Viral Infections in Livestock: Mode of Action



By: Gordy Jordahl, Water Physiologist

A virus is a small, infectious organism much smaller than a fungus or bacterium, that needs a living cell manifesting a low vibratory rate in order to reproduce. It attaches to the cell and once inside, the virus releases its DNA or RNA, which contains the information needed to create new virus particles. It then takes control of the cell’s metabolism. The components of the virus are then manufactured inside the cell and must be properly assembled for the virus to be release and remain infectious. Some viruses kill the cells they infect, and others alter the cell function so the cell loses control over normal cell division.

Viruses incorporate a part of all of their genetic information into the host cell DNA and remain silent until the cell is disturbed or challenged in any way that permits the virus to emerge again. Most viruses have a preferred host and some, such as influenza virus, infect a variety of animals. Some strains of influenza have adapted in a way that allows them to infect some species of animals more efficiently than others. An animal’s body has a number of specific defenses against viruses.

Infected cells make interferons, which is a family of glycoproteins that can make non-infected cells more resistant to infections. When a virus enters the body, various types of white blood cells such as lymphocytes are able to attack and destroy the infected cells. When exposed to a viral attack, T-lymphocytes (T-Cells) increase in numbers and mature into helper cells which aid antibody producing B-lymphocytes (killer cells), which can attack cells infected by a specific virus.

The T-lymphocytes produce chemicals called cytokines that speed the developing process. The cytokines from helper cells help B-lymphocytes and their derivatives (plasma cells) to produce more antibodies that target complex viruses and make them non-infectious before they can affect another cell.

Giving a specific vaccine to resemble a specific virus without causing a disease can produce immunity. In response to the vaccine, the body increases the number of T and B-lymphocytes that are able to recognize a specific virus. However, a virus mutates to avoid antibodies.

Immediate protection against complex viral infections can be achieved by infusion of immunoglobulins produced by another animal who has been exposed to the same virus.

Drugs that combat a specific viral infection are generally more difficult to design for their targeted organisms and are generally more toxic. They are designed for a specific organism; however, viruses are now becoming more complex. More antibody classes of immunoglobulin within the immune system need a broader spectrum of response and more immediate activation, manifesting a safety net against viruses mutated from a specific virus attached to a cell. Target Factors aids as a safety net to support immediate immune response.