LAUSR

&NA; Envenomation by the South American opisthoglyphous snake Philodryas olfersii causes local pain, edema, erythema and ecchymosis; systemic envenomation is rare. In this work, we examined the inflammatory activity of P. olfersii venom (10, 30 and 60 &mgr;g) in mouse gastrocnemius muscle 6 h after venom injection. Intramuscular injection of venom did not affect hematological parameters such as red cell count, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration. The venom caused thrombocytopenia (at all three doses), leukopenia and lymphopenia (both at the two highest doses), as well as neutrophilia (30 &mgr;g), monocytosis (30 &mgr;g) and basophilia (10 &mgr;g). Of the cytokines that were screened [IL‐1&bgr;, IL‐6, IL‐10, IL‐13, IL‐17, TNF‐&agr;, IFN‐&ggr;, MIP‐2 and KC] and IGF‐1, only IGF‐1 showed a significant increase in its circulating concentration, seen with 60 &mgr;g of venom; there were no significant changes in the cytokines compared to control mice. Histological analysis revealed the presence of edema, an inflammatory infiltrate and progressive myonecrosis. Edema and myonecrosis were greatest with 60 &mgr;g of venom, while the inflammatory infiltrate was greatest with 10 &mgr;g of venom. All venom doses caused the migration of polymorphonuclear and mononuclear leukocytes into muscle, but with no significant dose‐dependence in the response. These findings show that, at the doses tested, P. olfersii venom does not cause hematological alterations and has limited effect on circulating cytokine concentrations. These data also confirm that the principal effects of the venom in mice are local edema, inflammatory cell infiltration and myonecrosis. HighlightsP. olfersii venom injected intramuscularly caused edema and myonecrosis.The inflammatory infiltrate was predominantly polymorphonuclear.The venom caused leucopenia, lymphopenia and thrombocytopenia.There was an increase in plasma IGF‐1, but not cytokine, levels.These alterations indicate an acute inflammatory response.