SUMMARY

  The Soil Association's recommendations to the Agriculture Committee's inquiry into badgers and bovine tuberculosis can be summarised as follows:

  1.  Some farms with TB-free herds in the proactive culling areas should be allowed exemption from the compulsory culling of badgers in order to shield them from recolonisation by infected animals.

  2.  The responsibility for research into husbandry methods designed to separate badgers and cattle should rest with the government and not individual farmers.

  3.  New research should be carried out, concurrently with the cull, into other factors which may increase cattle susceptibility and reduce immunity to TB infection. The increasing number and geographical spread of organic farming provides a unique low-cost opportunity for some of this research to be carried out purely from an analysis of existing data. If this is not undertaken, the public spending implications of delaying such research until after the results of the Krebs experiments are known could be significant.

INTRODUCTION

  The Soil Association would like to comment on two areas of the government's proposals for implementing the recommendations contained in the Krebs Report in which it feels that the proposals might be improved:

—  on the design of the experiment;

—  on issues to be considered in the implementation of the experimental comparison of different husbandry methods.

  We would also like to draw attention to potentially important areas of research which it appears are being ignored and the extent to which a statistical, comparative, analysis of the incidence of bovine TB on organic and conventionally run farms could provide a cost-effective way of identifying management factors which may predispose cattle to tuberculosis infection.

CONCERNING THE DESIGN OF THE EXPERIMENT

  The Soil Association is concerned about the prospect of compulsory badger culling on farms with TB-free herds. The probability that the badgers on such farms are also TB-free means that the resident population of badgers there might be serving as an effective bulwark against colonisation by diseased animals. Krebs acknowledges the inevitability of eventual recolonisation (1998, 128) and it must therefore be accepted that there is a strong likelihood that were these badgers to be culled, some farms which currently enjoy TB-free status would eventually be recolonised by badgers from farms outside the culling area, some of which may be infected with M. bovis.

  While the precise method of transmission between badgers and cattle has not been established, Krebs is nevertheless confident that badgers are a significant factor in transmission. It is therefore likely that far from being protected by the culling of badgers at least some of the TB-free herds within the proactive culling areas in the experimental hot spots will later suffer a herd breakdown as a result of the experimental culling.

  Bourne (1998, 13) suggests that where the owner/occupier is unwilling to cooperate with the cull that exemptions might be accommodated during the design phase where nature reserves or sanctuaries are involved, but advises on balance against other dispensations due to the possibility of bias in the experiment.

  While all cattle farmers are seriously worried by the spread and increasing incidence of the bovine tuberculosis, and with no other apparent explanation than the involvement of badgers, most farming organisations have called for increased badger culling, it should be noted that some individual farmers with TB-free herds are known to be concerned about the increased risk of TB to their herds if there resident population of badgers is culled and eventually replaced by diseased animals. It is not known, at present, how many farmers within the proposed culling areas fall into this category. However, since these areas may be extended in future we feel it is important to make the case for possible exemptions which could be granted by MAFF under certain circumstances at the request of the landowner/occupier. If there is doubt about the TB status of such badgers this could be established by a small representative cull on the individual farms.

  The issue is of particular concern to some organic farmers, but may also be relevant to conventional farmers whose herds are TB-free. It could also have legal implications were a tuberculosis breakdown to occur on a previously TB-free farm after a compulsory badger cull imposed by MAFF. In the case of Green Top milk producers there could also be food safety implications.

  In the first instance it would seem wise to survey land owner/occupiers' attitudes prior to deciding which areas within the hot spots will be proactively culled. Our view, however, is that including a framework for exemptions to be granted in relation to proven TB-free badgers should be adopted by MAFF and that it would not compromise the results of the experiment, since any badgers from these farms which might move to settle on neighbouring land under the cull regime would clearly be TB-free and therefore have better status than badgers from surrounding areas, which will eventually recolonise and which will inevitably contain a proportion of diseased animals.

CONCERNING THE QUESTION OF HUSBANDRY METHODS

Husbandry and transmission

  The Soil Association believes it is unrealistic to expect farmers to conduct their own trials on certain known husbandry methods which aim simply to separate cattle from the badgers which could infect them with TB. Even if MAFF provides incentives to participate, implementation will be entirely outside the control of government. Moreover, it will rely on farmers, who are already under intense pressure from reduced incomes and greatly increased regulation, to show enough goodwill to take on research projects on top of their other activities. It is also not clear that such ad hoc arrangements would contribute in any dependable way to the overall understanding of the transmission problem.

