In classic cases, the results of CT or MRI studies along with the identification of fungal plaques with rhinoscopy or sinuscopy
are enough to establish a diagnosis of aspergillosis, and treatment (described later) can be performed during the same anesthetic
event.
Figure 5. Cytologic preparation of a fungal plaque from a dog with sinonasal aspergillosis. Numerous branching hyphæ are evident
(modified Romanowksi stain; 400X). (Image courtesy of Dr. Debra Zoran, Texas A&M College of Veterinary Medicine & Biomedical
Sciences.)
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Cytology and histology. Histologic and cytologic examinations can provide direct evidence of fungal hyphae (Figure 5), which is strongly supportive of a diagnosis of aspergillosis. The sensitivity of these methods is high if samples are taken
from the fungal plaques but tends to be lower if samples are collected without direct visualization.13
Classic histologic findings associated with aspergillosis in dogs include mucosal ulceration and inflammation, with a predominance
of lymphocytes and plasma cells.3 However, these changes are nonspecific and may be reported in dogs with severe idiopathic lymphoplasmacytic rhinitis.
Fungal culture. Fungal culture has been used in combination with other tests in the diagnosis of sinonasal aspergillosis in veterinary patients.
However, false positive and false negative results confound its diagnostic use. Aspergillus species are ubiquitous in the environment and can be cultured from normal dogs and those with neoplastic or inflammatory
nasal diseases.1 If a culture is warranted to confirm Aspergillus species vs. other fungal agents, positive results are more likely if the material is obtained by direct sampling of fungal
plaques during rhinoscopy.14
Treatment
Table 1 Selected Drugs for Treating Aspergillosis in Dogs
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Effective treatment of canine sinonasal aspergillosis is challenging. Different treatment modalities have been described,
including topical and systemic antifungal medications (Table 1) and invasive surgical procedures.
Topical antifungals. Topical antifungal medications are regarded as the treatment of choice if the cribriform plate is intact. When used topically,
both enilconazole and clotrimazole appear to be more effective in the treatment of sinonasal aspergillosis than oral antifungal
agents are. The topical azoles have poor solubility and minimal intestinal absorption and are fungicidal (rather than fungistatic)
at higher concentrations.
The first described technique for topical therapy in dogs required surgically placing tubes into the frontal sinus followed
by enilconazole instillation twice a day for one or two weeks. This method was 90% effective in dogs without extranasal infection.15
An alternative topical method involves one infusion via both nares of either clotrimazole or enilconazole, performed while
the patient is under general anesthesia. A detailed description is beyond the scope of this article, so veterinarians unfamiliar
with this procedure should consult additional resources or refer patients to a specialist. In a study to determine the efficacy
of nonsurgically placed intranasal catheters, topical clotrimazole was shown to resolve clinical disease in 65% of dogs after
one treatment and in 87% of dogs after two treatments.16 A similar study using topical enilconazole in dogs reported 57% resolution of clinical disease after one treatment and 94%
after one to three treatments.17 This study also evaluated the role of extensive rhinoscopic débridement before enilconazole infusion and concluded that
it improved patient outcome.
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