All About Anti Venom
By Timothy Zedi
Anti venom is the main treatment for venomous snake bites and is often the only reason people survive a bite. Knowledge of anti venom is not just interesting, but is essential for anyone who works with venomous snakes. This article will explain all you need to know about anti venom.
The concept of Vaccines
Anti Venom is basically a vaccine against venom. Bacterial and viral vaccines pre date the production of anti venom. The concept of how vaccines work is fairly simple to understand, take your annual flu vaccine for instance, you are injected with a small amount of inactive flu virus and your body then creates specific anti bodies to destroy the virus.Should you catch the flu, you already have anti bodies to destroy it, so the virus is killed before it can cause any symptoms and you are now immune to the flu virus. The same concept is used to create anti venom, but humans are not used to create the anti bodies required to neutralize the venom, rather horses or sheep are used ( the process would work with any animal) horses are used to make anti venom in South Africa due to their high blood yeild. Take note, the horses are treated humanely.
How Anti Venom is Produced
Venom is extracted from venomous snakes manually by getting them to bite down on a plastic sheet covering a glass beaker, this process is called milking. The amount of venom that can be extracted from a single snake in a single milking is dependent on species, size and whether the snake has recently eaten. Once the venom has been extracted it is freeze dried to prevent it from going off. The freeze dried venom is mixed with saline and injected into the horses in increasing doses until the horse develops immunity to the snake venom. Once immunity is reached the horses are bled. The blood is allowed to stand until the plasma separates from the red blood cells. The plasma is where the anti bodies for the venom are found. The red blood cells are then transfused back into the horse from which they came from. Now the anti bodies have to be processed into anti venom.
Venom Availability and Quality
The quality of anti venom is good in the developed world and in good supply. South Africa has very good quality anti venom and our stocks are currently enough to meet demand. India is producing very poor quality anti venom at very cheap prices which entices poorer countries to purchase it even when it is ineffective. The Thai Red Cross produces good anti venom which is used in Asian countries. Australia produces monovalent ( species specific) anti venom for all their venomous snake species and fatalities from snake bites down under are less than 10 per year on average. Anti venom has an expiry date, however there have been cases in Papua New Guinea were Taipan anti venom that had expired ten years ago was successfully used to treat a bite. Papua New Guinea has a severe anti venom shortage bordering on a health crisis, so any chances to save a patient are used,.Expired anti venom is unlikely to be used in most other countries. Iran produces the anti venom used to treat USA soldiers bitten by venomous snakes in Iraq and Afghanistan. Mexico and Costa Rica also produce good antivenim to be used in South American countries. Two companies in the USA produce anti venom for Rattle snake and North American pit vipers and a single manufacturer produces Coral Snake anti venom in the USA.
Polyvalent vs Monovalent
Polyvalent anti venom is where multiple species venom is used to produce the anti venom and this will be effective against all the species that were used. Monovalent anti venom is where a single species venom is used to produce the anti venom and this is effective for only that single species. In South Africa we produce three different anti venoms: one Polyvalent anti venom for bites from our cobra species, Rinkhals , Puff Adder, three species of Mambas and the Gaboon Adder and two monovalent anti venoms, one for Boomslangs and one for Saw Scaled Vipers. The anti venom for the Saw Scaled Vipers is exported to West Africa as this species does not occur in South Africa. You will have noticed that I mentioned above that our polyvalent anti venom covers three species of Mamba when only two species occur in South Africa. The Jameson’s Mamba from East Africa was added to the venom mixture when World War Two started so that the soldiers fighting in that part of the continent were protected from a bite from this species, it’s venom has stayed a part of our anti venom ever since then.
Anti Venom Usage
” Time is tissue” is a saying used in snake bite treatment where cytotoxic bites are concerned. The quicker anti venom is administered the less tissue damage will occur. Please note that anti venom cannot reverse tissue damage that has already occurred but can stop further necrosis from occurring. In neurotoxic bites where breathing is compromised the quick use of anti venom will be needed and possibly artificial respiration. In countries such as the USA and Australia anti venom seems to be more freely used than in South Africa, this could be cost related as the above countries are generally wealthier. There is also a great fear of allergic reaction from anti venom, the risk of allergic reaction is not as high as most people think and withholding anti venom can result in a less successful recovery. Hospitals are well equipped to deal with allergic reactions and the necessary equipment and medicine will be in the room with you before anti venom is given, just in case. That said not everyone who is bitten by a venomous snake will require anti venom due to the fact that they may have only received a small amount of venom when bitten so the effects will be milder. There is no maximum dose for anti venom, it is administered in increasing doses until the venom is neutralised. There is no paediatric dose and children receive the same dose as adults.
