Aspergillosis in Dogs: Symptoms, Diagnosis, Treatment, and Breed Guide
This article is reviewed for clinical accuracy. Always consult your veterinarian for diagnosis and treatment.
Key Takeaways
- Aspergillosis in dogs is caused by Aspergillus species, primarily Aspergillus fumigatus for sinonasal aspergillosis (SNA) and Aspergillus terreus for disseminated aspergillosis (DA); unlike the dimorphic fungi (Blastomyces, Histoplasma, Coccidioides, Cryptococcus), Aspergillus is a filamentous mold (not a yeast or dimorphic fungus) that grows as branching septate hyphae in infected tissue rather than converting to a yeast form at body temperature; the distinguishing histological feature is 45-degree branching septate hyphae (compared to the 90-degree branching of Zygomycetes/Mucor); Aspergillus species are ubiquitous in the environment, present in decaying organic matter, compost, soil, and stored grain, and the route of infection is inhalation of airborne conidia (asexual spores) that are produced in enormous quantities and are small enough (2 to 3 micrometers) to reach the nasal mucosa or distal airways.
- Sinonasal aspergillosis (SNA), the most common form of aspergillosis in dogs, is caused primarily by A. fumigatus and is a disease predominantly of medium to large-breed mesocephalic and dolichocephalic dogs (dogs with normal or long nasal passages): German Shepherds, Labrador Retrievers, Golden Retrievers, Rottweilers, and Border Collies are among the most commonly affected breeds; brachycephalic breeds (Bulldogs, Pugs, French Bulldogs) are substantially underrepresented in SNA case series, likely because their compressed nasal passages provide less surface area for fungal colonization and different airflow dynamics; the hallmark pathological change in SNA is progressive turbinate destruction caused by the direct invasion of Aspergillus hyphae into the turbinate mucosa and underlying bone, leading to loss of the normal delicate turbinate architecture, accumulation of fungal plaques (white to grey colonies adhering to the turbinate mucosa visible on rhinoscopy), mucopurulent or hemorrhagic nasal discharge, and secondary bacterial infection of the damaged sinonasal mucosa.
- The definitive treatment for sinonasal aspergillosis in dogs is topical antifungal infusion into the nasal cavity and frontal sinuses under general anesthesia; the most widely used and best-studied protocol uses 1% clotrimazole in polyethylene glycol 400 (PEG 400) infused into the nasal cavity and frontal sinuses while the nasopharynx is occluded with a Foley catheter balloon to prevent swallowing; the procedure is performed under general anesthesia with the dog in dorsal recumbency; the nares are sequentially infused with clotrimazole solution for a total contact time of approximately 1 hour; cure rates with a single infusion approach 50 to 60 percent, and repeat treatment at 3 to 6 months increases cumulative cure rates to 70 to 90 percent; systemic itraconazole at 5 mg/kg once daily for 6 months is an alternative (or adjunct) for dogs in whom topical infusion is not feasible, but systemic therapy alone has lower cure rates than topical infusion; the topical approach delivers a high local drug concentration directly to the site of infection while minimizing systemic exposure, and the local drug concentrations achieved during infusion far exceed the minimum inhibitory concentration (MIC) for A. fumigatus.
- Disseminated aspergillosis (DA) is a far rarer and considerably more severe form of aspergillosis that is distinct from SNA in causative species, breed predisposition, pathogenesis, and outcome; DA in dogs is caused predominantly by A. terreus (and occasionally A. deflectus, A. flavipes, or other non-fumigatus species) rather than A. fumigatus; German Shepherds are dramatically overrepresented in DA case series, comprising 50 percent or more of affected dogs in most published reports, suggesting a primary immunodeficiency specific to German Shepherds that permits systemic Aspergillus dissemination from an initial respiratory focus; the hallmark feature of DA is hematogenous dissemination to the vertebral column, producing a distinctive pattern of multi-site discospondylitis and vertebral osteomyelitis, often affecting multiple intervertebral disc spaces simultaneously; other sites of DA dissemination include the kidneys (producing granulomatous nephritis with renal failure), eyes (uveitis, chorioretinitis), spleen, liver, and lymph nodes; DA carries a guarded to grave prognosis, with most published survival series reporting median survival times of weeks to a few months, and cure is achieved in only a small fraction of affected dogs.
