Yes, I've been filtering my dog's water. My local vet (also a hiker) recommends this. The theory is that if the dog has already drunk his fill of filtered H2O, he won't take in very much non-filtered stuff when he's lapping while wading or swimming.

The vet was especially insistent that I avoid unfiltered water from lakes and ponds with no outlet where elk (or, worse yet, cattle) congregate as they can be sources of leptospirosis. She said if I limit his exposure to such lakes, then the chances of his getting it are small. I mentioned the Indian Heaven Wilderness in Washington and she said that's a prime example, although she hasn't actually seen any cases of lepto from there. There are shots for lepto but they are not by any means foolproof.

Per the University of California at Davis, the vaccine for giardia is ineffective and they don't recommend it. This is one of the most prestigious vet schools in the country, so presumably they know what they are talking about. Pet vaccination protocols from UC Davis.

I really had to argue with my vet the last few years not to give my dog shots every year. Adult dogs need the standard (DHPP) shots only every three years and this has been standard protocol since the mid-1990's. However, many vets have been afraid to make the switch, some because they didn't agree with the protocols and some because the dog does need a physical exam every year (it's like a human getting one every 4-5 years) and they're afraid that with no shots the owner won't bring him in. Interestingly, in the last year my vet clinic finally switched over to a three-year shot schedule! A few kennels, doggie day care and training facilities still insist on yearly shots, but more and more of them are allowing the three-year schedule (except for bordatella, which is still every 6 months).

I have an email in to my-daughter-the-veterinarian in California to get her take on this. However, this is her busy season so it may be a while before I hear back. I'll post again when she replies.