Page 89 - Problem-Based Feline Medicine

6 – THE CAT WITH HYDROTHORAX 81

Prevention Clinical signs

Taurine supplementation of commercial cat foods in No real age, sex or breed predisposition. Kittens 6–12
North America has dramatically decreased the inci- months old and purebred queens up to 5 years of age
dence of dilated cardiomyopathy in cats. Other causes are over-represented. Another peak is reported in aged
of cardiomyopathies remain unclear at this time. cats. Cats from multi-cat environments are as greatest
risk.
FELINE INFECTIOUS PERITONITIS (FIP)* Anorexia, weight loss, depression, fever or
hypothermia (terminally), and dehydration may all
Classical signs occur, but none are specific to FIP.
● Muffled heart and/or lung sounds ventrally. The effusive form is more rapid and fulminant than the
● Exaggerated chest excursions with poor non-effusive form.
airflow.
Progressive accumulation of ascites and pleural effu-
● Orthopnea (positional dyspnea with
sion in an inappetant, lethargic and pyrexic cat is char-
reluctance to lie in lateral recumbency).
acteristic of effusive FIP. Dyspnea occurs in about 1/3 of
● Anorexia, weight loss, depression,
cats and results from the pleural restriction of the pleu-
dehydration and fever are common early
ral effusion as well as the compromised diaphragmatic
signs.
excursions secondary to the ascites.
See main reference on page 372, for details (The Typically the wet form progresses to death within 5–7
Pyrexic Cat). weeks of onset of clinical signs. This progression may
be shortened to a few days in young kittens.
Pathogenesis
Feline infectious peritonitis (FIP) is caused by a strain Diagnosis
of feline coronavirus called feline infectious peritonitis
Clinical signs of pleural and abdominal effusion with
virus (FIPV).
normal heart sounds in an inappetant, lethargic and
● This virus specifically infects the mononuclear
often pyrexic cat are highly suggestive of FIP.
phagocytic cells of the spleen, liver and lymph
nodes. Replication of the virus occurs primarily in Serology
these cells and creates a systemic viremic state ● Up to 10–40% of healthy cats have positive coro-
within 1 week of experimental exposure. navirus titers. A positive titer means exposure to a
● Virus and virus-infected circulating monocytes feline coronavirus, but not necessarily FIPV.
deposit in the endothelial lining of venules. ● High titers in the presence of typical signs of FIP in
Immune complex interaction to the viral antigen a cat from a one- or two-cat household may suggest
creates an intense vasculitis with complement- FIP, however, methodology is not standard between
mediated damage to the vessel walls. labs. Some healthy cats, especially pure-bred or
● The “holes” created in the vessels result in the exu- from multi-cat households, have very high titers.
dation of the fibrin-rich characteristic “FIP ● PCR (polymerase chain reaction) may be more
fluid”. accurate at detecting viral antigens. One study, how-
ever, showed 8/9 cats suspected with FIP (87.5%)
Three forms of FIP exist. The effusive or “wet” form
were positive, but 51/84 cats (61%) were positive in
is of most significance in creating pleural effusion. It is
non-suspects.
the damage caused by the humoral immune system,
● A 7B FIP ELISA test is available which detects
rather than viral cytotoxicity per se, that is the major
antibody to the 7B protein, which is specific to some
pathogenic mechanism in the formation of the effusion.
coronavirus strains causing FIP. Specificity and sen-
The large body cavities such as the chest and abdomen sitivity data have not been published. Anecdotal evi-
are most prone to fluid accumulation. dence suggests this is not sensitive for FIP.