**1. Introduction**

Many diseases in modern animal farming are thought to have a direct link to the environment with the change of intensive systems with high animal densities on specialized farms; a change in the character of animal diseases took place [1].

Diseases no longer follow the traditional pattern, whereby one specific pathogen provoked clear clinical symptoms with a specific pathology. Intensification also meant that the animal became increasingly dependent on mechanical equipment for mechanical ventilation, feeding, and manure removal.

The considerable increase in herd size and the close contact between animals favor a quick passage of pathogens, which can lead to an increase in virulence and an increased infection pressure [2]. Some animal breeds are productive but may lack sufficient disease resistance and are sensitive to relatively small perturbation in their artificial environment, such as in temperature or air supply.

In contrast to the classical disease of specific etiology, these new disorders are called multifactorial diseases. Multifactorial diseases changed the pattern of diseases, morbidity, and productivity considerably. The characteristic of a multifactorial disease is that there is a variety of internal and external factors involved, and none of the factors alone can produce the disease itself. There are various formulations of the laws of causation, which are applicable to multifactorial infectious and noninfectious diseases [3]. The unified concept of causation by Evans marshals "formal epidemiology" can be applied where a causal hypothesis can be sufficiently probable to provide the rational basis for prophylactic and therapeutic measures. The causation of modem infectious diseases by the relationships between pathogen, host, route of transmission, and environment makes the transition of an infection into a disease possible. The external factors representing the environment include the physical, chemical, and biological environment, housing, management, feed, and water. Together with pathogens or facultative pathogens, these factors influence well-being, health, and performance. A disease, however, will develop only if the "internal factors" of the animal are unable to respond properly. The most important internal factors are genetic disposition (e.g., lack of resistance or adaptation, hormonal dysfunction) and immunity (e.g., maternal antibodies, immunosuppressant).

The aim of this chapter is to inform owners, veterinary professional, and others who are interested in Advanced Veterinary Science dealing with those bacterial infectious diseases, which occur relatively frequently in dairy and beef cattle and focus on general principles for the prevention and control of these diseases, providing detailed information on each disease. The information includes the following: economic impact, recognition of the disease, method of prevention for the spread

of bacterial diseases between animals in the farm, how to make the animals resist the disease, and the treatment of infected animals.
