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ENVIRONMENT, FOOD AND RURAL AFFAIRS

Avian Influenza

Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs (1) what instructions she has issued to (a) local authority environmental health departments, (b) the State Veterinary Service and (c) the Meat Hygiene Service in respect of actions to be taken to limit the spread of avian flu; [152171]

(2) how much imported food has been (a) condemned and (b) impounded or otherwise detained as a result of suspected contamination with avian influenza virus; [152172]

(3) what assessment she has made of whether the reported deaths of persons suffering from avian influenza resulted from (a) the handling of (i) live poultry and (ii) poultry meat and products and (b) the consumption of poultry meat; [152173]

(4) what tests are available to detect the avian influenza virus in imported food; whether screening is being carried out on existing stocks of imported food; and what the results were; [152174]

(5) what discussions she has had with the World Health Organisation on control measures necessary to limit the spread of avian influenza; [152175]

(6) what assessment she has made of the likelihood of the avian influenza virus mutating in a way which will increase its pathogenicity; [152177]

(7) whether the avian influenza virus is pathogenic to man; and whether it acts in concert with other pathogens to give rise to synergistic infection; [152178]

(8) what the route of infection of avian influenza is; and whether it is classified as a food-borne disease; [152179]

(9) what her assessment is of current risks to health from the (a) handling and (b) consumption of imported chicken meat in relation to avian influenza. [152180]

Mr. Bradshaw: As soon as the outbreak of avian influenza in Thailand, the only affected country with which we have regular commercial trade, was notified we put in place a prohibition on imports of poultry meat and uncooked poultry meat products from Thailand derived from animals slaughtered after 1 January 2004. Details were sent to all Border Inspection Posts, local authorities, the State Veterinary Service, Meat Hygiene Service and to HM Customs. All the enforcement bodies concerned deal with such safeguard measures on a regular basis and are familiar with the procedures and vigilance necessary for dealing with affected products. On 28 January a further prohibition on imports of live birds from affected countries was issued in line with action agreed by member states in the EU and guidance issued to The State Veterinary Service and HM Customs. Prior to this precautionary measure live

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captive birds, such as falcons and finches, could be imported from the region on the basis of strict controls, including 30-day post import quarantine and testing for avian influenza.

We are not aware of any food having been condemned as a result of avian influenza. Currently 31 consignments amounting to 489 tonnes of Thai poultry meat are detained at Border Inspection Posts, awaiting the required additional health certification.

The World Health Organisation are investigating a 'possible' human-to-human transmission of the disease in two sisters in Vietnam, but it is too early to say for definite whether or not this is the case. Human-to-human transmission of avian influenza is in any case rare and there have been no known cases of human-to-human transmission in this outbreak. The most likely source of infection resulting in human deaths from avian influenza remains in those known to have had direct contact with infected poultry.

Controls on production of poultry meat for export from Thailand, in place before the outbreak was confirmed, mean that the risk of infected meat being imported is very low. The normal tests for avian influenza are used to detect the disease in live animals, not meat. Testing of foods for microbial pathogens is seldom helpful in protecting public health because, if present at all, they are likely to be present in very small numbers and are not distributed evenly throughout foods. This means tests would be unlikely to detect the virus unless the level of sampling was impractically high and very expensive.

Defra has had no discussions with the World Health Organisation on this but the global strategy recommended by WHO includes the following:

the rapid elimination of H5N1 infection in bird populations by culling;

protection of those who are working with, and culling, chickens to protect their health and to reduce the risk of human infection;

improve surveillance of human respiratory disease and rapid case detection; and

development and production of a vaccine. This is a highly complicated process and four months is considered a minimum period before vaccine could be available. Additional issues of capacity and distribution would need to be resolved.

The WHO has said that, on the basis of presently available data, it does not conclude that any processed poultry products (whole refrigerated or frozen carcasses and products derived from them) and eggs in, or arriving from, areas currently experiencing outbreaks of avian influenza (H5N1) in poultry flocks, pose a risk to public health.

In the twentieth century there were four major influenza pandemics in 1918, 1957, 1968 and 1977. There is evidence suggesting that the 1957 and 1968 pandemics resulted from a major change to the previously circulating human virus by incorporation of genes from an avian influenza virus. Direct spread of the assumed progenitor avian virus to humans was not reproduced experimentally and it is thought that pigs, which are susceptible to both human and avian influenza viruses, may have played a role in supporting both viruses to allow gene re-assortment to take place.

