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Introduction
There are over 160 snake species in Mzantsi Afrika, of which most are not dangerous to humans. In Mzantsi Afrika, snakes and humans commonly coexist in the same territory, which results in a high number of snake bite incidents. Some snake bites may result in envenomation and require medical intervention.
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Species
There are between 160 and 180 snake species in Mzantsi Afrika, and the majority of these species are considered not to be dangerous to humans. Approximately 25 snake species are considered medically important. Table 1 lists snakes found in Mzantsi Afrika that are dangerous to humans.
| Snake | Links to Pictures | Locations in Mzantsi Afrika | |
| 1 | Mozambique spitting cobra (Naja mossambica) | Mozambique Spitting Cobra – African Snakebite Institute | Limpopo, Kwa-Zulu Natal, Gauteng, Mpumalanga , North West |
| 2 | Common Night adder (Causus rhombeatus) Rhombic Night Adder | Common Night Adder – African Snakebite Institute | Limpopo, Free State, Kwa-Zulu Natal Eastern Cape, Western Cape |
| 3 | Puff Adder (Bitis arietans) “Irhamba” | Puff Adder – African Snakebite Institute | Throughout Mzantsi Afrika |
| 4 | Rinkhals (Hemachatus haemachatus) “Iphimbi” | Hemachatus haemachatus – Rinkhals (tyroneping.co.za) | Free State, Western Cape, North West, Eastern Cape, Mpumalanga |
| 5 | Black Mamba (Dendroaspis polylepis) | Black mamba – SANBI Black Mamba – African Snakebite Institute | Limpopo, Kwa-Zulu Natal Mpumalanga, Northern Cape North West, Gauteng |
| 6 | Cape Cobra (Naja nivea) | Cape Cobra – African Snakebite Institute | Western Cape Western areas of Eastern Cape Western areas of Free State Western areas of North West |
| 7 | Eastern Green Mamba (Dendroaspis angusticeps) | Eastern Green Mamba – African Snakebite Institute | Coastal Kwa-Zulu Natal Coastal Eastern Cape, north areas |
| 8 | Mountain (Berg) adder (Bitis atropos) | Berg Adder (Bitis atropos) | Next Gen Herpetologist Berg Adder – African Snakebite Institute | South -western areas of Eastern Cape Southern areas of Western Cape Lesotho – spilling over into the Free State, KZN and Eastern Cape |
| 9 | Black spitting cobra (Naja nigricincta woodi) | Black Spitting Cobra (Naja nigricincta woodi) from the Cederberg, Western Cape. Dangerously venomous. : r/southafrica (reddit.com) Black Spitting Cobra – African Snakebite Institute | Northern Cape – north western areas Western Cape – north western border |
| 10 | Boomslang (Dispholidus typus) | Juvenile Boomslang Photos and Images (shutterstock.com) Boomslang – African Snakebite Institute | Limpopo, Mpumalanga, Northern Cape Western Cape, Kwa-Zulu Nata, Gauteng, Eastern Cape |
| 11 | Southern Vine Snake (Thelotornis capensis) Twig snake | Southern Vine Snake – African Snakebite Institute | Limpopo, Mpumalanga, Gauteng North West |
| 12 | Forest Cobra (Naja subfulva) | Forest Cobra – African Snakebite Institute Africa’s biggest cobra is five species, not one, study finds (mongabay.com) | Kwa-Zulu Natal – northern tip |
| 13 | Gaboon Viper (Bitis gabonica) | Our Hybrid of a hybrid viper. Info in comments : r/snakes (reddit.com) | Kwa-Zulu Natal – northern tip |
Snake bite prevalence
In Mzantsi Afrika, it is challenging to accurately document the incidence of snake bites. The majority of snake bites in Mzantsi Afrika are reported during the summer season, and the province reporting the most snake bites is the North West province. The incidence of snakebite in Mzantsi Afrika was 2.39 per 100,000. The mortality rate reported from hospitalized snakebite patients in Mzantsi Afrika is below 5%. Snake bites are more common in the rural areas as compared to the urban areas of Mzantsi Africa.
