About eight months back we started running out of antivenom for snakebite and the situation has become worse. While hospitals will have access to antivenom for serious snakebites, veterinarians have largely run out of stock, and pets are dying.
Antivenom is produced by the South African Vaccine Producers (SAVP), part of our National Health Laboratories. Two antivenoms are produced for snakebite in South Africa – a monovalent Boomslang antivenom that costs around R7,500 per vial, and a polyvalent antivenom that is made using the venom of ten snake species including the mambas, most cobras, rinkhals, puff adder and gaboon adder. It costs around R2,300 per vial.
Making antivenom is a slow process in which horses are injected with small quantities of snake venom to trigger their immune system. More and more venom is injected from time to time, and after about nine months the horses are immune – the venom then has no effect on them. Around ten liters of blood is drawn at two-month intervals, the serum removed, and the blood put back into the horse. The serum is purified and bottled in 10 ml glass vials and needs to be refrigerated. It lasts three years.
Antivenom is the only and correct treatment for serious snakebites. Boomslang bites are very rare as they live in trees and shrubs and have a pleasant disposition. They rarely bite and usually only if grabbed or stood on. Two or three bites are treated annually in South Africa, and patients usually receive two vials of monovalent boomslang antivenom. The venom of the boomslang is haemotoxic and compromises the blood clotting mechanism. It is slow-acting and can take anything from 5-30 hours before the first symptoms appear – bleeding from the site of the bite, bleeding from the nose, mucous membranes, and eventually uncontrolled bleeding from various organs. If treated with antivenom timeously, the recovery rate is excellent.
The dominant neurotoxic venoms, specifically from black mamba and Cape cobra bites, are the most dangerous, and these two snakes account for most fatal snake bites. Their venom affects breathing, and untreated cases may result in fatalities in anything from 1-7 hours, or even a shorter period of time. Patients need to be hospitalized urgently, they may have to be ventilated and often need around 10 – 15 vials of polyvalent antivenom.
Most bites are from snakes with cytotoxic venom – the puff adder and most cobras, especially the spitting cobras. Cytotoxic venom causes pain, swelling and blistering that may result in severe tissue damage. In serious cases it is vitally important to administer sufficient antivenom sooner rather than later.
While antivenom is life and limb-saving it also has its limitations. About four out of every ten patients that are treated with antivenom have a severe allergic reaction and go into anaphylaxis. Doctors immediately stop administering antivenom, treat the patient with adrenaline, and once stabilized, may continue with antivenom. For these reasons antivenom is only administered in a hospital environment.
Many pets survive bites from highly venomous snakes purely because they receive little venom, but in the case of serious bites, they need antivenom – nothing else works.
The situation seems to be improving slowly, and antivenom production is improving, but at this stage there still is a severe shortage and veterinarians do not have access to stock. Major hospitals usually have stock and also have the ability to move stock around when needed.
In the event of any snakebite, it is important to get the victim to the nearest hospital as soon as possible.
Johan Marais is one of Africa’s leading herpetologists and is CEO of the African Snakebite Institute. He is a best-selling author, a compulsive photographer, and a travel addict. Check out the website on www.africansnakebiteinstitute.com – get your FREE App on the link http://bit.ly/snakebiteapp
