Venomous snakes of the
family VIPERIDAE. Viperus berus is the only naturally occurring species responsible
for snake poisoning in the UK.
Animals most affected
Dogs, cattle, horses, sheep.
Envenomation occurs after biting and injection of venom by the snake, either while
the animal is in the field (cattle, horses), or during hunting (dogs). In general,
incidents of snake bites occur between the months of April and October.
The site of the bite is frequently on the abdomen or the udder in the case of cows
(when they lie down in open fields or in the cow shed); or on the nose and legs (dogs).
The venom contains a number of active compounds:
toxins: neurotoxin, cardiotoxin, haemotoxin, cytotoxin;
enzymes: L-amino acid oxidase (hydrolyses amino acids), hyaluronidase (facilitates
the penetration of the venom into underlying tissues), phospholipase A2 (destroys
nerve sheaths and crythrocytes), nucleases;
metals: predominantly Cu and Zn (which act as co-enzymes).
The severity of the envenomation depends not only on the size of the animal which
has been bitten, and its age, but also on the amount of venom involved, or whether
any venom was injected following the snake bite. (Two bites are considered an envenomation
The affected animal takes fright and runs off, distressed, bellowing or barking.
The clinical signs are relatively pronounced (albeit dependent on the amount of venom
injected and the body weight of the bitten animal).
At the site of the bite
rapid onset of oedema (within 20 minutes), acute pain; sometimes the puncture
marks are clearly visible;
haemorrhages, local necrosis;
persistent oedema, with the area of the swelling becoming hard and cold.
malaise, prostration, transient shock;
occasionally vomiting, diarrhoea, colic, abdominal pain;
vascular collapse (significant loss of serous fluid from the oedematous tissue);
haemolysis and haematuria;
haemorrhages of variable severity.
disinfection of the wound (proprietary antiseptics, skin disinfectants);
local application of ice packs or chilled water compresses.
administration of antivenom (10-20 ml per animal) should be undertaken with extreme
care: do not treat the animal until the characteristic signs of envenomation
are apparent (cold oedema). It is essential for the veterinary surgeon to have
an ampoule of adrenaline ready for prompt intramuscular injection should anaphylactic
shock occur (as a reaction to the anti-snake venom serum);
iv calcium heparinate 0.1 ml/kg, repeated every 12 hours during the first 36/72
hours post-envenomation, whilst blood clotting time is monitored regularly;
rehydration therapy by infusion (using Dextran 70 or Dextran 40 solutions, Raemaccel
or polygeline, or isotonic
NaCi): monitor the extent of the cedema, stopping the infusion if the swelling
becomes too distended.