OTHER AREAS WORTHY OF RESEARCH

  The Soil Association understands the desire of the inquiry to limit itself to consideration only of the implications of the recommendations made in the Krebs report. It further welcomes the fact that Professor Krebs and his team recommended research into husbandry methods which might prevent transmission of TB from badgers to cattle, as well as the culling experiment. However the lengthy nature of the research commitment recommended by Krebs and its single focus on badgers could create a serious problem in the longer term. If the experiment is inconclusive, or badgers prove to be a smaller factor in the spread and increase of bovine TB than was suspected, and if the incidence of bovine TB follows current trends and becomes continually worse in the meantime, public expenditure will be needed both to cope with this and to fund other areas of research. In the Soil Association's view there are other obvious areas where a good prima facie case could be made for investing in research (perhaps relatively simple and inexpensive research). As such we feel it would be imprudent not to begin this research as soon as possible in order to avoid further potential delays in resolving the problem of bovine tuberculosis in British cattle.

The possibility of reduced resistance

  In the human population it is established that poor housing, poor nutrition and overcrowded conditions predispose people to infection with tuberculosis. Even before the pasteurisation of milk in the 1930s and the development of effective antibiotics in the 1940s the incidence of TB in the human population had been falling dramatically for many decades (PHLS 1999) as a result, it is generally accepted, of improved living conditions and better nutrition. Immuno-suppressant illnesses such as AIDS and hepatitis C are also known to compromise individuals' natural immunity to the disease. These factors are known to relate to M. tuberculosis and the human population, but logic suggests they may also be relevant to M. bovis. and cattle. As a result it can be argued that one possible explanation for the lack of consistent results in relation to previous attempts to control bovine TB solely by badger culling is that transmission of the disease is only one of several factors which need to be considered.

  While we have no direct evidence to support this hypothesis, data contained in Appendix 5 of the Krebs Report clearly shows that badgers are not implicated in the problem of bovine TB in France, for example, where there is also a significant bovine tuberculosis problem. The question must also be asked whether the total absence of bovine TB from, for example, Austria and Switzerland (Krebs et al 1998, 152-4) is due to luck or the fact that these two countries have intensified their agriculture less than most other European countries, in part due to the difficult topography, but also in part due to agricultural policies which have encouraged a higher proportion of land into organic production.

  Cattle kept in many intensively-managed herds are exposed to conditions comparable to those which encourage the spread of human TB in the poorest and most overcrowded parts of the world. They can experience:

—  high stocking-levels

—  poorly ventilated housing,

—  poor or dirty living/transport conditions,

—  infection by viral diseases such as Bovine Viral Diarrhoea and Bovine Immunodeficiency-like Virus (detected in 1990 by MAFF in 10 per cent of random samples from hundreds of cattle throughout Britain, although these results were not validated (MAFF 1994)),

—  stress.

in addition they are:

—  bred to maximise milk yield at the expense of overall health

—  fed to maximise milk yield at the expense of overall health

—  treated with immuno-compromising substances such as organophosphates to control warbles (though this is no longer compulsory), corticosteroids (increasingly prescribed by vets for individual animals to reduce inflammation), anthelmintics (used routinely to compensate for poor grazing management and excessive stocking densities, routine long-acting intramammary antibiotics (given to the majority of dairy cows every year during the dry period to prevent mastitis), in-feed antibiotics permitted for inclusion in dairy cow rations for performance enhancement and improved feed efficiency until April 1997

  We feel that in the light of these glaringly obvious parallels, it would be foolish not to carry out research on other husbandry factors which might predispose cattle to infection with TB. At present, however, none of MAFF's £1.7 million TB research budget is directed towards this area. (Krebs et al 1998).

The opportunity offered by the expansion of organic farming

  One possible and highly cost-effective way of conducting such research would be to begin by looking at the incidence of bovine TB on organic farms and comparing this with conventional farms on an area by area basis. In a letter to the Welsh Office in March 1998 the Royal Welsh Agricultural Society stated "It would be helpful to know if the incidence of TB was greater or less on intensive dairy farms than on organic farms of which there are a significant number in Wales" (Anon 1998). We do not know what, if any response was received to this letter, but it is unlikely that a conclusive answer was given since as far as we are aware, no comparative studies have been undertaken.

  Such work would be relatively inexpensive and initially requires no more than a statistical analysis to be designed which could compare the data on tuberculin testing with that on organic farming held by the United Kingdom Register of Organic Food Standards. We would not expect the incidence of TB on organic farms to be zero (some herds having only recently changed to organic methods and husbandry and replacement stock practices varying even between organic farms), but there is a widespread belief within the organic farming movement that it is substantially lower and that organically-reared and managed animals will be significantly more resistant to TB infection. This view was stated as early as 1936 by the pioneering organic farmer Friend Sykes, who gave up the use of artificial fertilisers and other practices which he even at that time associated with intensive agriculture and began farming 750 acres organically because two third of his Friesian dairy herd had become infected with TB (Balfour 1975).

  The purpose of such a study, we would suggest, however, should not be to show that organic farming per se is better or worse than conventional agriculture in relation to TB. However, if statistically significant differences were found we feel this would merit further investigation to identify the specific factor or factors responsible.

