TISSUE AFFECTING TOXINS (CYTOTOXIC)
Major cytotoxic snakes include –
PUFF ADDERS, GABOON ADDERS, MOZAMBIQUE SPITTING COBRA, WESTERN BARRED SPITTING COBRA (Namibia), WOOD’S BLACK SPITTING COBRA.
Spitting Cobras have a Cytotoxic and to a lesser extent Neurotoxic venom.
Rinkhals in some areas have a strong cytotoxic effect as well.
Minor cytotoxic snakes include –
Stiletto snake (also known as the burrowing asp), Horned Adder and Many-horned Adder, Night Adder and Snouted Night Adder, Desert Mountain Adder and Plain Mountain Adder.
The venom and fangs: In the adder family, venom is injected most often just under the skin into subcutaneous tissue via hollow, movable fangs located in the anterior mouth although because of the size of the fangs intramuscular or intravenous injection also occurs. The cobras do not have movable fangs and these are much shorter so most bites are subcutaneous.
Cytotoxic venom is generally composed of several digestive enzymes and spreading factors, which result in local and systemic injury. Clinically, local effects progressing from pain and edema to ecchymosis (bleeds under the skin) and bullae (watery blisters) most commonly predominate. Hematological abnormalities including benign defibrination with or without thrombocytopenia (increased bleeding and decreased clotting) may result, but severe generalized bleeding is not common.
Pain and swelling occurs almost immediately after the bite from a cytotoxic snake and gradually becomes worse, in the next few hours. (Within 4 to 6 hours it will be more pronounced) It is often described as “cold fire” Later shock develops and this may cause death.
Findings of necrosis usually are evident by 48 hours following the bite. Necrosis begins with darkening of the area around the fang punctures. Blistering may follow. Necrosis usually is confined to the skin and subcutaneous tissue, but may be quite extensive. A putrid smell is characteristic.
Acute inflammation of the eye follows venom-spitting exposure and is characterized by ocular congestion, edema of the conjunctiva and cornea, and a whitish discharge.