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Clinical presentation of snake bites
The clinical presentation of snake bites is grouped into five syndromes, as listed below:
- Painful progressive swelling syndrome (cytotoxic)
- Progressive weakness syndrome (neurotoxic)
- Bleeding syndrome (haemotoxic)
- Mixed painful progressive swelling and bleeding syndrome (cytotoxic and haemotoxic)
- Mixed painful progressive swelling and progressive weakness syndrome (cytotoxic and neurotoxic)
It is not uncommon to have two envenomation syndromes present at the same time. Swelling is the most common syndrome that is encountered post-snake envenomation.
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Painful progressive swelling syndrome (cytotoxic)
The cytotoxic syndrome is the most commonly encountered syndrome among all the snakebite syndromes, and it is mainly due to the toxins found in the snake venom. The toxins found in the venom of the cytotoxic snakes destroy cell membranes, skeletal muscles, and other tissues, which ultimately results in increased vascular endothelial permeability, local swelling, and oedema. These toxins are mainly proteolytic enzymes, phospholipases, and polypeptides. Snakes that commonly present with this clinical syndrome are the puff adder, gaboon adder, night adder, and horned adder.
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Progressive weakness syndrome (neurotoxic)
Snakes that commonly cause a neurotic syndrome include the black mamba, eastern green mamba, and none-spitting cobras such as the Cape cobra, snouted cobra, and forest cobra. Neurotoxins in the venom of these snakes inhibit the binding of acetylcholine to nicotinic receptors at the neuromuscular junction. Included in the clinical picture are oral paraesthesia, facial paralysis, ptosis, ophthalmoplegia, midriasis, and diplopia. Speech is also affected, resulting in dysarthria and dysphonia. Hypersalvation and dysphagia are also noted. Envenomation later on manifests in descending flaccid paralysis and respiratory failure. The duration it takes for these venoms to cause respiratory failure varies widely between 1 and 8 hours.
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Bleeding syndrome (haemotoxic)
This clinical syndrome is mainly caused by gaboon adder, puff adder, boomslang, and vine snake. The venom of these snakes results in abnormally increased production of prothrombin, factor X, and factor IX, leading to a state where these factors are depleted, resulting in consumptive coagulopathy. These factors promote coagulation, and their consumption and depletion result in coagulopathy. Gastrointestinal signs and symptoms include abdominal pain, nausea, and vomiting.
| SYNDROME | CYTOTOXIC | NEUROTOXIC | HAEMOTOXIC | CYTOTOXIC + HAEMOTOXIC | CYTOTOXIC + NEUROTOXIC |
| CAUSATIVE SNAKES | Adders (Gaboon, Puff, Night, Horned) | Black mamba Eastern Green Mamba Non-spitting cobras | Puff Adder Gaboon Viper Boomslang Vine snake | Gaboon adder Puff adder | Rinkhals Berg adder Forest cobra Snouted cobra |
| TREATMENT | Supportive Polyvalent antivenom | Supportive Airway protection Polyvalent antivenom Consider cholinesterase inhibitor | Supportive Blood treatment Polyvalent antivenom – adders Monovalent – Boomslang | Supportive Blood treatment Polyvalent antivenom | Supportive Airway protection Polyvalent antivenom |
First aid after a snake bite
The patient must be moved away from the snake. Transport the snake bite victim to the nearest medical facility immediately. The patient should be calmed and immobilized in a sitting or recumbent position in order to minimize the spread of the snake venom. The use of tourniquets on a snake bite victim is contraindicated, as this worsens the snake bite due to the fact that tourniquets concentrate the venom near the snake bite, worsening the effects of the venom. Incising around the wound, using electrotherapy, putting ice on the wound, and sucking the wound are contraindicated. A crepe bandage should be applied approximately and over the snake bite; this is referred to as the Pressure Immobilization Technique (PIT). Application of crepe bandages is particularly important in the bites by cobras and black mambas. Respiratory failure is common in a neurotoxic snake bite, and therefore CPR should be given to the snake bite victim.
