Poultry Eggs May Yield Snake Antivenin, Experts Say

Pallava Bagla in New Delhi
for National Geographic News
February 11, 2003

Scientists in India have found a way to induce snake antivenin in common poultry eggs, offering the hope of an inexpensive antidote that could save thousands of lives of people bitten by poison snakes each year in India and other countries.

Biochemists working at the Vittal Mallya Scientific Research Foundation (VMSRF) in the southern Indian city of Bangalore announced in January the development of a novel therapeutic snake antivenin from the eggs of domestic hens that can be used to treat snakebites in humans. P. V. Subbarao, scientific director and chief executive officer at the foundation, said the egg antivenom technology could provide a safer solution to the deadly snakebites that are common in India.

About 300,000 cases of snakebites are recorded every year in the world's second most populous country, and ten per cent of these victims die—sometimes extremely painfully—because antivenin cannot be given to them in time.

This number could be higher as many deaths in rural areas go unreported.

In India, snake antivenin is produced by immunizing horses against a mixture of four different snake venoms—cobra, common krait, saw-scaled viper, and Russell's viper—and the horse antibodies that develop are used as the antidote in humans, administered in a process form. The recovery is slow and large volumes of antidote are required for treatment.

According to Subbarao, the egg-based antidote being developed by his group could eventually replace the conventional horse-produced antivenin, the administration of which can sometimes cause side effects in humans such as severe allergic reactions and, in extreme cases, death.

Unlike antivenin produced in horses or sheep, antitoxin produced in poultry does not involve as much discomfort for the animals. "One painful step, the collection of blood from horses, is replaced by antibody extraction from egg yolk," said Subbarao. "It also entails a reduction in the number of animals used because chickens produce larger amounts of antibodies."

How Eggs Yield Antivenin

Very young chickens are immunized with small doses of the target-snake venom and as these animals grow older they develop in their blood special proteins which act as antidotes against the toxin, according to the researchers.

As the chickens become hens and start egg production, it has been found that the antivenin proteins are passed on, accumulating in the yolk. The eggs are then harvested for extraction of the proteins used to make the antidote.

Maneka Gandhi, ardent animal rights activist and until recently a minister in the federal government of India, has greeted the announcement of the antivenin research with enthusiasm. "Production of diagnostic and therapeutic products in chicken represents a refinement and reduction in animal use, and the collection of blood is replaced by extraction of antibody from egg yolk. As chickens produce larger amounts of antibodies, there is a reduction in the number of animals we need to use," Gandhi said.

The scientists feel the egg-based antivenin should cost much less than its counterpart made from horses. By comparison, the amount of the antidote yielded from a liter (2 pints) of horse blood could be extracted from just 50 eggs, and a single immunized hen could lay over 240 eggs in a year, according to the researchers. "My optimistic aim is to develop the technology to get enough [antivenin] from one egg to treat one bite," said Subbarao.

Continued on Next Page >>




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