Coastal Carolina has mosquitoes most of the year. The gap between preventing this and treating it is enormous.
29 August 2026
People who move here from further north often keep a habit of stopping heartworm prevention in the autumn. On this coast that is a real risk. Our mosquito season barely closes, and it only takes one bite.
Prevention is a monthly chew or a topical dose. It is cheap, it is boring, and it works.
Treatment is a series of injections, and months of enforced rest — no walks, no stairs, no excitement — because as the worms die they can break loose and block a blood vessel. It is expensive, it is hard on the animal, and it is hard on the family. Some dogs do not survive it.
"He never misses a dose, so he does not need the test." Vets still test yearly, and there is a reason: a dose spat out behind the sofa looks exactly like a dose taken. The test is cheap and it is the only thing that actually knows.
"It is an indoor cat." Cats get heartworm too. There is no approved treatment for cats — only prevention. In a cat, the first sign is sometimes the last one.
Do not simply restart. Ring your vet and say exactly how long the gap was. Starting prevention in a dog that is already infected can cause a serious reaction, which is why the test comes first. Nobody is going to tell you off — they would far rather have the conversation than the diagnosis.