Page 1058 - Clinical Small Animal Internal Medicine

996 Section 9 Infectious Disease

cats, but diabetes mellitus has been identified in some (CT) or magnetic resonance imaging (MRI) can reveal
VetBooks.ir affected cats. loss of turbinates, defects in the nasal septum, and/or
increased soft tissue opacity within the nasal cavity. CT
Disseminated aspergillosis in dogs likely occurs as a
result of an uncharacterized genetic immunodeficiency,
phy, and are the preferred imaging modalities. Osteolysis
because young adult female German shepherds are and MRI have increased sensitivity over plain radiogra­
strongly predisposed, and immunosuppressive drug of the cribriform plate, orbit, and frontal bones may be
treatment is rarely present in the history of affected dogs. identified using advanced imaging. In some animals,
Disseminated aspergillosis is extremely rare in cats. lesions are limited to the frontal sinus. Visualization of
fungal plaques by rhinoscopy and sinuscopy confirms
the diagnosis. Trephination or surgical exploration of the
History and Clinical Signs
frontal sinuses may be necessary to visualize (and treat)
Clinical signs of SNA in dogs and cats consist of sneez­ this region. Cytologic examination of mucosal swabs,
ing, serous to mucopurulent nasal discharge, depigmen­ brush specimens of the nasal cavity, or nasal biopsies can
tation of the nasal planum (Figure 109.6), and, less reveal hyphae, which are septate and branch at 45°
commonly, epistaxis. angles, and sometimes also conidia. Culture of Aspergillus
Nasal pain may be manifest in dogs as pawing at the from nasal biopsies supports the diagnosis, although
face or withdrawal. Nasal airflow is usually normal or negative culture results do not rule out SNA.
increased. Serous ocular discharge may occur as a result Disseminated aspergillosis may be suspected on the
of destruction of the bones of the orbit. Rarely, palpation basis of signalment and clinical findings. In some cases,
of the nasal bones or the hard palate reveals defects. hyphae are visualized in tissue aspirates or urine sedi­
Osteolysis of the cribriform plate occasionally leads to ment from affected dogs. Growth of a typical Aspergillus
meningitis with neurologic signs such as obtundation or species (most commonly A. terreus or A. deflectus) from
seizures. a normally sterile site confirms the diagnosis.
Sites often involved in dogs with disseminated asper­ Both serum antibody and antigen assays have been
gillosis include the vertebral endplates and discs, renal evaluated for diagnosis of SNA and disseminated asper­
pelvis, long bones, and lymph nodes. However, any organ gillosis in dogs. Assays that detect serum antibodies to
may be affected, including the spleen, liver, heart, cardiac Aspergillus include ELISA and gel immunodiffusion (ID)
valves, pancreas, eyes, lungs, brain, meninges, small assays. Different antibody assays vary in their sensitivity
intestine, skin, spinal cord, thyroid, adrenal glands, pros­ and specificity for diagnosis of SNA but in general, posi­
tate, and trachea. The most frequent clinical signs are tive results suggest a diagnosis of SNA, but negative
lethargy, inappetence, pain, lameness, and ataxia and results do not rule out SNA. Dogs with disseminated
paresis secondary to discospondylitis. aspergillosis frequently test negative, and so serum
antibody testing is not recommended for diagnosis of
this disease.
Diagnosis
The sensitivity and specificity of serum Aspergillus
Imaging of the nasal cavity of dogs with SNA using plain galactomannan antigen ELISA (Platelia®) for diagnosis of
radiography (open mouth view), computed tomography SNA are low, and its use is not recommended for this
condition. However, serum or urine antigen testing has
high sensitivity for diagnosis of disseminated aspergillo­
sis in dogs, and a high specificity when using a cut‐off
galactomannan index of 1.5. High‐level false positives
(>1.5) appear to occur only in dogs with other fungal
infections, especially those caused by Penicillium or
Paecilomyces, and dogs treated with Plasmalyte® fluid
therapy.
In summary, a strong positive assay result in a dog with
clinical abnormalities consistent with disseminated
aspergillosis and no history of Plasmalyte administration
supports a diagnosis of a mold infection, but fungal cul­
ture is required to confirm that Aspergillus is the causa­
tive agent. A negative result in a dog with disseminated
disease suggests that Aspergillus is not the cause, but
Figure 109.6 Nasal depigmentation and ulceration in a dog with does not rule out the possibility of infection by another
sinonasal aspergillosis. fungal species.