Nasal aspergillosis in dogs: symptoms and treatment

Overview

Sinonasal aspergillosis is Aspergillus infection of the nose and sinuses. Aspergillus fumigatus is a common cause. Upper respiratory infection in dogs is usually superficial rather than deeply invasive. Nevertheless, the nasal lining can be damaged and underlying bone destroyed.

Fungal growth and dead tissue may form grey-white plaques in the nose and sinuses. Ordinary nasal aspergillosis differs from infection spread throughout the body. Extension into the eye socket is less common in dogs. A fungal mass behind the eye can then push it outwards.

The less common Penicillium mould can cause similar symptoms.

Causes

Aspergillus moulds are abundant in the environment. Their airborne spores can enter the respiratory tract. They grow in dead leaves, compost and other decaying plant material, for example. Spores entering the nose may grow if they overcome local defences.

Why an individual dog develops disease is not precisely known. Plaques may contain large amounts of fungal material and dead tissue. Destruction of the nasal turbinate bones changes the nasal cavity's structure. Structural damage may sustain chronic rhinitis after the infection itself has resolved.

Different fungal strains may vary in their ability to cause disease. A large spore burden can overwhelm local respiratory defences.

Risk factors

Nasal aspergillosis is found particularly in long-nosed dogs. However, the risk in an otherwise healthy dog is low. Median age among 475 British patients was 6.0 years. The middle half were aged 3.1–9.3 years.

Of these patients, 316, or 67%, were male. Golden Retrievers accounted for 80, or 17%, of all patients. Labrador Retrievers also accounted for 80, or 17%. These figures describe affected patients, rather than disease risk across every dog of each breed.

Concurrent disease was recorded in 164/427 dogs, or 38%, for which this information was available.

Typical symptoms

Common signs noticed at home include:

• Clear, mucus-like or pus-like discharge from a nostril.

• Repeated sneezing or snorting.

• A muzzle that is sensitive to touch or clearly painful.

• Loss of pigment on the nose surface.

• Crusting or ulcers around the nostril edges.

• Intermittent nosebleeds.

Discharge typically starts on one side. Over time, it may affect both sides. It can change from pus-like to bloody. Your dog may rub or paw at its muzzle.

Nasal discharge occurred in 406/464 dogs, or 87%, with recorded information. Among the British dogs, 367/475, or 77%, sneezed. Nosebleeding occurred in 292/461, or 63%, for which it was recorded. Median symptom duration before specialist investigation was 61 days.

Complications and consequences

Turbinate destruction was found in 414/420 dogs, or 99%, with known findings after CT. Inflammation may also affect frontal sinus bone. The cribriform plate between the nose and cranial cavity may be damaged. Central nervous system signs can be associated with this.

Seizures or head pressing suggesting forebrain involvement occurred in 3/475 dogs, or 1%.

In British treatment follow-up, complete clinical remission occurred in 274/412 dogs, or 66%. Partial symptom improvement occurred in 98/412, or 24%. Complete clinical remission meant symptoms resolved without ongoing treatment. However, symptom resolution does not reliably prove the fungal plaques have disappeared.

Symptoms returned in 55 of 258 dogs that had become symptom-free, or 21%. Median time from first treatment to recurrence was 245 days. Persistent discharge may instead result from residual structural damage. Recurrent discharge and active fungal infection therefore cannot automatically be treated as the same thing.

After more extensive nasal or sinus surgery, air beneath the skin occurred in 7/28 dogs, or 25%. Adverse effects were recorded in 23/153 dogs, or 15%, in the endoscopic debridement group. Other treatment groups had adverse event rates of 27–33%.

Diagnosis at the vet

A tumour or foreign body can also cause persistent nasal discharge. Primary bacterial rhinitis is extremely rare in dogs. Antibiotics given on symptoms alone therefore do not establish the underlying cause.

Investigating persistent nasal discharge

The vet assesses symptom duration and clinical nasal findings. Rhinoscopy, examination with an endoscope, helps find fungal plaques. A representative plaque sample is collected for fungal culture. Fungal filaments, or hyphae, may be identified microscopically.

Mandibular lymph nodes were enlarged in 169/380 dogs, or 44%, with recorded findings.

A positive culture alone does not confirm disease because Aspergillus may be found in a healthy dog's nose too. Positive blood antibodies may likewise indicate environmental exposure alone. A negative antibody result does not rule out infection. Imaging, directly visible lesions and sample results are assessed together.

Nasal Aspergillus cultures may be positive in up to 30% of healthy dogs. Positive cultures have been found in up to 40% of dogs with nasal tumours. Fungus demonstrated at a deeper site of inflammation is generally significant. Even then, possible sample contamination is considered.

Imaging and sample limitations

CT shows the location and extent of bone damage. Cribriform plate integrity is assessed particularly before topical treatment. Ordinary X-rays are less sensitive than CT or MRI for detecting changes. Frontal sinus involvement may influence the treatment access route.