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Supportive treatment
Away protection is very important. Intravenous fluids might be necessary due to fluid losses from cytotoxic snake bites.
Antivenom therapy
The majority of snake bite victims will not require antivenom and will not be given antivenom. There are two types of antivenoms for snake bites: polyvalent and monovalent.
The polyvalent antivenom is only effective against 10 snake bites, which are the Rinkhals, puff adder, gaboon adder, black mama, green mamba, Jameson’s mamba, Mozambique spitting cobra, Cape cobra, snouted cobra, and the forest cobra. The polyvalent antivenom is ineffective against the mountain adder, dwarf adder, night adder, boomslang, and vine snakes, and therefore it is contraindicated in these snake bites. The monovalent antivenom is only effective against Boomslang.
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Antivenom dosages
Polyvalent antivenom
- 50-100 ml for cytotoxic snake bites
- 80-100 ml for neurotoxic snake bites
Monovalent antivenom
- 20 ml for boomslang envenomation.
- 10 ml follow-up dose may be given in severe cases.
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Indications for antivenom therapy include:
- Neurotoxicity signs
- Unidentified snake bites and with evidence of progressive swelling such as:
- Swelling of the entire foot or hand within 1 hour following the snake bite.
- Progressive swelling to the knee or elbow joint within 6 hours following the snake bite.
- Swelling of the entire limb within 12 hours following the snake bite.
- Progressive swelling at a rate of more than 2 centimetres per hour
- A compromised away.
- Compartment syndrome
| Type of antivenom | Polyvalent | Monovalent |
| Dosage | 80 – 100 ml | 20 ml IV |
| Effective against | Rinkhals Puff adder Gaboon adder Black mamba Green mamba Jameson’s mamba Mozambique spitting cobra Cape Cobra Snouted Cobra Forest cobra | Boomslang |
Testing antivenom dose
A testing antivenom dose is no longer recommended.
Anaphylaxis prophylaxis
Life-threatening anaphylactic reactions may occur after antivenom administration. Patients who will require antivenom therapy should receive an adrenaline pre-dose of 0.25 mg intramuscularly for anaphylaxis prophylaxis. Prophylactic antihistamines and steroids are not recommended and should only be used when an anaphylactic reaction occurs.
Tetanus vaccination
Tetanus toxoid of 0.5 ml IM must be given to all snake bites patients who have not been immunised in the previous five years.
Antibiotic treatment
Antibiotics are not indicated, especially in the initial 72 hours after the snake bite.
Special investigations
The following special investigations are advised:
- Complete blood count
- Electrolytes
- Urea and creatinine
- Clotting screen
- Calcium
- Magnesium
- Phosphate
References
- Common highly dangerous snakes of South Africa (no date) Nature-reserve.co.za. Available at: https://www.nature-reserve.co.za/dangerous-snakes.html (Accessed: November 14, 2023).
- Assistance, F. (no date) SNAKE, SPIDER AND SCORPION BITES AND STINGS, Ampath.co.za. Available at: https://www.ampath.co.za/storage/37/Chapter-33-Snake-Spider-And-Scorpion-Bites.pdf (Accessed: November 20, 2023).
- Lermer, A., Marks, C. J. and Kellermann, T. A. (2023) “Snakebite in South Africa: A retrospective review May 2015–June 2020,” Toxicon: official journal of the International Society on Toxinology, 224(107031), p. 107031. doi: 10.1016/j.toxicon.2023.107031.
- Govender, I. and Tumbo, J. (no date) The management of snakebites in South Africa, Surgeon.co.za. Available at: https://www.surgeon.co.za/wp-content/uploads/2020/11/Snake-bites-2019.pdf (Accessed: November 19, 2023).
- Kemp, A. (2019) Everything you need to know about antivenom, African Snakebite Institute. Available at: https://www.africansnakebiteinstitute.com/articles/everything-you-need-to-know-about-antivenom/ (Accessed: November 29, 2023).
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