Development and evaluation of the neutralizing capacity of horse antivenomagainst the Brazilian spider Loxosceles intermedia

Spider bites due to Loxosceles intermedia are currently a major public heal th problem in South Brazil. About 3000 cases are reported annually. Specifi c treatment for spider bites is provided by the polyvalent anti-arachnidic antiserum produced by Butantan Institute, Sao Paulo, Brazil by immunizing h orses with mixtures of venoms from Tityus serrulatus and T. bahiensis scorp ions, as well as Phoneutria nigriventer and L. gaucho spiders. Due to the l arge amounts of the anti-arachnidic antivenom required and since L.intermed ia venom has some biochemical and pharmacological variations, we have produ ced a specific anti-L. intermedia antivenom. This study shows that horses i mmunized with crude L. intermedia venom produced IgG antibodies that neutra lized the dermonecrotic and lethal activities of the venom. The neutralizin g potency of the anti-loxoscelic antivenom was compared with that of the an ti-arachnidic antivenom. Our results indicate that both antivenoms were eff ective in terms of neutralization. However, the anti-loxoscelic antivenom w as more efficient than the anti-arachnidic. (C) 1999 Elsevier Science Ltd. All rights reserved.