Heartworm in 2010

Pet Tales
by Barry B. Burtis D.V.M.


Although most readers will have heard about heartworms before, I suspect many will not have heard of the American Heartworm Society (AHS). Yet, there is a very definite connection between the two.


For us in this part of the world, actually the AHS came first, before heartworm disease. They were formed in 1974. It was a few years later that the disease, itself, reached this part of Ontario and began to be a problem for dogs. The disease had slowly moved up the Mississippi valley and the eastern seaboard of the United States to reach Canada. It is now established as a threat for canines throughout our province, as well as in other parts of Canada.


This group of veterinarians and animal health experts came together with the stated mission of becoming " the global resource for the prevention, diagnosis and treatment of heartworm disease". They aim to achieve this goal by furthering scientific studies of heartworm disease, informing their members and the public, in general, of new developments regarding the disease problem and promoting effective diagnosis, treatment and prevention of heartworm disease.


In the almost forty years since the AHS was established there certainly have been many changes related to heartworm disease. I have already alluded to the very significantly increased geographical area where the disease now occurs. Heartworm disease occurs worldwide - Australia, South-east Asia, South America and southern Europe.


There also have been changes in how the disease is treated and how it can be prevented. The AHS has played a part in the research that has brought about these changes and has incorporated up-dated data into their recommendations to veterinarians on how to best deal with the disease.


There are new and less dangerous treatment protocols for dogs who are diagnosed with heartworms. However, it still is most definitely a disease that owners want to protect their dogs against and not have the worry and high cost associated with treatment. Prevention of infection is the goal.  There have been some significant changes in how to do this since dogs in our region of Ontario first had to be protected. In those days, it was daily medication given from June to November after a blood test to make sure the dog was not already infected with adult worms in the heart. If such an infection had been, present a possible life threatening reaction to the daily administered preventive medicine could occur.


While some things change, some things remain the same. The heartworm preventives we use today are given once a month. Whether using medicines given by mouth or those applied to the skin, no such reaction would occur, if adult worms were present. However, after for a few years of suggesting that it was likely safe to reduce the frequency of testing for adult parasites in the heart, this year the AHS is again recommending annual testing. Such a test is the only way to be sure a dog does not have adult worms in their body. Preventive medicine, given as directed, is very effective in safeguarding against infection, however, few things in this world are perfect. If for some reason a break in getting medication occurs, or for some reason fails to be absorbed and metabolized in the body properly, the dog is susceptible to infection. Also, if a dog is given certain preventive medicines after adult worms are present, it renders some tests ineffective in detecting the presence of the adult worm infection. If treatment for an adult worm infection is required, it is very important to do so early in the course of the disease.


Heartworm disease can be terrible for dogs and a confusing disease for owners to understand. However, it should be reassuring for pet owners to know that veterinarians, with the help of the American Heartworm Society, are working hard to reverse those facts. Barry Burtis is a local companion animal veterinarian. Past Pet Tales can be found at www.baycitiesanimalhospital.ca