Heartworms in cats

Overview

Heartworms are transmitted through the bite of an infected mosquito, and can migrate to the heart, lungs and the blood vessels near these vital organs within two to three months. The larvae complete their migration in six months, ending in the actual heart chamber And yes, all it takes is the bite of just one infected mosquito.

Although cats are more resistant to heartworms than are dogs, cats can also contract this disease. Heartworms can infect cats of all ages, living anywhere throughout the United States, but the disease is more prevalent in warmer areas where there are greater numbers of mosquitoes. Left untreated, heartworm can lead to heart and lung failure, kidney and liver damage, and eventually death. And yet, some cats appear to be able to rid themselves of the infection spontaneously.

Heartworms affect cats differently than dogs, but the disease they cause is equally serious. Heartworm larvae do not need to develop into adult worms to cause significant lung damage in cats. The syndrome caused by heartworms in cats is now known as Heartworm Associated Respiratory Disease (HARD). It is possible that many cats previously diagnosed with asthma, bronchitis, or other lung diseases may actually be infected with heartworms.

Cats do not have to go outside to be infected with heartworms. Mosquitoes enter the home every time someone opens and closes a door. Additionally, if there is a heartworm infected dog in the area, your cat’s likelihood of getting heartworm disease is increased. Obviously, cats that go outside frequently, even if they are supervised, are at a greater risk of contracting heartworm disease than a strictly indoor cat, but all cats are considered to be at risk if they are not on heartworm prevention.

Symptoms

• Coughing
• Lethargy
• Weight loss
• Difficulty breathing
• Fainting
• Rapid heart rate
• Vomiting
• Increased respiratory rate (the number of breaths taken per minute)
• Sudden death

Prevention

The smart route to travel is one of prevention because there is no cure for heartworm disease in cats. Preventive doses come in oral and topical versions and are only available from a veterinarian. If your cat already has heartworms, giving them oral or topical prevention will not harm them. In fact, it will prevent them from getting any additional worms. A blood test, therefore, is not required before starting your cat on heartworm prevention. Heartworm prevention must be given once a month to ensure continued protection. If you live in an area that has a lot of mosquitoes, your cat may require heartworm prevention year round. Talk to your veterinarian about how best to protect your cat from heartworm disease.

Treatment

There is no safe treatment available to kill adult heartworms in cats. Any symptoms that arise from your cat’s heartworm disease may be treated with inhaled corticosteroids, injectable anti-inflammatory drugs, anti-vomiting medications, or other drugs as deemed necessary by your veterinarian. 

References:

American Heartworm Society. Feline Heartworm Guidelines. 6 March 2008.

Dillon, Ray, DVM. Feline Heartworm Disease. 6 March 2008.

Pfizer Animal Health, Revolution (selamectin). 6 March 2008.