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Clinical Pearl: The "Pick Your Poison" of South African Serpents
In South Africa, we do not identify the snake to treat the patient; we identify the syndrome.
In South Africa, we do not identify the snake to treat the patient; we recognise the syndrome.
A "syndromic approach" is the gold standard because terrified patients often misidentify snakes, but the body does not lie. Here are the three dominant toxidromes, plus the deadly "mixed" exceptions.
1. The Cytotoxic Syndrome (The "Swellers")
The Culprits:
- Puff Adder (Bitis arietans) – Responsible for the majority of serious bites in SA.
- Spitting Cobras (M’fezi) & Rinkhals.
- Gaboon Adder (Rare, but massive venom yield).
Presentation:
- Painful Progressive Swelling: Starts at the bite site and spreads proximally.
- Tissue Destruction: Blistering, dermonecrosis, and potential compartmental syndrome.
- Systemic: Hypovolaemic shock (due to massive fluid shift into the limb), not usually systemic toxin effects.
Antivenom:
- SAIMR Polyvalent Antivenom: Effective.
- Caveat: Night Adders and Burrowing Snakes (Stiletto) cause cytotoxic symptoms but do not respond to antivenom. Treat supportively.
Morbidity:
- Permanent tissue loss, scarring, and amputation (necrosis is the enemy, not neurotoxicity).
2. The Neurotoxic Syndrome (The "Paralysers")
The Culprits:
- Mambas (Black & Green).
- Non-Spitting Cobras (Cape Cobra, Snouted Cobra).
Presentation:
- "Ptosis to Paralysis": Early signs are transient paraesthesia (tingling lips/tongue) and ptosis (drooping eyelids).
- Descending Flaccid Paralysis: Progresses to bulbar palsy (slurred speech, dysphagia) and eventually respiratory arrest.
- Local: Minimal to no swelling ("Dry" looking bite).
Antivenom:
- SAIMR Polyvalent Antivenom: Highly effective, but requires large doses (10–15 vials) for Mambas.
Morbidity:
- Anoxic brain injury or death from respiratory failure.
3. The Haematotoxic Syndrome (The "Bleeders")
The Culprits:
- Boomslang (Dispholidus typus).
- Vine Snake (Thelotornis capensis).
Presentation:
- The "Slow Burn": There is a long latent period (hours to 24h) before symptoms appear. The patient may try to go home, thinking they are fine.
- Symptoms: Oozing from IV sites, bleeding gums, epistaxis, haematuria, and eventual DIC (Disseminated Intravascular Coagulation).
Antivenom (The Critical Distinction):
- Boomslang: Requires SAIMR Boomslang Monovalent antivenom. (Polyvalent DOES NOT work).
- Vine Snake: NO Antivenom exists. Treatment is purely supportive (blood products/plasma) and highly challenging.
4. The "Trick" Category: Mixed Toxidromes
The Berg Adder (Bitis atropos)
- Venom: Unique mix of Neurotoxic + Cytotoxic.
- Presentation: Prominent swelling (cyto) PLUS ophthalmoplegia/ptosis (neuro) and loss of taste/smell (anosmia/ageusia).
- The Trap: It causes severe Hyponatraemia (SIADH-like syndrome), which can be fatal if mismanaged.
- Antivenom: NONE. The Polyvalent antivenom is ineffective. Treatment is supportive (ventilation if needed + fluid restriction for hyponatraemia).