title: Neutralization of Latrodectus mactans and L. hesperus venom by redback spider (L. hasseltii) antivenom.
abstract: OBJECTIVE
  To test the effectiveness of L. hasseltii (redback spider) antivenom in neutralizing the lethal effects of L. hesperus and L. mactans (North American black widow) venoms.
  
  
  METHODS
  LD50 values for the L. hesperus and L. mactans venom preparations were determined. A prospective, randomized, double-blind antivenom efficacy experiment was then performed for each venom using a mouse envenomation model. The following treatments were premixed and incubated at 25 degrees C for 1 hour prior to intraperitoneal injection: 1) saline control + protein control, 2) saline control + L. hasseltii antivenom, 3) L. hesperus or L. mactans venom + protein control, and 4) L. hesperus or L. mactans venom + L. hasseltii antivenom. The study endpoints were time elapsed until death and survival at 24 hours.
  
  
  RESULTS
  The mouse LD50 values for L. hesperus and L. mactans venoms were 0.64 mg/kg and 0.26 mg/kg, respectively. In the efficacy trial, all mice in group 3 (L. hesperus or L. mactans venom and protein control) died. In both experiments, all mice in group 4 (L. hesperus or L. mactans venom + antivenom) survived (p < 0.0001).
  
  
  CONCLUSIONS
  This is the first study to derive mouse LD50 values for L. hesperus and L. mactans venom obtained by electrical stimulation of live adult spiders. Redback spider antivenom is effective in neutralizing the lethal effects of L. hesperus and L. mactans venoms in a mouse envenomation model. While this study is limited by the optimized premixing of antigen with antibody, it generates the hypothesis that redback antivenom would be effective in the treatment of latrodectism in humans caused by the two clinically relevant species of North American widow spiders.
authors.affiliation: Rocky Mountain Poison and Drug Center-Denver Health Authority, Denver, Colorado, USA. frankdaly@hotmail.com
authors.forename: F F
authors.initials: FF
authors.lastname: Daly
authors.forename: R E
authors.initials: RE
authors.lastname: Hill
authors.forename: G M
authors.initials: GM
authors.lastname: Bogdan
authors.forename: R C
authors.initials: RC
authors.lastname: Dart
mesh_terms: D000818:Animals; D000997:Antivenins / Q000008:administration & dosage*; D001740:Black Widow Spider; D004195:Disease Models, Animal; D004306:Dose-Response Relationship, Immunologic; D004311:Double-Blind Method; D005260:Female; D007928:Lethal Dose 50; D008297:Male; D051379:Mice; D011897:Random Allocation; D013045:Species Specificity; D001098:Spider Bites / Q000517:prevention & control*; D013111:Spider Venoms / Q000276:immunology* / Q000302:isolation & purification / Q000633:toxicity
chemical_list: D000997:Antivenins; D013111:Spider Venoms