Felis ISSN 2398-2950

Adder bite poisoning

Synonym(s): Snake bite

Contributor(s): Glen Cousquer, Rosalind Dalefield


  • The adder, or viper (Vipera berus), is the only venomous snake in UK.
  • Cats appear to be bitten far less frequently than dogs.
  • Cases of envenomation generally occur between February and October, peaking in June to August, and should always be treated as an emergency.
  • Adder bites can be life-threatening where systemic envenoming occurs.
Print off the owner factsheet Adder bites in cats to give to your client.



  • Venom consituents are complex, containing a mixture of enzymes, proteins and peptides. Further details on the enzymatic activities of adder venom can be found in Siigur et al, (1979). The genomic DNA sequences encoding the phospholipases A2 from the venoms of a number of European vipers have been sequenced, together with genes encoding a number of neurotoxins (Guillemin et al, 2003).
  • The various consituents of venom may have a variety of effects including hemolysis, fibrinolysis and myonecrosis.


  • Only about 50% of bites by exotic venomous snakes inject sufficient venom to cause clinical envenoming (Warrell, 2005). Macintire et al, (2005) state that 20% of snakebites are "dry", ie contain little or no toxic venom. The percentage of dry adder bites is uncertain.
  • If injected, the complex nature of adder venom is largely responsible for the range of physiological and clinical effects reported:
    • An immediate drop in systemic blood pressure is commonly seen. This arises through arterial vasodilation, followed by increased peripheral vascular resistance, decreased cardiac output, hypoproteinemia Hypoproteinemia and increased PCV Hematology: packed cell volume. The hypoproteinemia and hypovolemia probably arise due to increases in vascular permeability and loss of circulating fluid and protein.
    • Bradykinin release may be seen, resulting in vasodilation.
  • Phospholipase A2, present in many viperid venoms, can cause release of prostaglandins. This can lead to further vasodilation and hypotension. Phospholipase A2 has significant anticoagulant properties.
  • Anticoagulation effects may be seen resulting in clinical features of a bleeding diathesis.
  • Renal failure can result for a variety of reasons, including myoglobinuria, hemoglobinuria Hemoglobinuria, and hypovolemic shock Shock.
  • Serous complications include ventricular arrhythmias, cardiac failure   Acute heart failure  , acute renal failure Kidney: acute renal failure, DIC Disseminated intravascular coagulation and airway obstruction.
  • Disseminated intravascular coagulation (DIC) can result in hemorrhage, shock Shock and death.


  • The bite is generally painful.
  • The signs of envenomation may appear within minutes, or be delayed up to an hour.
  • Envenomation does not always occur in snakebite. If no swelling apparent within 2 hours then envenomation has not occurred.
  • The swelling will gradually increase in size and may become hemorrhagic.
  • Swelling may become necrotic with overlying skin sloughing.
  • Death due to heart, renal and/or hepatic failure (if these occur) is within 5-7 days.
  • Death may occur acutely due to development of DIC.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Karlson-Stiber C, Salmonson H, Persson H (2006) A nationwide study of Vipera berus bites during one year-epidemiology and morbidity of 231 cases. Clin Toxicol (Phila) 44 (1), 25-30 PubMed.
  • Warrell D A (2005) Treatment of bites by adders and exotic venomous snakes. Br Med J 331 (7527), 1244-1247 PubMed.
  • Guillemin I, Bouchier C, Garrigues T et al (2003) Sequences and structural organiation of phospholipase A2 genes form Vipera aspis aspisV. aspis zinnikeri and Vipera berus berusvenom. Eur J Biochem 270 (13), 2697-2706 PubMed.
  • Kraft W, Reiner B & Bodner C (1998) Snake bites in dogs. Tieraztl Prax Ausg K Klientiere Heimtiere 26 (2), 104-109 PubMed.
  • Reading C J (1996) Incidence, pathology, and treatment of adder (Vipera berus L.) bites in man. J Acc Emerg Med 13 (5), 346-351 PubMed.
  • Hudelson S & Hudelson P (1995) Pathophysiology of snake envenomization and evaluation of treatments- part II. Comp Cont Ed Pract Vet 17 (8), 1035-1040 VetMedResource.
  • Puig J, Villafranca M, Font A et al (1995) Acute intrinsic renal failure and blood coagulation disorders after a snakebite in a dog. J Small Anim Pract 36 (7), 333-336 PubMed.
  • Harborne D J (1993) Emergency treatment of adder bites: case reports and literature review. Arch Emerg Med 10 (3), 239-243 PubMed.
  • Siigur E, Siigur J, Nômmeots M & Ilomets T (1979) Fractionation and enzymatic activities of common viper (Vipera berus berus) venom. Toxicon 17 (6), 623-630 PubMed.

Other sources of information

  • Macintire D, Drobataz K J, Haskins S C & Saxon W D (2005) Manual of Small Animal Emergency and Critical Care Medicine. Lippincott, Williams and Wilkins, Baltimore, USA.
  • Fowler M E (1992) Veterinary Zootoxicology. Sydney: CRC Press. ASIN:0 8493 6791 3.