Heartworm Treatment & Prevention: Urgent Update!
There are currently new challenges facing the treatment of heartworm disease in dogs. The only FDA licensed treatment for dogs infected with adult heartworms (i.e. Immiticide) is now unavailable as a result of manufacturing problems experienced by its maker Merial. It is uncertain how many weeks, months or even years that this product will be unavailable. The Village Vets would like to take this opportunity to review the implications of the unavailability of this drug and how we can all best proceed to reach a common goal in maintaining the well being of our four-legged buddies.
Of course, prevention of infection with adult heartworms is more important than ever in the absence of the drug used for treatment of the disease. Preventing infections with monthly medication makes all dogs safer because heartworm infected dogs are the source of this disease that requires the mosquito bite for transmission from one dog to another. The currently available heartworm preventions all belong to the same drug class, and these drugs are nearly 100% effective at preventing the disease when used every month year around per product label instructions.
If heartworm prevention is not given once monthly, then the risk of heartworm infection increases and this includes missing only a single monthly dose. Likewise, if an inadequate dose of heartworm prevention is administered, the risk of heartworm infection increases. Tablet and chewable heartworm preventatives cannot be broken in pieces in order to treat multiple dogs at a lower cost. This is because the active ingredient is not evenly dispersed through the tablet/chewable so there is great risk of under-dosing.
It has also been determined that there is a strain of heartworms that are beginning to develop resistance to available preventions. This emphasizes both the importance of routine annual heartworm testing for all dogs over 6 months of age or whenever dogs have missed doses of monthly prevention. Symptoms of heartworms may not be obvious until the disease is quite advanced.
When heartworm prevention is used at inadequate doses and/or at less than once a month frequency, then we are increasing the risk that more strains of heartworms will become resistant to the preventatives we use. This is a horrifying thought especially considering the unavailability of Immiticide to treat adult heartworm infections if they occur. We can simply not afford to take such chances that endanger the health of all dogs.
In the unfortunate event that a dog becomes infected with adult heartworms, without Immiticide, we are left with the alternative of a slow kill method that utilizes a specific monthly heartworm preventative and specific type of antibiotic. It can require one to two years to clear the infection using this method. During this time, the infected dog experiences continued damage to the heart and lungs as the ongoing disease persists. Restricting the activity of dogs treated with this method until the disease is cleared is necessary to avoid the risk of serious complications. Obviously, meticulous attention to disease prevention is much preferred to having to deal with the disease: in this case, an ounce of prevention is invaluable because the cure just isn’t available to us.
It is our hope that this information will help to stress the importance of the proper use of monthly heartworm prevention as well as the need to practice routine testing for heartworms. Please feel free to contact The Village Vets with any questions you may have. Another excellent source of information is the American Heartworm Society at http://www.heartwormsociety.org/veterinary-resources/canine-guidelines.html. As always, please know The Village Vets aims to be your partner in ensuring the health and well being of the animals we all love so much.
Kari Addante, D.V.M.
The Village Vets Decatur