Page 716 - Problem-Based Feline Medicine

708 PART 9 CAT WITH SIGNS OF GASTROINTESTINAL TRACT DISEASE

Cats are more likely to also have evidence of acute such as seizures, coma and behavioral changes. All of
or chronic large bowel diarrhea (with hematochezia, these are less common in cats than in dogs and are
increased mucus and tenesmus) than are other species reversible with discontinuation of treatment.
affected.
Other drugs that have been recommended for treatment
of giardiasis are quinacrine and furazolidine, but
Diagnosis these drugs may not eliminate the infection, only
improve the clinical signs.
The diagnosis is made by appropriate fecal examination
techniques. Zinc sulfate flotation is considered to be Albendazole and fenbendazole have been recently
the most accurate and practical test. Three consecu- shown to be effective in treatment of dogs and cats with
tive zinc sulfate flotations will identify 95% of giardiasis. Albendazole (25 mg/kg q 12 h × 2 days) is
infected animals. not approved for use in cats in the United States and is
teratogenic, hepatotoxic and causes bone marrow sup-
Other methods include examination of fresh fecal
pression, and thus is not recommended. Fenbendazole
saline smears (1 drop saline with a small amount of
(50 mg/kg/day × 3 days) has been recommended for
feces that is spread thin enough to read a newspaper
treatment of giardiasis in cats.
through) for trophozoites (only 40% of infected ani-
mals will be identified), duodenal aspiration (e.g. Proper disposal of feces and good sanitation is
instill 10 ml of saline into the duodenum, either through essential to remove any environmental contamination.
the accessory channel of the endoscope or injected
directly during laparotomy, and then aspirate the fluid
Prognosis
for examination) of fluid looking for trophozoites
(requires endoscopy or laparotomy, but is 88% effec- With proper diagnosis, treatment and sanitation proce-
tive), or fecal ELISA testing for Giardia specific anti- dures, Giardia infections can be completely controlled.
gens (95% sensitivity, but low specificity).

At this time, the zinc sulfate flotation test appears to be Prevention
the easiest, most reliable and most accurate method of
Since the cysts are susceptible to drying and many
identifying Giardia infections.
common disinfectants, good sanitation can prevent
Because of the small size of the cysts (1/8 the size of a once contaminated area from being a source of addi-
a Toxocara oocyst), the operator needs to scan the slide tional infections.
carefully and focus up and down through the different
Avoid allowing cats access to drinking water that may
planes to identify the cysts in the preparation.
have fecal contamination.
A vaccine is now available that purports to reduce
Differential diagnosis
shedding of Giardia cysts, however, immune system
Other infectious, parasitic, dietary, toxic and idiopathic activation has been shown to decrease shedding without
causes of small bowel diarrhea must be considered having an effect on the infection itself. The vaccine
since many cats have only mild signs. does not prevent infection or reduce severity, and in
a study in cats made no significant difference overall.
Treament
Metronidazole (50 mg/kg/day PO for 5 days) contin- Public health
ues to be recommended for treatment of giardiasis in
cats. However, resistant strains of the protozoan are Giardia cysts should be considered potentially zoonotic.
increasingly being reported, and thus this therapy
The infectivity of different strains of Giardia for differ-
may not be effective in all cases.
ent species is quite variable, but this fact should not
Side effects associated with metronidazole therapy preclude the need to take adequate precautions when
include gastrointestinal upset and neurologic signs, handling feces.