  Under normal circumstances undertaking research into comparative husbandry methods of this sort would be very expensive. However, the strict husbandry standards and detailed record-keeping followed by organic producers, the improving geographical spread of organic farms and the increasing rate at which producers, especially dairy farmers, are now converting to organic production provides a unique and extremely low cost opportunity for comparative analysis to be undertaken by MAFF. We would urge the Agriculture Committee to draw attention to this in its report.

The possibilities for increasing immunity

  While certain factors cleary predispose people to infection with tuberculosis it is also established that some people acquire natural immunity to TB through contact with microbacteria of the same genus asM. tuberculosis and M. bovis. All children are tested to see if they already have such immunity and those which do are not vaccinated with the TB vaccine BCG.

  What is true of the human population is also likely to be true of cattle and perhaps badgers, deer and other mammals capable of being infected by M. bovis. Building on this it has been suggested by researchers from University College London (Donoghue et al 1997) that changes in farming practice may be altering the balance of environmental mycobacteria in the soil in a way that is reducing those strains best able to confer immunity, while increasing others more likely to predispose for TB. In addition natural immunity could possibly also be influenced by:

—  the rearing of calves on milk replacers rather than whole milk;

—  the quality of grazing and fodder in relation to micro-nutrients such as trace elements.

Environmental mycobacteria

  It has been known for many years that over 50 strains of mycobacteria commonly found in the environment and closely related to the tuberculosis bacteria can prime the immune system and produce the effect of a "natural vaccination" against tuberculosis (Grange 1986). It is this effect which was exploited in the development of the TB vaccine BCG. While the government is funding work into the development of a possible TB vaccine for cattle no research is being funded by MAFF into the impact of different farming methods in conferring a natual immune response or the extent to which this may be changing with time.

  Dr Helen Donoghue and her colleagues at UCL followed changes in the population of different types of mycobacteria over three years on a farm in south-west England. They found that although there were seasonal effects and variations according to land type, the greatest difference was between the first and third years of the experiment, which coincided with a shift from conventional to organic farming methods (Donoghue et al 1997). Unpublished work by the same UCL team has demonstrated that young animals are expecially vulnerable to disease after weaning and before adulthood, a period when the development of their immune system is still incomplete. Despite this promising basis for further research, and the desire to extend their study to the effects of such changes on the priming of animals' immune systems against TB, the team do not have funding at present to do so.

  Work at the Rothamsted Institute of Arable Crops Research corroborates the hypothesis of the UCL researchers to the extent that research there has shown that different fertiliser regimes can have a radical effect on the habitat and hence the population and action of other types of environmental bacteria (Willison et al 1995). They found, for example, that inorganic ammonium-based fertilisers drastically inhibited the microorganisms which naturally break down methane into carbon dioxide, whereas other inorganic nitrate-based products and animal manure did not.

Rearing of calves on milk replacers

  The importance of colostrum during the first five days of a calf's life in developing its immune system is well recognised. However, calves suckled on their mothers through to weaning are generally perceived to be healthier and more naturally resistant to infection than those reared on the bucket. It is not known, though, if this extends to increased resistance to TB. It would therefore be helpful to establish in relation to all TB reactors whether as calves they were suckled on their dams, multiple-suckled, reared on whole milk from a bucket/mother feeder or reared on a milk substitute.

Quality of grazing and fodder in relation to trace elements

  Evidence that the low trace element status (particularly selenium) of much UK farmland, could be a factor in poor immune response to bovine TB from British cattle has been presented by other groups and will not therefore be repeated here. The Soil Association would, nevertheless, support calls that this issue should become the subject of further research which, in our view, should be broad enough to cover the impact of different farming practices in producing crops with a critically low trace element content.

5 February 1999

REFERENCES

  Anonymous 1998. "Badger—TB link organic status?" in Farmers Guardian, 27 March.

  Balfour, E B 1975. The Living Soil and the Haughley Experiment, New York: Universe Books.

  Donoghue, H D, Overend, E and Stanford, J L 1997. "A longitudinal study of environmental mycobacteria on a farm in south-west England", Journal of Applied Microbiology, 82, 57-67.

  Grange, J M 1986. "Environmental mycobacteria and BCG vaccination", Tubercle, 67, 1-4.

  Krebs, J and the Independent Scientific Review Group 1998. Bovine Tuberculosis in Cattle and Badgers: Report to The Rt Hon Dr Jack Cunningham MP. London: MAFF Publications.

  MAFF, 1994. Bovine Immunodeficiency-like Virus. London: MAFF Consumer Panel Secretariat (Briefing sheet).

  PHLS, 1999. Public Health Laboratory Website: Tuberculosis statistics.

  Willson, T, Goulding, K, Powlson, D and Webster, C 1995. "Farming fertilisers and the greenhouse effect", Outlook on Agriculture, 24, 241-247.