- Diagnosis of SNA relies on the combination of characteristic rhinoscopic findings (white to grey fungal plaques on the nasal turbinate mucosa, turbinate destruction, mucopurulent discharge), CT imaging of the nasal passages and frontal sinuses demonstrating turbinate lysis and irregular soft tissue opacity, and Aspergillus serology (gel diffusion or ELISA); cytology and fungal culture of nasal discharge or rhinoscopic biopsy specimens confirm the organism; the Aspergillus ELISA (galactomannan assay) has become the most sensitive serological test for SNA in dogs (sensitivity approximately 70 to 85 percent, specificity above 90 percent); rhinoscopy is the single most informative diagnostic test for SNA because direct visualization of fungal plaques is essentially pathognomonic; in contrast, DA diagnosis relies on multi-site imaging (CT, MRI, or radiographs) demonstrating multi-focal discospondylitis, culture of urine or tissue specimens (urine fungal culture has approximately 50 to 70 percent sensitivity in DA because renal involvement is common), and Aspergillus ELISA on serum.
- A critical practical distinction between SNA and DA is that dogs with SNA typically have an otherwise normal neurological and physical examination apart from nasal and facial signs (nasal discharge, depigmentation of the nasal planum, facial pain, sneezing), while dogs with DA typically present with systemic illness: fever, weight loss, progressive ataxia and pelvic limb paresis from vertebral/spinal cord involvement, and signs of renal insufficiency; a German Shepherd presenting with multi-site spinal pain, progressive neurological signs, weight loss, and fever should be considered to have DA until proven otherwise; the combination of German Shepherd breed, multi-site discospondylitis on spinal imaging, and a positive Aspergillus serology (or urine culture) is essentially diagnostic; early diagnosis before irreversible spinal cord injury has occurred is the key prognostic factor, but even early-diagnosed DA has a poor overall prognosis.
The 4-year-old German Shepherd had been evaluated for back pain three months earlier, and a single thoracolumbar disc lesion was suspected based on radiographs; a 4-week course of NSAIDs provided partial improvement that gradually reversed. When she returned, she was now unable to rise unassisted and had lost 3.5 kilograms. New radiographs showed lytic changes at three separate intervertebral disc spaces: T10-T11, L2-L3, and L5-L6. A CT of the entire spine revealed endplate erosion and disc space collapse at all three sites simultaneously, a pattern inconsistent with standard intervertebral disc disease. Urine fungal culture grew Aspergillus terreus. An Aspergillus ELISA on serum was strongly positive (optical density ratio of 6.8). Abdominal ultrasound showed bilateral renal echogenicity changes consistent with granulomatous nephritis. The diagnosis was disseminated aspergillosis. The owner was told the prognosis was grave; voriconazole was initiated and vertebral pain managed with gabapentin, but the dog’s neurological function continued to decline and she was euthanized six weeks after the definitive diagnosis.
The Organism: Environmental Mold with Two Distinct Disease Forms
| Feature | Sinonasal Aspergillosis (SNA) | Disseminated Aspergillosis (DA) |
|---|---|---|
| Primary causative species | Aspergillus fumigatus (most common); occasionally A. flavus or A. niger | Aspergillus terreus (most common); A. deflectus, A. flavipes, A. niger (less common) |
| Breed predisposition | Medium to large mesocephalic and dolichocephalic breeds: German Shepherds, Labrador Retrievers, Golden Retrievers, Rottweilers, Border Collies; brachycephalic breeds are underrepresented | German Shepherds are strikingly overrepresented (50 percent or more of all DA cases); some reports of other large breeds; likely reflects a German Shepherd-specific primary immunodeficiency |
| Pathogenesis | Local invasion of nasal turbinate mucosa and underlying bone by hyphae from inhaled conidia; the turbinate destruction is progressive but usually does not disseminate; cribriform plate erosion with intracranial extension is an uncommon but severe complication of advanced SNA | Hematogenous dissemination from an initial respiratory focus; hyphae invade blood vessel walls (angioinvasion) and spread to vertebral disc spaces, kidneys, eyes, and other organs; German Shepherd immune dysfunction allows this systemic spread that the normal canine immune system would contain |
| Primary clinical signs | Chronic unilateral or bilateral nasal discharge (serous to mucopurulent to bloody); sneezing; ulceration and depigmentation of the nasal planum (characteristic finding); facial pain; frontal sinus pressure pain; nasal mass visible at the naris in advanced cases | Progressive pelvic limb ataxia and paresis from multi-site discospondylitis; severe weight loss; fever; renal signs from granulomatous nephritis; uveitis; systemic malaise out of proportion to spinal signs alone |
