Biting by a poisonous snake is manifested by clinical findings of local swelling and nervous symptoms.
Etiology: The poisonous snakes have different types of toxins in variable amounts. These toxins have coagulant, anticoagulant, necrotising, haemolytic, neurotoxic or cardiotoxic fractions. Animals are bitten at the head or legs. Death is usually not seen in large animals because of their body size. However, small animals may succumb to death.
Pathogenesis: The neurotoxic fraction of venom causes paralysis, dilatation of pupil and respiratory failure. Cytolisin causes necrosis of tissue and cells. Coagulants cause clotting; haemolysin results in haemolysis while myotoxins result in muscle necrosis and myoglobinuria. The symptoms are dependent on the type of toxins present in venom and its amount.
Clinical signs: Initially there is local swelling and pain followed by excitement and anxiety. The animal shows dilatation of pupil, salivation, hyperesthesia, tetany, depression, incoordination, recumbency and paralysis. Later on, animal dies due to respiratory failure. There may be bacterial contamination of the wound leading to fever and septicaemia.
Diagnosis: It is diagnosed by history of snake bite, clinical symptoms and can be confirmed by ELISA test.
Treatment: About 15-20 cm above bites, tourniquet should be applied to prevent spread of venom. The bite area may be incised or pressure bandage be applied on the site of wound. Antivenom should be injected around the wound @ 1 unit/70 kg body weight in adults and 5 units in small animals. Broad-spectrum antibiotics like streptopenicillin, chloramphenicol or cephalosporin should be given to prevent the bacterial contamination of site. Fluid therapy is recommended to overcome shock. Use of corticosteriods and antihistaminics is of value in early recovery.