Page 717 - Problem-Based Feline Medicine

32 – THE CAT WITH SIGNS OF ACUTE SMALL BOWEL DIARRHEA 709

most cats, choosing a commercial diet that contains
FOOD ALLERGY (DIETARY
HYPERSENSITIVITY)* a single, novel protein source will work best for
long-term management of these cats.
● Diets that contain protein hydrolysates are less
Classical signs
antigenic than intact proteins because their molecu-
● Gastrointestinal signs are variable, but can lar structure is too short to bridge IgE receptors on
include vomiting, diarrhea, weight loss or the cell membrane. The usefulness of these diets in
anorexia. cats with food allergy is unknown. Type I (IgE-
● Food allergy may also produce mediated) hypersensitivity is thought to be involved
dermatologic signs usually in the absence in only about 25% of food allergy cases. However,
of GI signs. these diets give another option for both diagnosis
and treatment of cats with food allergy.
See main reference on page 667 for details.
Other diagnostic tests, including intradermal skin test-
ing, ELISA testing, RAST testing, and gastroscopic
Clinical signs food testing have all been tried in an attempt to find eas-
ier methods of making the diagnosis. However, the only
Gastrointestinal signs are more variable, but can
reliable test currently available is the food elimina-
include vomiting, diarrhea, weight loss or anorexia.
tion trial (which is also what is used in humans).
● In cats, vomiting is more common than diarrhea.
● Generally, signs of hypersensitivity involve either In most cats, the hemogram and chemistry profile
the GI tract or skin. will be completely normal or have mild non-specific
● Clinical signs can occur at any age. changes associated with inflammation.
Most common signs are dermatologic in origin (pruri-
tus, alopecia, miliary dermatitis, seborrhea), affect the
Differential diagnosis
head, face, ears and inner thigh especially, and are
non-seasonal in occurrence. Other differentials such as food intolerance, parasites,
and metabolic or neoplastic diseases should be consid-
There are no known breed or sex predispositions for
ered. Inflammatory bowel disease is also a disease
food allergy.
that mimics food allergy and is very difficult to differ-
entiate from it.
Diagnosis
Flea allergy is the most common cause of dermatologic
The definitive diagnosis of food allergy is only signs of allergy, but atopy and food allergy must be
obtained by feeding an elimination diet. The signs considered.
usually start to resolve after 4–7 days but may require
6–8 weeks for complete resolution, then reintroduction
Treatment
of the offending diet results in the reappearance of
signs. Once an elimination diet has been identified that suc-
● The elimination diet chosen depends on the cat’s cessfully relieves the clinical signs, the cat should remain
preferences for food, the owner’s willingness to on that diet indefinitely. However, it is best in most cases
make homemade foods, and the clinical situation; to try to identify a commercial diet that most closely
however, the best elimination diet is a diet con- resembles the elimination diet so that the cat receives
taining a single, novel protein source (turkey, a nutritionally complete and balanced diet.
venison, duck, kangoroo, etc.) and a single, novel
After a period on one diet, cats may develop hyper-
carbohydrate source (rice, potato, etc.), with no
sensitivity to that new diet, so new (even more novel)
other additives except a pet vitamin.
diets will be necessary.
● A homemade diet (1/3 cup protein, 2/3 cup carbo-
hydrate) can be used as a diagnostic trial, but is not Most cats with food allergy respond only partially or
a balanced diet for long-term maintenance. In not at all to prednisolone.