[Planning of epidemiologic studies using the example of parasitic diseases]

Epidemiology is concerned with the study of diseases and risk factors for diseases in populations. Livestock related studies require that the term disease is extended to cover all conditions that directly or indirectly may affect the economic, social and ecological value of livestock or constitute a public health risk. The objectives of epidemiologic studies range from the quantification of traits, e.g., prevalence of a disease in a population (descriptive approach), to the analysis of correlation between diseases and putative risk factors (analytic approach). The type of epidemiologic study must be selected accordingly. In this paper we present the most important types of epidemiologic studies using example data. Our aim is to give an orientation for the planning of epidemiologic studies.