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Heartworm Disease in Cats

Heartworm Disease continued...

Cats who pass through this phase of infection may be relatively fine until the adult heartworms start to die in two to three years. Labored breathing and mild, low-grade, chronic respiratory signs may go on for a while. Congestive heart failure, along with heart murmurs, loss of condition and appetite, and intermittent vomiting may all appear late in the disease. Worms may be discovered at autopsy following sudden, unexplained death.

Diagnosis is generally done by blood tests looking for the heartworm antigens or antibodies produced to fight them. Both types of tests are valuable before starting treatment for a suspected infection. X-rays of the chest and the use of echocardiography can be especially helpful in diagnosing heartworms in cats.

Treatment: Treatment is complex and potentially dangerous. If the cat seems reasonably healthy, monitoring his condition and following the lifespan of the heartworms may be the best option. Medical support may be needed for any respiratory or cardiac signs. Corticosteroids may be useful in reducing reactions to the worms. Ivermectin has been used to treat heartworm infections in cats, but the drug is still considered experimental as a treatment. Surgery can also be done to physically remove any heartworms, but it is not common.

Prevention: Heartworms are spread by mosquitoes, and areas along coastal regions with swamps or other brackish water provide ideal conditions for mosquitoes to breed. Areas with warm temperatures most of the year have a longer mosquito season, and any nearby areas of standing water can provide a mosquito habitat. In theory, the best way to prevent heartworms is to keep your cat from being bitten by a mosquito.

Even indoor-only cats can become infected, however, because mosquitoes often get through screens or open doors and windows, or come in on other pets. Preventive drugs for cats include ivermectin, selamectin, and milbemycin oxime, all of which guard against some internal parasites as well. A heartworm test (preferably both antigen and antibody) is recommended but is not absolutely necessary before starting your cat on a preventive regimen. Many practitioners now advocate year-round prevention, although theoretically cats need not be protected in the winter months in cold areas, because there are no mosquitoes alive outside.

WebMD Veterinary Reference from "Cat Owner's Home Veterinary Handbook"

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