Memorandum submitted by the Institute for Animal Health (SFS 46)

 

 

EXECUTIVE SUMMARY

 

Meat, eggs and dairy products are a major part of the UK diet and infectious diseases have a major impact on the efficiency of livestock production with huge losses caused by chronic, sub-clinical episodes of disease.

 

New disease scenarios are expected with changing UK agriculture/farming practices; changes in climate, demography and land use; increasing international movements; and a greater preference by the consumer for non drug-based methods of disease control.

 

Control of disease is absolutely essential for some sectors of livestock production, principally the intensive production of broiler chickens. In the absence of effective vaccines or drugs, the major pathogens of poultry would be uncontrolled, cause high rates of mortality and prevent large-scale poultry production.

 

Defra must continue to invest in the control of important livestock diseases, be prepared to ensure the long-term availability of key scientific and technical skills and adequately support the provision of key infrastructure.

 

Defra must continue to provide leadership in research for better control of disease. Current funding models within the UK for this topic are 'fragmentary' and may be dependent upon commercial or academic considerations yet the current statutory obligations of Defra for disease surveillance dictate a leadership role and much ownership of the agenda.

 

Given the national importance of diseases such as bovine tuberculosis, foot-and-mouth disease, bluetongue and avian influenza, Defra must also develop a stronger leadership role in the communication of science to a lay audience.

 

1. INTRODUCTION

The value to the UK of livestock production is estimated at around £8 billion arising from the annual production of around 10 million cattle, 35 million sheep, 6 million pigs and around 850 million chickens.

 

The impact of infectious diseases is considerable and directly accounts for a loss of around 20% of total production through a reduction of the value of livestock (poorer quality), less efficient rates of conversion of food to meat, less optimal weight gains, increased costs of production associated with use of vaccines and other medicines and poorer welfare. In addition, diseases such as bovine TB (bTB), bluetongue, avian influenza and foot-and-mouth disease (FMD) have impacts on the social fabric of the UK and, as illustrated graphically during the 2001 outbreak of FMD, the potential to restrict national and international trade in livestock and the rural economy more widely. Last but not least, some livestock diseases have the potential to establish in man (zoonotic pathogens).

 

In seeking to secure food supplies up to 2050, an important part of the UK national strategy must be to control infectious diseases of livestock.

 

Defra must continue to provide significant leadership of any multi-faceted strategy to control infectious diseases of livestock, backed by a consistent and realistic investment and be prepared to support longer-term research into key pathogens. They should continue to contribute to the provision of the necessary infrastructure, which includes trained scientists and technical staff, buildings and genetic resources of livestock, with the reasonable expectation that demand will increase for solutions to disease problems because:

 

• There will be a continuing need to protect animal health and welfare against new and variant pathogens.

• Infectious diseases will emerge and re-emerge with changing UK agriculture/ farming practices. For example, further demand for poultry reared less intensively will create opportunities for diseases that have been virtually eliminated by the husbandry practices associated with intensive production; for example diseases caused by worms.

• Infectious diseases will remain a global problem that is exacerbated by changes in climate, demography, globalisation, trade, animal movements, land use and diversity of livestock products.

• There will be increased threats to human health from zoonoses.

• There will be greater risks associated with bioterrorism to UK livestock and human health.

• There is already now a reduced availability globally of drug-treatment for food-producing animals.

• A rising global population, together with the factors above, increases further the need to protect UK food supply and food security.

 

If Defra do not show the appropriate leadership, there are no guarantees in place to ensure that other organisations in the UK have the capability to fund the breadth and depth of relevant scientific research needed to provide sustainable solutions for control of current livestock diseases, or to predict and prevent new incursions of disease. It is noteworthy that some viruses, e.g. African swine fever virus, now circulating within Eastern Europe are characterised by an ability to kill close to 100% of the animals they infect. Incursions of such pathogens (and BT virus killed 15 million sheep in Belgium in 2007) are now much more likely in the UK due to the factors bulleted above.

 

Defra investment will be necessary to help support a vision for the future production of disease-free livestock that contributes to ensuring the delivery of a pipeline of new and increasingly sophisticated control measures in collaboration and alignment with the best commercial companies. Defra and other funders, such as BBSRC, must continue to work closely together and, in turn, help create the best working environment for scientific collaborations with the commercial sector.

 

For control of disease in major livestock species, it is clear that vaccination is becoming the approach of choice. The poultry sector, especially, relies heavily on vaccines and given the importance of this sector to the UK Defra must have ongoing investment into poultry disease research so that the UK can best protect its breeding and egg-laying flocks from the many viral, bacterial and parasitic pathogens that they encounter.

2. A NEED FOR CONTINUED INVESTMENT BY DEFRA IN TO DISEASES OF LIVESTOCK: SOME EXAMPLES

 

POULTRY

 

A continued need for Defra to invest in relevant, longer-term research

 

Chicken meat and eggs comprise a major part of the UK diet. Chicken is often the meat of choice and consumption in the UK is about 25 kilograms per head per year - exceeding that that of any other meat and accounting for about one third of all meat consumed.

 

Chickens (broilers) reared commercially for their meat are housed in large numbers on the ground and at high stocking densities. The UK annually produces around 850 million broilers, 17 million turkeys, 19 million ducks, and around 100,000 geese. The degree of self-sufficiency in poultry meat in the UK has declined to about 89 per cent in the early 2000s from around 97 per cent in the late 1980s.

