Page 369 - Problem-Based Feline Medicine

18 – THE THIN, INAPPETENT CAT 361

Diagnosis ● Dyspnea and occasionally coughing may occur,
with increased respiratory noise on auscultation.
Diagnosis based on cytological identification of
● Absence of respiratory signs does not exclude sig-
cryptococcal organisms in nasal discharge, exu-
nificant lung involvement.
dates, fine-needle aspiration of masses and lymph
nodes and cerebrospinal fluid. Involvement of the gastrointestinal tract causes diar-
rhea and weight loss.
Histopathology may be required if cytology is not diag-
nostic. Peripheral lymphadenopathy and granulomatous,
ulcerating skin lesions may be noted.
Using a latex agglutination test to identify cryptococcal
capsular antigen (on serum, urine or cerebrospinal Ocular involvement is common, and may cause a
fluid) provides a non-invasive, sensitive and specific granulomatous retinitis, uveitis and panophthalmitis.
diagnostic test.
Hepatomegaly, splenomegaly and neurological signs
Nasal radiography may reveal increased soft tissue den- may also be seen.
sity and bone destruction.
Cats with disseminated disease are generally extremely ill.
PCR (polymerase chain reaction) assays are now avail-
able to detect cryptoccal antigens in biopsy material. Diagnosis

Diagnosis is based on cytological identification of
SYSTEMIC MYCOSES
the organisms in exudates, fine-needle aspiration of
lesions and lymph nodes, cerebrospinal fluid and
Classical signs
bronchoalveolar lavage fluid.
● Vague, non-specific signs of weight loss, ● Fungal culture may assist, but is not required for
inappetence and depression. identification of the organism.
● Dyspnea.
Histopathology may be required if cytology is not diag-
nostic, and shows pyogranulomatous lesions.
See main references on pages 371, 388 for details (The
Pyrexic Cat). Serology may be useful in the diagnosis of blastomy-
cosis, but false-negative results may occur both early
and late in the infection. It should be used in cases
Clinical signs
where there is a high level of suspicion of the disease,
The most common systemic mycoses (excluding cryp- but organisms can not be demonstrated.
tococcosis) are histoplasmosis and blastomycosis.
Thoracic radiography may show varying changes,
● Both are geographically restricted infections.
however a diffuse interstitial or nodular interstitial
– Histoplasma capsulatum, the agent causing
pattern is most commonly seen.
histoplasmosis, is endemic throughout large
areas of the temperate and subtropical regions of Hematological changes tend to be non-specific, and
the world. include the presence of a mild non-regenerative anemia
– Blastomycosis (caused by Blastomyces dermati- in some cases.
tidis) is principally a disease of North America,
but has occurred in Africa and Central America. PORTOSYSTEMIC SHUNTS
History tends to be vague and chronic, including
weight loss, inappetence and weakness. Classical signs
Mild to moderate fever. ● Congenital shunts usually show clinical
signs by 6 months of age.
Infection is commonly acquired by inhalation, and so
● Weight loss or stunting (congenital shunts).
clinical signs are often localized to respiratory tract.
continued