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SNAKES, DOGS AND TREATMENT Information for Members
By Dr.J. Danny Jedwab - Hampton Veterinary Hospital
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Snake envenomation is a common emergency faced by many Veterinarians throughout Australia. There are about twenty species of snakes in Australia that are known to be dangerous to animals and man. The Australian snakes are also amongst the most venomous in the world. In other words, snakebites should be dealt with most seriously, as deaths often result. It has been estimated that over 6000 animals and 3000 humans are bitten in Australia annually.
Toxins and their effects
The venoms of Australian snakes contain neurotoxic, (affecting the nervous system), haemolytic, (causing red cells to rupture), cytotoxic (killing cells) and coagulating (affecting the ability of blood to clot) components. The neurotoxic action is the most dangerous, but life may also be threatened by
haemo toxic actions.
Neurotoxins cause paralysis of voluntary muscles and in untreated cases may lead to paralysis of the respiratory muscles and death due to asphyxiation. Tiger snakes along with Death Adders, Copperheads, Taipans and Browns have venom that is very neurotoxic. Tiger snake venom for example has at least 3 separate neurotoxins. Black snakes and King Browns on the other hand are more weakly neurotoxic but are more
haemo toxic. Cytotoxic venom is found in several snakes including, King Brown, Black and the Copperhead. Most Australian snakes also contain a spreading factor, hyaluronidase, which results in the rapid and wide dispersal of the venom after a bite.
It should be noted that often the venom from a snake can have both neurotoxic and cytotoxic effects, this seen in both the Tiger and Brown snakes.
The conclusion to be drawn is that the venom of all the different Australian snakes is not the same and bites from different snakes can show different symptoms and may require different specific treatments. This is taken to the extreme case when antivenene is to be administered. Accurate snake identification is a most helpful first step in the treatment of snakebite.
Symptoms of Snakebite in dogs
All lethal envenomations by the dangerous Australian snakes will usually end in the flaccid paralysis of the victim, but there are considerable variations in the progression of the signs depending upon the type of snake, the amount of venom delivered and the site at which it was delivered. Dogs can show a wide variety of symptoms after envenomation. These may include, trembling, agitation, salivation, vomiting, difficulty in breathing, weakness, pale gums, dilated pupils, collapse and death.
Chances of Survival
Several studies have been done comparing the success of treatment (using antivenom and intensive care at Veterinary clinics) versus non-treatment of snakebites. In all studies the group that were treated had a higher survival then the group that wasn’t treated. One study reports that the chances of survival improved from 52% in the untreated group to 92% in the treated group.
The interesting feature in this study and in others is the relatively high survival of the untreated group. The venom of Australian snakes is certainly potent enough to kill dogs, the dose of venom delivered per bite and the site of the bite on the animal may in part explain why so many survive without treatment.
The relatively high success rates of survival in the dogs that were treated with antivenom and intensive nursing care clearly indicate that this form of treatment is highly successful. Successful treatment of these dogs often involves an accurate identification of the snake and the intravenous administration of snake specific antivenom. The administration of the antivenom is not without risk, but the risk is relatively small compared to the benefits gained. Respiratory support with a mechanical respirator may be required and several drugs are often given to minimise the other effects of the venom and support the animal over the critical period.
It is important to note that in some cases dogs will collapse initially and then appear to recover within a few minutes of being bitten. The danger is not over at this point and these dogs may relapse and die over the next few hours if not treated. It is important to note that it is important to get help quickly and try to ID the snake, (without getting bitten yourself !) for best results.
Traditional vs Other Therapies
One of the most interesting aspects of snakebite is that about 50% of bites are not lethal. It is very important to remember this when considering whether a treatment has been successful or not. In other words, if an animal is treated with a high dosage of Vitamin C intramuscularly after an envenomation and the dog survives, it may not have been the injection that “cured” it.
There have been a number of different treatment protocols offered as cures for snakebite in both man and animals. Apart from specific antivenom and intensive nursing, other treatments have included, cutting and sucking the site to remove venom, application of a suction device alone, the application of high voltage electricity to the bite wound and the direct and systemic (by injection) application of Vitamin C.
It is very difficult to obtain accurate data about the success of some of these treatments, as there have been no scientific trials done to my knowledge. It is quite possible that at least some of these treatments may in fact be detrimental to the animal rather than curative. Cutting down onto a bite site simply spreads the toxin faster and should not be done under any circumstances. Electrocuting an animal that has just been bitten by a snake is not a great help either. Removal of the toxin by suction may be of some small benefit if the venom is superficial. An instrument known as a Sawyer Extractor is sold in the USA for this purpose.
In Australia the injection of Vitamin C (10 to 20 mls of 500mg per ml), by intramuscular injection has been used to treat snakebite by owners caught out in the bush. Vitamin C will NOT, according to the latest scientific evidence, inactivate snake venom nor will it reverse the signs of envenomation. Vitamin C is synthesised in adequate amounts by the liver in the healthy dog. It is possible for dogs to have low Vitamin C blood values under certain circumstances. These include, stress, liver disease, pain, lactation or very high levels of activity. It may under these conditions, be beneficial to supplement with Vitamin C.
Vitamin C has several functions in the dog. It is an antioxidant and is required for the synthesis of collagen steroids and carnitine (required for muscle metabolism). Vitamin C also assists in the maintenance of the Immune system and in detoxification of various drugs and toxins by the liver. In a study in 1972, Vitamin C supplementation failed to offer any significant protection against infectious diseases. There may be a small benefit to stressed dogs in supplementing them with vitamin C to enable them to more efficiently use their liver detoxification systems. Just how effective a role high doses of Vitamin C plays in snakebites is unknown. It is certainly less harmful to your dog than cutting down over the bite site or electrocuting your dog, but I would under no circumstances use it as the sole treatment for snakebite. During snake “season” it may be worthwhile giving your dog a Vitamin C tablet daily to keep up their Vitamin C levels.
In conclusion, the best first aid treatment is to keep the animal calm and apply a bandage to the site, if possible, to stop the toxin spreading and then get to a Vet for antivenom and intensive care.
A recent article suggests that your best snake bite kit should contain just 1 thing, a set of car keys!!!!!
Dr Jedwab holds copyright on this article and it must not be reprinted or reproduced without his permission. Dr Jedwab has kindly given permission for the BAOV to place the article on our website.
By Dr. J. Danny Jedwab.
Hampton Veterinary Hospital
Hampton, Melbourne, Vic.