Page 908 - Clinical Small Animal Internal Medicine

846 Section 9 Infectious Disease

VetBooks.ir

Figure 79.3 Kidney aspirate from a cat. Note neutrophilic‐ Figure 79.5 Inguinal subcutaneous mass in a dog. Note the
macrophagic inflammation with infection of rod‐shaped bacteria marked neutrophilic inflammation and the evidence of unstained
(modified Wright stain, original magnification ×1000). and partially pale basophilic hyphae (modified Wright stain,
original magnification ×400).

Serologic Testing (Antibody and Antigen
Detection)
Serology is used in the clinical setting to diagnose fungal
disease in dogs and cats. However, interpretation of
serologic results in some fungal diseases might be diffi-
cult and will benefit from additional cytologic or molec-
ular evidence or culture. Limited studies are available
regarding sensitivity and specificity of serologic testing
of some fungal diseases. The majority of fungal serologic
tests currently in use in veterinary medicine detect the
antibody response to infection. A few tests detect fungal
antigens, providing a definitive diagnosis if the antigen is
sufficiently specific (such as the antigen‐based latex
agglutination test available for Cryptococcus neofor-
mans). As with any serological test, cross‐reactivity can
Figure 79.4 Thoracic mass from a German Shepherd dog. Note exist between fungal agents. Positive serology provides
the necrotic background, increased numbers of neutrophils and evidence of exposure and supports the clinical findings.
Aspergillus terreus hyphae (modified Wright stain, original Paired serum samples (2–4 weeks apart) should be run at
magnification ×1000).
the same time. A fourfold increase or decrease in the
antibody level is strong evidence of active disease. More
India ink staining is commonly used for the identifica- details on current serologic tests available for fungal dis-
tion of Cryptococcus species. The expertise of the indi- ease are described elsewhere in this section and in the
vidual evaluating the slide is the main variable in using literature.
cytology in the clinical setting. The sensitivity of cyto-
logic and histologic evaluation varies considerably Isolation and Identification (Including
although specificity is high. Cytologic and histopatho- Molecular Testing)
logic features cannot definitively identify the species and
therefore culture and biochemical characterization or Culture
molecular analysis are mandatory for identification. It is The specific identification of fungal organism is based on
important to highlight that morphologic features of culture of fluids or tissue. However, successful culture of
fungi in tissue differ when grown on fungal media. fungal agents depends on several variables, including the