HL Deb 10 May 2001 vol 625 c230WA
The Countess of Mar

asked Her Majesty's Government:

Whether they have considered the effects on natural immunity to a number of animal diseases in areas where large numbers of livestock have been slaughtered; what is the optimum percentage of the national herd that must be retained before the loss of immunity has effect; and whether this factor has been considered in determining whether to vaccinate against foot and mouth. [HL1680]

Baroness Hayman

Immunity to foot and mouth disease is acquired by exposure to the virus or by vaccination. As there has not been a case of foot and mouth disease in Great Britain since 1981, and we do not permit routine vaccination, all susceptible livestock are assumed to be susceptible to foot and mouth disease virus. Natural immunity has therefore not been a consideration in determining the strategy for combating the current outbreak.

It is posssible that there may be livestock, particularly sheep, which have been exposed to infection during the current outbreak but have not exhibited clinical symptoms. These animals may have acquired some degree of immunity. There is also a possibility that such animals may become carriers of the virus. The number of these animals is unknown but may be disclosed when animals are blood sampled as part of our sero-surveillance strategy.

Lord Greaves

asked Her Majesty's Government:

What research is taking place to establish whether foot and mouth disease was present in the sheep population before the start of the recent outbreak traced to a farm at Heddon-on-the-Wall, Northumberland; and what proportion of sheep population in the United Kingdom has antibodies to foot and mouth disease. [HL1756]

Baroness Hayman

There is no epidemiological evidence that foot and mouth disease was present in the sheep population before the start of the current outbreak. It is possible that some sheep which have been exposed to infection during the outbreak but have not exhibited clinical symptoms may have acquired some degree of immunity to the disease. The number of these animals is unknown but may be disclosed when animals are blood sampled as part of our sero-surveillance strategy.