Emet, I'm curious - is this true for livestock vaccines as well?
I wouldn't know. I hung up my hoof pick when I graduated. And gave it away, along with my leash with the big chain on the end

(we had to purchase them in school).
I'm no historian, but if I had to guess, the downward trend in pet vaccinations may be attributable to at least two things I know about:
1. Dr. Jean Dodds, who is/was well respected, but may now be dabbling in CAM.
Linky
She started speaking out a long time ago. You can find lots of articles she's written about vaccines on the Interwebz.
2.
Vaccine associated Feline fibrosarcomas.
Another link.
We've taken a lot of steps to reduce the incidence of these tumors.
This, along with the fact that vaccine testing in animals vs. humans is quite different, I think, and the duration of immunity is not tested the same way. But don't quote me on that.
The reason I ask is I knew a person up in CO who owned a facility for testing vaccines, wormers, antibiotics etc. for livestock. Also, some of that stuff is labeled for specific species, but it's fairly common to use it in others, what they call "extra label" I think. So while cydectin may be used in cattle and sheep, it's not on the label that you can use it for goats, although it works of course. My impression was, it had been thoroughly tested in cattle and sheep but not goats. Maybe I was wrong though, and that is not true.
Extra label use is very common in small animal medicine, and presumably also in large animal medicine. A lot of small animal dewormers came from large animal medicine. Some eventually were tested and formulated for small animals, where concentrations were more convenient. But many small animal practitioners still use the large animal formulations, as they're less expensive.
Some small animal drugs are only approved in one species, usually dogs. They often are used for cats. Look at the label for a very commonly used product
here.
And I wonder where all these rich vets are? I've known and worked with about two dozen different vets and *none* of them were rich...
Well, I can only speak about small animal practitioners. Those that own their own practice, or multiple practices do well to very well, as do most specialists. The rest of us... well, I live in an apartment and drive a compact car.
