Haemotoxic Venom (signs and symptoms)
Haemotoxic venom destroys the coagulent properties of blood.
This type of
causes severe internal bleeding, as well as bleeding from mucous membrane surfaces, and the bite site.
Haemotoxic venom acts as a pro-coagulant, removing fibrinogen from blood and reducing blood platelets. The venom also weakens the capillary endothelium ( a thin layer of cells that line the interior walls of blood vessels) which results in internal haemorrhaging.
This is a slow acting venom, and death usually occurs between 24-72 hours if untreated.
Death usually results from multiple organ failure or bleeding of the brain.
In South Africa, these bites account for less than 1% of all recorded bites.
Immediate symptoms of a Haemotoxic venom:
* No immediate pain.
* Symptomatic signs of envenomation usually presents itself within a hour after a bite.
* Physical symptoms occur much later.
* No physical signs are apparent, apart from bite marks.
* If there is a suspected haemotoxic envenomation (eg Boomslang), then blood clotting time should be tested. The normal clotting time for blood is between 5-8 minutes.
Other signs and symptoms of a Haemotoxic venom:
* Fang marks. This is usually a good indication of a potential envenomation. This could either be distinct puncture marks at the site, or merely a scratch.
* Minimal Edema (swelling). Victims may experience slight swelling around the bite site. This is not immediate, and may occur some time after a bite. Unlike cytotoxic venom the swelling does not progress further along the affected limb.
* Slight pain and discomfort may be experienced by the victim usually 1-3 hours after envenomation has occured.
* Continuous bleeding from bite mark. This occurs as a result of the venom destroying the coagulent properties of blood.
* Irregularities in victims blood.
* Bruising(echymosis) usually occurs as a result of the weakening of the capillary endothelium. The damaged capillaries allow blood to seep through into the surrounding tissue.
* Overall general weakness.
* Hematemesis (Vomiting blood). As the mucous membrane surfaces of the upper gastrointestinal tract (mouth, pharynx, oesophagus,stomach, and small intestine) begin to bleed it causes involuntary regurgitation causing the victim to vomit blood.
* Anaemia and shock may develop in certain bite victims.
* Bleeding from stractches and mucus surfaces.
* Victims may also experience Epistaxis (nose bleed).
* Another possible symptom of a haemotoxic envenomation is the presence of blood in the victims urine (hematuria).
* Mental confusion. Victims often experience feelings of disorientation, and their decision-making ability may become impaired.
* Increased sweating may occur.
* Hypertension, (increase in blood pressure) may occur in certain victims.
* In some cases the opposite occurs and victims may experience hypotension (decrease in blood pressure).
* Multiple organ dysfunction syndrome, previously known as multiple organ failure occurs if untreated.
Examples of Haemotoxic snakes that are classified as dangerous and life threatening:
Boomslang (Dispholidus typus).
Vine snakes (Thelotornis species).
Certain members of the genus Bitis eg
Puff adder Bitis arietans.
Gaboon adder Bitis gabonica.
Although predominantly cytotoxic both the Puff adder, and Gaboon adder, venoms contain haemotoxic properties.
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