Dogs are a natural host for heartworms, which means that heartworms that live inside the dog mature into adults, mate and produce offspring. Foot-long heartworms live in the heart, lungs and associated blood vessels of affected pets, causing severe lung disease, heart failure and damage to other organs in the body. They can affect the dog’s health and quality of life long after the parasites are gone if left untreated.

Heartworm Treatment

Lab Rescue takes in a lot of dogs that are Heartworm (HW) positive.  This condition is easily prevented if you give your lab a once a month yummy heartworm preventative like Interceptor or Heartguard.  Giving your lab their monthly heartworm prevention is one of the contractual obligations of adopting from Lab Rescue.

If you adopt a lab that is already heartworm positive, that dog will need to receive a vet administered treatment. Heartworms can be successfully treated with no ill effect to your lab's long term prognosis or quality of life.  You should not be afraid to adopt a heartworm positive dog but you will need to understand the treatment protocol and follow the directions of your veterinarian to the letter.

Heartworm Treatment Overview


Heartworm positive dogs will be placed on an Ivermectin based heartworm prevention (Heartguard / Triheart) for 3 months prior to treatment to kill the juvenile heartworms. Dogs will get the first preventative at the time of diagnosis and will normally be given at the vet’s office and two additional preventatives to be given over the next two months.

Heartworm positive dogs will be given Doxycycline for 30 days. Recent studies have shown that treatment of heartworm positive dogs with an antibiotic (specifically, doxycycline) can decrease the inflammatory reactions from dying worms during treatment. Studies have also shown that doxycycline treatment prevents adult heartworms from reproducing, decreases their body size, and decreases the ability of early larval stages to develop into later larval stages. This again, decreases the total amount of worm volume within an infected dog. Less worm volume can decrease the amount of inflammation in the body when these worms are killed by medical treatment.


The treatment of the adult heartworm is required in all cases.  Adult heartworm treatment should be initiated 3 months after diagnosis (and thus the dog will have been on heartworm prevention for 3 months). Treatment of Heartworm is accomplished by giving injections of Immiticide which is currently the only approved medicine to kill the Heartworms.

Non-symptomatic dogs (most dogs that are diagnosed with Heartworms). Dogs will go to one of our vets for treatment. They will be given 2 shots of Immiticide 24 hours apart and go home on the 3rd day.

Symptomatic and older dogs will receive a split treatment and will go  to one of our vets for treatment They will be given 1 shot of Immiticide and observed for 24 hours. This is followed by a 30 day rest period. Then they will be returned to the vet and  will be given 2 shots of Immiticide 24 hours apart and go home on the 3rd day.

The protocol for treatment of Heartworms will be decided by the Veterinarian doing the treatment and may vary somewhat from the above.


NOTE: Once the adult heartworm treatment has been started it is VERY IMPORTANT that these dogs be STRICTLY confined.  This means: NO RUNNING, JUMPING, PLAYING. CRATE CONFINEMENT IS IDEAL NO WALKS LONGER THAN 5 MINUTES (ideally they do their business and then go back in the crate).  These strict restrictions are necessary for 1 month following the final adult heartworm treatment.

Following these restrictions, gradual return to normal exercise is recommended (over several weeks).

The injections of the adult heartworm treatment can be painful, so if necessary some dogs are placed on pain medications for a few days after the injection(s).

Other side effects of worm die-off include pneumonitis (lung tissue inflammation) and thrombi ernbollsm (throwing clots to the lungs or other tissues).

Clinical signs to look out for are: lethargy, decreased appetite, cough, exercise intolerance.

NOTE: If ANY of these signs are noted the dog needs to be seen by a veterinarian for evaluation.

We can minimize these effects with strict confinement following the adult heartworm treatment.

Additional information may be found at the American Heartworm Society website: http://www.heartwormsociety.org . They have a series of articles for owners under the "Pet Owner Resources" tab including a series of “Frequently Asked Questions” at http://www.heartwormsociety.org/pet-owner-resources/faqs.html .