Podcast Transcript: Heartworms

Heartworm disease is a potentially deadly disease that affects dogs, cats, ferrets, and other mammals. While heartworm infection is serious, the good news is that it's entirely preventable.

In today's podcast we'll discuss what veterinarians and their hospital teams need to know about heartworm disease, what causes the disease, where it is found and how it is transmitted, what are the clinical signs of heartworm disease, and how it is treated, and perhaps most importantly, how it is prevented.

Heartworm disease is caused by Dirofilaria immitis, which are spaghetti-like worms that can grow to twelve inches long. Of all the mammal species affected by heartworms, dogs are the most likely to be infected and are said to be the most competent hosts.

Heartworm infection is transmitted from animal to animal by mosquitoes. Based on the pets seen at Banfield Hospitals, we know that heartworm is among the top serious and preventable infectious disease risks in the Southern United States and that it is also widespread throughout the country. Indeed, data from Banfield's electronic medical records show that dogs are testing positive for heartworm in every state where Banfield has a hospital.

Once a pet is infected, heartworms migrate to the blood vessels of the lungs and to the right side of the heart where they can cause permanent damage before the pet shows any sign of disease. You'll find that the clinical signs most commonly observed in dogs are similar to those of right-sided congestive heart failure, most notably fever, cough, lethargy, difficult breathing, and sometimes coughing up blood.

Cats may have no clinical signs, however infected cats may show signs of acute respiratory distress or may die suddenly. It is important to understand that indoor housing does not protect pets from infection.

Diagnosis of canine heartworm disease is usually by antigen test, which detects proteins from the reproductive tract of adult female worms. It's recommended that when a dog tests positive another heartworm test be performed to ensure the results are accurate. Confirmation of a positive test result is often followed by diagnostic imaging to determine the extent of disease. Diagnosis of feline heartworm disease can be challenging and typically requires a combination of multiple tests.

Treatment of heartworm disease can be tricky and may involve complications. Treatment with melarsomine is usually the treatment of choice to kill adult worms and infected dogs. In cats there is no adulticide so the immotherapy is usually to reproduce the severity of clinical signs.

Most complications of therapy in dogs and cats are thought to be associated with worm fragments becoming lodged in the blood vessels within the lungs, causing pulmonary embolism.

Heartworm disease is easily prevented yet over compliance remains the biggest barrier to effective prevention. The American Heartworm Society recommends year round preventive medications that can either be given monthly, such as pills or topical solutions, or given twice annually, such as injectable products.

Preventive treatment is recommended for all dogs nationwide. Cats in heartworm endemic areas should receive topical or oral medication on a monthly basis. An injectable drug has not yet been approved for cats. The American Heartworm Society also recommends annual heartworm tests for all dogs. It is highly recommended that practitioners and hospital teams understand the biology and lifecycle of heartworms and become familiar with the American Heartworm Society's recommended protocols.

Many hospitals make it their goal to make sure every pet is on year-round heartworm prevention. Dr. Mitch Clemmer, a charter owner of two Banfield Hospitals in Mississippi, says that every client gets offered a single dose of heartworm and flea prevention for their pet in the exam room on their first visit. He prefers to start with the single doses, particularly in puppies and kittens, due to weight changes, and he says that also helps get the client used to monthly prevention. Dr. Clemmer is also a big believer in education. Educating clients on year-round heartworm prevention in his hospital is just a part of the regular education. He tells his clients it's not a question of whether or not it is needed, it just is.

Likewise, many hospitals make sure all staff participate in the education process. John Ashley, a Banfield veterinary technician in Georgia, asks all veterinary professionals to educate themselves on all of the recommended products because they can't properly educate clients if they aren't educated themselves. By gaining a thorough understanding of heartworm disease, and communicating effectively to clients, veterinary professionals will be helping to prevent heartworm infection before it becomes a problem.


This podcast was created and developed by Banfield Pet Hospital and is brought to you by the Banfield Applied Research and Knowledge team. For additional content, or to view the whitepaper for this topic, please visit Banfield.com.

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