Felis ISSN 2398-2950

Venomous animals of North America

Contributor(s): Rosalind Dalefield, Dawn Ruben

Introduction

Pathogenesis

Etiology

  • Crotalid venoms contain a wide variety of lytic enzymes and nonenzymatic proteins. Effects include proteolysis leading to necrosis, hemorrhage, shock, hypotension. Neurotoxic components are present in some crotalid venoms. Disseminated intravascular coagulation may occur.
  • Coral snake venom is primarily neurotoxic leading to depression, weakness, paralysis, hypotension and respiratory distress.
  • Latrodectus venom is primarily neurotoxic, interfering with neurotransmission and neuromuscular function, causing pain, ataxia, muscle tremors, muscle cramping and restlessness, and ultimately fatal paralysis.  Nausea, vomiting and diarrhea are also common.
  • Loxosceles bites in domestic pets typically lead to an indolent ulcer that takes a long time to heal. Systemic effects are rare but may include hemolytic anemia with hemoglobinuria, fever, nausea and weakness.
  • Scorpion venoms are complex, containing a variety of enzymes and neurotoxins. Reported effects in pets include parasympathomimetic syndrome, skeletal muscle stimulation, hypertension and respiratory failure. Cranial nerve dysfunctions occur in human beings.
  • The toxin responsible for tick paralysis appears to interfere with acetylcholine synthesis or release at neuromuscular endings.
  • Heloderma venom is complex including hydrolytic enzymes and a neurotoxin. Heloderma lizards typically hang on and chew when they bite, causing local tissue damage. Systemic signs in the cat include hyperpnea, emesis, polyuria, salivation, lacrimation and aphonia.
  • Hymenoptera venoms are a complex mixture of toxic chemicals. Locally there is pain and swelling. Systemic effects may include cardiovascular and respiratory collapse. CNS depression, nerve dysfunction and severe gastrointestinal effects have been reported in the dog.  In the cat, bee venom has been shown to cause hypotension, bronchiolar contraction and derangement of cardiac conduction. Anaphylcatic shock may also occur.

Timecourse

  • Crotalid bites are painful and onset of clinical signs is usually rapid but may be delayed for several hours.
  • Envenomation does not always occur in snakebite. If no swelling apparent within 2 hours of a crotalid bite then envenomation has not occurred.
  • Coral snake envenomation may be painless and onset of clinical signs may be delayed for up to 18 hours.
  • Onset of clinical signs of Latrodectus envenomation occurs within 8 hours of the bite. Average survival time in cats is 115 hours. Cats exhibit paralytic signs relatively early.
  • Loxosceles bites typically take several days to become evident but may take months to heal.
  • Scorpion stings are painful and onset of clinical signs is generally rapid.
  • Tick paralysis is gradual in onset.
  • Heloderma bites are intensely painful and local trauma is immediately apparent.  It may be necessary to prise the lizard off the patient.
  • Hymenoptera stings cause an immediate reaction.

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

Other sources of information

  • Oehme F W (1987) Clinical Toxicology in Small Animals. Proceedings  # 103 Veterinary Clinical Toxicology University of Sydney Postgraduate Committee in Veterinary Science 1987.
  • Murray E Fowler Veterinary Zootoxicology. CRC Press, 1992.
  • Peterson M E (2001) Poisonous Lizards In Small Animal Toxicology. Eds Peterson and Talcott.  Saunders 2001.
  • Peterson M E (2001) Snake Bite: Pit Vipers and Coral Snakes. In: Small Animal Toxicology. Eds Peterson and Talcott. Saunders 2001.
  • Peterson M E & McNalley J (2001) Black Widow Spider Envenomation. In: Small Animal Toxicology. Eds Peterson and Talcott. Saunders 2001.
  • Peterson M E & McNalley J (2001) Brown Spider Envenomation. In: Small Animal Toxicology. Eds Peterson and Talcott. Saunders 2001.

Organisation(s)


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