Vipera palaestinae envenomation in 327 dogs: A retrospective cohort study and analysis of risk factors for mortality

Vipera palaestinae (Vp), formerly a subspecies of the near east viper Vipera xanthina, is the most common poisonous snake in Israel and neighbouring countries (Jordan, Lebanon and Syria), and is responsible for most envenomations in humans and domestic animals. Hospital records were retrospectively reviewed for confirmed cases of Vp envenomations in dogs over a 13-year period and 327 cases were included in the study. Most envenomations occurred between May and October, and between 02:00 and 10:00 PM. The most frequent clinical signs included: local swelling and oedema (99.6%), viper teeth penetration marks (51%), tachypnoea (50%), panting (44%), increased body temperature (19.2%), tachycardia (>160/min, 19%), salivation (18%) and lameness (15.6%). Common haematological findings included: increased haematocrit (47%), increased haemoglobin concentration (45%), leucocytosis (39%), and thrombocytopenia (30%). The prothrombin time and activated partial thromboplastin time were prolonged in 68 and 21% of the dogs, respectively. Blood biochemistry abnormalities included increased activities of muscle enzymes, hyperglycaemia, hyperbilirubinaemia, hyperglobulinaemia and hypocholesterolaemia. The mortality rate was 4% (13 dogs). The following variables were significantly (p<0.05) associated with mortality: body weight below 15 kg (p=0.01), limb envenomation (0.008), envenomation at night (p=0.025), severe lethargy (p<0.001), hypothermia (p=0.04), systemic bleeding (p=0.001), shock (p=0.007), dyspnoea (p=0.002), tachycardia (p=0.002), thrombocytopenia (p=0.02) and glucocorticosteroid therapy (p=0.002). Dogs younger than 4 years had a lower death risk (p=0.01). The association of steroid therapy with increased mortality suggests that the use of steroids in Vp envenomations may be harmful. Specific antivenom therapy (10 ml/dog) was not associated with a higher survival rate, thus its use, dose and timing of administration should be further investigated.