Here's why:
* Positive Test: A positive heartworm test means the dog has a heartworm infection. This doesn't change, even with preventative medication.
* Preventative Medication: Year-round heartworm preventative medication kills newly acquired heartworm larvae, preventing the infection from worsening.
* Focus on Treatment: The primary focus for a heartworm-positive dog is following the veterinarian's prescribed treatment plan. This usually involves a series of injections to kill adult worms.
However:
* Testing is Crucial: While annual testing is not necessary for a positive, medicated dog, it is *crucial* for dogs on preventative medication to be tested annually for heartworms. This ensures the medication is working and that no new infections have occurred.
* Possible False Negative: In some cases, a dog that is on preventative medication may have a false-negative heartworm test. This can happen if the test is performed too early after starting medication or if the dog has a low level of infection.
* Veterinarian's Guidance: Ultimately, it's best to follow your veterinarian's advice. They can assess your dog's individual situation and determine the best testing schedule.
Important Note: It's vital to keep your dog on heartworm preventative medication year-round, even if they're positive for heartworms, as directed by your veterinarian. This helps prevent the infection from worsening.