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Adult pig small intestinal villus Adult pig small intestinal villus. Red, CD8; green, CD4; blue capillary endothelium.

Concerns about antibiotic and growth promoter usage in agriculture have stimulated interest in sustainable alternatives for controlling infectious diseases, particularly where replacement systems improve animal welfare. To optimise these systems, it is important to examine the whole, multi-factorial, infection process. Veterinary undergraduates and graduates are uniquely placed to acquire this broad view of infectious disease.

Susceptibility to infection depends on many factors involving pathogen, host, environment and husbandry. These factors are particularly important in the case of pigs and chickens, which are farmed intensively. Husbandry systems will affect the dose of pathogen delivered, while strain of pathogen and individual susceptibility will determine the outcome of exposure to any particular dose. The intensity of production systems facilitates the spread of pathogens by aerosols or by the faecal-oral route: however, individual susceptibility is also influenced by factors controlled by the husbandry system. Thus, chickens and pigs exposed to Salmonella in aerosols are highly susceptible to infection at very low doses, compared to very high ones necessary orally. The newborn animal has an undeveloped immune system, particularly at mucosal surfaces, and requires colonisation by commensal micro-organisms to expand immunological compartments and repertoire. Increasing resistance to infection with age may be attributable either to microbial competition or to expanded immunological capacity. These, in turn, are affected by factors such as diet, mixing, pain and temperature.

This project brings together expertise in microbiology, immunology, behaviour, welfare and epidemiology to address the key question of the extent to which husbandry systems influence susceptibility to infectious disease.

Neonatal piglet small intestinal villus Neonatal piglet small intestinal villus. Red, CD8; green, CD4; blue capillary endothelium

Scientific Background

Given the pressure to reduce anti-microbial usage and the movement towards higher welfare, more sustainable husbandry (e.g. bans on battery cages, farrowing crates), rational disease control strategies for the future need co-ordinated, integrated studies by experts in infectious diseases and animal behaviour and welfare. A better understanding of how bacterial, host and environmental factors interrelate, and their effects on resistance to infectious disease, will allow the identification of strategies for reducing the use of antimicrobials, improving animal welfare and reducing pathogens entering the human food chain.

The intensive nature of the production systems, and the fact that they are the major sources of human Salmonella and Campylobacter food-poisoning, makes pigs and chickens important animals for study. The proposed projects will explore the role of environmental factors (normal gut flora, social and physical environment) on susceptibility to colonisation by these pathogens. The hypothesis to be examined is that improvements in husbandry and diet will lead to the identification of sustainable production systems, which will reduce susceptibility to infectious and zoonotic disease. The work will identify critical control points, which, we believe, will allow improvements in immune competence by manipulating husbandry systems or by directly influencing the development of protective, commensal micro-organisms.

Work packages: