Natural and Acquired Immunity
Although individuals can vary in their physiopathological response and sensitivity to animal venoms, there is no natural immunity to them in humans. Some ophiophagic animals are immune to the venoms produced by some species of venomous snakes, by the presence of antihemorrhagic and antineurotoxic factors in their blood. These animals include Kingsnakes, opossums, mongooses, and hedgehogs.
It is quite possible to immunize a person directly with small and graded doses of venom rather than an animal. According to Greek history, King Mithridates did this in order to protect himself against attempts of poisoning, therefore this procedure is often called mithridatization. However, unlike a vaccination against disease which must only produce a latent immunity that can be roused in case of infection, to neutralize a sudden and large dose of venom requires maintaining a high level of circulating antibody (a hyperimmunized state), through repeated venom injections (typically every 21 days). The long-term health effects of this process have not been studied. For some large snakes, the total amount of antibody it is possible to maintain in one human being is not enough to neutralize one envenomation. Further, cytotoxic venom components can cause pain and scarring at the immunization site. Finally, the resistance is specific to the particular venom used; maintaining resistance to a variety of venoms requires multiple monthly venom injections. Thus, there is no practical purpose or favorable cost/benefit ratio for this, except for people like zoo handlers, researchers, and circus artists who deal closely with venomous animals. Mithridatization has been tried with success in Australia and Brazil and total immunity has been achieved even to multiple bites of extremely venomous cobras and pit vipers. Starting in 1950, Bill Haast successfully immunized himself to the venoms of Cape, Indian and King cobras.
Because neurotoxic venoms must travel farther in the body to do harm and are produced in smaller quantities, it is easier to develop resistance to them than directly cytotoxic venoms (such as those of most vipers) that are injected in large quantity and do damage immediately upon injection.
Read more about this topic: Antivenom
Famous quotes containing the words natural, acquired and/or immunity:
“There is a natural aristocracy among men. The grounds of this are virtue and talents.”
—Thomas Jefferson (1743–1826)
“Hardly a man in the world has an opinion upon morals, politics or religion which he got otherwise than through his associations and sympathies. Broadly speaking, there are none but corn-pone opinions. And broadly speaking, Corn-Pone stands for Self- Approval. Self-approval is acquired mainly from the approval of other people. The result is Conformity.”
—Mark Twain [Samuel Langhorne Clemens] (1835–1910)
“There is immunity in reading, immunity in formal society, in office routine, in the company of old friends and in the giving of officious help to strangers, but there is no sanctuary in one bed from the memory of another. The past with its anguish will break through every defence-line of custom and habit; we must sleep and therefore we must dream.”
—Cyril Connolly (1903–1974)