Hooo-Hooo Volume 10, Nr 3 - Page 12

WildLife Group of the SAVA Vet Diagnostix Pathology of Acute Adverse Drug Reactions Dr Rick Last – BVSc; M.Med.Vet (Pathology) Specialist Veterinary Pathologist Vetdiagnostix – Veterinary Pathology Services hypersensitivity response which is an IgE mediated immune reaction to the capture drugs. IgE is produced by eosinophils and cross linking of IgE on the surface of mast cells results in degranulation of mast cells with release of vasoactive amines, which are central in the pathogenesis of type I hypersensitivity. The purpose of this paper is to guide wildlife veterinarians as too the gross pathology they may encounter with acute adverse drug reaction related deaths, the target tissue samples to collect and what certain histological findings might mean. Acute death during or shortly following immobilization in game is usually associated cardiovascular collapse (shock). The hypotension (drop in blood pressure) that follows results in impaired tissue perfusion, cellular hypoxia, shift to anaerobic metabolism and cell death. When compensatory mechanisms are inadequate, which is more likely in the uncontrolled field conditions of game capture, shock is rapidly progressive and fatal. Types of shock reactions that are most likely to be encountered would be • Anaphylactic shock • Cardiogenic shock • Disseminated intravascular coagulation (DIC) Anaphylactic shock is a generalized systemic type I 12 This type of hypersensitivity usually requires sensitization of the host against the allergen on initial exposure (mast cells become coated with antigen specific IgE) followed by re-exposure (cross linking of IgE on the surface of mast cells occurs with degranulation). This scenario is therefore more likely in a situation where game are held in a camp system and repeatedly darted to carry out various management procedures. However, prolonged initial exposure to an allergenic agent (drug) is also capable of initiating mast cell degranulation (in the absence of IgE) and therefore animals being darted for the first time could under the correct set of circumstances develop an acute anaphylactoid reaction. The primary target tissues for the vasoactive amines (histamine) released from the degranulating mast cells are blood vessels and smooth muscle. Clinical signs and pathology may vary between species due to species differences in the distribution of mast cells, mediator content of mast cell granules and the primary shock organ. In most domestic species where the lung is the primary shock organ, pulmonary