Heartworm Disease in Dogs: Causes, Symptoms and Prevention

Heartworm disease in dogs is caused by a bite from a mosquito infected with the larva of the Dirofilaria immitis worm. The larva migrates to the heart of the dog and grows into adult heartworms. These adult heartworms then produce more larva which lives in the blood vessels of the dog.

Heartworm Disease in Dogs - Symptoms of Heartworm Disease

Heartworm disease causes damage to the heart and blood vessels and triggers several symptoms in most dogs. Symptoms include coughing, coughing up blood, heavy breathing, lethargy and pulsation of the jugular veins.

Heartworm Disease in Dogs - Testing for Heartworm Disease

Veterinarians test for heartworm disease in dogs using two types of blood tests. The most commonly used is the microfilaria screen which detects heartworm larva. The second test used is the heartworm serology test which identifies proteins created by heartworms in the dog's blood vessels.

Heartworm Disease in Dogs - Heartworm Disease Prevention

Heartworm disease is easily prevented. There are many heartworm disease preventative medications which are available by prescription from your veterinarian. These medications work by destroying heartworm larva and preventing it from growing into adult heartworms.

However, the dog must be tested for heartworm disease first. If testing shows that the dog is not infected with heartworm disease, a heartworm preventative should be given to the dog once a month.

The three most popular heartworm preventative medications are Interceptor, Sentinel and Heartguard Plus.

The active ingredient in Interceptor, manufactured by Novartis, is milbemycin oxime. This ingredient not only kills heartworm larva, but also destroys roundworms, hookworms, and whipworms.

The active ingredient in Sentinel, also made by Novartis, is also milbemycin oxime. In addition Sentinel also includes the ingredient lufenuron which kills flea eggs.

The active ingredients in Heartgard Plus are ivermectin and pyrantel. These ingredients destroy heartworm larva, roundworms and hookworms.

Heartworm Disease in Dogs - Heartworm Disease Treatment

If testing shows that the dog is infected with heartworm disease, extensive treatment must begin as soon as possible.

Since an increase in blood circulation may cause congestive heart failure in a dog infected with heartworm disease, the dog's activity must be strictly limited. A heartworm preventative, usually Interceptor, must be given immediately, as well as daily doses of doxycycline, an antibiotic used for bacterial infections and prednisone, an anti-inflammatory steroid.

Two months later the dog must return to the veterinarian. The veterinarian will administer an injection of Immiticide, a drug which contains arsenic, into the muscle. A sedative, usually xylazine, is given first. Afterward, injections of buprenorphine, a synthetic narcotic, are given for pain as needed. The dog must spend at least two days in the veterinarian hospital following this treatment. When the dog returns home, he will continue taking prednisone daily and his activity will still be severely restricted.

One month later the dog must return for another injection of Immiticide along with xylazine and buprenorphine as needed. The dog must remain in the veterinarian hospital at least three days. After returning home, again the dog must continue with prednisone and strictly limited activity for at least four to five weeks. Monthly follow up visits to the veterinarian are recommended.

Heartworm Disease in Dogs - Conclusion

As stated above, heartworm disease is easily prevented by monthly heartworm disease preventative medication. Heartworm preventatives are much easier on your dog and your pocketbook than the intensive heartworm disease treatment described above.