HEARTWORM DISEASE TREATMENT
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.
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, which are 8-12 inches long, are present in the pet’s body the more damage occurs.
The 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. In cats, just 1 worm can be fatal due to the small size of the cat’s heart and the large size of the worm. In cats the blood tests are not as accurate - heartworm disease in cats can be a hidden disease, difficult to diagnose but slowly damaging the heart and lungs.
The signs of heartworm disease which you are most likely to notice include coughing, sluggishness, rapid tiring, and labored 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. It will be six or seven months after exposure before microfilaria or antigen can be detected in the blood. Cats show heartworm symptoms differently from dogs. In cats, chronic vomiting or sudden death are symptoms that may be seen instead of or in addition to the signs seen in dogs.
Treatment for heartworms in dogs consists of killing the adult worms with injectable medication. This medication is not safe for cats, however. 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.
Dogs may be required to stay at the hospital for 2-4 days. Injections are given on the first and second day and then the pet is observed closely for problems. After treatment, the adult worms die and are carried by the blood to the lungs where they lodge in small blood vessels. There they decompose and are absorbed by the body over a period of several months. 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.
Reactions to the drugs used to kill the heartworms are also possible. There IS ALWAYS some risk involved in treating a dog for heartworms.
The microfilaria stage, or larval heartworms circulating in the bloodstream, will be killed with an injection or oral medication approximately 4-6 weeks after treatment of the adult heartworms. Then regular heartworm preventatives will be used to prevent re-infection. Treatment does not provide protection against repeated heartworm infection.
There is a high degree of success in treating heartworm disease when the diagnosis is made early in the disease process, before severe heart damage has taken place. Physical examination and laboratory testing will determine whether or not your pet should undergo treatment once heartworms are diagnosed. Your veterinarian will stage the disease with 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.