| Prognosis with treatment | Good to excellent for SNA limited to nasal passages; topical clotrimazole infusion achieves 70 to 90 percent cure with one or two treatments; frontal sinus involvement reduces cure rate; cribriform plate erosion with CNS extension is a poor prognostic indicator | Grave; most dogs with DA die or are euthanized within weeks to months of diagnosis despite aggressive antifungal therapy; sustained remission is achieved in fewer than 20 to 25 percent of cases in most published series; early diagnosis before extensive vertebral destruction or renal failure is the only factor associated with improved outcome |
| Key diagnostic finding | Rhinoscopic visualization of grey-white fungal plaques on the nasal turbinate mucosa (pathognomonic when present); turbinate lysis on CT | Multi-site discospondylitis on spinal CT or MRI in a German Shepherd; positive Aspergillus ELISA or urine culture growing Aspergillus terreus |
| Preferred treatment | 1% clotrimazole nasal infusion under anesthesia (topical infusion procedure); systemic itraconazole as alternative or adjunct | Voriconazole (3 to 4 mg/kg twice daily orally); itraconazole as alternative; terbinafine added in some protocols; long-term treatment (months to years) required; cure is rarely achieved |
Comparison: Aspergillosis vs. Other Nasal Diseases in Dogs
| Feature | Sinonasal Aspergillosis | Cryptococcosis (Nasal) | Nasal Adenocarcinoma | Dental Fistula / Tooth Root Abscess |
|---|---|---|---|---|
| Age at presentation | Young to middle-aged adults (2 to 8 years) | Any age | Older dogs (7 to 12 years) | Any age (usually older dogs with dental disease) |
| Nasal planum changes | Ulceration and depigmentation of nasal planum (distinctive feature) | Nodular mass on bridge of nose; facial deformity from granuloma | Usually none; deformity of facial bones in advanced cases | None typically |
| CT findings | Turbinate lysis; irregular soft tissue; frontal sinus opacification | Soft tissue mass; possible cribriform plate erosion | Soft tissue mass; bone invasion often unilateral | Periapical lucency around tooth root; involvement of hard palate or nasal floor |
| Best rapid diagnostic test | Rhinoscopy + Aspergillus ELISA | CrAg lateral flow assay | Rhinoscopy with biopsy and histopathology | Dental radiographs; oral examination |
| Treatment | Topical clotrimazole infusion | Fluconazole | Radiation therapy; surgery; palliative care | Tooth extraction; antibiotics |
Clinical Signs in Detail
Sinonasal Aspergillosis
The clinical presentation of SNA in dogs follows a recognizable progression that begins months to over a year before diagnosis in many cases; the initial sign is typically unilateral nasal discharge that starts as serous and progresses to mucopurulent or bloody over weeks to months; owners frequently report that the discharge was initially attributed to a cold or seasonal allergy and was treated with antibiotics that provided brief improvement before the discharge returned; the two most clinically distinctive features of SNA are nasal planum changes and facial pain; nasal planum ulceration and depigmentation (loss of the normal cobblestone texture and black pigmentation of the nasal planum, replaced by pale, smooth, ulcerated skin) are seen in approximately 30 to 50 percent of dogs with SNA and are essentially specific for aspergillosis among the causes of chronic nasal disease; this finding is sometimes the first clinical sign that prompts the clinician to consider aspergillosis; facial pain is manifested by reluctance to have the muzzle touched, rubbing the face on surfaces, or resisting nasal examination; sneezing is common, occasionally with blood-tinged mucus; epistaxis (nasal bleeding) occurs in approximately 25 to 40 percent of cases; bilateral discharge develops as fungal disease spreads from the initially affected side through the nasal septum.
Disseminated Aspergillosis
Disseminated aspergillosis in German Shepherds presents as a systemic febrile illness with progressive neurological decline; the vertebral/spinal involvement produces spinal pain (hyperesthesia on spinal palpation at one or more sites), progressive pelvic limb weakness that evolves to ataxia and paresis, and eventually loss of conscious proprioception and urinary dysfunction; the systemic nature of the disease is reflected in pronounced weight loss (often 3 to 5 kilograms over 2 to 3 months in an adult German Shepherd), persistent low-grade to moderate fever, reduced appetite, and general malaise; renal involvement (granulomatous nephritis) produces progressive azotemia and renal failure in many cases; ocular signs (uveitis, chorioretinitis, acute blindness) occur in approximately 25 to 35 percent of DA cases; the combination of vertebral pain, weight loss, and systemic illness in a young to middle-aged German Shepherd should trigger immediate consideration of DA as the primary diagnosis; importantly, respiratory signs (cough, nasal discharge) are often minimal or absent in DA even though infection originated via inhalation, because the immune deficit allows hematogenous spread before nasal disease becomes clinically evident.
