Water is an important link in spreading infectious diseases in humans and animals. It is a significant secondary source of contamination, being also a vector for microbial infections. Contaminated well water can ordinarily cause focal illnesses, limited to a certain area; contaminated river water used for animals poses much more hazard. In such cases epidemics transmitted via water can spread over vast areas and continue for long periods. Another significant factor in contamination of farm-bred animals is fodder: it threatens animal health and can pose a hazard to human health. The conditions under which animal fodder is stored can affect considerably the development of pathogenic microflora.