Yikes.
Thanks for writing. My dog is my best friend and I would feel awful forever if I neglected her health and it led to an experience like your own. I'm sorry for your losses.
By no means are you throwing your money away on heartworm tests or preventive medicartion. In the early 90's I had three seperate animals diagonised with heartworms with three different outcomes. The first little dog "Benny" became paralyzied, which after numerous x-rays showed no spinal defect. it was because he was so badly infected with heartworm that they blocked his vessels leading to his heart causing a blood clot or embolism to lodge in his blood vessels leading to his spine. After trying everything he had to be euthanized. So we then had all our other dogs tested and two more were positive. "Tippy the beagle was treated with a asernic compound"yes that's what they use, and was on strict confinement for over a month. He was left with chronic lung problems, because when the worms are killed they can logde in the lungs and cause damage. He remained on asthma like medicine for years and one day we found him dead by his water bowl. The third dog "barney" was to old the vet said for treatment, he passed away 2 years later at the age of 19 and a half. The last little dog "herbie" was the only one who did not have heartworms. The reason for the yearly blood test is that maybe you forget to give the pill one month or your dog vomited it up without you knowing, and it is dangerous to give the pills if possilby they are infected. i know what you are saying people really didn't take there animals to the vet years ago, we didn't, but now with what I went through I will never miss a month of pills or the cost of the yearly blood tests, because it can lead to heartbreak for you and your precious pet. thanks for listening