Diagnosis
CT of Nasal Passages and Frontal Sinuses (SNA)
Computed tomography of the nasal passages and frontal sinuses is the most informative imaging study for SNA and should precede rhinoscopy whenever possible to map the extent of disease; CT findings in SNA include: destruction of the normal delicate turbinate architecture with replacement by irregular soft tissue opacity (the contrast between the normal lacy turbinate pattern and the soft tissue-obliterated cavity is dramatic); frontal sinus opacification and mucosal thickening; fungal plaques may be visible as heterogeneous soft tissue densities adherent to the turbinate remnants; cribriform plate integrity should be specifically assessed because erosion indicates potential CNS extension and changes the treatment approach; CT images also guide placement of infusion catheters during the topical clotrimazole procedure by identifying which sinuses require treatment; dogs with frontal sinus involvement require infusion catheter placement through a frontal sinus trephination hole in addition to nasal infusion.
Rhinoscopy
Rhinoscopy under general anesthesia is the definitive diagnostic procedure for SNA because direct visualization of white to grey fungal plaques (Aspergillus colonies adhering to the turbinate mucosa) is essentially pathognomonic when found in the context of turbinate destruction and compatible clinical signs; rhinoscopy also reveals the degree of turbinate destruction, the extent of mucopurulent material, and the presence of secondary bacterial infection; biopsy samples collected rhinoscopically should be submitted for fungal culture and histopathology (demonstrating 45-degree branching septate hyphae); rhinoscopy can immediately precede or follow topical clotrimazole infusion under the same anesthetic episode, minimizing the number of anesthetic events.
Aspergillus ELISA (Galactomannan Assay)
Galactomannan is a polysaccharide cell wall component shed by Aspergillus species during active mycelial growth; the Aspergillus ELISA detects galactomannan in serum or bronchoalveolar lavage fluid; for SNA in dogs, the ELISA has sensitivity of approximately 70 to 85 percent (false negatives occur in early or mild disease) and specificity above 90 percent; a strongly positive ELISA in a dog with compatible nasal signs, CT turbinate lysis, and rhinoscopic findings confirming fungal plaques is essentially diagnostic; the ELISA is particularly useful when rhinoscopy is equivocal (diffuse mucosal changes without visible plaques) or when frontal sinus disease without nasal cavity plaques is suspected; for DA, the serum ELISA is strongly positive in most cases (sensitivity above 80 to 90 percent in published DA series) and should be a first-line test in any German Shepherd with multi-site discospondylitis.
Urine Fungal Culture (DA)
Because DA involves the kidneys in a high proportion of cases, urine fungal culture using a midstream clean-catch or cystocentesis sample has approximately 50 to 70 percent sensitivity for isolating Aspergillus terreus or the causative species; urine culture is non-invasive and should be performed before more invasive sampling (vertebral biopsy, renal aspirate) in any German Shepherd with multi-site discospondylitis; isolation of Aspergillus terreus from urine in a German Shepherd with compatible imaging is diagnostic for DA; antifungal susceptibility testing on the isolate is important because A. terreus is intrinsically resistant to amphotericin B (unlike A. fumigatus), which means empirical amphotericin B therapy that would be appropriate for other systemic mycoses is ineffective and contraindicated for DA caused by A. terreus; this intrinsic AMB resistance is a critical therapeutic consideration that distinguishes DA treatment from other fungal diseases.
Treatment
Topical Clotrimazole Nasal Infusion (SNA)
The topical clotrimazole nasal infusion procedure is the preferred treatment for SNA limited to the nasal passages and frontal sinuses; the procedure is performed under general anesthesia with the dog in dorsal recumbency; the pharynx is packed with moistened gauze to prevent clotrimazole solution from reaching the larynx and trachea, and a Foley catheter is placed in the nasopharynx with the balloon inflated to occlude the nasopharyngeal opening; 60 mL of 1% clotrimazole in polyethylene glycol 400 is infused through tubes placed in both nares alternately, and the infusion is maintained in contact with the nasal mucosa and frontal sinuses for a total of 60 minutes; the dog’s position may be rotated between dorsal, right lateral, and left lateral recumbency during the procedure to distribute the solution into all sinus compartments; at the end of the procedure, the clotrimazole solution is suctioned from the nasal cavity, the pharyngeal packing and Foley catheter are removed, and the dog is recovered; for dogs with frontal sinus involvement confirmed on CT, bilateral frontal sinus trephination holes are drilled through the frontal bone under the same anesthetic, and the sinuses are infused separately to ensure adequate drug distribution into the sinus cavity; side effects of the infusion procedure include transient rhinitis and sneezing for several days post-procedure, and occasional reports of corneal ulceration from clotrimazole contact with the eyes (mitigated by lubricating eye ointment application before the procedure); owner-observed improvement in nasal discharge typically begins within 2 to 4 weeks after treatment.
