Daboia (Vipera) palaestinae Envenomation in 123 Horses: Treatment and Efficacy of Antivenom Administration.

Envenomation by venomous snakes is life threatening for horses. However, the efficacy of available treatments for this occurrence, in horses, has not yet been adequately determined. The aim of this study was to describe the treatments provided in cases of Daboia palaestinae envenomation in horses and to evaluate the safety and efficacy of antivenom administration. Data regarding 123 equine snakebite cases were collected over four years from 25 veterinarians. The majority of horses were treated with procaine-penicillin (92.7%), non-steroidal anti-inflammatory drugs (82.3%), dexamethasone (81.4%), tetanus toxoid (91.1%) and antivenom (65.3%). The time interval between treatment and either cessation or 50% reduction of local swelling was linearly associated with case fatality (p < 0.001). The overall mortality rate was 20.3%. Treatment with procaine-penicillin was significantly associated with reduced mortality (OR = 0.11). Three horse-derived antivenom products were available during the study period, of which the horses were administered different brands of varying dosages. Administration of the recommended dosage of any of the aforementioned products led to a significant decrease in mortality (p = 0.014), even in severe cases (scoring 2 or greater on the equine snakebite severity scale). No adverse reactions were reported. The results of this study show that species-specific D. palaestinae antivenom administered at the manufacturer-recommended dosage is effective in significantly reducing mortality in cases of envenomation in horses.

Daboia (Vipera) palaestinae envenomation in horses: Clinical and hematological signs, risk factors for mortality and construction of a novel severity scoring system.

Daboia palaestinae is the most common venomous snake in Israel and an important cause of envenomations in humans and animals. Although specific antivenom is produced from horses, little documentation exists regarding the characteristics of envenomed horses. This survey was constructed to describe the clinical, hematological and biochemical characteristics of D. palaestinae envenomation in horses, to identify risk factors for fatality and to construct a prognostic snakebite severity scale (SSS) to be used by veterinarians in the field. Data regarding 123 equine snakebite cases were collected over four years. Clinical signs most frequently described were local swelling (100%), tachycardia (67%), increased respiratory effort (62%), bite marks (44%) and reduced appetite (50%). Blood samples were collected at initial presentation from 23 of these horses. Hematological and biochemical abnormalities described in the majority of the sampled cases included leukocytosis (52%), neutrophilia (78%), increased creatine phosphokinase (77%), hypoproteinemia (50%), decreased total carbon dioxide (54%), and hyperphosphatemia (54%). The overall case fatality rate was 20.3% (25/123 horses). Risk factors associated with increased mortality (P < 0.05) were body weight below 200 kg, hind limb envenomation, severity of local swelling, mental status, respiratory effort, bleeding disorders, dehydration, basophilia, monocytosis, bilirubinemia, hypocalcemia and hyperphosphatemia. These risk factors were used to construct an SSS adapted for the assessment of envenomed horses in the field, consisting of seven dichotomous parameters. A cutoff value of 1.5 predicted mortality with 95% sensitivity and 68% specificity. In the future, this tool could assist clinicians with case management and communication with owners.