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Most avian flu viruses do not affect man, or cause very mild illness, such as mild influenza-like illness or conjunctivitis. Occasionally strains of avian flu emerge which are particularly nasty. The human cases in Asia have been severe respiratory infections with a high mortality.

The Food Standards Agency have advised that there is no risk of acquiring the Avian influenza virus through eating poultry meat. They consider the risk of infection through handling poultry meat is very low. There are no substantiated reports of people becoming infected through these routes.

Bovine TB

Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs what the sensitivity of the test used on translocated badgers is in (a) positive response and (b) negative response. [150583]

Mr. Bradshaw: The test, which is generally used, for the detection of TB in translocated badgers is a test for antibodies (the Brock Test). This is generally accepted to have a low sensitivity (the ability to detect diseased animals). However it is difficult to give accurate values for the sensitivity because euthanased animals are not always subject to laboratory culture.

Where a badger translocation is carried out under licence (from Defra or English Nature) each individual badger is tested three times. If any of the three results are positive, the badger is euthanased. Any other badger that has been in contact with the positive testing badger is also euthanased, regardless of the results of its own tests

Where an orphaned or previously injured badger is translocated by an animal centre or similar body they follow a voluntary code of practice (drawn up by the RSPCA, National Federation of Badgers Groups and Secret World Wildlife Rescue). Any animal to be relocated is tested three times and, if it tests positive, is euthanased. This protocol does not advise in the destruction of badgers who have had contact with a test positive badger. It should be emphasised that this voluntary protocol was not devised or approved by Defra.

The Veterinary Laboratories Agency is trying to develop a range of TB tests for badgers with improved accuracy, including a gamma-interferon test.

Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs how many herds were placed under TB restriction in December 2002; and how many of those same herds were still under restriction in October 2003. [150571]

Mr. Bradshaw: A total of 725 herds were placed under movement restriction in December 2002. This includes 294 herds placed under movement restriction following disclosure of a new TB incident. The remainder were herds placed under movement restriction because the routine herd test was overdue.

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Ninety six herds placed under restriction in December 2002 were still under restriction on 31 October 2003 (66 of those as a result of an ongoing TB incident).

Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs how many herds require 60-day testing for tuberculosis; and what the estimated annual cost is for this testing programme in 2003–04. [150587]

Mr. Bradshaw: All herds suffering a TB breakdown are subject to at least one short interval ("60-day") test. A total of 7,275 short-interval tests were carried out from April to December 2003, at an estimated cost (including administration costs) of £3,485k. The forecast cost for 2003–04 is £4,600k.

Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs (1) pursuant to her answer of 8 December 2003, Official Report, column 215W, what epidemiological inferences can be drawn from the observed seasonal trends in the incidence of TB in cattle; [150596]

(2) what further research she is planning into seasonal trends in the incidence of TB in cattle. [150712]

Mr. Bradshaw: The absolute number of new TB incidents disclosed every month is closely correlated to the rate of testing. Hence, the majority of incidents are detected in the winter months (October through March), when most herds are tested.

However, if the data are adjusted to take into account the seasonality of TB testing, there does not appear to be a clear seasonal pattern in the rate of new TB incidents disclosed each month (i.e. it is not possible to conclude that the herd incidence of bovine TB in certain months of the year is consistently higher than in other months).

Because of the difficulty in studying seasonality of TB infection, there are few reports investigating this aspect of the disease. However, the results of one such investigation was reported in a paper by Wilesmith et al (1982) ¹ . They examined seasonal variations in the risk of acquiring infection between 1971 and 1976 for a Dorset cattle herd during an extensive TB herd breakdown. The data indicated that the April/May period presented the time of greatest risk. This correlated with possible exposure to re-infection at the start of the grazing season, exposure lasting for a relatively short time. However, re-exposure to infection was not necessarily the same as re-exposure to pasture, since some stock were out-wintered.

The Veterinary Laboratories Agency will continue to monitor epidemiological trends, including seasonality.

