Canis ISSN: 2398-2942

Anaphylaxis, urticaria and angioedema

Contributor(s): Michael Day

Introduction

  • Cause: type I hypersensitivity response.
  • Signs: dependent upon clinical syndrome (anaphylaxis, urticaria or angioedema).
  • Diagnosis: history and clinical signs.
  • Treatment: adrenaline, intravenous corticosteroids, antihistamine, fluids.
  • Prognosis: good if responds to immediate emergency treatment.

Pathogenesis

Etiology

Pathophysiology

  • Classical type 1 hypersensitivity reaction (Gel and Coombs classification).
  • Animal must first be sensitized to antigen (allergen) to produce anaphylactic reaction. In some instances, sensitization is inapparent. For example, urticarial and angioedematous reactions can occur after the first vaccination in puppies or kittens, and in this instance the passive transfer of IgE through colostrum is implicated.
  • Production of IgE occurs initially. Allergen-specific IgE binds to tissue mast cells and circulating blood basophils which renders these cells 'sensitized'.
  • On second or subsequent exposure antigen binds to IgE on mast cells and basophils. Antigen cross-links two IgE molecules bound to surface IgE receptors. Such cross-linking initiates signaling pathways within the mast cell or basophil that leads to degranulation and release of pre-formed and de-novo synthesized vasoactive amines and pro-inflammatory mediators.
  • The effect of this degranulation initiates the spectrum of clinical changes.
  • Urticaria and angioedema involved local cutaneous or subcutaneous vasodilation and edema with activation of neural pathways leading to pruritus. In anaphylaxis, vasodilation is systemic so there is generalized edema and lowering of blood pressure leading to shock. In the dog, the target 'shock organ' is the liver, so hepatic veins are particularly affected.

Timecourse

  • Acute (within minutes of exposure in sensitized animal).
  • Urticarial reactions that are not life-threatening are generally transient and may resolve within 24 hours.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Søland J & Bolt G (1996) Hypovolemic shock after anthelmintic treatment of canine angiostrongylosis. JSAP 37 (12), 594-596 PubMed.
  • Kushner L I & Trim C M (1994) Suspected thiopental-induced anaphylaxis in a dog. JAAHA 30 (5), 451-456 VetMedResource.
  • Mueller D L & Noxon J O (1990) Anaphylaxis: pathophysiology and treatment. Comp Cont Ed Pract Vet 12 (2), 157-170 VetMedResource.

Other sources of information

  • Day M J (2008) Clinical Immunology of the Dog and Cat. 2nd edn. Manson Publishing Ltd., London.
  • Cohen R D (1995) Systemic anaphylaxis. In: Kirk's Current Veterinary Therapy XII. Bonagura J D (ed). W B Saunders, Philadelphia. pp 150-152.


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