Warning: 6 Deadly Heartworm Myths

Kate Barrington
by Kate Barrington
The truth about heartworm is out there – you just need to know the difference between fact and fiction. Here are 6 heartworm myths you shouldn’t be fooled by.


You may already know the basics about heartworm including the fact that it is a serious and potentially deadly disease. Unfortunately, many pet parents are undereducated about this issue and many of them fall prey to myths that are simply untrue. To make sure you understand the facts about this disease, make sure you haven’t fallen prey to these common and hazardous myths about heartworm.


Related: How Do Dogs Get Heartworm?


  1. Heartworm only happens in the southern states where it is warm all year. While it is true that more cases of heartworm occur in the southern states, heartworm has been diagnosed in all 50 states – including Alaska and Hawaii.
  2. A dog with heartworm can pass it to another dog. The only way heartworm can be transmitted is by mosquito. When a mosquito bites an infected dog, it takes in some of the baby heartworms, called microfilaria, which then develop into infective larvae over the following 10 to 14 days. At that point, the mosquito can bite another dog and pass some of the larvae into its blood stream. Those larvae will then develop over the next six months into adults at which point the dog will test positive for heartworm.


Related: 5 Heartworm Facts You Need To Know


  1. If my dog is up to date with vaccines, I don’t need to use a heartworm preventive. There is no vaccine for heartworm. The only way to protect your dog from heartworm is to have him tested yearly and to give him monthly heartworm preventive pills. Your dog can’t start on a preventive program, however, unless he has been tested, so get your pup tested ASAP.
  2. The mosquitos carrying heartworm are only active during the summer. There are 22 different species of mosquito that have been shown to carry heartworm. These species are not only active at different times of year, but different times of the day as well. This means that your dog is literally at risk for contracting heart worm all year long.
  3. Dogs that get heartworm will always show symptoms. Unfortunately, clinical signs of heartworm often do not develop until the later stages of the disease. It takes 6 months after a dog has been infected with heartworm larvae for those larvae to travel to the heart and lungs where they develop as adults and begin reproducing. At this stage, dogs may develop symptoms like coughing, unexplained weight loss, difficulty breathing, and fatigue after moderate activity.
  4. Heartworm is rarely fatal in dogs. Heartworm is an incredibly serious disease, made even more dangerous by the fact that dogs typically don’t develop symptoms until the disease has progressed to the final stages. If left untreated, a single heartworm can multiply up to 100 times. A dog can have as many as 250 heartworms in his body at one time and those heartworms can grow up to 12 inches long and live up to seven years.


By educating yourself about this deadly disease you can help to prevent your dog from getting it. The key to preventing heartworm lies not only in testing your dog annually and giving him monthly heartworm preventives, but in understanding the risks of the disease and helping others to understand them as well.


What other heartworm myths have you heard? If we missed one, be sure to tell us in the comment section below.

Kate Barrington
Kate Barrington

Kate Barrington is the loving owner of two cats (Bagel and Munchkin) and a noisy herd of guinea pigs. Having grown up with golden retrievers, Kate has a great deal of experience with dogs but labels herself a lover of all pets. Having received a Bachelor's degree in English, Kate has combined her love for pets and her passion for writing to create her own freelance writing business, specializing in the pet niche.

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