First reported case of African viper bite treated with Indian polyvalent anti snake venom

Abstract

Dear Editor, The compositional differences between venoms among different geographic regions may be due to evolutionary environmental pressure acting on isolated populations. The polyvalent variety of anti snake venom (ASV) with local specificity remains the mainstay of therapy in most countries. ASV against the venom of one species occasionally may have partial cross neutralizing activity against other venoms, usually from closely related species, known as paraspecific activity. We managed a case of an African viper bite successfully using Indian polyvalent ASV as the specific African variety was not available to us. A 25 year old serving soldier of a foreign army contingent in UN mission in the Democratic Republic of Congo, was brought on 29 Sep 07 at 0025 hours, with a history of a mildly painful snake bite of about two hours duration on the left foot. There was no history suggestive of neurological involvement. Clinical examination revealed normal vital parameters and a normal general examination. Local exam revealed swelling and tenderness of left foot extending beyond the ankle to the distal leg. Two fang marks 1.5 cm apart were visible on dorsum of left foot along with a small patch of ecchymosis (Fig. 1). Fig. 1 Fang marks with swelling of foot. A bed side whole blood clotting time revealed no clotting at 30 minutes, with a clotting time of 35 minutes by capillary method. Bleeding time was in normal range. Since specific ASV for the regional area was not available, a decision to give Indian polyvalent ASV (which was available) was taken as an emergency life saving measure. A total of 150 ml of reconstituted ASV (15 vials of polyvalent Indian variety) was administered as per standard protocol over next nine hours in view of progressively increasing swelling in the leg and deranged clotting time in range of 15 to 21 minutes. The progression of the swelling of the limb halted and clotting parameters started improving (Fig. 2). Antibiotics and other supportive therapy were given. The patient had a haemoglobin drop from 16.3 to 13.6 gm per dl and mild thrombocytopenia in range of 1,20,000 to 1,40,000/mm2 during the initial few days which subsequently recovered. He also developed an uncomplicated resolving small abdominal wall hematoma (confirmed by ultrasound). He was discharged at three weeks with a complete and uneventful recovery. Fig. 2 Reduction of swelling of the limb by day three. The mortality after untreated viper bites like Crotalus durissus terrificus is said to have been up to 70 %, but this has been reduced to less than 12% by ASV treatment and in African varieties like Atractaspis and bush vipers (like those found in the Congo basin) the mortality ranges from 8-43% [1, 2]. “Specific” antivenom, implies that the antivenom has been raised against the venom of a particular snake that has bitten the patient (Monovalent or monospecific antivenom). Polyvalent antivenom neutralises the venoms of several different species of snakes. FAV AFRICA is the polyvalent equine ASV recommended for Sub-Saharan African snakes. The Indian ASV contains sera against the saw scaled viper, Russel's viper. Indian Cobra (Naja naja) and the banded krait. Analysis of Indian cobra (Naja naja) venom samples from eastern, western and southern India revealed differences in composition, biochemical, and pharmacological properties emphasizing regional variation: continents will logically be different [3]. There are only a handful of documented cases of snake bites managed with ASV pertaining to different geographical locations. Use of Tiger Snake ASV in Stephen's Banded Snake envenomation in Australia, pit viper envenomation (South American) treated with nonspecific ASV and two North American coral snake venoms treated with Mexican ASV have been described [4, 5, 6]. A study was performed to assess the ability of polyvalent anti snake venom VACSERA (produced by Egypt), to neutralize venoms of snakes not only from Egypt but also African and Middle Eastern habitats showed encouraging results [7]. There is a description of a severe systemic envenomation of a African bush viper managed successfully with Near Middle East ASV [8]. Ours is possibly the first reported case of an African viper bite successfully managed with Indian polyvalent ASV given in the backdrop of unavailability of specific antisera. We recommend that more studies be carried out on this paraspecific activity of the Indian ASV.