With societal and political pressure surrounding antibiotic use in food animals, preventing disease outbreaks is increasingly important.
The words “immunization, not just vaccination” may sound familiar in the context of discussing vaccines, but what is really meant?
Multiple factors influence an immune response and how it performs when faced with a natural infection, said veterinarian Dr. Jason Anderson.
The immune system is a complex organization of chemical mediators, cells, tissues, and organs that work in collaboration to address potential invading pathogens.
Immunity is developed through a cascade of events that are dependent on multiple interconnected elements.
The mechanisms that result in protection are active processes dependent on energy and other proper nutrients.
While it may seem the job is done once a vaccine is administered through a syringe, there are far more intricacies that must align for a successful response.
Precautions, warnings, and directions on the label are important. Statements regarding the number of needle punctures in the rubber stopper and the time frame are meant to reduce the risk of contamination.
Attention is often given to ensuring vaccines do not become too warm prior to use, yet the opposite extreme is counterproductive as well. Freezing certain types of vaccines is extremely problematic.
When these fractions have been affected by cold temperatures, it is unlikely the vaccine will behave as intended, and the animals receiving it could experience severe adverse reactions.
There are careful considerations to weigh when choosing a syringe type with tradeoffs between multidose and single-use options.
Pistol grip syringes are convenient for reducing fills when working with a group of cattle, but a good amount of effort is necessary to maintain them in clean condition.
Bottle-mount syringes seem like a logical choice when the number of cattle to work is large. However, the drawbacks are similar to pistol grip syringes, with an additional concern because the gauge of the needle that draws the product into the chamber is quite large.
The hole that is created following use is unlikely to seal well for reuse if there are doses remaining. With single-use syringes being sterile when first opened and easily discarded afterward, there is an advantage over the other options.
Vaccines need to be given early enough to include the proper number of doses and spaced the appropriate distance apart prior to disease exposure. Many products recommend an initial two-dose series when animals have not been given it before.
Two to four weeks later is commonly listed. Newer research on principles of immunology suggests aiming for the latter part of that interval.
After the booster dose, there is yet another lag for antibodies to appear. Generally, it takes 10 days to two weeks for this to happen.
It might be necessary to start a vaccination protocol four to seven weeks prior to a known risk period for a disease to have elicited protection in place before a challenge.
If there are circumstances negatively impacting individual cattle, immune function can be hindered, and it becomes increasingly unlikely that herd-level immunity can be achieved.
Young age, previous or current infections, stressors, and suboptimal nutrition can be reasons why the intended outcome might not happen.
Calves are born equipped with a working immune system. However, the machinery is immature and may not respond with the same vigor that occurs when they are older.
Disease either in the past or present adversely impacts vaccine immunity. The dependence on finite internal resources for fuel to drive this process means concurrent demands can limit the desired response to vaccination.
One specific infection, bovine viral diarrhea virus, is particularly worrisome because it can cause immunosuppression.
A persistently infected calf in the herd can wreak havoc by constantly shedding infectious particles to herd mates and contributing to the downregulation of the immune system in increasing numbers of animals.
Stressors such as extreme heat or cold, weaning, commingling, changes in accessibility to food and water, diet alterations and transportation can have a dampening effect in much the same way as with an existing infection.
The transition stages of cattle are accompanied by fluctuations in the availability or levels of various nutrients.
Nutrients become restricted when partitioned to power bodily needs. A shortage or a need by other life processes occurring simultaneously creates an impediment for the immune system.
Not all circumstances with a potential negative impact are avoidable, but the key is to limit as much as possible having multiple conditions collide or overlap at the same time.
Refining the ways in which cattle and vaccines are managed together will enhance the function of the natural defenses, build robust immunity, and improve disease prevention for healthier, more productive livestock.
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