Features July 2011 Issue

Some Heartworm Preventative Medications Have Become Less Effective - Here's How to Protect Your Dog!

Even dogs who have received preventives year-round can become infected with heartworms. This photo of a drop of canine blood was taken through a microscope. The worm-like thing is a microfilaria or first stage of the offspring resulting from reproducing adult heartworms, a.k.a. Dirofilaria immitis.

Some Heartworm Preventative Medications Have Become Less Effective - Here's How to Protect Your Dog!

The protocols used to protect dogs from heartworm may have lost some effectiveness; here’s what you can do to protect your dog now.

As we reported in Whole Dog Journal in March 2011, there is now ample evidence that at least one strain of heartworms has developed resistance to some of the market’s best-known preventives. In addition, there is evidence to suggest that one of the most popular heartworm preventives, Heartgard, has an efficacy rate of less than 100 percent. The U.S. Food and Drug Administration’s Center for Veterinary Medicine has sent at least one warning letter to Merial, the maker of Heartgard, asking the company to stop claiming 100 percent effectiveness for heartworm prevention. Given these developments, what should responsible dog owners do differently to better protect their dogs? The answer depends a bit on where you live and what you’ve already been doing to prevent heartworm infection.

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