Systemic Antifungal Therapy (SNA)
Systemic itraconazole at 5 mg/kg orally once daily with a fatty meal for 3 to 6 months is the systemic alternative for dogs in whom topical infusion is not feasible (owner financial constraints, anesthetic risk) or as an adjunct to topical infusion in dogs with frontal sinus involvement or disease recurrence; cure rates with systemic itraconazole alone are approximately 30 to 40 percent at 6 months; voriconazole at 4 mg/kg orally twice daily is used in dogs unresponsive to itraconazole, though voriconazole has a narrow safety margin in dogs (neurological adverse effects including tremors, ataxia, and behavior changes have been reported with voriconazole in dogs at doses above 4 to 5 mg/kg twice daily); treatment response is monitored by clinical improvement in nasal discharge and rhinoscopic re-examination at 3 to 6 months.
Treatment of Disseminated Aspergillosis
Treatment of DA requires systemic antifungal therapy with an agent active against the causative Aspergillus species; because A. terreus is intrinsically resistant to amphotericin B (the drug that would typically be used for induction therapy in serious systemic mycoses), DA treatment relies on triazole antifungals:
- Voriconazole: 3 to 4 mg/kg orally twice daily is the preferred agent for DA in dogs because of its broad-spectrum activity against A. terreus and other non-fumigatus species and its acceptable oral bioavailability; drug monitoring (measuring voriconazole serum trough concentrations targeting 1 to 5 micrograms/mL) is recommended to ensure adequate exposure while minimizing toxicity; hepatotoxicity, neurological effects (ataxia, behavior changes), and photosensitivity are the primary adverse effects; CBC and liver enzymes should be monitored monthly
- Itraconazole: 5 mg/kg once daily is an alternative that is less expensive and generally better tolerated than voriconazole, though its activity against A. terreus is considered less reliable; used when voriconazole is not tolerated or affordable
- Terbinafine: 30 to 40 mg/kg orally once daily is sometimes added to a triazole as combination therapy given its in vitro synergy with azoles against Aspergillus; clinical evidence for combination therapy in DA is limited to case series
- Treatment duration: Long-term treatment (6 to 24 months, potentially lifelong) is required; relapse is nearly universal when treatment is stopped, and sustainable control rather than cure is a realistic goal for most DA cases
US Cost Overview for Aspergillosis
| Service | Typical US Cost |
|---|---|
| Veterinary examination | $60 to $150 |
| Aspergillus ELISA (serum galactomannan) | $80 to $160 |
| Complete blood count and chemistry panel | $150 to $300 |
| CT of nasal passages and sinuses (SNA) | $500 to $1,200 |
| CT of full spine (DA) | $1,200 to $2,500 |
| Rhinoscopy with biopsy | $600 to $1,400 |
| Topical clotrimazole nasal infusion (single treatment) | $800 to $2,000 (includes anesthesia and procedure) |
| Frontal sinus trephination (added to nasal infusion) | $300 to $600 additional |
| Itraconazole (6-month course, 30 kg dog) | $150 to $400 |
| Voriconazole (monthly, 30 kg dog) | $150 to $350 per month |
| Voriconazole trough monitoring (serum level) | $80 to $180 per measurement |
| Monthly CBC and liver enzymes (voriconazole monitoring) | $100 to $200 |
| Urine fungal culture (DA) | $60 to $120 |
| MRI of spine (DA) | $1,500 to $3,500 |
Age-Specific Considerations
Puppies (Under 12 Months)
- SNA in puppies is uncommon because the disease typically requires months of Aspergillus colonization of the nasal mucosa before turbinate destruction becomes clinically apparent; puppies have a shorter exposure history and a more vigorous mucosal immune response that typically contains Aspergillus conidia before they establish a productive infection; however, puppies from environments with high Aspergillus exposure (farms with moldy hay or grain stores, kennel facilities with compost nearby) can develop nasal aspergillosis; any puppy with persistent unilateral nasal discharge that has failed antibiotic therapy should have nasal disease evaluated with rhinoscopy and Aspergillus serology before attributing the discharge to viral infection or a structural nasal abnormality
- Disseminated aspergillosis in puppies is exceptionally rare because DA requires the specific German Shepherd immune deficiency that allows hematogenous dissemination; if a puppy German Shepherd develops systemic signs with multi-site spinal involvement, congenital immunodeficiency should be considered alongside DA; routine immunological testing (serum immunoglobulin quantification, lymphocyte subset enumeration) is warranted in young German Shepherds with severe fungal infections to assess whether a primary immunodeficiency underlies the susceptibility
