April 13, 2016
Categories: Shelter Medicine, Caring for Special Populations of Animals, Learning Tracks

It’s Heartworm Awareness Month. Do you know as much as you think you do about heartworm disease in dogs and cats?

Feline Heartworm Infection: The big surprise!

Yes, we said cats. While only 5 percent of cats are on heartworm preventive, the American Heartworm Society reports rates of diagnosed heartworm infections in cats are on the rise. And while there are preventives for cats, there are no approved treatments, leaving an expensive and sometimes-fatal surgical procedure as the only available cure.

What’s more, since lifestyle factors that lead to feline heartworm exposure also put cats at risk of FelV and FIV, shelter cats may be dealing with multiple conditions that complicate each other. Testing these cats for heartworm as well as retroviruses can help shelters provide the appropriate treatment in-shelter, and better support and advice to adopters.

For example, in a presentation on feline disease at the 2016 NAVC Veterinary Conference, Dr. Julie Levy pointed out that cats with access to the outdoors have a three times higher chance of having heartworm than cats who don’t. Additionally, she said, even when cats are tested for heartworm, preventive is dispensed only 12.6 percent of the time. Her recommendations:

  • Heartworm infection should be considered in cats with respiratory, oral, and abscess conditions as well as in cats with retroviral infections.
  • Given the difficulty in diagnosing heartworm infection at all clinically relevant parasite stages and lack of curative treatment options, veterinarians should prioritize increased compliance with national guidelines to provide heartworm preventive medication to all cats.

Canine Heartworm Infection: Slow isn’t the way to go, even in shelters

There is an approved heartworm treatment in dogs, but it’s both costly and time-consuming. Still, many animal shelters find themselves with heartworm-positive dogs in need of that treatment. Is there a safer, cheaper way? No, says Association of Shelter Veterinarians President Dr. Brian DiGangi:

“Slow kill,” meaning the administration of ivermectin products alone to kill adult heartworms, is not recommended. It will take many months to a few years before adult heartworms are killed; all the while they continue to damage the heart and lungs of the infected dog. Although still not ideal, alternative protocols, such as those that use combinations of doxycycline and ivermectin-based products are a safer option when adulticidal therapy with melarsomine is not possible.

This question arises because many animal shelters or rescue groups cannot afford the expense of heartworm treatment, and if they can, may be unable to hold an animal through the entire treatment protocol. At the University of Florida, veterinarians and students of the Veterinary Community Outreach Program have developed a successful and affordable treatment plan for these dogs and have treated over 500 animals with heartworm infection since 2008.

You can find out how they do it, and how you can work with local rescue groups in your area to provide treatment, from Dr. Natalie Isaza in Treating Heartworm Disease in Shelter Dogs: 500 Dogs and Counting!

Want to know more? Have other questions? Try these resources:

The American Heartworm Society’s Guidelines for Dogs

The American Heartworm Society’s Guidelines for Cats

How Animal Shelters Can Treat and Prevent Heartworm in Dogs: Q&A with Dr. Brian DiGangi

Maddie’s Institute Heartworm Disease in Dogs and Cats Learning Track

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