Page 783 - Problem-Based Feline Medicine

34 – THE CAT WITH SIGNS OF LARGE BOWEL DIARRHEA 775

Prognosis Tritrichomonas is the exception, as kittens or young
cats with Tritrichomonas infection will have persistent
Long-term prognosis is poor. However, many cats
foul-smelling diarrhea.
will have lengthy (up to 15 months) periods of good-
quality life following surgical resection. Hematochezia, mucoid stools, large bowel diarrhea
and flatulence have all been infrequently reported in
cats with these parasites, but are secondary to the pri-
PARASITIC INFECTIONS (GIARDIA, mary disease (often FIV).
TRITRICHOMONAS, CRYPTOSPORIDIA,
ISOSPORA, TOXOPLASMA, BALANTIDIUM
AND TRICHURIS)* Diagnosis
Fecal floatation, direct smears of feces, and fecal
Classical signs cytology have all been used to identify these parasites.
● Mucus- or blood-streaked, soft (semi- Multiple (at least three) zinc sulfate solutions on
formed) feces. consecutive days are best to float Giardia and
● Rarely, overt large bowel diarrhea in Cryptospordia oocyts.
immunocompromised or very young cats.
Cryptosporidia are so small that identification is diffi-
cult without special stains or advanced microscopy
Pathogenesis techniques.
There are no major parasitic causes of large bowel Cryptosporidia can also be identified by use of a fecal
diarrhea in the cat. ELISA test (human test but effective in cat feces).
However, occasional infections with Giardia, Tritri- Toxoplasma will float in salt solution but are very
chomonas, Cryptosporidia, Isospora, Toxoplasma, and small (< 5 micron) and may be missed without careful
Balantidium may be observed. examination of the slide.

Each of these parasites has a different life cycle and Diagnosis of Tritrichomonas is best confirmed by PCR
degree of pathogenicity in the host, but none of these is testing or culture of the organism in feces using a spe-
a strictly large bowel parasite and most cause disease cial technique.
only in the very young, the very old, or sick, debili-
tated cats (especially FIV- or FeLV-positive cats).
Differential diagnosis
Whipworm eggs (Trichuris serrate and T. campanula)
Because these are rare causes of large bowel disease
are occasionally observed in cats, but do not cause
in cats, all other, more common, causes of colitis
clinical disease and are believed to be either mis-diag-
should be ruled out first.
nosed (e.g. Capillaria spp.) or are present because the
cat ingested rodent or canine whipworm eggs in the If these parasites are found in the feces of an adult cat
environment. that is symptomatic, an immediate search for an
immunosuppressive disease should be initiated (ie.
Most of these protozoan parasites (e.g. Giardia,
rule out FeLV, FIV, FIP, etc.).
Toxoplasma, Cryptosporidia) are pathogenic (zoonotic)
to humans.
Treatment
Clinical signs Tritrichomonas: Ronidazole (30–50 mg/kg PO q 12h)
Most infections of these parasites in cats are asympto- Giardia: Metronidazole (10–25 mg/kg PO q 12 h for
matic and are accidentally found on a routine fecal 5–10 days) or fenbendazole (25–50 mg/kg PO q 24 h
examination. for 5–7 days)