All You Need To Know About Antivenom

All 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, 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. You are 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.

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.

Anti Venom Processing

Anti Venom can include the entire antibody or it can include just the fragment which will bind to the venom molecules. The anti body is shaped like a Y with the bottom specific to the horse and the arms of the Y are where the specific antigens for the venom lie. Peptin is used to cutone of the arms of the Y off that contains the antibodies this is called Fab 2 antivenin, where the arm of the Y and the base is cut off this is Fab 1 antivenom. By processing it this way the risk of an allergic reaction is reduced. Our South African anti venom is a Fab 2, the North American anti venom Crofab is a Fab 1which filters through the kidneys quicker than Fab 2 which means more anti venom needs to be used, that is why you hear of cases were 20-30 vials of Crofab have been used for a rattlesnake bite. The recommended starting dose of Crofab for a Copperhead bite is 8 vials, Crofab costs over $1000 per vial so even if you could get hold of Crofab in SA it would cost a small fortune to treat a bite and the medical aids will not pay. Still want to keep that Western Diamond Back Rattlesnake or Copperhead?

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 bite down under are less than 10 per year on average. Anti venom has an expiry date however there has 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 antivenin to be used in South American countries.

Anti Venom Usage

” Time is tissue” is a saying used in snake bite treatment were 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 were 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. If I was bitten by a cytotoxic snake I would personally choose anti venom should it mean that I get to keep my fingers or hand largely intact.

Self Immunization

Self immunization is were people inject themselves with dilute snake venom in order to gain immunity from 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. Self immunizers often have hospital trips due to overdosing with anti venom. Self immunization is not recommended by most doctors that treat snake bite.