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Snakebite in tropical Africa
Cahiers d'études et de recherches francophones / Santé . Volume 2, Number 4, 221-34, Juillet-Août 1992, Synthèse
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Author(s) : Jean-Philippe Chippaux
Summary : In Africa, two snake families are dangerous for man : Elapidae and Viperidae. Venomous species can be attracted to man-made environments such as plantations and towns, and it has been reported that some species are associated with particular crops or farming methods. Most bites occur among farm laborers, but people collecting firewood or water and those simply walking or playing are also at risk. Elapids ( Naja sp and Dendroaspis sp) can cause neurotoxic manifestations and respiratory failure. Systemic Elapid envenomation can develop rapidly. Neuromuscular paralysis affects the facial muscles, leading to eyelid droping, dysphagia, dysphonia and trismus. Involvement of the respiratory muscles results in coma and respiratory failure. Limited, dry necrosis can also occur, Viperids ( Bitis sp and Echis sp) give rise to severe local reactions (edema, necrosis), as well as bleeding. Viperid envenomation is always painful. Edema and extensive wet necrosis due to proteolytic enzymes occur at an early stage and can be the main symptoms. The bleeding in such circumstances may be difficult to diagnose and treat. Thrombin-like enzymes are the main cause of clotting, which is followed by bleeding when the clotting factors are exhausted. One of the most important complications, in addition to necrosis, is renal failure. First-aid measures should not be aggressive. After thoroughly cleansing the area of the bite, a bandage should be applied (not too tightly) and the patient should be transported to hospital immediately. Anti-venom therapy is the only specific treatment and is generally effective provided that it is used correctly and at the appropriate dosage. These products should be reserved for patients with severe envenomation. They are given intravenously, together with steroids, and several vials (up to 100 ml) may be required. Treatment is most effective when given within 15 minutes and should be continued until all signs (paralysis in the case of Elapid bites and bleeding in the case of Viperid bites) resolve completely. Symptomatic treatment should also be given, with mechanical ventilation if respiratory failure occurs. Anti-inflammatory and analgesic drugs should be administered as soon as possible after Viperid envenomation. Heparin and clotting factors are usually not indicated.
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Snakebite in tropical Africa