Canis ISSN: 2398-2942

Thallium toxicity

Contributor(s): Rhea Morgan

Introduction

  • Rare toxicant in young dogs.
  • Present in some rodenticides (eg mole, gopher bate) and other pesticides.
  • Signs: gastrointestinal, cutaneous, neurologic signs.
  • Treatment: supportive care, ferric hexacyanoferrate.
  • Diagnosis: thallium detected in urine.
  • Prognosis: variable, good with mild signs or chronic, low toxicity.

Pathogenesis

Etiology

  • Clinical signs arise from ingestion of thallium.
  • Three clinical syndromes may occur: acute toxicosis, subacute toxicosis, and chronic toxicosis.

Predisposing factors

General
  • Requires exposure to a substance containing thallium.

Pathophysiology

  • Thallium is a heavy metal with an atomic weight and toxic effects similar to lead and mercury.
  • Thallous sulfate is usually the active component in most pesticides. It is the most pharmacologically active form, and is odorless, colorless and tasteless.
  • The mechanism of action in thallium toxicity is not well understood, but thallium has an affinity for sulfhydryl groups.
  • Oxidative phosphorylation may be inhibited by the interaction of thallium with sulfhydryl groups in mitochondrial enzymes.
  • Thallium also selectively exchanges for potassium in many cellular reactions, making it a direct cellular toxin.
  • Thallium has an adverse effect on the cilia of respiratory epithelium.
  • The LD50 dose of thallium is 10-15 mg/kg in most species. Fatal dose is 20-25 mg/kg in most species.

Timecourse

  • Acute toxicosis occurs from 12 hours to 4 days after ingestion.
  • Subacute toxicosis occurs from 3- 7 days after ingestion.
  • Chronic toxicosis develops 7 days to several weeks after exposure.

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.
  • Gassner G, Tholen V, Ternes W (2000) Chronic thallium intoxication in five German pointers of one litter. Berl Munch Tierarztl Wochenschr 113 (7-8), 295-298 PubMed.
  • Fikes J D, Dorman D C (1994) Diagnosis and therapy of neurotoxicological syndromes in dogs and cats: neurotoxic metals. Part 3. Prog Vet Neurol 5 (1), 5-12 VetMedResource.
  • Waters C B, Hawking E C, Knapp D W (1992) Acute thallium toxicosis in a dog. J Am Vet Med Assoc 201 (6), 883-885 PubMed.
  • Ruhr L P, Andries J K (1985) Thallium intoxication in a dog. J Am Vet Med Assoc 186 (5), 498-499 PubMed.
  • Zook B C, Gilmore C E (1967) Thallium poisoning in dogs. J Am Vet Med Assoc 151 (2), 206-217 PubMed.

Other sources of information

  • Grauer G F, Hjelle J J (1988) Rodenticides. In: Morgan RV (ed)Handbook of Small Animal Practice.Churchill Livingstone, Philadelphia, pp 1087-1093.
  • Smith H A, Jones T C, Hunt R D (1972) Veterinary Pathology. 4th Ed. Lea & Febiger, Philadelphia, pp 935-938.

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