Diarrhea is one of the most common presenting complaints in feline medicine. There are many potential causes of diarrhea in
kittens, but they are usually narrowed to infectious, dietary (intolerance and food allergy), parasitic, and foreign bodies.
However, while the differential list for adult cats should include these causes, other causes of diarrhea, including endocrinopathies
(e.g. hyperthyroidism), metabolic disease (e.g. renal failure), inflammatory or immune mediated disease (e.g. IBD), and neoplasia
(especially alimentary lymphoma) must also be considered. This lecture will review some of the more important causes of diarrhea
in cats and the approach to diagnosis and management necessary to resolve the problem.
Giardia spp. is a frequent cause of diarrhea in cats and kittens, with a prevalence rate reported to be at 4 percent nationally, but
the infection rate is much higher in shelters or catteries where it may be nearly 12%. In many adult cats, Giardia spp. infections are subclinical or transient, but in kittens, infection is classically associated with an acute onset of malodorous,
pale, mucoid diarrhea. The diagnosis is relatively straightforward when the trophozoites or cysts are identified on fresh
fecal smears or a flotation. However, because the cysts are shed intermittently, and they can be misidentified or confused
with other fecal artifacts, the sensitivity of this approach is only about 50%. The sensitivity increases to 90% if zinc sulfate
flotation is used to examine 3 separate fecal samples. Recently, a SNAP Giardia test kit (IDEXX laboratories) for detection
of Giardia cyst wall protein 1 (GCWP-1) in canine and feline feces has been made available for use as an in house diagnostic test for
diagnosis of the infection. The test has not been performance tested in large numbers of field studies, but if the sensitivity
is found to be > 90% (e.g. like commercial ELISA microplate readers used in commercial labs), the ease, simplicity and cost
will make this test a great addition to the veterinarian's diagnostic armamentarium. Treatment of giardiasis in cats and kittens
has not changed drastically for many years, and includes specific anti-protozoal therapy combined with environmental control.
Metronidazole, at a dose of 25 mg/kg po q12h for 7 days, continues to be a highly effective therapy for the disease in affected
cats. Fenbendazole has been anecdotally reported to be effective in cats at a dose of 50 mg/kg po q24h, but only one clinical
study has been reported and in that study the cats were co-infected with cryptosporidium, and the response to treatment was
less optimal (50%). So, the true effectiveness of this drug against Giardia spp. is not known. Finally, experimentally infected cats were effectively treated with a combination product containing febantel
(Drontal Plus, Bayer Animal Health). In that study, the kittens did not have diarrhea from the Giardia infection, but the Giardia antigen tests became negative after therapy, suggesting complete removal of the organism. One note of caution is suggested
as this drug is not approved for use in cats, primarily because neurologic signs were observed in some cats when the drug
was administered them during initial testing. Because re-infection is a major cause of persistence or recurrence of infection
in a household, cattery, or shelter setting, institution of appropriate environment control measures is essential. These measures
include environmental decontamination (cleaning of all floors, cages, litter pans and surfaces that have been in contact with
feces with quaternary ammonium or Clorox containing disinfectants), coat cleaning (bathing or shaving of long haired cats),
and isolation of affected animals during the diarrheic phase to prevent infection by co-grooming, etc.