Virsal E was developed by Biovac Biological Laboratories, a veterinary vaccine manufacturer in Israel, using metabolic drift mutations. These are negative mutations in essential enzymes and metabolic regulatory centers, as a consequence of which the resulting metabolic processes lead to prolonged generation times and corresponding reductions in virulence.
The Virsal E vaccine is invasive but still safe to induce durable immunity but not causing any disease in vaccinated birds or in their progeny, according ot the company. It is totally avirulent both for animals and humans, the comapny contiues, adding that the immunity induced by Virsal E is genetically stable possessing attenuating defined deletion mutations.