- Anesthetic safety for the topical clotrimazole infusion procedure is a consideration in small or young puppies where the risk of excessive PEG 400 absorption or hypothermia during the prolonged anesthetic procedure is higher than in adult dogs; a puppy weighing less than 5 kilograms should have the clotrimazole infusion volume scaled appropriately, and active warming throughout the procedure is essential; the nasopharyngeal Foley catheter occlusion requires an appropriately sized balloon catheter to seal the smaller nasopharyngeal opening in puppies
Adult Dogs (1 to 8 Years)
- The peak age for SNA diagnosis is 2 to 8 years; the disease typically has a prolonged subacute onset with months of nasal discharge before the dog is evaluated and aspergillosis is considered; many SNA cases receive multiple rounds of antibiotics for presumed bacterial rhinitis before rhinoscopy reveals fungal plaques; the characteristic nasal planum ulceration is the most specific clinical clue and should prompt immediate consideration of aspergillosis in any adult dog with chronic nasal discharge; once SNA is diagnosed, adult dogs with normal cardiac and hepatic function tolerate the topical clotrimazole infusion procedure and systemic itraconazole well; baseline liver enzymes should be checked before starting itraconazole because hepatotoxicity (though uncommon) can occur with long-term azole therapy
- DA in adult German Shepherds (typically 2 to 8 years at diagnosis) is the most important differential for multi-site discospondylitis and should be considered before pursuing aggressive surgical treatment or empirical antibiotics for what might be mistaken for bacterial discospondylitis; bacterial discospondylitis typically affects a single disc space (or occasionally two adjacent spaces) and is associated with a urinary tract infection or bacteremia from a remote site; multi-site discospondylitis affecting three or more non-contiguous disc spaces is characteristic of DA and is very uncommon in bacterial discospondylitis; MRI of the full spine is superior to radiographs for identifying early endplate changes and the number of affected sites; an adult German Shepherd with two or more disc spaces involved on imaging should have an Aspergillus ELISA and urine fungal culture before spinal surgery is considered
- Adult dogs receiving prolonged corticosteroid therapy (for immune-mediated hemolytic anemia, inflammatory bowel disease, or immune-mediated polyarthritis) are at elevated risk for secondary aspergillosis because corticosteroids impair neutrophil and macrophage fungicidal activity and inhibit the mucosal immune response that normally prevents Aspergillus colonization; a dog on chronic corticosteroids that develops unilateral nasal discharge, epistaxis, or nasal planum changes should be evaluated for SNA promptly
Senior Dogs (9 Years and Older)
- Senior dogs with SNA tolerate the topical clotrimazole infusion procedure when anesthetic risk is acceptable; dogs with significant concurrent cardiac or hepatic disease require a thorough pre-anesthetic assessment and may require modification of the anesthetic protocol; the 60-minute anesthetic time for a standard nasal infusion is longer than many routine procedures, and older dogs with reduced cardiac reserve or pulmonary disease need careful monitoring throughout; in senior dogs where anesthetic risk is high, systemic itraconazole as the primary treatment modality (instead of topical infusion) is reasonable, accepting that cure rates are lower, with the goal of controlling disease and maintaining quality of life
- Senior German Shepherds with DA present a treatment dilemma because the concurrent renal insufficiency from granulomatous nephritis (common in DA) limits the use of nephrotoxic agents and changes voriconazole pharmacokinetics; voriconazole is primarily hepatically metabolized (not renally eliminated), so dose adjustment based on renal function alone is not required, but concurrent CKD reduces overall physiological reserve and increases the risk of adverse effects from prolonged antifungal therapy; goals of therapy in senior DA cases often shift from curative intent to palliative quality-of-life maintenance
- Nasal tumors (adenocarcinoma, chondrosarcoma, lymphoma) are far more common in senior dogs than in younger adults and are an important differential for unilateral nasal disease in dogs over 9 years of age; senior dogs with nasal discharge should have CT imaging and rhinoscopic biopsy to distinguish aspergillosis from neoplasia before starting antifungal treatment; Aspergillus ELISA can be falsely positive in dogs with nasal neoplasia due to secondary fungal colonization of necrotic tumor tissue, so serology alone is insufficient for the diagnosis; histopathology of rhinoscopic biopsies is essential to exclude nasal tumor in senior dogs
Myths and Facts About Aspergillosis in Dogs
Aspergillosis is the same type of disease as blastomycosis or histoplasmosis, so the same treatment should work.