¹ Wilesmith, J. W, T. W. A. Little, H. V. Thompson and C. Swan. (1982). Bovine tuberculosis in domestic and wild mammals in an area of Dorset. I. Tuberculosis in cattle. Journal of Hygiene, Cambridge 89: 195–210.

Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs what percentage of M. bovis was isolated from (a) carcases and (b) faeces from wildlife species tested in studies carried out by or on behalf of her Department and its predecessor since 1974. [150611]

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Mr. Bradshaw: The information is as follows:

(a) All previous Defra information on M. bovis isolated from wildlife carcases was collated in the following review paper: Delahay, R. J., de Leeuw, A. N. S., Barlow, A. M., Clifton-Hadley, R. S. and Cheeseman, C. L. (2002). "The Status of Mycobacterium bovis Infection in British Wild Mammals: A Review". Veterinary Journal 163, 1–16.

(b) Two projects currently in progress involve sampling both live animals and carcase material from a variety of species. The data from these projects have not been fully analysed at this point so accurate figures are not available. Results from carcase material published in the OIE report on Wildlife disease 2003 showed that the prevalence of M. bovis infection was 2.9 per cent. in wildlife (669 cadavers, 20 positive cultures). The culture positive species were fallow deer, fox and muntjac.

Live sampling (samples including faeces) from over 4,000 small mammals (<30g) have shown that the prevalence of M. bovis is less than 0.3 per cent. The spoligotypes associated with these animals are largely of a type only found in small mammals.

Mr. Paterson: To ask the Secretary of State for Environment, Food and Rural Affairs pursuant to the answer of 8 December 2003, Official Report, columns 21–18W, under what circumstances genetic structures of M. bovis undergo mutation following sequences of transmission, with particular reference to transmission between species; at what rate mutations occur; whether techniques and facilities are available to detect these changes; and whether back-mutation of bacilli from final host species would assist in the determination of the direction of inter-species transmission. [150847]

Mr. Bradshaw: As Mycobacterium bovis is transmitted over time there is evidence that hyper variable regions of its genome change, although most of the genome remains stable. Changes can be identified using molecular biological techniques. Hyper variable regions may change in both intra and interspecies transmission. There is no reason to believe that, except for very rare adaptive changes, the rate of mutation will increase as a strain moves between species.

The rate at which mutations occur depends on the region of the genome. Hence, single nucleotides have an average rate of change of about 10 ^{- 9} per nucleotide per generation. However, tandem repeats that show variable numbers (variable numbers of tandem repeats, or VNTRs), show a greater rate of change. Spoligotype changes are intermediate in rate between VNTR and single nucleotide mutations.

We use two main techniques to detect genetic variation in M. bovis. The first of these, spoligotyping, exploits a polymorphic region direct repeat (DR) locus in the genome that is composed of multiple 36bp DR copies interspersed by unique spacers, with strains varying in the presence or absence of spacers. The VNTR method targets 6 alleles (A-F) that vary in the length of internal repeat units, permitting strains to be differentiated on the number of repeats at each target; i.e. 7–5-5–4-3–3-3 would have 7 copies of allele A, 5 of B, etc. High throughput facilities for both of these techniques exist at the Veterinary Laboratories Agency

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(VLA), allowing the molecular typing of about 4,000 to 5,000 strains per year. Our current models of the population structure of M. bovis suggest that the VNTR loci evolve faster than the DR repeat locus. Thus spoligotyping provides a global picture of the population structure and epidemiology of M. bovis in Great Britain, while VNTR typing has proved useful as a fine scale method for detecting local changes in the M. bovis population.

The evolution of the members of the Mycobacterium tuberculosis complex has led to specific host preferences; hence M. tuberculosis appears human restricted, while M. bovis consists of a series of clones with a wider mammalian host range. The process of host adaptation probably involves a number of discreet mutations, which would all need to revert to reverse the host adaptation. Back-mutation i.e. the reversion of mutations, occurs very infrequently. The rate for a specific single nucleotide reversion would be about 10 ^{- 9} X 10 ^{- 9} ( or 10 ^{- 1 8} ) per nucleotide per generation. Indeed, if some of these mutation events were deletions they could not revert without the re introduction of the DNA. These questions are being investigated using laboratory based molecular biological techniques at the VLA.

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