First of all, the television advertisement and news story/stories that you may have seen are part of a large advertising campaign funded by Bayer, the company that makes Advantage Multi. Advantage Multi is a monthly heartworm, intestinal parasite, and flea prevention. Taken at face value, these ads seems to indicate that there is a new resistant strain of heartworms in Jacksonville, known as the MP3 strain, and that their product is the only heartworm preventative (hwp) which is 100% effective against this new and deadly strain.

As your pets' veterinarian, I wanted to make sure that all of my clients have the proper facts, because, as is often the case, truth in advertising appears to be in the eye of the beholder.

Reports of what seems to be increasing resistance of heartworms to many of the monthly preventatives have surfaced, however no resistance has been seen in our area at this time. Confirmed reports seem to be limited to the Mississippi Delta area, and they are being investigated by some of the brightest veterinarians in the world. At this time, there have yet to be any creditable reports of resistant strains of heartworms in Northeast Florida.

The MP3 strain is not the same as the resistant strains that are showing up in the Mississippi Delta. The MP3 strain was isolated from a dog years ago in Athens, Georgia. The reason the Bayer advertising references the MP3 strain is that it is used to test hwp in laboratories, and it does display some resistance to monthly hwp products.

Bayer is making claims that only Advantage Multi is 100% effective against the MP3 strain because of a recent study known as the Blagburn study. What Bayer is not telling you is that, while only Advantage Multi was 100% effective after only one dose, the study showed that ALL of the monthly hwp products they tested were 100% effective after 3 monthly doses. The test included Heartgard, Interceptor (the same hwp that is in Trifexis), and others.

Because we are in Florida and give our pets monthly hwp every single month all year round, all of the monthly heartworm preventatives studied should be expected to be 100% effective.

In conclusion, at this time there is no reason for you to be worried that your dogs may not be protected if they are not on Advantage Multi. I have my personal dogs on Trifexis now, with no reason to change at this time, and my cats are on Advantage Multi (since they won’t eat pills!). The situation with resistance in the Mississippi Delta is concerning for sure, and I will continue to monitor it. If at any time a change in current recommendation is required, I will make sure that we get that information out to you right away. Although Advantage Multi is a fine product and Bayer has done much for animal health over the years, I am disappointed in the choices Bayer has made with the current advertising campaign. I am hopeful that the other companies who make hwp will work hard to correct the misinformation that is out there.

For additional information, you may visit the American Heartworm Society’s website at www.heartwormsociety.org.

Sincerely,

Michal Harris, DVM