You may be able to get it at your farm store. They usually have the paste, but what you want is the liquid. Paste is harder to get the correct dosage with. I don't think there is a liquid version of panacur that you would be able to find at feed or tractor supply, but Safeguard goat wormer is the same thing(liquid fenbendazole), and you can usually find it at these stores, or online. It has a shelf life, probably of a couple years, it will be printed on the bottle.
It's hard to say if giving it preventatively will do any good. E. cuniculi is a parasite, and it can be picked up from rabbits just eating their hay. Plus from what I've read, most rabbits seem to already have been exposed to it. I suppose that if your rabbit was carrying the active parasite but wasn't sick, and you treated preventatively, then yes giving the fenbendazole would help. But if your rabbit doesn't have the parasite at the time you treat, then the treatment wouldn't really make any difference, because once the treatment is stopped your rabbit is still susceptible to getting it. If you are concerned that your rabbit might be exposed to the active parasite, then you could have a blood test done for it, but you would need to have two different blood tests done if the first test shows antibodies.
