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Heartworms 101

May 1, 2021

Summer is coming … and so are fleas, ticks, and other creepy-crawlies. One parasite that is particularly dangerous to our furry friends is the heartworm. These disgusting worms can make Fluffy and Fido very sick, and can even be fatal! Read on as a Cornelius, NC vet discusses heartworms, and why it’s so important to protect your pet from them.

Life Cycle

Heartworms are transmitted from dog to dog by everyone’s favorite insect: the mosquito. They are in larval form at the time Fido is infected, but soon begin to grow. It takes about 6 months for them to reach adult size and start reproducing. This is when things get dangerous for Man’s Best Friend. The worms infest dogs’ hearts, as well as their lungs and arteries. Needless to say, interfering with these vital organs can be very dangerous. Left untreated, infestations can be deadly.


The signs of heartworm infestations can be fairly subtle at first. You may notice your pooch panting heavily and/or getting tired more quickly than he used to. As the infestation continues, the symptoms will get worse. These include coughing, weight loss, reduced interest in play, lethargy, trembling, and weakness. Severe infestations can lead to seizures, heart attacks, comas, and, unfortunately, death.

Keeping Fido Safe

It’s actually quite easy for you to keep your canine buddy safe from these horrible parasites. Just keep up with his heartworm prevention! There are quite a few different products to choose from, so ask your vet for specific recommendations. If your pup has had any lapses in his preventative care, he’ll need to be tested before starting treatment. This is because preventative products do not kill live worms. If Fido were to be infested, he would need to go through some fairly intense treatments, which could even include surgery.


Cats can and do get heartworms. However, the worms don’t affect kitties in the same way they do dogs. Feline bodies aren’t as hospitable to the worms as canine ones are, so most of their heartworms will die before maturing. This means infestations often do resolve naturally in kitties. However, they are still extremely dangerous. Even a single worm can cause severe—and permanent–damage to your furry buddy’s vital organs, which can be fatal. Keep up with Fluffy’s parasite control!

Our Advice on Heartworms in 2024

What are the dangers of heartworms for pets, especially dogs and cats?

Heartworms pose a significant threat to pets, particularly dogs and cats. Transmitted by mosquitoes, these parasites infest the heart, lungs, and arteries. In dogs, heartworms can grow and reproduce, causing severe damage to vital organs. Symptoms include coughing, fatigue, and, in advanced stages, heart failure or death. Cats, while less hospitable hosts for heartworms aren’t immune. Even a single worm can be fatal, causing sudden respiratory issues or organ damage. Early detection and prevention are crucial, as treatment can be intense and challenging, especially in dogs. Regular heartworm prevention medication is critical to safeguarding pet health.

What are the symptoms of a heartworm infestation in dogs?

In dogs, heartworm infestation often starts with subtle symptoms that gradually worsen. Initially, dogs may exhibit increased fatigue, difficulty breathing, and a mild, persistent cough. As the infestation progresses, these symptoms intensify. Dogs might experience a more severe cough, decreased appetite leading to weight loss, and reduced interest in play or exercise. In advanced stages, dogs can show signs of heart failure, such as a swollen abdomen due to fluid accumulation. In severe cases, they might collapse or suffer from life-threatening cardiovascular complications. Early detection and treatment are crucial for better outcomes.

How can heartworm infestations in dogs escalate if left untreated?

If left untreated, heartworm infestation in dogs can escalate into a severe, life-threatening condition. Initially, heartworms lodge in the lungs and heart, causing mild symptoms. Over time, as worms increase, they can severely damage these organs. This leads to a condition known as heartworm disease, characterized by heart failure, lung disease, and damage to other organs. The dog’s heart and lungs work harder to compensate, leading to a swollen abdomen, severe cough, and decreased physical ability. In extreme cases, untreated heartworm infestation can be fatal.

How do heartworms affect cats differently than dogs?

Heartworms affect cats differently than dogs due to cats’ unique physiological responses. While dogs are natural hosts for heartworms, allowing the parasites to thrive and reproduce, cats are not. In cats, many heartworms don’t reach maturity. However, even immature worms can cause significant health issues, known as heartworm-associated respiratory disease (HARD). Symptoms in cats can be subtle or dramatic, ranging from coughing and difficulty breathing to rapid heart rate and weight loss. In some cases, cats may suffer acute lung injury or sudden death. Unlike in dogs, heartworm infestations in cats often resolve independently, but they can still cause severe and permanent damage to the cat’s health.

Why is parasite control important for both dogs and cats?

Parasite control is crucial for dogs and cats as it safeguards them from harmful parasites that can cause serious health issues. These parasites, including fleas, ticks, heartworms, and intestinal worms, can lead to conditions ranging from skin irritations and allergic reactions to life-threatening diseases like heartworm disease and Lyme disease. Regular parasite prevention is important not only for the health of pets but also for their owners. This is because some parasites can be transferred from pets to people. By maintaining consistent parasite control, we ensure our pets’ and families’ overall health and well-being.

Contact us, your Cornelius, NC pet clinic, for your pet’s veterinary care needs. We’re here to help!