Life After Heartworm Treatment for Dogs

I have to rest after my heartworm treatment.
i Dog image by Lea Petrasova from

If your dog has been diagnosed with heartworms, the most difficult part comes after the vet gives your dog medication to kill these parasites. You are responsible for keeping your dog quiet for a prolonged period -- a difficult task if your dog is young and active.


Spread by mosquitoes, Dirofilaria immitis -- the name for this parasite -- can eventually kill infected dogs. The worms work their way through the animal's bloodstream, ending up at the heart approximately six months after that initial infecting mosquito bite. At maturity, heartworms can be up to a foot long, although most top out at about half that length. If your dog tests positive for heartworms, your vet will discuss the best way to treat him given your particular situation.


Heartworm treatment consists of killing both the mature heartworms and the babies, known as the microfilariae. Your dog will receive oral medication to kill off the immature worms. To kill adult worms, your vet injects Melarsomine into the deep muscles in the dog's lumbar region, either two or three times. The second and third injections follow the first by a month. Spacing the drug out helps prevent the dog from going into shock because of a huge worm die-off. Melarsomine is the only currently approved Food and Drug Administration pharmaceutical for killing grown heartworms. The injection site may swell or bother your dog for a few days.


In severely affected dogs, surgical extraction of large worms may be performed by your vet before the dog receives drugs to kill off the remaining heartworms. The vet must view echocardiograms of the dog's heart and pulmonary arteries to determine whether the worms are in area accessible to the surgeon, according to the American Heartworm Society. When the dog recovers from his surgery a few weeks later, he can begin receiving the injectable heartworm medications.


For a month after each injection, you must keep your dog as quiet and inactive as possible while the heartworms within him die off. That's two months of rest, no recreation. You might need to keep him in a crate or cage. As much as he hates it, remember it's for his own good. Keep walks to a minimum, just long enough for him to do his business. Discourage visitors if possible, as they may get him excited. If he becomes active and his heart rate increases, the dying worms inside his body may kill him as they break up.

Six Months Later

Six months after your dog receives injectable heartworm treatment, he should return to the vet for a heartworm antigen test to ensure the worms are gone. He is already on a monthly heartworm preventative, as that is what kills the baby heartworms. If he gets the all-clear, he returns to the vet every year for a heartworm test and continues on preventative for the rest of his life.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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