Aspergillosis in Dogs

What is observed depends heavily on which form is present:

Nasal aspergillosis:

• Nosebleeds or bloody nasal discharge – often on only one side, which can be an early warning sign.
• Severe, persistent sneezing.
• Swelling or pain in the nose and facial area.
• Swollen lymph nodes.
• Loss of sense of smell.
• Crusting or inflammation in the nose.
• In severe cases, bone damage can occur in the area of the nasal sinuses.

Systemic aspergillosis:

• Persistent fever that does not respond to usual treatments.
• Weakness and weight loss.
• Pain in joints or spine, often triggered by bone involvement.
• Coughing or shortness of breath if the lungs are affected.
• Kidney failure or other organ complications.
• Neurological deficits, once the central nervous system is involved.

Diagnosis of Aspergillosis

A reliable diagnosis is not trivial – the symptoms overlap with those of many other infections. Therefore, the vet usually relies on several methods:

1. Clinical examination: Thorough assessment of nasal discharge, the inside of the nose, and facial bones.
2. Imaging: X-rays or a CT scan of the nose and skull show bone damage or fungal growth in the nasal sinuses. If systemic form is suspected, ultrasound or CT of internal organs are added.
3. Nasal flushing and biopsy: A flushing of the nasal cavities or a tissue sample from the nasal mucosa allows direct identification of the fungus.
4. Blood tests: Detection of Aspergillus antibodies or a culture from nasal swabs provide further clues.
5. Culture and microscopy: Through fungal culture and microscopic examination of swabs or biopsy samples, the pathogen can be directly confirmed.

Treatment of Aspergillosis in Dogs

The therapy is based on the respective course form:

Nasal aspergillosis:

• The treatment of choice is local flushing of the nasal sinuses with antifungal agents such as clotrimazole or enilconazole – performed under anaesthesia.
• If this is insufficient, systemic antifungals such as itraconazole or fluconazole are added as oral medication.
• Regular follow-up checks are essential; not infrequently, several rounds of treatment are necessary to completely eliminate the fungus.

Systemic aspergillosis:

• An intensive long-term therapy is required here – usually with voriconazole, itraconazole, or amphotericin B over several months.
• In cases of severe organ involvement, especially of the spine, additional surgical intervention may become necessary.
• The prognosis for this form is generally poorer than for the nasal variant; patience and intensive support are required.

Prognosis

If nasal aspergillosis is detected early and treated consistently, the chances are good. However, relapses do occur, and some dogs need more than one treatment cycle before the fungus has truly disappeared.

The outlook is significantly grimmer with systemic aspergillosis. It is harder to control, often affects vital organs and frequently leads to serious complications in immunocompromised dogs. An honest assessment by the vet is particularly important here.

Prevention

Because aspergillosis is transmitted via inhaled spores, it can never be prevented to one hundred percent. A few measures can, however, noticeably reduce the risk:

• Clean environment: Keep your dog away from damp, rotting materials – compost heaps, old hay and wet autumn leaves are classic sources of spores.
• Strong immune system: Balanced nutrition and regular veterinary check-ups help keep your dog’s immune system stable.
• Act early: At the first signs such as nosebleeds, violent sneezing or persistent nasal discharge, you should not wait but see the vet promptly.