Anaphylaxis is an acute, potentially life-threatening hypersensitivity reaction, involving IgE-induced degranulation of mast cells and basophils that release potent pro-inflammatory molecules. The incidence of these anaphylactic reactions has not been established in veterinary medicine and strong evidence for the use of antihistamines and steroids is lacking. In this study, we aimed to characterize these anaphylactic reactions in dogs, estimate their incidence, and identify a potential correlation between outcome and treatments.
We conducted a tiered keyword-based search of the hospital and diagnostic laboratory databases over 11 years. Tier 1 keywords were specific to type I hypersensitivity: e.g. anaphylaxis, angioedema. Tier 2 keywords included clinical signs that are frequently associated with anaphylaxis: e.g. urticarial, asthma. Tier 3 keywords matched clinical signs that can be seen in more various circumstances: e.g. swollen nose.
Eighty-eight cases of anaphylactic reactions were found out of the 5,413 cases identified by the keyword search (0.2 % incidence), with a female : male ratio of 2.3 : 1 (compared to 1:1 in the hospital dog population). The median age was 2.2 years (2.4 mo-14 yo). The most represented breeds were mixed breed dogs (18.2 %), dachshunds (10.2 %), Chihuahuas (6.8 %), Labrador retrievers (6.8 %), boxers (5.7 %), and American PitBull Terriers and pugs (both 4.5 %). The reactions were linked to a vaccine (35.2 %), a drug (10.2 %), an insect bite/sting (9.1 %), bedding/chemical (3 %), or remained of unknown origin (42 %). Reported clinical signs were cutaneous (87.5 % cases; 65.9 % angioedema, 34.1 % erythema, 32.9 % urticaria, and 5.7 % pruritus), gastrointestinal (9.1 % cases), shock signs (9.1 %), and respiratory (2.3 %). One patient died, but 75 % of survivors had improved by the time they left the hospital (including 16.1 % with full recovery), and 10.3 % remained unchanged. A medicine was administered in 93 % cases: injectable antihistamines (87.5 %), corticosteroids (50 %), both (44.3 %), and a vasopressor (3.4 %). Thirty-one percents of survivors went home with oral diphenhydramine, 2.1 % with prednisone, and 3.4 % with both. No difference in outcome was found between treatment groups (P = 0.9571) or based on etiology (P = 0.07516). Clinical signs impacting negatively the outcome include respiratory signs (P = 0.0059), particularly respiratory distress (P = 8.581e-16) and signs of cardiovascular shock (P = 0.00491).
In our study, anaphylactic reactions appeared to be a relatively common motivation for consultation. They appeared to be more common in female dogs than their male counterparts. Cutaneous signs were the most common presentation of anaphylaxis in dogs. Overall, these allergic reactions had a good prognosis. Based on our data, the administration of corticosteroids in addition to antihistamines to treat anaphylactic reactions in dogs is not warranted.
Emergency and Critical Care Medicine Resident
Oradell Animal Hospital
Dr. Fabrice Fosset earned his veterinary degree from the University of Liege, School of Veterinary Medicine in Belgium, and practiced for two years in the ICU at the University of Liege. He has completed a small animal rotation internship at the University of Montreal in Canada, and a small animal emergency and critical care internship at the University of Illinois. After completion of a Master’s degree in pharmaco-immunotoxicology at the University of Illinois, he completed a small animal emergency and critical care internship at the University of California as well as a certification in veterinary extracorporeal therapies. He is currently ECC resident at Oradell Animal Hospital, NJ. His special interests include transfusion medicine, CPR, immune-mediated diseases, nephrology and extracorporeal therapies.
Thursday, June 14
5:15 PM – 5:30 PM
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