Aspergillus is fundamentally different from the dimorphic endemic fungi. Aspergillus is a non-dimorphic filamentous mold that grows as branching hyphae in both the environment and in host tissue; it does not convert to a yeast form. The preferred treatment for sinonasal aspergillosis is topical clotrimazole nasal infusion, not systemic itraconazole monotherapy (the first-line drug for blastomycosis and histoplasmosis). For disseminated aspergillosis caused by Aspergillus terreus, amphotericin B is actually contraindicated because A. terreus is intrinsically resistant to it, unlike Blastomyces and Histoplasma which are amphotericin B-sensitive.
My dog was cured of SNA after the clotrimazole infusion because the nasal discharge stopped, so no follow-up is needed.
Clinical improvement (reduced nasal discharge) after topical clotrimazole infusion is encouraging but does not confirm mycological cure. Approximately 30 to 50 percent of dogs require a second infusion treatment at 3 to 6 months to achieve sustained remission. Rhinoscopic re-examination and repeat Aspergillus ELISA at 3 to 6 months after treatment are recommended to confirm that fungal plaques have resolved and turbinate healing is proceeding. Relapse is common if treatment is stopped prematurely or if follow-up is not performed.
My German Shepherd has back pain from a slipped disc, not aspergillosis, because aspergillosis is a lung infection.
Disseminated aspergillosis in German Shepherds characteristically produces vertebral discospondylitis as its primary manifestation, not respiratory illness. Most German Shepherds with DA lack prominent nasal or pulmonary signs even though infection entered via the respiratory tract. Multi-site discospondylitis (two or more non-contiguous disc spaces affected on spinal imaging) in a German Shepherd is the hallmark presentation of DA and should trigger an Aspergillus ELISA and urine fungal culture before the dog is treated for bacterial discospondylitis or sent to surgery for disc disease.
Red Flags: Signs Requiring Prompt Veterinary Evaluation
- Ulceration and loss of pigmentation of the nasal planum (the normally black, moist cobblestone surface at the tip of the nose) in a dog with chronic nasal discharge: nasal planum depigmentation and ulceration in the context of unilateral or bilateral mucopurulent nasal discharge is essentially specific for sinonasal aspergillosis among the common causes of chronic nasal disease in dogs; this finding should prompt immediate referral for rhinoscopy, CT, and Aspergillus ELISA rather than another course of antibiotics; antibiotics prescribed without a specific diagnosis of aspergillosis provide only short-term secondary benefit and allow progressive turbinate destruction to continue untreated
- Progressive pelvic limb weakness and difficulty rising in a German Shepherd, particularly accompanied by weight loss and fever: this combination is the hallmark clinical presentation of disseminated aspergillosis and constitutes a diagnostic emergency; the window between initial vertebral involvement and irreversible spinal cord compression from vertebral collapse is limited, and diagnostic delay directly worsens the prognosis; spinal imaging and Aspergillus ELISA should be performed urgently, not after empirical antibiotic therapy has failed over weeks
- Spinal pain at multiple sites simultaneously in a German Shepherd: standard bacterial discospondylitis caused by hematogenous bacterial seeding (Staphylococcus, Brucella, Streptococcus, Escherichia coli) almost always affects a single disc space or two adjacent spaces; multi-site non-contiguous disc involvement in a German Shepherd is a strong indicator of DA; vertebral biopsy at multiple sites, urine fungal culture, and Aspergillus ELISA should precede empirical antibiotics or spinal surgery in this scenario
- Sudden blindness or severe uveitis in a German Shepherd with concurrent spinal signs or weight loss: ocular aspergillosis (chorioretinitis, optic neuritis, uveal invasion) occurs in approximately 25 to 35 percent of DA cases; sudden bilateral blindness from optic nerve or retinal involvement in a German Shepherd with systemic illness should trigger immediate consideration of DA; fundoscopic examination revealing focal white retinal lesions or disc swelling in this breed context is a near-diagnostic finding
- Epistaxis (active nasal bleeding) with nasal discharge unresponsive to antibiotics: epistaxis in the context of chronic unilateral or bilateral mucopurulent discharge that has not responded to antibiotic therapy suggests either SNA with turbinate erosion into a nasal vessel, nasal neoplasia with mucosal invasion, or a coagulopathy; each of these requires urgent investigation beyond antibiotic treatment; a platelet count and coagulation panel should be combined with rhinoscopy and Aspergillus serology rather than simply repeating antibiotic courses
Frequently Asked Questions About Aspergillosis in Dogs
What is aspergillosis in dogs?
