VPT 421: Veterinary Toxicology (2+0)

SPIDER POISONING

• Spiders use their venom toparalyze prey while they eat victim’s body fluids.

• The venom of spiders is acomplex mixture of neuroactive proteins and other chemicals.

• Toxic principle is p roteins which include protease, hyaluronidase, sphingomyelinase D and esterase.
• They have direct lytic effect on RBCs.
• The most venomous spiders in the world include Brown recluse spider, Hobo spider and Black widow spider.
• Some spider venoms can kill a mouse at a dose as low as 0.006 mg.

• The black widow species venom is made up of large proteins thought to affect the transmission of calcium ions of nervous system cells.

• The initial sting of the bite is followed by muscle cramps, sweating and possibly decreased blood pressure.

• There is no adequate treatment but the bite is seldom fatal.

Brown reculse spider	Hobo Spider	Black widow Spider

Signs

• The bite initially stings, then any one of the two forms may take place.
  • The cutaneous form begins as edema, progresses to an ulcerated wound.
  • The viscerocutaneous form, which is severe, produces hemolytic anemia, hemoglobinuria, icterus and hyperthermia.
• Ninety percent of the cases heal in 1 - 3 weeks. Some may need skin grafting.

Mechanism

• Unidentified venom component is cytotoxic to endothelial cells. This triggers intravascular coagulation and microthrombi formation within capillaries. Capillary occlusion, hemorrhage, and necrosis occur.
• Polymononuclear leukocytes and complements play important roles in potentiating the response to envenomation.

Treatment

• Steroids may be used to protect against systemic effects.
• Hemolytic anemia can be managed by use of fluids and bicarbonate to minimize hemoglobin deposition in renal tubules and by blood transfusion if anemia is severe enough to justify.