Frontline
I used to get Frontline from Doctor Bob, here in Sosua, the type mentioned above where you put a few drop on the dogs back, right at the joint where the shoulders meet.
It worked like a miracle on my dog Rocky, who was a veritable tick hotel.
Now, for some reason, we can't get it around here anymore.
I asked a Canadian friend to bring some down to me, and he said that the vet up there refused to sell it to him without seeing the dog first.
Go figure...
Anyhow, it's supposed to work for one month, but I always found it good for three.
If anybody locates any, I would like to know where.
They came in packs of three, calibrated to the weight of the dog, and the liquid came in a type of small vial, which you broke the neck off of, then applied it to the dog.