This document presents the most important epidemiological components of the animal diseases and their role in the design of control strategies. The multifactorial character of the diseases makes difficult to define the limit between health and disease, both of them are depending on the balance of three elements, animal, pathogen and environment. This means it is important to know the factors of every one of the three elements that are associated to disease presentation, and according to this, it will be possible to design the different preventive medicine strategies to control it. The paper also presents the observational epidemiological studies as the most important epidemiological tool to use in the identification of that risk factors associated to disease presentation.