The Saga Continues
Well, the election came and went; the new year came and went; inauguration came and went; and much to everyone’s chagrin, COVID came and stayed. In the last article I wrote for “the Dairy Dispatch,” I drew on some of the biosecurity lessons we have learned from COVID and promised to continue to discussion in the next issue. Well, here we are again, so grab a bowl of popcorn and a Pepsi and let’s discuss vaccination. I mean, after all it is only fitting that we discuss this topic in a dairy newsletter as the term vaccination originates from the Latin word for cow – “vaca”.
When you look into the history of vaccination, I think it is fascinating the Chinese were employing the practice of inoculation as early as 1000 AD – centuries before bacteria were even discovered. However, the practice of vaccination did not become successful until a man by the name of Edward Jenner began to use cowpox material to create immunity to the smallpox virus towards the end of the 18th century. Since then, the science of vaccination has progressed and allowed for the successful control and even eradication of diseases. Thus, when we start thinking about disease control, vaccination is definitely one tool that we want to have in our toolbox to help us improve the health and wellbeing of our livestock. And yet like any tool, it is a tool that should be understood and used appropriately, as it is hard to screw in a standard screw with a stripped off Phillips screwdriver.
In general vaccines can be lumped into two different, broad categories - modified live vaccines (MLV) and killed vaccines. MLV’s contain a small quantity of virus or bacteria that has been altered so that it can multiply in the animal and cause an infection, but not clinical signs of a disease. MLV’s require reconstitution with diluent prior to use and should be used within two hours of mixing. If we do not use them up in this amount of time, the vaccine efficacy and usefulness of this tool will start to decrease. Killed vaccines contain virus particles, bacteria, or other pathogens that have been grown in culture and destroyed. They do not replicate within the animal but are still able to elicit an immune response. Killed vaccines do not require mixing.
So, what vaccines should you use on your operation and when should you give them? I’ll go with the good, old academic answer here – “it depends.” But, really it does, so I think this is a discussion that you should have with your herd veterinarian. The disease pressures and management of each operation are going to be different, so when you use which tool is going to also vary. Nonetheless, as vaccines are not innocuous, I will say that I think we tend to over-vaccinate. My in-laws recently received the Shingles vaccine, and they said it was pretty miserable. If we listen to our cows, they will tell us the same thing about some of the vaccines we use; it is not uncommon to see a drop in milk production following vaccination. Thus, it is important to time the administration of some vaccines to limit the impact on production. Yet, some vaccines need to be given at certain stages of production to provide the most protection against certain diseases. Moreover, other vaccines may provide protection against diseases that are not even a concern to your operation. These are risks and rewards that you need to discuss with your veterinarian as you work together to develop a protocol for your operation.
Once we have that protocol in place, there are a few things that we need to do so that we don’t break a good tool. First, vaccines need to be stored according to the manufacturer’s recommendations. This almost always means out of direct sunlight and at 35°-46°F. I don’t think their recommendation ever includes storing (or transporting) on the dash of the pick-up, even in the frigid temperatures that we have recently had. When we mix vaccines (whether reconstituting a MLV or resuspending a killed vaccine), it is important to gently roll or swirl the vaccine, not to shake as shaking can damage the vaccine, decreasing the efficacy and increasing the likelihood of an adverse event.
When we administer vaccines, we need to change needles often. Unless you are sterilely prepping cows prior to vaccination, needles become contaminated with bacteria as soon as an injection is given. In addition, they also become burred as soon as they are used. These burs tend to hold bacteria. The more injections that are given with a needle, the more burred and contaminated they become. Then, when the vaccine is injected into the animal, some of the contamination on the needle is also injected. As a result, instead of focusing solely on mounting an immune response to the vaccine, the immune system also has to devote some of its energy to fighting off a local infection. This can decrease the efficacy of the vaccine and lead to more injection site lesions. I recommend changing needles every six to eight head, and at an absolute minimum, every time you refill a syringe. Refilling a syringe with a dirty needle contaminates the bottle of vaccine and inoculates every animal vaccinated after that with whatever bacteria was on our dirty needle prior to entry into the bottle.
When we are done vaccinating we need to make sure that we clean up our syringes appropriately. I like to rinse them out with distilled water and then draw up and discard a syringe full of nearly boiling distilled water three to four times. Soap is safe to use on the outside of the syringes, but should never be used to clean the inside as soapy residue can damage the vaccine. In addition, it is recommended that rubber washers should be replaced rather than lubricated, as lubricants can also damage vaccines. Lastly, store the syringes in a clean, dry place. I like to put mine inside a Ziplock baggie and place them in the freezer or refrigerator.
Is your popcorn and Pepsi gone yet? Well then, that is probably enough on vaccines for now. How about COVID? Is it gone yet? Hmm, yeah, at this point I think it is probably safe to say that it is here for a while, so we had probably better learn to deal with it. However, I don’t think that will be an issue for you all, as you all are part of the livestock industry and that is what you do – you learn to adapt and deal with challenges. Until next time, keep up the hard work!
This article appeared in the Dairy Dispatch Volume 14, Issue 1 published by Kansas Dairy