The clinical and immunological reaction to a flavoured monthly oral heartworm prophylatic in 12 dogs with spontaneous food allergy

Abstract

There is debate among practicing veterinary dermatologists as to whether flavoured prophylactics should be avoided in the food‐allergic dog. At North Carolina State University we have a colony of dogs with spontaneous food allergy. They are maintained on a hypoallergenic diet (Prescription diet d/d Duck and Rice, Hills Pet Nutrition, Topeka, KS). A flavoured chewable tablet containing pork liver, soy and 2.3 mg of milbemycin (Interceptor Flavor Tabs, Novartis Animal Health, Greensboro, NC) was administered under controlled conditions to 12 dogs. Previous exposure to this medication was documented. A physical examination was performed prior to, and on four occasions after, tablet administration. A clinical score (CS) was assigned to determine the severity of skin and otic disease. Serum was collected at 3‐ to 5‐day intervals. Allergen‐specific IgE (soy, pork and corn) was measured by ELISA. Statistical analysis was performed using SAS software (Cary, NC, USA) and a longitudinal mixed model was employed for the evaluation of the clinical response. An increased CS was observed in 10 dogs post‐challenge; peak values were measured on day 2 (five dogs) and day 5 (five dogs). When compared with pre‐treatment CS this increase was statistically significant (P < 0.05). Significant peaks in serum allergen‐specific IgE were measured on days 5 and 20 to soy, pork and corn. The authors conclude that these dogs have a rapid adverse clinical response to this flavoured medication which is accompanied by a significant increase in serum allergen‐specific IgE, although this does not necessarily correlate with the orally administered allergen.