VACCINES AND CATTLE: AN UNEXPECTED HISTORY
By Julia Herman, DVM, MS, DACVPM Beef Cattle Specialist Veterinarian, NCBA, a contractor to the Beef Checkoff
Cattle are amazing creatures. Producers and veterinarians get to experience this daily from how cattle behave, grow and interact with us and their environment. The Beef Checkoff-funded Beef Quality Assurance( BQA) program provides guidance on caring for cattle, improving herd health and welfare. Cattle have also played a critical role in developing one of the most used preventive medicine techniques in the livestock industry— vaccines.
Did you know the word vaccine, and early vaccination, was created using the cowpox virus? The term‘ vaccine’ is rooted from the Latin word for cow, vacca, and the cowpox virus name is vaccinia. In the late 1700s, farmers and milkmaids exposed to cowpox virus from handling cattle were seen to be protected from smallpox. A physician then inoculated a boy using material from the cowpox sore, leading to the first vaccination against smallpox.
Since then, health technologies including vaccines have progressed dramatically. In the spring of 2023, NCBA hosted a Cattlemen’ s Webinar on new vaccine technologies( which is available on YouTube). This article will be the first of three diving into topics discussed on the webinar— how vaccines work in cattle, how livestock vaccines are regulated and tested for safety and efficacy, and how vaccines are integrated into herd health planning. Evaluating all tools in our animal health toolbox is key as producers and veterinarians make daily care decisions. Introduction to the Immune System
The immune system is the first line of defense to keep disease agents out of the body and, if they get in, the body must clear them without harming the animal or the unborn fetus. The innate( generalized) and adaptive( specific) immune systems work together to protect the body in their different tasks. This complex system protects the animal( or an individual) against disease agents such as bacteria, viruses, parasites and fungi. To protect against infection, the immune system recognizes cells / organisms that are‘ not self’ and can cause damage when entering the body.
The innate immune system consists of skin and mucous membranes lining the gastrointestinal tract, respiratory tract, mammary gland, urogenital tract and the whole body surface act as physical barriers to disease agents. There are also immune cells that digest germs or release substances to kill bacteria and germs. Chemical signals called cytokines are produced to recruit other immune cells and stimulate the inflammatory process.
The adaptive immune system takes over if the innate strategies are not enough. There are many immune cells activated in this process, including T cells, B cells and antibodies, that are specifically trained to fight a single type of germ or disease agent. This response takes time because the cells need to be alerted to the site of infection by messenger cells that present the antigen and trigger a response. These cells travel from the lymph nodes and other tissues to the site of infection.
Between the two systems, some cells get rid of the disease agent directly, while others clean up any damage. Some B cells turn into memory cells or antibodies which help the immune system remember the infectious agent in the future. This immunological memory can prepare to keep out the infection in the future by neutralizing them or minimizing damage in future infections by attaching to immune cell receptors and preventing infection.
All of this happens when an infection occurs. While activating this useful immune response that can protect the individual in the future at the time of infection, it could also make the animal very sick and may even result in death if the immune system overresponds. Recognizing the Threat
The body can distinguish‘ not self’ cells / organisms based on their genetic information carried on double-stranded DNA( deoxyribonucleic acid) or single-stranded RNA( ribonucleic acid). RNA is found in every living cell on earth while DNA is found in the nucleus of cells( fun fact— mature red blood cells have no nucleus and therefore do not contain DNA). DNA provides the blueprint for all the proteins cells can make. RNA carries out that blueprint by copying the DNA to make proteins. These proteins are used by immune cells to protect the animal from infection or to clear an infection. After the proteins are made, the RNA is broken down by enzymes inside the cell.
Viruses, bacteria and parasites that make animals sick contain RNA. Some viruses contain RNA which the immune system recognizes as foreign and responds to. Others do not contain RNA and contain DNA, so when DNA infects a cell, it will stimulate the cell to make RNA for the immune system to recognize. Role of Vaccination
When a virus infects cells in a natural infection, RNA starts to be copied, then makes proteins that will become a new virus. That new virus emerges from the infected cell and infects other cells and possibly spreads to other individuals. This may have severe systemic effects due to inflammation and immune response.
Vaccinations are key pieces to herd health plans because the cattle get the benefits of immune memory without the harm of a natural infection.
Vaccination is one way to stimulate the animal’ s immune system to protect them. A vaccine can activate all the same effects as infection without making the animal sick or killing them. Vaccinations are key pieces to herd health plans because the cattle get the benefits of immune memory without the harm of a natural infection.
When cattle are vaccinated, such as with a modified live virus( MLV), the same sequence of events occurs— MLV starts growing, copies RNA, makes proteins, and makes new virus. The immune response to this vaccine virus protects the cattle from future infections. The immune system sends cells in to break down those viruses into proteins and RNA and activates protective immune response. This has become one of the most practical ways to improve animal health on cattle operations.
In the next article, we will look at how cattle vaccines are regulated, including the process to determine safety and efficacy. Withdrawal times and food safety, as discussed in the BQA program, are key to this process. For more information on herd health protocols and training or to check your BQA certification status, visit the BQA website at www. bqa. org.
10 JUNE 2025 www. NCBA. org