HEARTWORM PREVENTION IN CATS

VetSuite Veterinarians
Cardiology - General Practice & Preventative Medicine

Heartworm disease, caused by Dirofilaria immitis, is a serious parasitic disease endemic in most parts of the United States and in many parts of North America. The highest rates of infection are found in subtropical climates like those of the southeastern United States, the Gulf states and Hawaii. However, heartworms are also found throughout the central and eastern United States, particularly near oceans, lakes and rivers. When compared to dogs, cats are naturally resistant to heartworm disease; they are about one-fifth as likely to become seriously infected as dogs in the same region. However, heartworm disease in cats is often more severe than in dogs. The presence of even a single adult heartworm in a cat can result in very serious consequences. Heartworm infection in cats can be difficult to diagnose but prevention is simple as long as owners are compliant. Unfortunately, studies have shown that owner compliance is often poor.

AVAILABLE PRODUCTS

• Ivermectin (Heartgard for cats®) is the most commonly prescribed heartworm preventative for cats. It kills migrating larva during the first 6 to 8 weeks after L3 heartworm larvae inoculation. In addition to preventing heartworm infection, it also kills roundworms and hookworms. Heartgard is a pill that is administered monthly and should be administered one month prior to the mosquito season and continued until after the first frost. It is often recommended year round in warmer climates.

• Selamectin (Revolution®) is a topical medication that prevents heartworms and also kills fleas, hookworms, roundworms and ear mites. It belongs to the family of drugs known as avermectins, similar to ivermectin.

RECOMMENDATIONS

Owners of all cats living in areas endemic for heartworms should consider heartworm prophylaxis. If dogs in the area receive heartworm prevention, it is likely that cats also may benefit from this protection. The canine formulations cannot be safely used in cats. Cats should be on heartworm preventative whenever the average daily temperature exceeds 55 degrees Fahrenheit. Year round prevention is recommended in warmer climates. Some veterinarians recommend a heartworm antibody test in any cat over 7 months of age before beginning therapy. But since heartworm disease is difficult to diagnose in cats, testing is not mandatory.