Heartworms in dogs: Prevention is key to save your pet’s life

Vet getting blood work for heartworms testing from a medium sized dog

Canine heartworm disease, spread through the bite of infected mosquitoes, was once thought to be predominantly a concern for Latin America.  Bayer Health statistics show that almost a decade ago, most Latin American countries were considered “high risk” for heartworms in dogs.  

Now, heartworm disease is on the rise in the United States, and veterinarians are recommending year-round prevention for canine companions.  Information about dog heartworm symptoms and prevention has spread slower than the disease itself, however, and many dogs around the country remain at risk for this parasitic infection.

What is heartworm disease in dogs and what are the symptoms?

Heartworms in dogs are caused by the parasite Dirofilaria immitis, also known simply as a heartworm.  Larvae are transmitted from animal to animal through the bite of an infected mosquito, maturing in an animal’s system for approximately 120 days. By the end of the parasite’s growth cycle, heartworms — which can grow up to 12 inches long — will have migrated to the arteries, chambers of the heart, and lobes of the lungs.  

Dog heartworm symptoms are similar to congestive heart failure or lung cancer:

  • Coughing
  • Fatigue
  • Difficulty breathing
  • Weight loss
  • Reduced appetite
  • Sudden death from organ failure

Though most commonly seen in dogs, heartworm disease is not limited to canines. The Merck Veterinary Manual indicates wolves, coyotes, foxes, California gray seals, sea lions, raccoons, ferrets, and cats may also be susceptible to the disease.

Does my dog really need heartworm prevention?

Heartworm disease thrives in warmer regions of the country where mosquitoes tend to dwell, but with climate change more reports of heartworm are surfacing even in the most northern areas of the country.  The warmer temperatures, combined with increased pet travel, has facilitated the spread of this disease, and veterinarians are now recommending heartworm prevention in most states.

“Prevention is much easier than treatment,”  Martine Hartogensis, D.V.M., a veterinarian in FDA’s Center for Veterinary Medicine (CVM), said in FDA materials.

“Treatment for dogs can have serious side effects, requires multiple injections, and may involve blood work and x-rays before treatment. Dogs need to be closely monitored during treatment and for up to 24 hours after treatment. Also, the drug used to kill adult heartworms in dogs is currently only available in limited quantities.”

Heartworm preventatives, available as monthly chewables, topicals, or a 6-month injectable, are available in most veterinary clinics and in some pet store settings. Compared to the cost of heartworm disease treatment, monthly prevention is far more reasonable.

Dogs will be required to have a heartworm test prior to the administration of preventatives to ensure the pet does not already have the disease. According to the American Heartworm Society, annual testing is then required while a dog is on heartworm prevention to ensure the program is working. Even one missed dose puts a dog at risk for the disease.

Pets testing positive for heartworms will need to receive treatment dependent on the progression of their parasitic infection.

Not all pets are candidates for heartworm prevention, so it is important to discuss the options with your veterinarian.

“Talk to your veterinarian about testing, and the best heartworm preventive program, for you and your pet,” said Hartogensis. “Your veterinarian’s recommendation may depend on where you live and whether your pet spends time inside or outside.”

Even if heartworms are not a concern, pet owners may consider heartworm prevention products monthly on the merit that some offer intestinal deworming and flea control.
Photo by Shutterstock

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