Viruses are a large, diverse group of very small infectious agents, whose early history of discovery from smallpox to polio encompasses a period of almost 150 yrs. They are filterable, obligate, intracellular parasites which invade, spread and are pathogenic.
They can be propagated using life host systems, among which are laboratory animals, embryonated chicken eggs and tissue cultures.

Cultivation of viruses outside the host was first restricted to inoculation of animals and progress in virology has been dependant on the use of laboratory animals. This, in the modern world tends to be far less acceptable. Use of animals has now been restricted mainly to growth of difficult viruses and preparation of reagents.

Embryonated chicken eggs, since initial use in 1930, advanced the study of viruses and were the first alternative to the use of animals. Eggs serve as suitable hosts for virus isolation, identification and production of vaccines. Antibodies are not present in eggs from unvaccinated flocks and not produced by the chicken embryo.

Cell cultures then allowed for the use of antibiotics to combat contamination and also for the in-vitro replication of viruses for their further study and characterization.

This module will familiarize you with some of the basic techniques used in Veterinary Virology, with the aim of providing the knowledge to allow you to get started in your own laboratory using these techniques in your field of research. You will have the opportunity to learn more about the basics of the following techniques:

• The isolation and identification of viruses using cell cultures
• The use of embryonated chicken eggs for the isolation of viruses
• The use of laboratory animals for the study of viruses.