Heart Worms

Heart worms, also known as Dirofilaria immitis, affect dogs, cats, coyotes, wolves, and other wild animals around the world. Heart worm, a parasite, was first found in dogs over a century ago. Heart worm has been found to be most prevalent within 150 miles of the gulf and Atlantic coasts. Since mosquitoes are the culprit that infect animals with this heart worm, it only makes sense that mosquito-infected areas have a larger number of pets infected with heart worm disease. Dogs are often found to be the more common host to this parasite.

A mosquito ingests the heart worm larva when it bites an infected dog. This infected mosquito will then bite another dog or animal and transfers the larva. This small larva, called a microfilariae, will then burrow into the dog and continue to mature into a heart worm. Heart worms can take up to seven months to grow into adult heart worms. Once mature the heart worm will then move to the dog’s heart and wait there until it can reproduce. The adult heart worms can grow up to 14 inches in length and can survive in the dog’s heart for years.

UPDATE! All About Worms has partnered with HealthLabs so that
you can get tested for parasites at a fully-qualified lab near you,
no doctor's visit required
! Check it out at HealthLabs.com!

When a female heartworm reproduces, it will bear thousands of live microfilariae which will move around the bloodstream waiting to be transmitted to a biting mosquito. When the mosquito bites the infected dog, the cycle begins again. This can also cause the same dog to become infected yet again, which means several heart worms may infect its heart. Often heart worm disease can go undetected for long periods of time. A soft cough, listlessness, and a loss of weight are all early signs of heart worm. As the disease progresses, breathing will become difficult for the dog and can lead to the pet’s traumatic death.

A simple blood test performed on the dog can detect microfilariae in the blood or adult worms in the heart. X-rays can also be used to detect adult heart worms in dogs. Though heart worm has been found to be treatable if it has not progressed too far, it can be a long and debilitating procedure. The first step will be to treat the dog for any secondary problems that can cause heart failure. Once treated, the adult heart worms will need to be killed with an arsenic compound which can have side effects. The worms will need to pass out of the dog’s heart with the dog kept sedentary for several weeks, sometimes longer. Any exertion from the dog can cause these dead worms to travel to the lungs, which will then cause the death of the dog. Continued treatment will be necessary to avoid a recurrence of heart worm. In severe cases of heart worm, surgery may be needed to remove adult heart worms.

Veterinarians can prescribe a preventive oral or topical medication. There is also a six-month time-release injection available. These preventive measures must be started before mosquito season begins. All dogs that will be receiving preventive treatment should first be checked for microfilariae and heart worm infestation. If the dog is already infected with heart worm, whether microfilariae or adult heart worms, then preventive medications can not be used as they would be harmful to the dog, possibly causing death. For this reason you should never begin preventive heart worm treatment without first checking with your veterinarian.

No Paywall Here!
All About Worms is and always has been a free resource. We don't hide our articles behind a paywall, or make you give us your email address, or restrict the number of articles you can read in a month if you don't give us money. That said, it does cost us money to pay our research authors, and to run and maintain the site, so if something you read here was helpful or useful, won't you consider donating something to help keep All About Worms free?
Click for amount options
Other Amount:
What info did we provide for you today?:

Recommended Reading (click on the picture for details):
Dr. Pitcairn's New Complete Guide to Natural Health for Dogs and Cats

Leave a Comment (but to submit a question please use the "Submit a Question" link above; we can't respond to questions posted as a comment)

Menu / Search

All About Worms