My Dog Has Heartworms - What Do I Do Now?

My Dog Has Heartworms - What Do I Do Now?

The canine heartworm is a mosquito-borne parasite that kills countless numbers of dogs each year. As adults, heartworms occupy the heart and surrounding blood vessels, placing a tremendous strain on the heart and lungs. In addition, their effects can wreak havoc on other organs as well, such as the liver and kidneys. In some cases, the worm burden can become so great that circulation of blood is actually compromised, resulting in sudden death. Other infested dogs can go years without showing any signs of the disease, seemingly forming a symbiotic relationship with the parasites; that is, until the heartworms decide to end the union.

Regardless of how it presents, heartworm disease is a direct threat to both lifespan and quality of life. As a result, treatment is a must. If your dog is diagnosed with heartworms, there are two options available to you. The first is called the "fast kill" or standard treatment. The second treatment option is the "slow kill" treatment. Here is a summary of both options:

Fast Kill (Standard) Treatment

The fast kill treatment for canine heartworm disease involved the use of melarsomine, a drug that kills heartworms when administered to your dog as a series of injections. In most instances, the adult heartworms will die off within four to six weeks after the last injection is given.

Prior to the fast kill treatment, bloodwork and radiographs (x-rays) should be performed on your dog to determine whether or not he/she is healthy enough to receive the treatment. If potential problems do exist, a "priming" dose of medication may be administered to allow your dog's body to adjust to the drug. Then in a month or so, if all looks well, the standard treatment may be attempted.

Because of melarsomine's effectiveness, complications can arise that could prompt cancellation of the treatment series. Remember: Once they die, heartworms aren't simply passed from the body as they would be if they were intestinal worms. Dead heartworms must be processed and dissolved by your dog's immune system just like any other type of internal "infection". Fast kill complications can include loss of appetite, vomiting, and/or the development of icterus, indicating liver inflammation. As the adult worms die, pieces lodge within the blood vessels of the lungs. If the number of dead worms is extensive, clots can form in the lungs, leading to severe coughing fits and, in some instances, lung hemorrhage.

If the treatment is completed without immediate complications, the patient is discharged from the hospital to begin a four to six week convalescence at home during which physical activity must be restricted. Heartworm preventative will be given either during or after this time to kill any microfilaria (immature heartworms) that may still be circulating in the bloodstream. Again, exercise and activity MUST be restricted during this convalescent period, since the heartworms are continuing to die and clots could form if a dog gets its pulse or blood pressure up too high.

Advantages of Fast Kill:

1. Provides a fast kill that reduces ongoing organ damage caused by the presence of heartworms.
2. Kills up to 100% of heartworms, regardless of the ages of the worms involved.
3. Dogs can generally resume normal activities within forty-five days of treatment without fear of sudden clots forming in the lungs.

Disadvantages of Fast Kill:

1. Expensive ($500 to $1500).
2. Multiple clots in the lungs could result from the massive worm die-out following the melarsomine injections, sometimes with fatal consequences.
3. Treated dogs must be kept in strict confinement to limit activity for at least four weeks.
4. Some dogs may have a reaction to the melarsomine itself, including injection site pain and, in severe instances, organ damage.

Slow Kill Treatment

Ivermectin-based heartworm preventive medications, when given to a heartworm positive dog on a monthly basis, will eventually kill most heartworms, although it can take up to thirty months for this "slow kill" approach to work. Although the slow kill treatment is frowned upon by many veterinarians, others feel it provides a viable option for those cases where owner finances are a concern or where the fast kill treatment is deemed too risky for the pet. This latter group includes dogs with heavy worm burdens, dogs that weigh in less than twenty pounds, and dogs exhibiting clinical signs at the time of diagnosis.

Advantages of Slow Kill:

1. Inexpensive.
2. Prevents new worm infestations while weakening and killing existing worm populations.
3. Weakens existing worms in the heart and lung vessels, improving the efficacy of the fast kill treatment if that mode of treatment is desired later on.
4. Avoids the safety concerns associated with the fast kill treatment.
5. Can exhibit up to 100% killing efficacy against immature and young heartworms.

Disadvantages of Slow Kill:

1. Blood clot in the lungs could occur suddenly at any time during the prolonged treatment period, especially during exercise or rigorous activity.
2. As long as living worms are present inside the heart and vessels, ongoing damage to the heart, lungs, and other organs can occur.
3. May not work well against older heartworms, especially older female heartworms.

Regardless of which treatment approach you choose for your dog, either one is better than doing nothing at all. And once your best friend is finally free of these threatening parasites, be sure to keep him/her on heartworm preventive medication each and every month. Its cheap protection and your pet is worth it!