Page 34 - Problem-Based Feline Medicine

26 PART 1 CAT WITH UPPER RESPIRATORY TRACT SIGNS

Depression, anorexia or inappetence and weight loss are Differential diagnosis
often present with nasal or CNS involvement.
Neoplasia may have similar signs. The presence of a
Submandibular lymph nodes are often enlarged. polyp-like mass in the nose, or swelling over the bridge
of the nose suggest cryptococcosis rather than neopla-
Skin lesions consist of papules or nodules varying
sia. Cats with neoplasia are on average older than cats
from 0.1–1 cm in diameter.
with cryptococcosis.
● Lesions may ulcerate and exude serous fluid, or
remain as intact nodules. Chronic bacterial infection of the nasal cavity sec-
● Skin lesions may be single or multiple, and occur ondary to viral upper respiratory disease has similar
alone, or with involvement of other organs. signs. However, it is only rarely associated with nasal
distortion.
Central nervous system signs result from inflamma-
tion of the brain and meninges or a mass lesion (granu-
Treatment
loma).
● Signs reported are referable to the cerebrum Best success occurs using a multi-drug regime
(seizures, circling, ataxia, behavioral change, head comprising of amphotericin (fungicidal) plus 5-fluo-
pressing, blindness), or brainstem (head tilt, nys- rocytosine (flucytosine), combined with or followed by
tagmus, facial paralysis, paresis, ataxia, circling). fluconazole or itraconazole (fungistatic).
● Occasionally, signs are referable to the spinal cord. ● Amphotericin B is very nephrotoxic, so use
diuresis to protect the kidneys. Liposomal or lipid-
Ocular signs include epiphora, dilated unresponsive
encapsulated amphotericin B are safer than regular
pupils, blindness and anterior uveitis.
amphotericin B but are expensive.
Occasionally, other organs are involved, e.g. bone, – Amphotericin B can be given IV (see standard texts)
kidney. or SC (0.5–0.8 mg/kg) in 400 ml of 0.45% saline
containing 2.5% dextrose. Administer subcuta-
Diagnosis neously two or three times a week for 1–3 months,
until a total cumulative dose of 12–26 mg/kg is
Diagnosis is based on cytological identification of the
reached. Monitor serum creatinine, urea (more sen-
organism in nasal discharge, exudate from skin
sitive, but influenced by many non-renal factors)
lesions, lymph node aspirate, cerebrospinal fluid (CSF)
and urine specific gravity and sediment for casts. If
or ocular aspirate.
azotemia develops, discontinue amphotericin until
● Stain sample with new methylene blue, Indian ink
it resolves and reduce dose (Malik et al. 1996).
or Diff-Quick.
● Cryptococcus appears as yeast-like organisms Sensitivity to amphotericin toxicity varies consider-
(5–15 μm) surrounded by a wide, clear capsule. ably between cats, and some cats develop acute renal
● Organism buds from a narrow base, in contrast to failure with relatively small doses. It is imperative that
Blastomyces which has broad-based budding and serum urea concentration and urine are checked prior
thinner capsule. to each dose. The client should be instructed to return
immediately if the cat becomes lethargic, inappetent or
Serology to detect cryptococcal capsular antigen in
is vomiting.
blood, CSF, or urine is sensitive and specific.
Combine with 5-fluorocytosine 50 mg/kg q 8 h PO.
Tissue biopsy of the granulomatous mass or skin lesion,
and histological identification of the organism may be Either during or after the course of amphotericin is
required if cytology is negative. completed, use an imadizole/triazole to mop up infec-
tion (fungistatic):
Fungal isolation with culture is rarely required for
● Ketaconazole is cheapest, but has most side effects
diagnosis, but is useful for sensitivity testing.
(anorexia, vomiting, hepatic disease) and is perhaps
Radiographs often reveal turbinate lysis and opacity least potent (10 mg/kg PO q 12–24 h).
of the nasal cavity (soft-tissue density). Sinus involve- ● Itraconazole may work better than ketaconazole,
ment is common. and has fewer side effects (5 mg/kg PO q 12–24 h).