Suspected envenomation by the common European adder (Vipera berus berus) in 28 horses in Finland.

Overview

• This study examines 28 cases of suspected common European adder (Vipera berus berus) snakebite envenomation in horses in Finland, analyzing their clinical signs, treatments administered, and survival outcomes.

Background

• Species involved: Vipera berus berus, the only venomous snake species in Nordic countries.
• Relevance: Snakebite envenomation in horses is reported during warmer months but remains poorly characterized in terms of clinical presentation, management, and outcomes.

Purpose of the Study

• To detail the clinical and laboratory findings observed in horses suspected of being envenomated by the common European adder.
• To evaluate the treatments given and their effectiveness, particularly the use of antivenom and supportive therapies.
• To assess survival rates and hospitalization duration among affected horses.

Methods

• Retrospective review of 28 horses admitted to Helsinki University Equine Hospital from 2008 to 2023 with suspected Vipera berus envenomation.
• Collection of clinical signs, laboratory data, treatment modalities, and outcomes.
• Comparison of treatment impact, especially antivenom use, on length of hospital stay and survival.

Key Findings

• Treatments administered:
  • Antivenom: 11 out of 28 horses received antivenom therapy.
  • Non-steroidal anti-inflammatory drugs (NSAIDs): Used in 22 horses.
  • Antimicrobial drugs: Administered to 19 horses despite limited evidence.
  • Intravenous fluid therapy: Given to 11 horses.
  • Corticosteroids: Used in 9 horses, although evidence for benefit is lacking.
  • Local treatments (wound care, etc.): Used in 11 cases.
• Clinical outcome: All 28 horses survived to hospital discharge, indicating favorable short-term outcomes.
• Hospitalization:
  • Horses with moderate envenomation were more likely to receive antivenom and required longer hospital stays compared to those with mild symptoms.
  • Administration of antivenom was not associated with a reduced length of hospital stay.
• Implications for treatment:
  • Corticosteroids and antibiotics are commonly used but appear to have little supporting evidence for effectiveness in this context.
  • Current data do not definitively support antivenom reducing hospitalization time, but its role in survival or long-term recovery remains to be clarified.

Conclusions and Future Directions

• Horses with suspected Vipera berus envenomation generally survive with proper medical care, including supportive treatments and sometimes antivenom.
• Further research with larger sample sizes is necessary to definitively evaluate:
  • The long-term benefits and impact of antivenom therapy on survival and health outcomes.
  • The necessity and efficacy of corticosteroids and antibiotics in treatment protocols.
  • Optimal management strategies tailored to the severity of envenomation.
• This study provides valuable baseline information for veterinarians treating adder envenomation in horses in Nordic regions.