Many beef producers have started planning for weaning season. The stress of weaning on calves can be a precursor to disease -- especially respiratory disease -- which is why it is so important to protect the integrity and function of a young animal's immune system prior to and during weaning.
In order to accomplish this, it's beneficial to understand the effects of stress on the bovine immune system, as well as the basics of cattle immunology, including key terminology. Armed with this foundation, producers can work with their veterinarians to make more informed decisions on vaccination protocols appropriate for their operations.
Latest Advancements in Immunology
Until recently, cattle immunology models were based on that of the mouse, which has a different type of immune development – specifically, much slower development. What we now know is the immune system of cattle is functional at approximately 150 to 170 days of gestation. This means it is capable of effectively responding to vaccination even before birth.
We've also learned the importance of cell-mediated immunity (CMI), which means an immune response is generated through cellular events versus humoral events (protective immune function associated with cell-free bodily fluid or serum). CMI is particularly important when it comes to protection against common respiratory diseases, such as Bovine Viral Diarrhea Type 1 and Type 2, Infectious Bovine Rhinotracheitis, Bovine Respiratory Syncytial Virus and Parainfluenza3.
In an effort to control these costly diseases, modern research applications strive to create this optimal CMI response while creating an immune response at the site of infection prior to disease exposure. This is crucial to rapid protection against respiratory diseases; and achieving all of this with fewer injections.
Key Immunology Terms
- Active immunity: Immunity acquired through exposure to an antigen and response of one's own immune system
- Antigen: Substance that stimulates production of antibodies (i.e., virus, bacteria)
- Antibodies: Proteins that fight infection, produced in response to an antigen
- Cell-mediated immunity (CMI): Immunity resulting from the immune system being activated by a vaccine or natural infection. It is important in immunity of intracellular organisms such as viruses and also in the creation of immune memory (cell-mediated immune response)
- Humoral immunity: Immunity based on antibody formation
- Innate immunity: Immunity present from birth and not dependent on prior antigen exposure. Innate immunity includes physical and chemical barriers to infection
- Maternally derived antibodies: Antibodies that are transferred from the mother to the newborn to protect it until its immune system is built up enough to protect it
- Memory response: Repeat response to an antigen that is faster and larger than a primary response
- Modified-live vaccine: Vaccine made by taking the real, disease-causing virus and altering (attenuating) it in a laboratory to a non-disease causing virus
- Mucosal immune system: Consists of molecules, cells, and organized lymphoid structures intended to provide immunity to pathogens that impinge upon mucosal surfaces
- Parenteral vaccination: Vaccination received through a subcutaneous, intramuscular or intravenous injection
- Passive (maternal) immunity: The transfer of antibodies from a donor in which they were produced to a recipient for temporary immunity. This can be in the form of serum or colostrum
- Pathogen: Disease-causing organism
In the next issue, we'll explore why building the immune system of calves is so important and the practical application of recent advancements in our understanding of calf immunology.
Scott Nordstrom, DVM, is manager veterinary technical services at Intervet/Schering-Plough Animal Health. For more information contact Scott.Nordstrom@sp.intervet.com.