 

Vaccination against many pathogens is an integral part of the poultry industry and it is unlikely that poultry production on the current scale would be achievable if just one of the major diseases were to become uncontrollable. Many pathogens of poultry evolve with time, through the selection of genetic variants which can lead to dramatic changes in their virulence and pathogenicity; the sector has also had to deal with incursions of entirely new diseases on occasion. To illustrate that continuity of current poultry meat supplies cannot be taken for granted, reference can be made to Marek's disease, a highly contagious neoplastic disease caused by Marek's disease virus (MDV). This disease can cause devastating losses through high mortality and morbidity and the UK provides world-leading skills on this pathogen. The first ever vaccine against Marek's disease in poultry (in fact the first ever vaccine against a cancer-causing virus) was developed by UK scientists and the vaccine was a critical component in the transformation of the developing poultry industry. The current use of Marek's disease vaccines is colossal and the economic impact of control of Marek's disease by the principles and vaccine arising from UK research can be measured in £ billions. Unfortunately, every decade or so, markedly more aggressive forms of MDV evolve and there is an ongoing need to develop and introduce new vaccines otherwise poultry production and supplies of meat worldwide would be seriously compromised. Increasingly sophisticated solutions to new vaccine development are needed and the UK commercial sector has an absolute long-term commitment to invest in the use of each new generation of product. Currently much of the critical expertise needed to develop the new vaccines resides within Government-sponsored Institutes such as IAH and provides cutting edge research that complements the manufacturing capacity of the commercial sector for delivery of the next generation of vaccines.

 

A critical point about the example with Marek's diseases is that the relationship between the host (chicken) and the pathogen (Marek's disease virus) can be viewed as a classic "Arms Race" in which the continued evolution of the pathogen through natural genetic mutation enables the selection of viruses that can overcome an intervention strategy such as vaccination. Thus, whilst vaccines may "win" for a period of time, a rapidly mutating pathogen that cycles rapidly through livestock reared under highly intensive conditions of husbandry has the potential to become the ultimate "victor". History indicates that, in the case of Marek's disease, perhaps five or more new control measures will be required by 2050

 

3. CATTLE AND SHEEP PRODUCTION

 

A continued need for Defra to invest in relevant, longer-term research and science communication

 

The UK cattle population is about 10 million and the total value of cattle, pigs and sheep in the UK is about £8 billion per annum.

In view of the changing livestock diseases and patterns of disease experienced in the UK, increasingly as a result of climate change, Defra will again need to continue to support a range of scientific research activities with a preparedness to invest in the infrastructures necessary, be they facilities, scientific and technical experts or tools and reagents, to ensure that the UK is adequately equipped with the resources necessary to control, contain and eradicate diseases as necessary.

 

There is now the prospect that diseases currently given the status of "exotic" to the UK, such as bluetongue, will become established in the UK and a revision of their status may be warranted. The example of BT illustrates well the need for investments in potential disease scenarios because there may be no time for a "catch-up" of scientific activity in the event of a new entry of disease. Prior investments in BT virus research enabled the UK to be best prepared in 2008 and they provide a good lesson of the need for advance planning and an acceptance that the next disease threat may come from an hitherto unlikely source, e.g. Africa.

 

The dairy sector provides a good example of the opportunity that exists for Defra to help lead on the agendas of communicating scientific advice and improving the relationship between scientific experts and the lay public. It is probable that improvements to the quality of cattle products could be achieved through some relatively simple steps, but some culture changes will be needed in the farming sector and Defra are well placed to help lead.

 

o Ongoing changes in the UK dairy industry, which include reduction in herd numbers, increase in herd sizes, geographic concentration of dairy herds and small profit margins leading to rationalisation of husbandry, are likely to have an impact on the way animal diseases are spread within the dairy cow population and on the way diseases and their impact are viewed and dealt with by the industry.

o Establishing a greater farm-level biosecurity culture in the farming sector would improve control of the spread of endemic diseases and better prevent incursions of exotic diseases, but farmers and others within the dairy industry seem reluctant to pursue this approach.

o There is a need to understand more fully the reasons why farmers adopt or resist disease control mechanisms. A key factor in the adoption of disease control measures is the communication of scientific advice and the relationship between scientific experts and the lay public.

o New forms of engagement between expert and lay actors (e.g. participatory and deliberative experiments) may foster better uptake of science-based disease control measures by resolving conflicts between different perceptions of knowledge and best practice.

o A key requirement is, therefore, to understand how disease control advice is communicated to farmers and to identify the main conflicts between scientists, veterinarians and farmers in developing disease control solutions.

o Important examples of endemic disease with increasing prevalence in the UK dairy herd are Bovine Virus Diarrhoea (BVD) and bovine tuberculosis (bTB). Ninety percent of UK dairy herds now show evidence of infection with BVD, but convincing farmers to control BVD is a challenge because the virus does not cause overt clinical signs. However, BVD has a significant deleterious economic effect on cattle production causing infertility, abortion and poor calf health and profound immunosuppression for at least two weeks.

o The immunosuppression caused by BVD may have two outcomes in relation to bTB

§ some cases of bTB may not be revealed by testing; and

§ subclinical cases of bTB may be exacerbated by unhindered dissemination of tubercle and become clinical "open" cases allowing spread of infection to other cattle and humans.

o The presence of these two diseases in British cattle may, either singly or in combination, be affecting the viability of dairy farms, thus having a major impact on rural communities and on the dairy product and live animal value chains, thus affecting the wider economy. bTB is also a zoonosis and an increase of bTB in cattle is causing a risk of a corresponding rise in the number of human cases.

o In other countries, both within and outside the European Union, BVD and bTB have been eradicated, or there are on-going eradication programmes. By not following this example and eradicating these diseases, the UK is putting at risk the chance of regaining valuable export markets for British livestock, which were lost during the BSE epidemic.

o During the next four decades, Defra has an opportunity to work with others to eradicate some important disease and, in so doing, ensure that cattle production is optimised further.

 

 

 

Martin Shirley,

Director

Institute for Animal Health

 

January 2009