Owners and veterinarians recognize the need for regular administration of broad-spectrum heartworm medications alone or combined with other drugs to control internal and external parasites in dogs. What is not recognized is that the same is true for cats. This can be accomplished by routine administration of approved broad-spectrum heartworm medications alone or in combination with other drugs. Heartgard for Cats (Merial; oral ivermectin), Interceptor (Novartis; oral milbemycin oxime), and Revolution (Pfizer; topical selamectin) are approved for use in cats in the United States and are effective for control of feline heartworm disease. Because cats are nocturnal predators, no owner can say for sure whether their cat has ingested mouse feces. Therefore, control of Toxocara cati, an important zoonotic disease, needs to be part of routine parasite control. Milbemycin and selamectin have been shown to be effective in eliminating T. cati infections. Hookworms are another common parasite of cats that can be controlled with ivermectin, selamectin, or milbemycin. However, none of the approved cat heartworm preventatives treat or prevent ticks. Repeated monthly administration of selamectin can be used to prevent and treat flea infestations. Ivermectin and milbemycin can be administered concurrently with an approved flea control product (eg, fipronil) for treating lice. Selamectin is effective against Cheyletiella and Notoedres as well as ear mites; repeated applications may be needed and are recommended. Topical otic preparations of ivermectin and milbemycin oxime are effective for treatment of ear mites.

COMMENTARY: This article contains 2 major take-home points. The first is that proactive parasite control in cats is rapidly becoming the standard of care. The second is that such parasite control needs to be year-round in both dogs and cats even in regions of the country with a true winter. It is hard to predict when 1 period of transmission begins and the other ends. A further complication is changing climatic conditions from 1 year to another, which can greatly affect parasite populations. Indeed, the number of "mystery" skin disorders affecting cats that present in the dead of winter in Wisconsin that respond to flea control never ceases to amaze me!

Preventing parasites in cats. Dryden MW, Payne PA. VET THER 6:260-267, 2005.