I probably should have posted this a long time ago. Apologies.
My boy has tested mild positive for lyme once, mild positive for ehrliciosis once, and high positive for lyme once (requiring treatment).
All this while he was on Vectra-3D, faithfully and carefully applied. I've applied spot-ons to hundreds of dogs here at the kennel, so it's not like I don't know what I'm doing. Have never forgotten one of his doses. I don't get him wet for 48 hours before or after a dose.
So I called the folks at Vectra-3D and told them I was not a very happy customer. Immediately they questioned me about his swimming and bathing habits. I told them that he swims and/or gets a bath about 2-3 times per week.
They said that the eficacy of ALL of the spot-ons declines to less than 80 percent by 3 weeks with that level of water exposure. I pointed out that their literature says that it's still effective after swimming or bathing, and was told that the assumption is that the dog baths/swims a couple of times a month, not a couple of times per week. I was told to talk to my vet about "alternative treatment schedules" because they are not allowed to recommend anything that would be considered "off-label" but that "vets are aware that a different treatment schedule is necessary for dogs with high water exposure".
So I talked to my vet. Yep. If your dog has that much water exposure, you need to appy the spot-on treatments every 3 weeks, not once per month. At the end of 3 weeks, only 4 out of 5 ticks are being killed, to put it in different terms.
I called and confirmed this with both Frontline Plus and Advantage. It's true for all of them.
SO....you may think your dog is protected.....but he may not be.
We have gone to an every 3 week dose during tick season here, and in his most recent blood panel he tested negative for all the TBS (we send out a full panel, not an in-office read panel) for the first time in a long time.
BTW, the folks from Vectra gave me 9 free doses because he contracted the TBDs while on Vectra.