Heartworm Disease Treatment

About Heartworm Disease

It takes about six months for the heartworm to reach adulthood after infecting the pet. The blood tests that we do to diagnose heartworm disease detect these adult heartworms living in the heart and blood vessels. Therefore, the test will not be positive when the dog is initially infected with heartworm - it takes at least 6 months for the worms to mature and to be detectable with heartworm testing. A positive test means the pet acquired the worms at least 6 months earlier. The longer the adult worms are present in the pet’s body the more damage occurs. Adult worms grow to be 8-12 inches long.

The heartworm lives primarily in the right side of the heart, and in the nearby large blood vessels. The female worms produce large numbers of immature heartworms which circulate in the blood. These microfilaria (baby heartworms) are ingested by a mosquito biting an infected dog. After living in the mosquito for 1-2 weeks, the microfilaria are injected into another dog or cat when the mosquito feeds.

Cats typically have fewer and smaller worms than dogs and the life span of worms is shorter, approximately 2-3 years, compared to 5-7 years in dogs. In experimental infections of heartworm larvae in cats, the percentage of worms developing into the adult stage is low (0% to 25%) compared to dogs (40% to 90%).

Signs and Diagnosis of Heartworm Disease

The most important thing for dog and cat owners to remember is that a great deal of damage can occur before any obvious signs are noticed. Delayed treatment may result in heart failure and/or permanent damage to the liver, lungs, and kidneys -- with eventual death.

The signs of heartworm disease in dogs that you are most likely to notice include: coughing, sluggishness, rapid tiring, and difficulty breathing. Diagnosis is made by finding the microfilaria in a blood sample, or by detecting antigens, the proteins produced by invading organisms, that are present on the body of the worm.

Clinical Signs Associated with Canine Heartworm Disease

Signs of heartworm disease in cats can be very non-specific, and may mimic many other feline diseases. Diagnosis by clinical signs alone is nearly impossible, but a cat may exhibit generic signs of illness, such as vomiting, lethargy, coughing, asthma-like signs (intermittent difficulty in breathing, panting, open-mouthed breathing), difficulty breathing. Signs associated with feline heartworm disease are often misdiagnosed as asthma, when in fact they are due to a syndrome newly defined as Heartworm Associated Respiratory Disease (HARD). Occasionally, misdiagnosed cats die suddenly without allowing sufficient time to make a diagnosis or offer appropriate treatment.

Clinical Signs Associated with Feline Heartworm Disease

Canine Heartworm Treatment

There is a high degree of success in treating canine heartworm disease when the diagnosis is made early in the disease process, before severe heart damage has taken place. Your veterinarian will stage the disease with a physical examination, x-rays, and blood tests to determine how much damage has been done to the vital organs and what precautions may be needed as to the treatment of the problem.

Treatment for heartworms in dogs consists of killing the adult worms with injectable medication. Your pet may be required to stay at the hospital for 2-4 days. One injection is given on the first day of treatment, and then 30 days later the pet will return for two more injections. One injection will be given on the first day, and then 24 hours later, the second will be given. The pet is observed closely for any signs of problems. Reactions to the drugs used to kill the heartworms are possible. There is ALWAYS some risk involved in treating a dog for heartworms.

After treatment, the adult worms die and are carried by the blood stream to the lungs where they lodge in small blood vessels. There they decompose and are absorbed by the body over approximately 4-6 weeks. The decomposing worms are irritating to the tissues of the blood vessels and lungs, causing a great deal of inflammation.

Following treatment, COMPLETE REST for 6-8 weeks is needed to prevent lung damage from the dead, decomposing worms. Then regular heartworm preventatives will be used to prevent re-infection. Treatment does not provide protection against repeated heartworm infection.

Feline Heartworm Treatment

Currently, there are no products in the United States approved for the treatment of feline heartworm disease. Most cats with heartworm disease that are not demonstrating clinical signs have time for a spontaneous cure to occur. Cats that have been diagnosed with heartworm disease may benefit from intravenous fluids, oxygen therapy, cage confinement, cardiovascular drugs, and/or antibiotics. All we can do for cats is support them and prevent further infection while waiting 2-3 years for the worms to age and die on their own. Heartworm disease is often fatal in cats because of the lack of safe treatments for them. Visit www.knowheartworms.org for more information.

Heartworm Prevention

Prevention is the best cure - it’s safer, less expensive, and better for your pet! There are a variety of options for preventing heartworm infection, including monthly chewable tablets. Preventative medications are extremely effective and when given properly, on a regular basis, can completely prevent your pet from contracting heartworm. As a pet owner, it is your responsibility to faithfully maintain the prevention program you have selected to use with your veterinarian. Dr. Skees recommends using Sentinel Flavor Tabs, Iverhart Plus, Advantage Multi, or Revolution for the prevention of canine heartworm disease, and suggests that felines use Revolution or Advantage Multi as a heartworm disease preventative.

All of the products mentioned above are available at Family Pet Hospital. For more information on our heartworm prevention products, please visit our "Product Line" page.

For more information about heartworm disease, visit the American Heartworm Society at www.heartwormsociety.org.