§ LORD RUSSELL OF LIVERPOOLasked Her Majesty's Government:
Whether, now that live fowl pest vaccine has been satisfactorily proved in a number of countries to be more effective than the dead vaccine as well as easier to administer, they will allow reliable brands of such vaccine to be manufactured in the United Kingdom, or to be imported from abroad.
LORD ST. OSWALDLive vaccines are favoured in some countries because they are usually easier to apply than dead vaccines. But there are many objections to their use. They are liable under certain conditions to set up at least some of the symptoms of the disease, and these symptoms vary with the strain of the virus employed. In fact, one form of live vaccine cannot be used in young birds because of the high mortality which follows. Because the virus in such vaccines is live and can spread from bird to bird, it is liable, particularly under intensive conditions, to depress powers of resistance1008WA and thus lead to the emergence of other latent respiratory diseases. To counteract this, it is a common practice to use live vaccines against these otner diseases as well, so that eventually birds have to be vaccinated with a number of viruses. Although the viruses used in live vaccine production are commonly produced from attenuated strains, there is always the danger that they may revert to full virulence.
Dead vaccines do not have these disadvantages. Neither live nor dead vaccines give permanent protection, and re-vaccination is necessary whichever kind is used.
The Plant Committee on Fowl Pest Policy advised against the use of live vaccines in this country, a view that was accepted both by the Government and by the Fowl Pest Consultative Committee on behalf of the poultry industry. It would be wrong to consider introducing live vaccine when dead vaccines are available from four manufacturers which can provide adequate protection if they are widely and properly used.
House adjourned at twenty-eight minutes past six o'clock.