Canine nasal diseases are a commonly diagnosed, with fungal infections being a serious cause. Among these, Aspergillus species are the most common fungal pathogen affecting the nasal cavity and paranasal sinuses in dogs (nasal Aspergillosis). This review will discuss the symptoms, diagnosis, treatment, and prognosis of canine Aspergillosis.
What is Aspergillus ?
Aspergillus is a ubiquitous fungus found globally, commonly inhabiting decaying organic matter such as compost and environments associated with large animals (hay, straw). It is considered an opportunistic pathogen, exploiting individuals with compromised immune systems or underlying nasal conditions. Predisposing factors include trauma, foreign body presence, nasal or paranasal surgery, systemic diseases (renal, hepatic, or cancer), and immunosuppression (from disease or medications).
Inhalation of Aspergillus spores is the primary route of infection causing Aspergillosis. The severity of infection may be influenced by the amount of spore inhaled combined with a patient’s concurrent underlying health issues. Once within the nasal cavity or sinuses, the fungus can establish a persistent infection, leading to the formation of characteristic fungal plaques. Although possible, it is uncommon for nasal Aspergillosis to spread to other parts of the body.
Inhalation of Aspergillus spores is the primary route of infection causing Aspergillosis.
Common Symptoms:
- Nasal Discharge: Mucopurulent or bloody nasal discharge
- Respiratory Signs: Sneezing, stertor (loud breathing), or reverse sneezing
- Facial Deformity: Facial swelling or distortion of the nasal bones
- Olfactory Dysfunction: Reduced or absent sense of smell
- Epistaxis: Bleeding from the nose
- Behavioral: Pawing at the nose, Lack of appetite
Less Common Symptoms:
- Neurological Signs: Seizures or head pressing due to intracranial extension
- Ocular Signs: Inflamed eye region secondary to nasal discharge
It’s important to note that the severity and duration of symptoms can vary widely. Chronic infections are common, with owners often reporting a gradual onset of symptoms over several months.
Diagnostic Tests for Canine Nasal Aspergillosis
Laboratory Tests
- Complete Blood Count (CBC): May show an elevated white blood cell (WBC) count.
- Cytology: Microscopic cytological examination of nasal swabs can reveal fungal elements, although sensitivity can be low, especially with only nasal discharge samples.
- Fungal Culture: Culture of nasal samples can confirm the diagnosis and identify the fungal species. Interpretation requires caution, as Aspergillus are common environmental contaminants and a positive culture does not necessarily mean that it is the primary source of any nasal symptoms.
- Serology: Antibody tests can detect immune response to Aspergillus. However, these tests have limitations, including low sensitivity and potential cross-reactivity with other fungal organisms. A positive antibody test cannot differentiate active infection from previous exposure.
Imaging
- X-rays (Radiography): Can reveal bony destruction and nasal deformity.
- Computed Tomography (CT): CT imaging provides detailed visualization of nasal and paranasal sinus structures, allowing for accurate assessment of bony changes, soft tissue masses, and cavitary lesions. CT is helpful to determine if there is any invasion of the infection through the nasal or sinus bones thereby allowing infection into the central nervous system (CNS).
Endoscopy
- Rhinoscopy: Endoscopic examination of the nasal cavity allows for direct visualization of fungal plaques, and enables targeted sampling for histopathology, and culture. “Plaques” are white or green or gray mass-like growth of fungus. Other changes seen during endoscopy include mucus, blood clots, destruction of the normal bony scrolls (turbinates) and inflammation. As the first step towards treatment, debriding (removing) as much of the fungal plaques as possible (through the scope with forceps) improves treatment response and prognosis.
Histopathology
- Biopsy: Biopsy of nasal lesions can provide definitive diagnosis through histopathological tissue examination, which reveals characteristic fungal elements (hyphae) as well as nasal mucosal and turbinate inflammation and destruction.
Treatments for Canine Nasal Aspergillosis
Treatment for canine nasal aspergillosis typically involves a combination of debridement (manual removal of fungus) and medical therapy. The specific treatment protocol should be tailored to each patient’s clinical presentation, severity of disease, other medical considerations, and response to initial therapy.
Surgical or Endoscopic Debridement
- Endoscopic Debridement: Endoscopic removal of fungal plaques and necrotic tissue from the nasal cavity and sinuses can improve response to treatments.
- Open Surgical Techniques: In cases of extensive disease, or granulomas not accessible by rhinoscopy, open surgical techniques such as sinus trephination, sinusotomy, or rhinotomy may be necessary.
Medical Therapy
- Topical Antifungal Therapy: Topical antifungal ointments and solutions, such as enilconazole and clotrimazole, can be administered directly into the sinus and nasal cavities through temporary placement of tubes and catheters by endoscopic or surgical methods.
- Systemic Antifungal Therapy: Oral antifungal agents, including itraconazole, posaconazole, and terbinafine, may be used to treat systemic fungal infections or refractory cases of nasal Aspergillosis. Recent studies show that oral therapy alone has the lowest response rate and should not be used in place of topical therapy, unless medically indicated by a patient’s specific considerations.
By combining debridement and topical therapy, many dogs can achieve significant improvement and often complete resolution of their disease. However, it is important to note that treatment can be challenging, and long-term management with repeated treatments may be necessary in some dogs.
Prognosis for Canine Nasal Aspergillosis
The prognosis for canine nasal aspergillosis is generally very good, however it does vary depending on several factors, including the severity of the disease, the extent of tissue involvement, and a patient’s individual response to treatment.
Factors Affecting Prognosis
- Treatment Modality: Aggressive treatment, including debridement and appropriate antifungal therapy, is associated with a better prognosis.
- Disease Severity: Extensive infection, particularly those involving the paranasal sinuses, eye region and CNS, may have a more guarded prognosis.
- Immunosuppression: Underlying immunosuppressive conditions can reduce the effectiveness of treatment.
Potential Complications and Long-Term Outcomes
- Relapse: Even after successful treatment, some dogs may experience a recurrence of the infection, particularly if underlying immunosuppressive conditions are present.
- Persistent Nasal Discharge: Chronic nasal discharge may persist, even after successful treatment, due to residual tissue damage or persistent inflammation.
- Immunosuppression: In some cases for reasons unknown, Aspergillosis can lead to transient immunosuppression, which may increase susceptibility to other infections.
With appropriate diagnosis and timely intervention, the prognosis for many dogs with CNA is favorable.
Overall, with appropriate diagnosis and timely intervention, the prognosis for many dogs with CNA is favorable: cures are achievable. However, it is important to recognize that the disease can be challenging to treat and may require long-term management.
Risk to Humans and Other Household Pets
Canine nasal aspergillosis is not considered zoonotic (contagious to humans) or other dogs. While these fungal infections can occur in immunocompromised people, they are primarily acquired through environmental exposure and not through direct contact with infected animals. If your dog has been diagnosed with Aspergillosis and you have concerns about your own health, consultation with your physician is recommended.
Your Pet’s Safety and Your Confidence is Our Priority
Rhinoscopy is a valuable tool in veterinary medicine, providing a minimally invasive method for diagnosing and treating nasal Aspergillosis. However, like any medical procedure, it has its limitations and risks.
We understand that you worry about your furry family member, and we will spend as much time discussing all aspects of the procedure with you to ensure that you are comfortable and confident. Please contact us if you have questions about nasal fungal infections or wonder if your pet would benefit from evaluation.
Learn More
Visit our additional blogs to learn more about Veterinary Endoscopy and Veterinary Rhinoscopy.
Author:
James Woods DVM, MS, DACVIM (SAIM)
Ph: (912) 721-6410
Contact Us
