Heartworm disease is a serious, often fatal infection that can cause severe lung disease, heart failure, organ damage, and other complications in dogs. Our Los Angeles veterinarians explain why preventing heartworm disease is better for your dog and for your wallet than treating it once it has developed.


Heartworm disease is caused by a parasitic worm called dirofilaria immitis which is primarily spread through the bite of an infected mosquito.

Your dog will become a 'definitive host' for this parasite once infected, which means the worms will mature into adults, mate, and produce offspring. Heartworm disease is a serious condition caused by worms that live in the heart, lungs, and blood vessels of infected pets.

Signs of Heartworm in Dogs

Unfortunately, heartworm disease has no early warning signs. Once the disease has progressed to more advanced stages, symptoms of this condition begin to appear in dogs. Fatigue, swollen abdomen, coughing, difficulty breathing, and weight loss are some of the symptoms that appear when they do.

Diagnosing Heartworm 

Heartworm proteins, known as antigens, are released into the bloodstream of infected animals, and blood tests can be performed at your veterinarian's office to detect them. These antigens, however, are not detectable until 6-7 months after your pet has been infected. Clinic signs of heartworm infection include fluid buildup in your dog's lungs, a swollen abdomen, coughing (in some cases coughing up blood), and poor overall condition, which your veterinarian will look for.

Treatment for Heartworm Disease in Dogs

The reason that heartworm prevention is so important is that the treatment for this disease can be toxic and cause serious health complications in your pet. Not only that, but treatment can be costly due to multiple visits to the veterinarian, bloodwork, x-rays, hospitalization, medications, and injections.

If your dog has heartworms, your veterinarian may recommend a 4-week course of doxycycline and three doses of melarsomine dihydrochloride (an arsenic-containing drug that kills adult heartworms).

Melarsomine dihydrochloride is given to the dog as an injection into the back muscles to kill the parasites. Your veterinarian may prescribe sedation medication to help your dog relax during the injection process.

In cases where immature parasites could be present your dog may also be treated with heartworm preventive medication for 2 months before beginning the melarsomine treatment.

Prednisone is also frequently prescribed for dogs during the melarsomine treatment to help prevent complications. Strict crate rest is essential throughout your dog's heartworm treatment.

Heartworm Prevention

The best way to avoid heartworm disease affecting your dog's health is to keep him on preventative medication. Even if your dog is on heartworm prevention, it is recommended that your dog be tested for this parasite once a year.

Heartworm prevention is much safer, easier, and less expensive than treating the disease once it has progressed. Other parasites such as hookworms, whipworms, and roundworms can be protected by a variety of heartworm preventive medications.

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.

Find out how to protect your dog against heartworm disease. Contact our Los Angeles vets today to book an appointment for your pet.