Cross-Reactivity againstNaja sumatrana(Black Spitting Cobra) Envenoming from the Haffkine Antivenom in a Mouse Model

Naja sumatrana is the dominant cobra species in Malaysia, Singapore, Borneo, and Sumatra, and it does not have specific antivenom. The Haffkine antivenom has been advocated instead. This study aims to determine the efficacy of this antivenom against Naja sumatrana envenoming using a mouse model. Methods . Male Swiss albino mice were used. Intravenous LD 50 was first determined separately for Naja naja and Naja sumatrana venom. ED 50 was determined by preincubating antivenom with each venom at 2.5 LD 50 before administering the mixture into the tail vein. Validation was carried out using a challenge test. Each mouse received 111  µ g of Naja sumatrana venom intramuscularly followed by intraperitoneal administration of dilute Haffkine antivenom. Survival was recorded 24 hours after envenoming. Results . The LD 50 of Naja naja venom was 78.13  µ g, standard error (SE) 13.3  µ g. The ED 50 of the Haffkine antivenom against Naja naja venom was 45.9 mg, SE 7.5 mg. The LD 50 and ED 50 of Naja sumatrana venom were 55.5  µ g, SE 12.0  µ g; and 73.9 mg, SE 12.0 mg, respectively. The intra-peritoneal ED 50 against 111  µ g intramuscular Naja sumatrana venom was 136.95 mg, SE 36.74 mg. Conclusion . The Haffkine polyvalent antivenom exhibited cross-neutralisation against Naja sumatrana venom when used at a higher dose.