Nasal examination and aspergillosis (Proceedings)

Nasal problems are a frequent reason for seeking veterinary care. Sneezing that produces a nasal discharge or frank hemorrhage must be evaluated to identify the underlying cause. A variety of historical factors such as age of the dog, vaccination status, the breed and the environment will influence the likelihood of certain diseases. A mucopurulent nasal discharge in a young, sick dog with a questionable vaccination history requires exclusion of distemper. In sporting dogs with an acute onset of violent sneezing, nasal foreign bodies especially grass awns must be considered. Nasal fungal infections with Aspergillus sp. occur most commonly in dolichocephalic dogs that are under 5 years of age while nasal tumors are more common in older dogs but can occur in dogs as young as 18 months of age. Seasonal episodes of nasal discharge suggest an allergic component. Most nasal conditions do not produce lethargy or fever except for infectious diseases like distemper and some cases of aspergillosis.

Dogs with acute hemorrhagic discharge must be evaluated for bleeding disorders especially platelet abnormalities. Hypertension has also been associated with nosebleeds. While bleeding occurs in aspergillosis and nasal tumors, there is usually a long history of mucopurulent nasal discharge. Unilateral discharges can occur with foreign bodies, tumors and aspergillosis initially but aspergillosis and tumors often progress to bilateral discharges when there is destruction of the nasal septum. Tooth root abscesses of the upper 4th premolar tooth that drain into the nasal passages may also produce unilateral nasal discharges. Nasal discharges may improve with antibiotic treatment but most nasal diseases have secondary bacterial involvement that will temporarily respond. Primary bacterial infection of the nose of the dog is not a common condition.

A thorough physical examination to identify more generalized conditions may reveal the generalized lymphadenopathy associated with lymphoma of the nasal passages, dental disease with root abscesses, cleft palate with food entry into the nose, metastatic nasal tumors, chorioretinitis associated with distemper or cryptococcosis, pharyngeal masses, ulcerative depigmented lesions of the nares characteristic of aspergillosis and other abnormalities that would limit anesthesia for imaging and rhinoscopy. Neurologic abnormalities may be seen in invasion of the brain by aspergillosis or tumors. It is very helpful to obstruct one nostril and listen to the airflow through the other nostril. Complete obstruction of airflow is usually associated with nasal tumors though some conditions such as aspergillosis have large amounts of discharge that can obstruct the nostril.

A complete blood count, chemistry panel and urinalysis is a good basic data base in dogs with persistent nasal problems. While the changes are not usually diagnostic certain conditions such as hypergammaglobulinemia and thrombocytopenia may be noted with ehrlichiosis. Aspergillosis and sinusitis may have a leukocytosis. Imaging is very helpful in identifying the etiology of nasal problems. Lateral and open mouth VD views of the nasal passages are helpful but CT or MR scans of the head are more likely to characterize and localize the disease process. A sky line view of the frontal sinuses also identifies sinus involvement. Imaging defines the best area to search for a diagnosis. Aspergillosis produces destruction of the turbinates resulting in cavernous areas in the nose. Nasal tumors also destroy the turbinates and nasal bones but the area becomes filled with tumor. Under anesthesia, examine the hard palate for soft spots suggestive of boney destruction and explored the area under the soft palate with a finger to identify polyps and tumors in the area. The area can be visualized and biopsied with a flexible scope. The nasal passages can be examined with a rigid or flexible scope but a lot of information can be obtained by examining the nose with an otoscope speculum. Use the largest speculum that you can pass through the nares. Tumors lack the smooth, glistening appearance of normal turbinates. Whitish-grey plaques can be seen on inflamed mucosa in some aspergillosis cases. In aspergillosis, the destruction of the turbinates can be appreciated by noting the openness of the nasal passages. Abnormal areas that are visualized can be biopsied for culture and histopathology. The biopsied tissue should be cultured not the exudate. With luck, nasal foreign bodies can be identified and removed. When there are excessive discharges or hemorrhage blind biopsies of "areas of interest" noted on imaging can be done. Aggressive sampling will identify an etiology in many cases. Care must be taken in the biopsy procedure because many dogs have erosion of the cribriform plate. To avoid the area of the cribriform plate, biopsies must not be taken caudally to a vertical plane in the area of the medial canthus of the eyes.

Nasal aspergillosis is a common finding in dogs with chronic nasal discharges. The most common organism found is Aspergillus fumigatus but other types of Aspergillus may be identified on culture. Because Aspergillus organisms are common in the environment and can be lab contaminants, identification of hyphae in the tissues on histopathology is required to confirm the diagnosis. Even when hyphae cannot be found, a tentative diagnosis can be made from a typical history of chronic nasal discharge unresponsive to antibiotics, serologic identification of antibodies to Aspergillus and the exclusion of tumor. Successful treatment confirms the diagnosis in dogs that have a tentative diagnosis of aspergillosis.

Most dogs with nasal aspergillosis are large dogs and the best treatment is an 1 hour infusion of a 1% clotrimazole into the nasal passages. The clotrimazole can be irritating to the lower respiratory tract therefore great care is necessary to block off the nasopharynx and to protect the trachea with a well inflated endotracheal tube. It is helpful to flush out the nasal passages of excessive discharges before infusion of the clotrimazole. Up to 80% of dogs with nasal aspergillosis can be cured with 2 treatments of clotrimazole given at 2 to 3 week intervals. In small dogs, systemic therapy with itraconazole at 10 mg/kg day for 90 days will be effective in 60-70% of the dogs. Itraconazole would be considered cost prohibitive by many clients of large dogs.

Systemic aspergillosis is fortunately an uncommon condition. German Shepherds are at higher risk of systemic aspergillosis. The usual presenting signs are back pain and lameness. There are often destructive and proliferative lesions of the body of the vertebrae and in the intervertebral disc space. There are also lesions of osteomyelitis in some of the long bones. Cultures of the lesions will identify Aspergillus terreus in most cases. Renal infection occurs commonly in association with the vertebral lesions and the organism can often be identified by culture of the urine. A. terreus is resistant to many of the commonly used antifungal drugs so isolates should be sent for antifungal drug sensitivity to the Fungus Testing Lab of the University of Texas in San Antonio- phone 210-567-4131. Some improvement or stabilization of the disease has been noted with itraconazole but cures are rare. Some of the new antifungal drugs such as voriconazole, caspofungin and posaconazole in vitro can kill this organism. We currently are studying posaconazole in dogs with systemic aspergillosis. The posaconazole seems effective in treating the infection but sites of fungal pyelonephritis remain because the posaconazole is not excreted in the urine. Please contact me if you have a case of systemic aspergillosis due to A. terreus that could be included in the posaconazole study. These drugs are very expensive but have promise in the treatment of this frustrating condition.