Heartworms can seriously damage your pet’s heart and lungs, yet misconceptions abound about this dangerous parasitic infection, putting your pet’s health at risk. Our Animal Care and Emergency Services team wants to clear up the confusion, and we provide the truth behind common misunderstandings about heartworm disease. 

#1: Misconception: My pet can catch heartworms from infected cats and dogs

Truth: Heartworms are not transmitted directly between animals. Dogs and wild canids, such as coyotes, wolves, and foxes, are natural heartworm hosts, and a mosquito (i.e., the vector) that takes a blood meal from an infected host ingests baby heartworms (i.e.,microfilariae). The young heartworms mature inside the mosquito to an infective stage over two to three weeks, and when ready, travel to the mosquito’s salivary glands, and are transmitted to the next vulnerable pet the mosquito bites. Only one heartworm positive dog or fox in your neighborhood greatly increases your pet’s risk of infection.

#2: Misconception: Cats can’t get heartworm disease

Truth: While dogs are the heartworms’ preferred host, cats can also be infected by the parasites. However, cats are atypical heartworm hosts, and when the microfilariae enter the cat’s body, their immune system mounts a sizable response that causes the death of many parasites. This means that many heartworms don’t grow to adulthood while parasitizing the cat, but the young parasites can still cause significant health issues. When the parasites reach the cat’s lungs, the cat responds with a severe inflammation that results in a condition called heartworm-associated respiratory disease (HARD). In addition, when the heartworms reach adulthood, only one or two worms can wreak havoc on the cat’s minuscule heart.

#3: Misconception: I would know if my pet had heartworms

Truth: Most pets don’t exhibit disease signs in the initial stages, and typically show signs only when their heart and lungs are significantly damaged. In some cases, the first sign is sudden collapse or death. When signs are present, they include:

  • Signs in dogs — Heartworm disease in dogs is mostly a vascular disease, and signs include lethargy, exercise intolerance, a persistent cough, and weight loss. As the condition progresses and the heart starts to fail, fluid can accumulate in the abdomen, resulting in a pot-bellied appearance.
  • Signs in cats — In cats, heartworm disease is mostly a respiratory disease, with signs that include open-mouthed breathing, wheezing, increased respiration rate and effort, and weight loss.

#4: Misconception: My indoor pet does not need heartworm protection

Truth: Mosquitoes can easily enter your home through vents, open doors and windows, and torn screens, and only one mosquito bite can transmit heartworms to your pet. In addition, many indoor pets are allowed outside on protected balconies or in enclosed patios, where they can easily be targeted by mosquitoes. 

#5: Misconception: I can stop my pet’s heartworm preventive during the winter

Truth: Many owners are tempted to stop their pet’s heartworm preventive during the winter to save money, but this puts your pet at risk. The weather is often unpredictable, and mosquitos can easily become active and hungry on any day with temperatures about 50 degrees. In addition, stopping the monthly dosing gets you out of the habit, and remembering to dose your pet becomes harder. Year-round heartworm preventives are imperative for all pets.

#6: Misconception: My pet is protected if I forget a dose of their heartworm preventive

Truth: Missing a single dose of heartworm preventive puts your pet at risk for infection. These products work retroactively, killing heartworm larvae that were transmitted to your pet in the previous month. If you miss a dose, the young heartworms continue to grow and are no longer susceptible to heartworm prevention medication once they reach a certain developmental stage. Set a reminder on your phone or mark your calendar to ensure you never miss your pet’s heartworm preventive.

#7: Misconception: My pet doesn’t need annual heartworm testing if they receive a preventive

Truth: The American Heartworm Society recommends that dogs be tested every year using a microfilariae and antigen test. This is important, because some heartworms have developed resistance to common heartworm preventives, and we want to ensure your pet is protected. In addition, some pets are sneaky, and spit out their dose when you aren’t looking, putting them at risk.

#8: Misconception: My pet can easily be treated if they get heartworms

Truth: No treatment is available for cats, making heartworm prevention the only way to protect your feline friend. For dogs, treatment is dangerous, prolonged, and expensive, and involves:

  • Exercise restriction — Your dog must be kept as still and quiet as possible, because exercise exacerbates the damage caused by heartworms.
  • Stabilization — Your dog’s condition must be stabilized to ensure they are healthy enough to start heartworm treatment.
  • Killing the microfilariae — We prescribe medications to kill the circulating baby heartworms.
  • Antibiotics — Heartworms live in concert with a bacteria, called Wolbachia, and we prescribe antibiotics to help address the infection.
  • Anti-inflammatories — We use anti-inflammatories, such as steroids, to control the inflammation caused by the parasites.
  • Killing adult worms — Medication is injected deep into your dog’s lumbar muscles to kill the adult worms. 
  • Monitoring — Your dog must be closely monitored to watch for side effects, such as anaphylaxis and blood clots. 

Providing year-round heartworm prevention for all pets, including those who live solely indoors, is the best way to protect your pet from these dangerous parasites. Contact our Animal Care and Emergency Services team to schedule your pet’s annual heartworm test and discuss the product that will offer them the best protection.