Livestock species are an important part of the human food chain but their health and our agricultural productivity is challenged constantly by infectious diseases. The livestock sector in the UK is worth around £8Bn per annum and the overall costs of animal diseases during the past 15 years are an estimated £15Bn. These costs come from production losses, the eradication of pathogens whose arrival leads to restrictions in livestock trade, and the implementation of strategies to prevent potentially high rates of mortality.
Threats from diseases are predictably unpredictable – think BSE, foot-and-mouth disease, and the avian and swine influenzas. 40 new species of pathogens have been recognised in livestock and man during the past 25 years; most are RNA viruses but diseases caused by prions, bacteria, rickettsia, fungi, protozoa and worms are also represented.
The recent incursions of Bluetongue (BT) virus into northern Europe have provided an effective reminder that livestock can quickly become exposed to a new and serious disease introduced because of changing weather patterns. In this case, a warming climate across northern Europe created conditions favourable for the spread in sheep and cattle of the BT virus typically found in Africa and the Mediterranean. In 2008 up to 10% of the sheep died in some European countries and only the UK’s introduction of a national plan for vaccination prevented similar establishment and spread of the disease.
In addition to completely new disease threats such as bluetongue, the livestock sector has to contend with re-emerging pathogens that were once thought to be controlled, only for them to reappear in more aggressive or virulent forms that are no longer well controlled by existing vaccines.
A classic example is presented by Marek’s disease in poultry. This herpes virus produces rapid-onset tumours in the heart, ovaries, testes, muscle tissue and lungs (with mortality rates as high as 80%) and continues to change in virulence such that every decade or so a new vaccine is required.
Let’s take a specific look at poultry production. The UN’s Food and Agriculture Organisation (FAO) regards poultry products as a key component of growth in food production. An estimated 51Bn chickens are now produced each year worldwide, of which 46Bn are broilers (for meat) and 5Bn are layers (for eggs). Developing countries share of world poultry meat consumption rose from 43 to 54% between 1990 and 2005, with major contributions from east and southeast Asia, Latin America, China and Brazil. The FAO estimates that production and consumption of poultry meat will increase by around 3.6 percent per annum from 2005 to 2030.
The poultry sector is especially dependent up on the availability of vaccines and several diseases, if uncontrolled, have the potential to seriously derail the productivity of the poultry industry at a time when in some parts of the world up to 1M birds are reared together in order to meet increasing demand.
The sheer size and scale of poultry industry presents a great strength for the efficient production of meat, but a potential weakness if the control of devastating diseases such as Marek’s disease ever becomes unachievable.
The production of poultry and livestock is clearly ever dependent upon continued scientific innovation to deliver effective strategies for the control of infectious diseases. My task is to ensure that a public sector-funded institution such as the Institute for Animal Health is able to provide a network of global intelligence on the spread of pathogens, assess risk to specific countries, and deliver effective vaccine strategies to control new and existing livestock pathogens which distinguish between animals that are infected naturally or vaccinated deliberately.
It is sometimes tempting to think that the availability of a vaccine delivers a permanent solution; it is but a lull in the arms race between host and pathogen.
The livestock industries must therefore contend with a succession of emerging and re-emerging pathogens at a time when world population is increasing and meat consumption rises in the world’s most populous countries.
Finally, there are now fewer ‘easy wins’ available to researchers to develop vaccines at a time when consumer resistance to the use of drugs (especially those given in-feed) is changing. Unfortunately, the rate at which the commercial animal sector is able to introduce new drug therapies and vaccines might slow further because of increasing costs of both research and development, and of getting new products into the field.
About Professor Martin Shirley, Director of the Institute for Animal Health
Martin Shirley started his career at the Houghton Poultry Research Station (HPRS) as a junior technician upon leaving school in 1967. Ten years later, he returned to HPRS and was awarded a PhD by Brunel University for research on protozoan parasites from the domestic fowl.
Martin is now a world authority and author of more than 150 scientific papers and articles on coccidial parasites of poultry.
Martin was appointed Director of the Institute for Animal Health in July 2006 and his awards and honours include Honorary Professor at the Royal Veterinary College (2007) and Research Medal of the Royal Agricultural Society of England (2002).
Professor Martin Shirley, Director
Institute for Animal Health
Tel: 01483 232441