Protecting cattle from disease is the foundation of building a healthy herd. Vaccines, along with good nutrition, play a role in helping animals develop immunity against key reproductive and respiratory diseases.
It is important to begin with immunology basics. “Vaccination does not equal immunization,” says Mark van der List, Professional Services Veterinarian with Boehringer Ingelheim Vetmedica, Inc. “When we talk about immunization, we actually mean protection from the invasion of a foreign protein into the body. Vaccination is simply the process of giving a vaccine. Vaccination can lead to immunization, but not if vaccines are improperly handled or administered.”
When a foreign protein (antigen) enters a cow, systems that can identify self versus non-self are activated, explains Dr. van der List. Once the antigen is identified as non-self, the cow’s immune system will set off a cascade of events and develop either a cell-mediated immunity or a humoral immunity, or a combination of both, to rid the antigen from the body. The immune system will also develop memory cells, which will enable the body to react much more rapidly the next time the same foreign antigen is encountered. Immunization is the development of these memory cells so that the body can rapidly deal with disease.
“When developing vaccines, we modify the organisms that we want protection against so that the animal doesn’t have to suffer the full-blown disease to develop immunity,” says Dr. van der List. “While one method is to expose the animal to others with the disease, there are huge risks involved with this. With a vaccine, we can take away a lot of that risk and still get the protection we desire.”
Vaccinating when an animal is stressed can lead to problems, says Dr. van der List. To develop a good immune response, the animal needs to be healthy and stress-free. Stress releases cortisol, which interferes with immunity. This can lessen the animal’s response to vaccination, as well as predispose the animal to disease. Producers should plan to administer vaccine ahead of an anticipated disease challenge, which is often associated with a stressful event.
With a modified-live virus vaccine development of immunity can be rapid, however it is still advisable to have two to three weeks between administration and requirement of immunity, says Dr. van der List. For heifers that have never been vaccinated before, a four-week period is especially recommended prior to breeding.