Dr Caswell's research interests centre on innate resistance to opportunistic bacterial infection, and on the pathogenesis of infectious diseases of the respiratory system. Bacterial pneumonia is a major cause of death and production loss in food-producing animals, particularly beef calves and swine, yet most animals are innately resistant to infection with the bacteria that cause pneumonia. Stress and viral infection are two well-recognized predisposing causes of bacterial pneumonia, yet much remains to be learned of how these factors impair lung defences. Pneumonia in beef cattle and swine is a useful system for investigating how stress and viral infection influence the interaction between the host, the pathogen, and the environment. Potential applications include identification of animals at risk of developing bacterial pneumonia, better identification of risk factors for disease susceptibility; genetic improvement of innate resistance to bacterial infection; and augmentation of innate resistance through strategies of animal management, nutrition, or therapeutic intervention other than antibiotics.