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Basics ⬇

Basics

Definition

  • Nasal disease caused by Aspergillus spp., primarily A. fumigatus.
  • Saprophytic fungus that is ubiquitous in the environment.
  • Opportunistic pathogen.

Pathophysiology

  • Inhalation of fungus leads to disease in the nasal cavity and frontal sinus with destruction of turbinates, formation of plaque lesions, and overproduction of mucus causing clinical signs of nasal disease.
  • Rarely may be associated with underlying foreign body or previous trauma.
  • Causes a locally aggressive and invasive disease but does not result in systemic mycosis.
  • Confined to nasal cavity and frontal sinus-sinonasal form (most common in dogs).
  • Can result in sino-nasal or sino-orbital disease in cats.

Systems Affected

Respiratory-nasal cavity, sinus, orbit (cats, rare in dogs)

Genetics

Unknown

Incidence/Prevalence

Unknown, but a common diagnosis in dogs with nasal discharge in many locations.

Geographic Distribution

Worldwide

Signalment

Species

Dog and cat (less common)

Breed Predilections

  • Dogs-dolichocephalic and mesocephalic breeds
  • Cats-brachycephalic breeds may be overrepresented

Mean Age and Range

  • Dogs-predominantly young to middle-aged
  • Cats-no predilection

Predominant Sex

None identified

Signs

Historical Findings

  • Unilateral or bilateral nasal discharge-typically mucoid, mucopurulent, or serosanguinous but may be primarily epistaxis.
  • Sneezing.
  • Typically chronic signs-several months.
  • Many patients will have been treated with antibiotics for a possible bacterial infection before presentation with variable response.

Physical Examination Findings

  • Unilateral or bilateral nasal discharge.
  • Increased nasal airflow on the affected side.
  • Depigmentation with ulceration of the nasal planum-∼40% of dogs.
  • Facial pain.
  • Ipsilateral mandibular lymphadenopathy.
  • Stertor, exophthalmos, hard palate ulceration, facial asymmetry, loss of nasal airflow-sino-orbital disease in cats.

Causes

  • No underlying cause identified, although preexisting foreign body or trauma is occasionally implicated.
  • Likely due to inhalation of a large bolus of fungus that is ubiqutous in the environment.
  • Species-most commonly A. fumigatus in dogs, A. felis in cats others-A. niger, A. flavus.

Risk Factors

Unknown

Diagnosis ⬆ ⬇

Diagnosis

Differential Diagnosis

  • Foreign body
  • Oronasal fistula
  • Lymphoplasmacytic rhinitis
  • Neoplasia
  • Nasopharyngeal polyp, nasal tumor, or cryptococcus-cats only

CBC/Biochemistry/Urinalysis

  • Often normal
  • Possible inflammatory leukogram

Other Laboratory Tests

Serology

  • Detects fungi-specific serum antibodies.
  • AGID-commercially available; 98% specificity, 67% sensitivity in dogs; 43% sensitivity in cats. Serial serology does not appear to correlate with clinical status.
  • ELISA-88% sensitivity, 97% specificity in dogs, 90% sensitivity in cats.
  • Counter-immunoelectrophoresis-85% specificity in dogs.
  • Serum galactomannan-unreliable.

Culture

  • Tissue fungal culture of affected area; visualized biopsy sample taken from a region of suspected fungal growth showed 100% specificity, 81% sensitivity in dogs.
  • Culture of nasal discharge is less specific and insensitive.

Imaging

Computed Tomography

  • Imaging method of choice.
  • Cavitated turbinate lysis.
  • Thickening of the mucosa along the nasal turbinates.
  • Frontal sinus proliferative mass effect.
  • Soft tissue mass in the choana or nasopharynx-cats.
  • Necessary for evaluation of the cribriform plate before topical antifungal treatment.

Skull Radiography

  • Intraoral dorsoventral radiograph of the nasal cavity shows turbinate lysis.
  • Rostrocaudal or skyline frontal sinus view may show increased soft tissue density in the frontal sinus.
  • Cannot evaluate cribriform plate.

Diagnostic Procedures

Rhinoscopy

  • Flexible rhinoscopy in dogs allows examination of the nasopharynx and possibly the frontal sinus if the opening of the nasofrontal duct is destroyed by fungal infection.
  • Rigid rhinoscopy-examination of the nasal cavity alone; good visualization is possible due to large airspaces caused by turbinate lysis; excessive mucus and bleeding can make full examination difficult.
  • Visualization of fungal plaques (white, yellow, black, or light-green) on the mucosa of the nasal cavity and/or frontal sinus confirms fungal infection.
  • Sinuscopy-may be required to confirm the diagnosis in dogs that lack nasal plaques.

Pathologic Findings

  • Biopsies obtained of affected area under direct rhinoscopic visualization using cup biopsy instruments.
  • Samples immersion-fixed in buffered 10% formalin, routinely processed.
  • Evidence supportive of a diagnosis of aspergillosis-identification of septate, branching hyphae and conidia on histopathology. Surrounding inflammation is commonly neutrophilic or lymphoplasmacytic, rarely eosinophilic.
  • Blind biopsies in an unaffected area of the nasal cavity can result in a false diagnosis of inflammation.

Treatment ⬆ ⬇

Treatment

Appropriate Health Care

Overnight hospitalization advised after topical treatment or surgery.

Nursing Care

Maintain the nares free of nasal discharge.

Activity

Restriction of activity is not required if no bleeding is documented.

Diet

N/A

Client Education

  • Dogs-inform client that multiple topical treatments are usually necessary to cure the disease; follow-up with rhinoscopy is highly recommended to ensure resolution.
  • No established protocols for treatment in cats.

Surgical Considerations

Endoscopic Debridement

  • Extensive curettage and removal of fungal material from the nose and frontal sinus are essential to allow efficacy of topical medication.

Trephination of the Frontal Sinus

  • Can be required for dogs with frontal sinus involvement.
  • Performed using a Jacob's chuck and intramedullary pin.
  • Allows direct visualization of the frontal sinus with a rigid rhinoscope and local debridement of fungal plaques.
  • Allows for lavage and topical treatment of the area using a red rubber catheter.

Surgical Debridement and Exenteration

  • Used in some cats with sino-orbital disease.

Medications ⬆ ⬇

Medications

Drug(s) Of Choice

Topical Clotrimazole or Enilconazole Therapy

  • 1-hour infusion into nasal cavity under anesthesia.
  • Treatment is usually performed during the same anesthesia as diagnostics.
  • Treatment of choice in dogs; reported efficacy 85–89% with multiple treatments.
  • Foley catheters are used to occlude the nares and nasopharynx.
  • Dose-Clotrimazole: 1 gram in 100 mL of polyethylene glycol 200 (1% solution) evenly divided between two 60 mL syringes slowly infused over 1 hour into each side for large dogs; if trephination is used, divide the amount between the nasal cavity and sinus on the same side; less volume in smaller dogs. Enilconazole: 100 mL of 1%, 2%, or 5% solution.
  • Dog is placed in dorsal recumbency with head turned to each side every 15 minutes during the infusion.
  • Dog is placed in sternal recumbency with head down at the end of the procedure to drain all medication from the nasal cavity.
  • Has been used in cats without orbital involvement in combination with oral antifungal therapy with varying success.

Systemic Therapy

  • Antifungal triazole drugs should be considered if the cribriform plate is not intact; also used as primary therapy in some cats.
  • Can also be used in combination with topical therapy.
  • May be cost-prohibitive.
  • Itraconazole 5 mg/kg PO q12h in dogs with a reported efficacy of 60–70%; 10 mg/kg PO q24h in cats.
  • Voriconazole 5 mg/kg PO q12h; efficacy as sole therapy has not been established, neurotoxicity in cats.
  • Posaconazole: dogs, 5–10 mg/kg PO q12–24h, cats, 5 mg/kg PO q24h or divided q12h; efficacy as sole therapy has not been established.
  • Fluconazole is not recommended due to resistance.