Fungal culture sensitivity was 59% in the large British series. Cytology sensitivity was 67%. Histological tissue examination sensitivity was 47%. These estimates concerned dogs with fungal plaques consistent with the diagnosis.

Precise fungal species identification may require culture or molecular testing. Microscopic tissue examination alone does not confirm Aspergillus identity. Species identification may matter for treatment selection and prognosis.

Culture of plaque samples was positive in 67/93, or 72%. Mucosal biopsies were positive in 37/80, or 46%. Sampling site therefore affects diagnostic success. A tumour or foreign body is also investigated.

Treatment

Plaque removal and topical treatment

The vet plans treatment according to infection extent and nasal anatomy. The first-choice approach is removal of fungal material followed by topical antifungal treatment. Plaques can be removed during rhinoscopy. Cleaning the frontal sinuses may require surgical access.

Trephination creates an opening into the frontal sinus for treatment. More extensive nasal or sinus surgery is another possible approach. After cleaning, the area is flushed and fluid removed by suction. Topical drugs may include clotrimazole or enilconazole.

After complete plaque removal, 60/112 dogs, or 54%, became symptom-free after the first treatment. After incomplete removal, the corresponding proportion was 6/28, or 21%. This supports the importance of thorough mechanical debridement. However, bleeding and complex sinus anatomy may make complete cleaning difficult.

After all treatment stages, 86/111 dogs, or 77%, were symptom-free in the complete debridement group. The corresponding figure after incomplete debridement was 14/27, or 52%. However, treatments were not randomly allocated. More severe cases may have received different methods from milder ones.

Medicine selection and difficult cases

Oral antifungal treatment alone produced no complete first-treatment clinical remissions among 15 dogs. The added benefit of oral treatment in localised nasal infection is uncertain. In deeply invasive infection, however, systemic antifungal medication is essential. Cribriform plate damage creates a particular risk if medicine enters the cranial cavity.

Plate damage is not an absolute contraindication to every topical method. In a group of 9 dogs with plate damage, all went home without serious complications 1–7 days after surgery. A dog with previous seizures had another seizure 2 months after treatment. Topical treatments are performed under general anaesthesia.

Checking treatment response

Nasal discharge may stop within 2–4 weeks of treatment. Repeat endoscopy at about 1 month may assess persistent infection. In the large British series, the median number of treatment procedures was 2 and the maximum 9. Adverse events were recorded in 24% of cases across all methods.

After the first treatment, 38% of patients became symptom-free with endoscopic debridement. The corresponding proportion after trephination was 29%. After more extensive nasal or sinus surgery, it was 55%. Repeated procedures may be needed to remove every difficult-to-reach plaque.

Prevention

Abundant environmental and airborne spores make exposure difficult to avoid completely. Exposure alone does not mean disease, as risk in an otherwise healthy dog is low. Nasal mucus traps inhaled particles. Sneezing helps remove inhaled foreign material from the nose.

Airway cilia move material trapped in mucus outwards. A functioning immune system protects the whole body against invasive fungi. The environment is the source of human Aspergillus infections. Transmission from dogs to people has not been described.

Important for dog owners

Record when nasal discharge began and which side it comes from. Note changes to pus-like or bloody discharge too. Tell the vet about previous antibiotics and their effects on symptoms. Watch for renewed sneezing and nasal discharge after treatment.

Arrange follow-up even if your dog seems symptom-free, because plaques may remain. Persistent discharge may instead need further investigation to distinguish active infection from chronic rhinitis. Muzzle pain and nostril ulcers also form part of monitoring treatment response.

Frequently asked questions

Does nasal discharge always mean aspergillosis?

No: a tumour, foreign body or other nasal inflammation can also cause persistent discharge. Visible fungal plaques on rhinoscopy support aspergillosis. Sample results and imaging are assessed together so treatment targets the identified cause. CT also helps establish the extent of bone damage.

Is a positive fungal culture enough for diagnosis?

No, because Aspergillus moulds occur in the environment and may be found in a healthy dog's nose. A representative culture sample is taken directly from a plaque. Demonstrating hyphae and other clinical findings adds to the diagnosis. A negative antibody test does not reliably rule out infection either.

Can tablets alone treat the disease?

The main approach to localised nasal aspergillosis is plaque removal and topical antifungal medication. Deep infections also need systemic antifungals. Infection extent and available techniques affect treatment choice. Procedures are performed under general anaesthesia in veterinary care.

Can aspergillosis recur after treatment?

Symptoms can return: 55/258 dogs, or 21%, that had become symptom-free developed symptoms again. However, recurrent discharge may also result from structural damage and chronic rhinitis. Further investigations assess whether active fungal plaques remain.

Can I catch it from my dog?

Aspergillus transmission from dogs to people has not been described. Human infection originates in the environment. Nevertheless, the same species, Aspergillus fumigatus, causes disease in people and small animals. Deeply invasive human aspergillosis generally occurs in severely immunocompromised people.