Page 677 - Problem-Based Feline Medicine

31 – THE CAT WITH SIGNS OF CHRONIC VOMITING 669

dogs, but not in cats, and its utility remains to be estab- possible and affected animals will have recurrent or
lished for the routine diagnosis of food hypersensitivity. persistent clinical signs.

Differential diagnosis FOOD INTOLERANCE***

The main differential diagnosis for food allergy is food
Classical signs
intolerance and they are usually clinically indistin-
guishable. ● Chronic vomiting, usually < once per day,
immediately to >12 h after eating.
Cats with food allergy causing dermatologic signs
● Diarrhea is less frequent and more often
must be differentiated from cats with atopy, flea allergy
large bowel in character.
dermatitis, psychogenic alopecia or insect bite hyper-
● Weight loss.
sensitivity.
● Dermatological signs in some cats (miliary
The gastrointestinal signs of either syndrome can dermatitis, pruritus).
mimic many other causes of chronic GI disease, includ-
ing gastritis, pancreatitis, and small bowel diseases such
Pathogenesis
as IBD or colitis. The severity and duration of each event
depends on the amount of antigen ingested, the immune Food intolerance is a non-immunologic reaction to
response and the sensitivity of the patient. The more a substance or multiple substances in food. This
severe the presentation, the more differentials that must reaction can occur to proteins or other food compo-
be included, e.g. neoplasia, extra-intestinal disease, etc. nents, but it can also be associated with food coloring,
additives, preservatives or flavorings. Naturally occur-
ring chemicals such as amines, salicylates and
Treatment
monosodium glutamate are present in food, especially
Treatment is initiated during the diagnostic phase by highly flavored rich food.
feeding the elimination diet. The key to effective ther-
These distinctions are difficult to distinguish clini-
apy is to find the offending agent(s) and remove
cally.
them from the diet.
Food sensitivity may also be associated with dermato-
Corticosteroids may provide partial relief, especially
logical signs.
where type I hypersensitivity reactions are involved,
but in general are not effective in maintaining remission Approximately 25% of cats with GI signs from food
or symptomatic relief for cats with food allergies. sensitivity also have dermatologic signs consisting of
pruritus, miliary dermatitis and alopecia.
Antihistamines have not been proved effective in
preventing the gastrointestinal symptoms associated The pathogenic mechanisms of food intolerance are
with food allergy. poorly understood, but a combination of direct toxicity
caused by the ingestion of the food causing release of
Some animals will eventually develop allergies to com-
histamine and other vasoactive amines, and indirect
ponents in the elimination diet. In these cases, feeding
effects that are mediated via an amplification system
diets containing protein hydrolysates will be most
which responds to the food by releasing mast cell prod-
effective. Unlike regular protein molecules, the molec-
ucts, production of eicosanoids and other inflammatory
ular size of these hydrolysates is too small to crosslink
mediators, initiation of the kinin cascade, and other
IgE bound to mast cells.
events that result in the clinical syndrome.
Prognosis Clinical signs
The prognosis for control of food allergy is excellent if Cats with food intolerance traditionally have been
the offending agent(s) can be identified and eliminated thought to have gastrointestinal tract signs only,
from the diet. However, in some cases, that is not because the syndrome is not an immunologic reaction.