Contraindications

  • Breach in the cribriform plate can allow contact of antifungal medication with brain resulting in neurologic signs and possible death.
  • Sino-orbital disease necessitates the use of systemic therapy. Amphotericin B should be considered.

Precautions

  • Topical clotrimazole and enilconazole are caustic to all mucosal surfaces-protective gear (gloves, goggles) should be worn by all staff that are in close contact.
  • Enilconazole can be associated with tissue swelling and upper airway obstruction.

Alternative Drug(s)

Enilconazole

  • Also active in the vapor phase.

Combined Clotrimazole Irrigation and Depot Therapy

  • Clotrimazole (1%) is flushed through a trephine hole in the frontal sinus over 5 minutes; 50 mL in each side in dogs >10 kg; 25 mL in each side in dogs <10 kg.
  • Clotrimazole cream (1%) is then introduced into the front sinuses; 20 g in each side in dogs >10 kg, 10 g in each side in dogs <10 kg.
  • Reported efficacy similar to topical clotrimazole or enilconazole alone (86%).

Follow-Up ⬆ ⬇

Follow-Up

Patient Monitoring

Dogs

  • Monitor clinical signs, although reduction of clinical signs does not establish resolution of disease.
  • Follow-up rhinoscopy is recommended in all cases to establish response to treatment, regardless of clinical signs-histopathology and culture can help establish response.
  • Serial serology (AGID) appears not to correlate with clinical status.
  • Repeat CT scan should be considered for reassessment of the cribriform plate before repeat topical treatment if a worsening clinical signs are seen.
  • Monitor liver enzymes in animals on triazole therapy.
  • Monitor renal parameters in animals on Amphotericin B.

Cats

  • Monitor clinical signs for improvement or resolution.
  • Monitor liver enzymes in animals on triazole therapy.
  • Monitor renal parameters in animals on Amphotericin B.

Prevention/Avoidance

N/A

Possible Complications

  • Topical therapy-monitor after treatment for any complications such as swelling of oropharynx, neurologic signs, infection/swelling of trephine site.
  • Triazoles can cause anorexia and can be hepatotoxic.
  • Amphotericin B can be nephrotoxic.

Expected Course and Prognosis

  • Studies have shown an 87% response rate to topical therapy in dogs after one to three treatments.
  • A newer study showed that recurrence or reinfection is more common than previously thought and can occur years after supposedly successful therapy.
  • The prognosis for cats with sinonasal aspergillosis is better than with the sino-orbital form.

Miscellaneous ⬆

Miscellaneous

Associated Conditions

N/A

Zoonotic Potential

There are no documented cases of human infection from an affected dog or cat.

Pregnancy/Fertility/Breeding

N/A

Synonyms

None

Abbreviations

  • AGID = agar gel immunodiffusion
  • CT = computed tomography
  • ELISA = enzyme-linked immunosorbent assay

Author Jill S. Pomrantz

Consulting Editor Lynelle R. Johnson

Suggested Reading

Barrs VR, Talbot JJ. Feline aspergillosis. Vet Clin North Am 2014, 44(1):51–73.

Friend E, Anderson DM, White RAS. Combined clotrimazole irrigation and depot therapy for canine nasal aspergillosis. J Small Anim Pract 2006, 47(6):312–315.

Mathews KG, Davidson AP, Koblik PD, et al. Comparison of topical administration of clotrimazole through surgically placed versus nonsurgically placed catheters for treatment of nasal aspergillosis in dogs: 60 cases (1990–1996). J Am Vet Med Assoc 1998, 213:501–506.

McLellan GJ, Aquino SM, Mason DR, Myers RK. Use of posaconazole in the management of invasive orbital aspergillosis in a cat. J Am Anim Hosp Assoc 2006, 42:302–307.

Pomrantz JS, Johnson LR, Nelson RW, Wisner ER. Comparison of serologic evaluation via agar gel immunodiffusion and fungal culture of tissue for diagnosis of nasal aspergillosis in dog. J Am Vet Med Assoc 2007, 230:1319–1323.