Felis ISSN 2398-2950

Organophosphorus insecticide poisoning

Synonym(s): Organophosphate toxicity, Organophosphate toxicosis

Contributor(s): Phil Dobson, Agnes Delauche, Rosalind Dalefield, Nicola Bates

Introduction

  • Organophosphate insecticides (OPs) are commonly used pesticides.
  • Cause: ingestion of pesticide or following treatment for external parasites.
  • Action: organophosphates form a temporarily reversible bond with acetylcholinesterase (AChE) and butyrylcholinesterase (pseudocholinesterase), which becomes permanent with time.
  • Signs: cholinergic crisis (excessive parasympathetic stimulation, skeletal muscle stimulation and central stimulation) varying with the compound involved and individual susceptibility.
  • Treatment: prompt action requiring atropine and symptomatic support.
  • Prognosis: good if prompt treatment.

Pathogenesis

Etiology

  • Ingestion of liquid concentrates/granules of organophosphates/carbamate compounds (widely used for control of external parasites in dogs or control of insects in the home/garden) or from excessive skin or hair coat dusting or painting.
  • Ingestion of organophosphate insecticide-containing flea collars or cattle ear tags.

Pathophysiology

  • Organophosphate insecticides and carbamates are acetylcholinesterase enzyme inhibitors; organophosphates are irreversible inhibitors of the enzyme, whereas carbamates are reversible inhibitors of acetylcholinesterase.
  • Organophosphate compound  →  bond with acetylcholinesterase  →  inhibition of action of acetylcholinesterase  →  build-up of acetyl choline at the synapses and the neuromuscular junctions  →  stimulation of parasympathetic cholinergic synapses and neuromuscular junctions  →  eventual reduction in nerve sensitivity to stimulation causing depression  →  central respiratory depression, bronchial fluid accumulation and bronchoconstriction  →  asphyxia.

Timecourse

  • Signs develop within minutes or hours of exposure to organophosphate.
  • Time depends on individual susceptibility, compound, route of absorption and dose.

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.
  • Fikes J D (1990) Toxicology of selected pesticides, drugs, and chemicals - organophosphorus and carbamate insecticides. Vet Clin North Am Small Anim Pract 20 (2), 353-367 PubMed.
  • Jaggy A & Oliver J E (1990) Chlorpyrifos toxicosis in two cats. J Vet Intern Med 4 (3), 135-139 PubMed.

Other sources of information

  • Talcott P A (2016) Organophosphorus and carbamate insectides. In: Blackwell's Five Minute Veterinary Consult. Small Animal Toxicology. 2nd edn. Hovda L, Brutlag A, Poppenga R, Petersen K (eds). Wiley-Blackwell, Ames, Iowa. pp 689-696.
  • Means C (2013) Organophosphate and carbamate insecticides. In: Peterson M E, Talcott P A Small Animal Toxicology. 3rd edn. St Louis, Missouri: Elsvier. pp 715-724.
  • Wismer T, Means C (2012) Toxicology of newer insecticides in small animals. Vet Clin Small Anim 42, 335-347.
  • Rosendale M E (2003) Disulfoton: a deadly threat to pets. Vet Med 98 (6), 466-469.
  • Osweiler G D (1995) Toxicology. Philadelphia: Williams and Wilkins. ISBN: 0 6830 6664 1.

Organisation(s)


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