If diseases of food-producing animals or zoonoses (re-)emerge, early clinical decision making is of major importance. In this particular condition, it is difficult to apply a classic evidence-based veterinary medicine process, because of a lack of available published data. A method based on the partition of field clinical observations (evidences) could be developed as an interesting alternative approach. The classification and regression tree (CART) analysis was used to improve the early clinical detection in two cases of emerging diseases: bovine spongiform encephalopathy (mad cow disease) and bluetongue due to the serotype 8-virus in cattle.