The Nature of Viruses

This chapter discusses the animal virology that defines human development, which is shaped by at least three major recurring elements: environmental changes, human conflicts, and infectious diseases. It states that the origins of veterinary medicine are rooted in efforts to maintain the health of animals for food and fiber production and animals essential for work-related activities. The early phase of virology was one of skepticism and uncertainty because of the limited tools available to define the filterable agents. Even with filtration, there were differences among the agents as to their size as defined by filter retention. The bacterial viruses assisted in defining some of the basic principles of genetics through the study of mutations and the inheritance of phenotypic changes. Veterinary virology began as a discipline focusing on the effects of viral infections on animals of agricultural significance. Control of these infections relied on advances in understanding the disease process, in the characterization of the viruses, in the development of the fields of immunology and diagnostic technologies, and in the establishment of regulations controlling the movement of production animals. Initial experiences confirmed that eradication of some infectious diseases from defined areas could be achieved with a test and slaughter program, even in the absence of an effective vaccine. This chapter also explores characteristics of viruses, viral morphology, and taxonomy.