Myths & Facts: Heartworm Edition

Heartworms are all too common in the warm southern states, and can affect both dogs and cats. Most people are aware that heartworms pose a very real risk to their pets, but do they know why? Below is a list of myths and facts about these parasites. 

  • MYTH: Heartworms are the same worms that I see in my dog's poop.

FACT: Heartworms do not cross into the gastrointestinal tract of a dog. Heartworms live and feed in the chambers of the heart of dogs. The exception to this is the larvae stage of this parasite, called microfilariae. These larvae travel around the body through your dog's veins in the blood until they are mature enough to take up permanent residence in your dog's heart. 

  • MYTH: Cats aren't affected by heartworms.

FACT: While dogs are the preferred host, cats can be infected with heartworms as well. Cats suffer from respiratory symptoms such as coughing and difficulty breathing when mature heartworms take hold. Other symptoms can include lethargy, vomiting, decreased appetite, and weight loss. Since these symptoms can be linked to a number of diseases, it's important to have your cat evaluated by a veterinarian if a combination of these symptoms occur. Additionally, there is no approved treatment for heartworms in cats, making the disease all the more dangerous for felines. Prevention is the only effective method for protecting your cat from heartworms. 

  • MYTH: Heartworms are contagious. 

FACT: Heartworms are spread through mosquito bites, not through casual contact. An infected mosquito has to bite your pet in order for them to become infected. It is important to note however that if a heartworm positive pet lives with healthy housemates, mosquitoes can spread the disease to the other pets. 

  • MYTH: Mosquito repellent is enough to protect my pet.

FACT: While repellent may deter mosquitoes, it only takes one singular bite from an infected mosquito to spread heartworms to your pet. The best and most effective way to protect your pet from heartworms is through prescription preventions. These products are given orally, transdermally (on the skin), or as long-acting injections. If a pet is current on heartworm prevention and is infected through a mosquito bite, the larvae will be killed before becoming adult heartworms. 

  • MYTH: My pet only goes outside for potty breaks, so heartworms aren't a real threat. 

FACT: Again, one bite, one time can infect your pet. Mosquitoes are small and fast, and heartworms can be transmitted in seconds! 

  • MYTH: Heartworms are always fatal to dogs. 

FACT: There are approved methods for treating heartworm disease in dogs. However, they take a toll on your dog, and require lots of recovery time. Blood work, x-rays, medications, injections and a month of kennel rest is required to effectively kill adult heartworms. Protect your pet from contracting heartworms to bypass the risky business of treatment!  

  • MYTH: My dog doesn't need to be tested before starting on heartworm prevention. 

FACT: Because heartworm prevention kills adolescent parasites, some products are not safe to give to heartworm positive dogs. These preventions are so good at what they do that they can actually dislodge a newly rooted adult heartworm and cause severe medical complications such as stroke. While some preventions are safe to use in preparation for heartworm treatment in heartworm positive dogs, all dogs should be tested to ensure they are not heartworm positive before starting on prevention. The exception to this is puppies under 6 months of age. It takes about 6 months for a heartworm to fully mature from start to finish, so puppies under 6 months of age can start prevention safely. 

  • MYTH: My dogs take their prevention all year long, so they don't need an annual heartworm test. 

FACT: While heartworm prevention is highly effective, no medication is 100% effective. Annual tests ensure that your dog's prevention is working as it should. Additionally, dogs can contract heartworms after missing just one or two doses of prevention, due to the nature of the heartworm lifecycle. The idea is similar to needing to see the optomitrist every year before you can renew your contact lense prescription. While you may not have noticed a change, your doctor wants to test and make sure that the same product is effective enough for you to continue with.

  • MYTH: My pet only needs prevention during peak mosquito season. 

FACT: Mosquitoes are annoyingly resiliant creatures. In the south, the warm humid weather allows them to thrive. For most Texans, mosquito season lasts from mid spring-early fall. If pets are only given prevention during this time, the stray mosquitoes that were holding out for a warm snap in late fall or early winter can emerge and infect your pet. Additionally, if your pet is infected with heartworms toward the end of the last dose of prevention given, and is not given another dose until the mosquitoes appear again, they could have a full-blown heartworm infestation. 


Some final notes:

Be sure to check that your dog isn't "hiding" their pill after you've given it to them- we've seen dogs that hide several pills under furniture, behind food bowls, etc. Watch to make sure that your pet's pill makes it all the way down! 

Does your dog hate taking pills? There are other options! Ask your pet's veterinarian about topical or injectable heartworm preventions. 

Prevention is safe, effective, and affordable. Heartworm treatment, while effective, poses risks and is very costly. Have your dog tested yearly and on prevention year-round to keep them protected!