Allergic Reactions to Anti Venom
Because anti venom is produced from horses your body can view their anti bodies as a foreign invader and can release anti bodies against it, which will result in an allergic reaction. Allergic reactions can be as mild as a rash or in severe cases can cause anaphylaxis. Anaphylaxis is when your body has a severe reaction to the anti venom, causing your throat to close and therefore you cannot breath and if not treated you will die. Anaphylaxis is treated with adrenaline and goes away very quickly when treated properly. The adrenaline should be with you in the same hospital room where you are being treated in case this happens. Anaphylaxis is more dangerous than the venom so this is a major concern when anti venom is administered. The risk of an allergic reaction is increased if the person has been bitten before or if they deal with venomous snakes and come in contact with venom particles while cleaning cages ect. Serum sickness can occur after administration of anti venom. Serum sickness is an allergic reaction to an injection of anti venom which is typically mild and characterized by skin rashes, joint stiffness, and fever.
Self immunization is were people inject themselves with diluted snake venom in order to gain immunity from a snake bite. I have seen footage of one of these individuals take a bite from a black mamba followed soon after by a Taipan and only show some swelling. Bill Haast, from the Miami Serpentarium, self immunized for decades and died at the ripe old age of over 100. This could have been due to his injecting of snake venom or from other factors such as genetics, people do live to 100 without injections of snake venom! Self immunization is very dangerous as the exact amount of venom needed to immunize but not kill you has to be calculated, This is not a good idea to do in your home office, often the correct dosage is simply found by chance. People who Self immunize often have hospital trips due to overdosing with venom. Self immunization is not recommended by most doctors who treat snake bites.
Cross reactivity is when anti venom made for a specific snake works on venom from a snake it is not intended to be used for. Saw Scaled Viper anti venom for instance is somewhat effective against a bite from an African Bush Viper. It has also recently been discovered that our South African polyvalent anti venom is effective against Rhombic Night Adder bites which it was previously not thought to be. Also of interest is that the same anti venom is not as effective on Snouted Night Adder Bites even though these two species are extremely closely related. Also recently found is that our South African Polyvalent anti venom is also effective against bites from Coral Cobras and Shield Nosed Snakes, this anti venom was again not intended to treat bites from this species. Dr Bryan Fry, a leading venom researcher, has found that Boomslang anti venom in very high doses is effective against Vine Snakes. Vine Snakes have no specific anti venom for their bites.
Anti Venom for Exotic Snakes in South Africa
There is little to no anti venom for exotic venomous snakes in South Africa. I have spoken to a few reptile parks and they do not stock any anti venom for their exotic snakes. I do however know that at least one snake park that does stock anti venom for all its venomous snakes including exotic ones. If you are bitten by your Western Diamond Back Rattle Snake and can’t get hold of the scarce anti venom all the doctors can do is treat you symptomatically. If the bite is bad enough that it would require anti venom you are in big trouble. It would be ideal for all keepers of exotic venomous snakes to have their own stock of anti venom. This is easier said than done. Other than the huge expense of the actual anti venom it is also classed as a pharmaceutical drug and cannot be brought into the country without permission from the Medicine Control Council. Having Anti venom available is something a keeper should seriously consider before buying any venomous snake. If you are keeping local species or species whose venom has cross reactivity with our local anti venom, you can purchase SAVP polyvalent anti venom without a script. The monovalent Boomslang anti venom requires a script from a doctor should you wish to have your own supply. There are some venomous snake keepers in the USA who will not keep Rattlesnakes or other venomous snakes that require Crofab ( the anti venom for these snakes) due to its high cost. It is cheaper for them to import our South African anti venom than to pay for their locally produced anti venom, therefore it is cheaper for them to treat a bite from a Black Mamba than it is to treat a bite from a Western Diamond Back Rattlesnake. I have seen medical bills as high as $100 000 for people bitten by rattle snakes in the USA. In South Africa a bite can cost upwards of several hundred thousand Rand if treated in a private hospital. Most medical aids will not cover the cost of treatment for an exotic snake bite. A substantial portion of these high medical bills is the cost of the anti venom that is used.
The Future of Anti Venom
There has been talk of an anti venom made from synthetic anti bodies. This would result in no more snakes needing to be milked and no allergic reactions. Recently an anti venom has been produced using snakes. This process uses the plasma from snakes such as King Snakes which eat venomous snakes and have an immunity to their venom. Blood is taken directly from the snake and since it is already immune to the venom, anti venom can be manufactured very quickly. This anti venom will also be cheaper as the production costs are less. I should think however that in order to mass produce anti venom, hundred of snakes would need to be used as the blood yield from a snake is very low.
Before the development of anti venom many snake bites were fatal and many people were left with permanent disabilities. The development of anti venom was a medical breakthrough allowing doctors to safe life and limb. The production of anti venom is likely to change and in the 21st century better products could replace traditional anti venom. So we welcome anti venom 2.0 but we must not forget the millions of lives saved by anti venom in its current form.