Heartworm Disease

article_drpolheartwormHeartworm disease is a serious matter. Without proper prevention these long, noodle-like worms, which enter your pet through bites from infected mosquitos, can invade your dog’s heart and lungs among other vital organs. Once heartworms enter the bloodstream, they thrive, mature and grow, leading to blood flow obstruction. Without treatment, heartworm disease can make your dog sick, sometimes leading to death. Though less common, cats can get heartworms too.

As mosquito season begins, let’s explore some little known facts about heartworm disease, common symptoms, treatments, prevention, and advice that pet owners will find surprisingly helpful.

Heartworm_Life_CycleInteresting Facts

  • Did you know heartworms born inside an infected animal are not actually capable of causing heartworm disease? The baby worms, known as “microfilariae,” must first pass through a mosquito that bites your dog. Only then do they transform into infected larvae. The mosquito goes on to bite another animal transferring the now infectious larvae into the host’s bloodstream.
  • Coyotes, foxes and wolves, along with dogs and cats, are all carriers of heartworm disease. Heartworms have even been found in sea lions.
  • Heartworms in dogs can grow to a foot in length and live up to seven years in host dogs. Numbers can exceed 50 worms in one infected animal.
  • While cats can host heartworms and become sick with the disease, it is far less common since the worms do not typically survive to reproductive maturity.
  • Pets in hot humid regions such as the Southeastern and Midwestern United States are at greatest risk of contracting heartworm disease due to the high mosquito population.
  • Alaska has only had a few recorded cases of heartworm disease. Don’t let that stop you from giving preventatives to your Alaskan Malamute though!



  • Heartworm symptoms in your dog could include persistent coughing, inactivity (lethargy), decreased appetite and weight loss.
  • Cats may exhibit signs of respiratory problems such as wheezing, but may also begin vomiting and losing weight.
  • It’s important to note that not all animals show signs of heartworm disease until it has progressed into a life-threatening situation. Prevention is the best solution.


  • Typically treatment of heartworms in dogs requires injections directly into the muscle. Your dog may be hospitalized for much of this time.
  • Outpatient heartworm treatments are also available, depending on the health of the animal and other circumstances.
  • Preventative heartworm meds are always recommended after disease treatment to minimize infection and reoccurrence.
  • There are currently no FDA-approved heartworm treatments for cats.


  • Tasty, chewable, monthly heartworm pills are the most common form of prevention for dogs and can be acquired by prescription from your local veterinarian. There are monthly topical heartworm meds available as well.
  • Because remembering to give you dog a monthly heartworm pill is not always easy, you may want to ask your vet about an injectable option that protects your dog for six months.
  • While you can start your puppy on heartworm prevention at eight weeks old, dogs older than six months must first be screened for the disease before starting preventatives.
  • Some prevention medications can be given only during mosquito season (Spring) but Dr. Pol agrees with the American Heartworm Society who recommends year-round monthly administration.


Quick Tips

  • Schedule your pet’s annual wellness exam in the spring, when mosquito season begins, so that heartworm blood testing can rule out the disease and prevention medicine can be started.
  • Ensure that your dog is tested every year for heartworm disease to ensure the prevention program is working.
  • “Think12” – Administer preventative heartworm meds 12 months per year AND test your pet every 12 months (annually) for the best year-round prevention and diagnosis. (“Think12” is a campaign of the American Heartworm Society).

The Final Word from Dr. Pol. . .

“Holy Moses! Heartworms look like a mess of tangled wires and that definitely DOES NOT belong in your dog’s body! Make sure to schedule an annual exam for your pet and speak to your veterinarian about options to prevent this serious disease.”

Alex Tosian, Production Assistant brings in her puppy to see Dr. Brenda Grettenberger.