Part 2 – Symptoms and Treatment of Heartworm

The Symptoms of Heartworm Infection

In the early stages, there will be no signs of disease and it won’t show up on a blood test.  Around six to eight months after the mosquito bite, blood tests will reveal the presence of antigens or microfilaria, according to the AHS. Other blood tests can measure antigens secreted by the female heartworm.

As the worms grow and multiply, the following symptoms will become evident, increasing in severity as the disease progresses. There are four classes of infection:

• Class one has no symptoms or just mild cough.
• Class two is marked by mild exercise intolerance and persistent cough.
• Class three will result in greater exercise intolerance, abnormal lung sounds, weak pulse, syncope (fainting caused by impaired blood flow to the brain), decreased appetite, weight loss, ascites (swollen belly due to heart failure).
• Class four is known as caval syndrome, a life-threatening cardiovascular collapse, which is marked by labored breathing, pale gums, and dark coffee-colored urine, leading to complete organ failure and death.

Diagnosis and Treatment of Heartworm Disease

If your dog is diagnosed with heartworm through a blood test, your veterinarian will use different tests as confirmation. These include:

• Radiographs to pinpoint abnormalities in the right side of the heart and pulmonary arteries.
• Ultrasounds to show abnormal organ shape as well as wriggling worms.
• Echocardiogram to see inside heart chambers and visualize worms.

Once the diagnosis is confirmed, your vet will advise you to:

• Restrict activity. Exertion will worsen heartworm damage. Crate confinement may be necessary.
• Kill adult worms. One drug is available for this purpose in the U.S. — Immiticide, manufactured and marketed by Merial. It is administered by deep intramuscular injection into the dog’s lumbar region of the lower back and is recommended for disease that has not progressed past class three. In addition, other drugs such as heartworm preventives, antibiotics, and steroids may be part of your veterinarian’s protocol.
• Surgery. In extreme cases, veterinarians will resort to surgery, physically pulling the worms out.
• Follow up with heartworm tests. The first should take place six months after successful treatment.

Preventing Heartworm

Treatment for heartworm is very hard on the dog, which is why veterinarians are so adamant about yearly testing and administration of preventative compounds — what scientists call chemoprophylaxis. These medications are also effective against other parasites, such as roundworms, hookworms, fleas, and tapeworms. Different formulations are available for dogs and cats, and it is important that you do not mix them up.

Following is a list of some preventatives. Discuss with your veterinarian about which one best fits your dog’s needs:

• Heartgard ®Plus for Dogs (chewable, ivermectin/pyrantel)
• Tri-Heart®Plus for Dogs (chewable, ivermectin/pyrantel)
• Iverhart Max® for Dogs (chewable, ivermectin/pyrantel permeate/prziquantel)
• Sentinel® for Dogs (chewable, milbemycin oxime/lufenuron/praziquantel)
• Revolution® for Dogs (topical, selamectin)
• Advantage Multi™for Dogs (topical, imidacloprid + moxidectin)
• Trifexis (Milbemycin and spinosad)
• ProHeart® 6 (injectable, given only by a veterinarian) — Lasts 6 months. Not effective against intestinal parasites.