Aspergillosis is a fungal infection caused by Aspergillus species, primarily A. fumigatus (sinonasal form) and A. terreus (disseminated form). Unlike the dimorphic endemic fungi, Aspergillus is a filamentous mold that grows as branching septate hyphae in tissue. Sinonasal aspergillosis destroys the nasal turbinates in medium to large-breed dogs. Disseminated aspergillosis, driven by a suspected German Shepherd-specific immunodeficiency, spreads to vertebrae, kidneys, and eyes with a grave prognosis.
What are the symptoms of aspergillosis in dogs?
Sinonasal aspergillosis produces chronic nasal discharge (serous to bloody), sneezing, facial pain, and the characteristic finding of nasal planum ulceration and depigmentation (loss of normal black pigmentation at the tip of the nose). Disseminated aspergillosis in German Shepherds presents with progressive rear leg weakness and ataxia from multi-site vertebral involvement, severe weight loss, fever, and signs of renal disease. Respiratory signs are often minimal in the disseminated form.
How is aspergillosis diagnosed in dogs?
For sinonasal aspergillosis: CT of the nasal passages showing turbinate lysis, rhinoscopy demonstrating white-grey fungal plaques on the turbinate mucosa, and Aspergillus ELISA (galactomannan) on serum. For disseminated aspergillosis: CT or MRI of the full spine showing multi-site discospondylitis, urine fungal culture growing A. terreus, and serum Aspergillus ELISA. The breed (German Shepherd) and multi-site spinal involvement together are strongly suggestive of disseminated aspergillosis.
How is sinonasal aspergillosis treated?
The definitive treatment is topical 1% clotrimazole nasal infusion under general anesthesia, with the solution held in contact with the nasal mucosa and frontal sinuses for approximately 60 minutes. Cure rates of 70 to 90 percent are achievable with one or two treatments. Systemic itraconazole (5 mg/kg once daily for 6 months) is used when topical infusion is not feasible or as adjunct therapy. Rhinoscopic debridement of fungal plaques during the same anesthetic episode improves outcomes.
Why can’t amphotericin B be used for disseminated aspergillosis in dogs?
Disseminated aspergillosis in German Shepherds is caused primarily by Aspergillus terreus, a species that is intrinsically resistant to amphotericin B due to a cell membrane characteristic that prevents AMB from binding effectively. Using amphotericin B for A. terreus DA is ineffective and exposes the dog to nephrotoxicity without therapeutic benefit. Voriconazole is the preferred agent because it retains activity against A. terreus that AMB lacks.
What breeds are most at risk for aspergillosis?
For sinonasal aspergillosis: medium to large mesocephalic and dolichocephalic breeds including German Shepherds, Labrador Retrievers, Golden Retrievers, and Rottweilers. Brachycephalic breeds (Bulldogs, Pugs) are rarely affected. For disseminated aspergillosis: German Shepherds represent 50 percent or more of published cases, strongly suggesting a breed-specific primary immune deficiency that permits systemic fungal dissemination. No other breed carries anywhere near the same risk for DA.
What is the prognosis for a dog with aspergillosis?
Sinonasal aspergillosis has a good to excellent prognosis: 70 to 90 percent cure rate with topical clotrimazole infusion, particularly when disease is limited to the nasal passages. Frontal sinus involvement or cribriform plate erosion reduces the cure rate. Disseminated aspergillosis has a grave prognosis; most affected dogs die or are euthanized within weeks to a few months of diagnosis despite aggressive antifungal therapy. Sustained remission is achieved in fewer than 20 to 25 percent of DA cases in most published series.
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