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Heartworm Diseases - Facts vs Fiction


One of the most serious parasites your pet could become infected with is heartworm. This disease has always been quite common in southern states, but in recent years, the rates of infection in pets in the north have been increasing at an alarming rate. While the term “heartworm” is often familiar to many pet owners, there are often a lot of misconceptions surrounding it. Below we will break down the most common misconceptions and discuss the facts surrounding this deadly disease.


MYTH: Heartworm is a Mild Infection Causing GI Symptoms

Heartworm is, just as it sounds, a parasitic worm that invades a host’s body. When people hear parasites, they often assume an infection will cause mild symptoms and usually affect the GI tract. Unlike intestinal parasites, however, heartworm enters an animal through the bloodstream. Tiny worms enter the blood in their immature larval state from a mosquito bite. Over the course of several months, the larvae travel through the body until they finally reach the lungs. The larvae slowly grow and, by about six months after infection, reach adulthood. Female worms can grow up to a whopping 14 inches in length inside an animal’s body. As the worms grow, they begin to damage blood vessels and reduce the heart’s pumping abilities leading to symptoms of heart and lung disease. If male and female worms are both present in the body, they can mate and produce infant heartworms known as “microfilaria.” Microfilaria can cause the animals’ body to mount an immune reaction causing damage to other organs.



"As the worms grow, they begin to damage blood vessels and reduce the heart's pumping abilities leading to symptoms of heart and lung disease."



MYTH: Cats Don’t Get Heartworm

While heartworm disease might be more common in dogs than cats, it is a mistake to think cats cannot get heartworm disease. In cats, heartworm disease is often characterized by a different disease process, and diagnosing heartworm infection is much more challenging in cats. When a cat becomes infected with heartworm, the worms typically only live for 3-4 months. This might make it seem like cats can fight an infection on their own, but unfortunately, during that 3-4 month span the heartworms can cause significant damage to the cat’s body. Cats who have been infected with heartworm often show signs of what is known as heartworm-associated respiratory disease. Some symptoms include coughing, wheezing, vomiting, decreased appetite, and nausea as the worms cause an inflammatory response. There is no safe treatment for cats with heartworm disease; it can only be prevented.

"Cats who have been infected with heartworm often show signs of what is known as heartworm-associated respiratory disease."


MYTH – Heartworm Disease is Not a Concern in Pennsylvania

While heartworm disease used to be considered a problem in the south, in recent years we have seen an alarming increase in dogs in our area that are testing positive and requiring treatment for heartworms. As we experience milder winters in the north, and an influx of puppies and adult dogs rescued from other parts of the country, the trend looks to continue. Mosquitos are the most common host to transmit the disease and even indoor-only pets are at risk of infection. Mosquitos are often able to enter homes, and many indoor-only animals spend at least a small percentage of time outdoors whether intentionally or unintentionally. One bite from an infected mosquito is all it takes to cause infection.

"Mosquitos are the most common host to transmit the disease and even indoor only pets are at risk of infection."

MYTH – Heartworm is Easily Treated

While parasites that live in the GI tract are typically easy to treat and leave little to no lasting complications, heartworms are much more serious. The treatment for heartworm in dogs involves a series of painful injections spread out over many weeks, and time spent in the hospital. The goal of treatment is


to kill the adult worms while ensuring the pet’s body does not experience an inflammatory reaction to the dying worms. During treatment, dogs’ activity must be restricted, as exertion could lead to the dying heartworms causing too much inflammation and internal damage. It can take months of treatment and follow-up care to be sure a dog is heartworm free. Testing cats for heartworm infection is not very straightforward, and there is no safe treatment option. If your veterinarian suspects your cat might have heartworm, they will typically use supportive care and medications to treat inflammation and symptoms.



MYTH – Preventatives Are Not Needed in Winter

Many people believe that heartworm prevention is not needed during the winter months when mosquitos die off. While the risks might be lower during the colder months, mosquitos are a risk year-round in our area. Over the winter, mosquitos do not actually die, they become dormant and will hibernate until the weather warms again. Studies have found that mosquitoes are able to function during weather above 50 degrees. As those who have seen Pennsylvania winters in recent years recognize, there are often unseasonably warm days that climb into the 50s and 60s even during the “coldest” months of the year.

"Studies have found that mosquitoes are able to function during weather above 50 degrees."


FACT - Heartworm is Preventable


The good news when it comes to heartworms is that infection is almost 100% preventable. The best way to prevent heartworm disease is to keep your cat or dog on monthly prescription heartworm preventatives all year long. At Main Street Vet, we carry both dog and cat-specific preventatives that are easy to give and offer comprehensive protection. Call or stop in and ask a member of our team to discuss options for protecting your pet. When it comes to heartworm disease, an ounce of prevention truly is worth a pound of cure.




PERKIOMENVILLE 1335 N. Gravel Pike, Perkiomenville, PA 18074 Telephone: 610-287-5100


SOUDERTON 201 North Main Street, Souderton, PA 18964 Telephone: 215-660-3699

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Perkiomenville 610.287.5100   Souderton 215.660.3699

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