From New Scientist, 28 November 1998
Snakebite Antidotes From Chicken Eggs
snakebite antidotes could soon be harvested from the yolks of chicken eggs, say Brazilian scientists. An affordable treatment for snakebite victims could save tens of thousands of lives each year in developing countries. Until now, anti-venom for neutralising snakebite toxins has been made by injecting horses or sheep with small quantities of venom to produce an immune reaction. Antibodies are then harvested from the animals' blood. However, a single dose of anti-venom costs around $15 and several may be needed to treat each patient. Moreover, the anti-venom contains a mixture of foreign proteins and causes severe allergic reactions in many patients.
The vast majority of the 100,000 deaths from snakebite each year occur in developing countries which cannot afford to keep large stocks of anti-venom. Biotechnology companies are working on a new generation of purer anti-venoms which should be safer. But this involves altering the structure of the antibody and will make the treatments even more expensive.Now a team from the State Universityof Norte Fluminense in Rio de Janeirois working on a method proposed byresearchers at the University of Wisconsin. Claudia Almeida and colleagueshave been immunising hens with small quantities of venom from pit vipers and rattlesnakes and collecting antibodiesdeposited in the yolk of their eggs.
Tests described in the current issue of the Veterinary Record (vol 143, p 579) showed that chicken anti-venom was up to six times as potent as horse antibodies. Equally important, the antibodies in egg yolk are highly concentrated and purer than those in mammalian blood. Laboratories in developing countries would only need relatively simple equipment to produce a safe product. The Brazilian vets believe that the new method could be cheap enough for use in domestic and farm animals as well ashumans. Some 20 000 people are bitten by snakes each year in Brazil, says Almeida. David Theakston of the Liverpool School of Tropical Medicine, says there is no reason why the technology should not work. "Egg anti-venom is easy to produce and should cause fewer adverse reactions than existing treatments," he says.