Ovine footrot is a contagious disease affecting the hooves of sheep. The principal causative agent is the anaerobic bacterium, 'Dichelobacter nodosus'. Different strains of 'D. nodosus' cause disease of differing severity, ranging from benign to virulent. The severity of the disease is also affected by environmental factors, such as temperature and rainfall, and by the breed of sheep. In the early stages of infection, it is difficult to distinguish between benign and virulent footrot by examination of the hooves of affected sheep. However, early diagnosis is essential for footrot management, as sheep affected by virulent, (but not benign), footrot are subject to quarantine. A variety of laboratory tests have been used for the diagnosis of virulent footrot. ... At the University of New England, located in the prime wool producing area of the northern tablelands of NSW, we have been using DNA analysis to investigate genes involved with virulence in 'D. nodosus'.