Heartworm medications are not actually "preventative." What they do is kill the very youngest stage of heartworms. After your dog has been bitten by a carrier mosquito the heartworms stay in an immature state (microfilaria) in the bloodstream for six weeks. During this time the heartworm medication easily kills the microfilaria. So the time to dose your dog is AFTER exposure, not before.
Your dog can't get heartworm from drinking water with mosquito larvae in it, only adult mosquitoes carry heartworm. The mosquito needs to bite an infected animal, and then bite your dog.
I don't live in a high risk area either, so my dogs are not normally on heartworm. What we do is if we travel to a high risk area, is give our dog a single dose after we return. So that is one option. If you want to wait and test later, the time you have to wait after exposure before getting a test is six or seven months.
http://www.heartwormsociety.org/pet-owner-resources/canine-heartworm.html
Your dog can't get heartworm from drinking water with mosquito larvae in it, only adult mosquitoes carry heartworm. The mosquito needs to bite an infected animal, and then bite your dog.
I don't live in a high risk area either, so my dogs are not normally on heartworm. What we do is if we travel to a high risk area, is give our dog a single dose after we return. So that is one option. If you want to wait and test later, the time you have to wait after exposure before getting a test is six or seven months.
http://www.heartwormsociety.org/pet-owner-resources/canine-heartworm.html
