Heartworm infections and heartworm disease affect thousands of pets each year, despite readily available control methods. April is Heartworm Awareness Month, so the Haskell Valley Veterinary Clinic team is taking this opportunity to dispel common heartworm myths and help pet owners understand how best to protect their pets from this preventable disease.

Heartworm basics

Heartworms are transmitted by mosquitoes, which pick up larvae from infected wildlife or pets and transmit them to a new host through bites. The worms mature over several months, eventually becoming adults and reproducing, and taking up residence in the pet’s heart and nearby large blood vessels. Over time, the heartworms grow large and cause damage to the heart and respiratory system. High worm burdens—sometimes in the hundreds—also can cause physical blockages that lead to sudden heart failure or death.

Heartworm disease is easily prevented by giving pets a monthly medication that kills immature heartworms before they reach adulthood, reproduce, and cause disease. Pets who are not given regular, consistent prevention are at risk for infection, and, if infected, may require expensive and painful treatments, accompanied by several months of cage rest. No treatment options are available for cats.

Myth #1: Pets don’t need heartworm prevention during the winter months because mosquitoes are not active.

Heartworms are transmitted by mosquitoes, and since mosquitoes are less active during colder months, many people believe their pets are not at risk during this time. However, weather patterns and mosquito activity can be unpredictable, and your pet’s heartworm prevention actually works retroactively rather than proactively. When you give a dose each month, you kill larvae that were transmitted within the previous few weeks. That means skipping doses could allow larvae to mature past the stage where they are easily killed. Keep in mind that most heartworm preventives also control intestinal parasites, something your pet could encounter during any season.

Myth #2: Cats aren’t preferred heartworm hosts, so I don’t need to worry about infection.

While dogs and wild canids are the preferred hosts for heartworms, cats also can become infected. The worms thrive easily and reproduce in large numbers in dogs, but cats generally host only one to three worms. However, having a lower number does not necessarily reduce the consequences of infection. Cats with heartworm disease often suffer from respiratory problems, vomiting, and weight loss, and can experience seizures or sudden death. Cats also cannot be safely treated for heartworm infection in the same way as dogs, so prevention is the best strategy to keep them healthy.

Myth #3: A fecal test can detect heartworms, and standard deworming treatments will kill them.

Many pet owners are confused about the differences between heartworms and other worms, such as roundworms or hookworms. These other worms live in your pet’s intestines, and can be detected through a routine fecal examination and killed with easy-to-administer oral medications. Heartworms live in your pet’s heart and circulate in the bloodstream, and the adults can only be killed with one specific, expensive, injectable drug. Heartworms are their own parasite category and require specific blood tests to detect and specific preventives to control.

Myth #4: I can skip heartworm testing if my pet takes prevention year-round.

No parasite medication is ever 100% effective. While the chances are low that your pet will become infected if you have been giving them their preventive medication each month, the possibility remains—especially if you skipped a month here or there. Heartworm prevention manufacturers build a guarantee into their products and will pay for your pet’s treatment if they become infected. However, you must prove you purchased a full 12-month supply of the medication from your veterinarian and have your pet tested for heartworms each year for the manufacturer to honor the guarantee.

Myth #5: Heartworm risk is low in our area.

Historically, heartworm disease was prevalent mostly in the warm, humid Southern states where mosquitoes thrive and pets are overpopulated. However, changing global weather patterns and temperatures are allowing mosquitoes to thrive in more places. In addition, starting with the aftermath of Hurricane Katrina in 2005, many rescues put transport programs in place to move unwanted pets from the South to other areas for adoption—which also helped heartworm to spread. Heartworm has been detected in all 50 states, so all pets are at risk.

Heartworms are small creatures that can cause big problems for your pet, but you can prevent infection with a simple, monthly medication. Contact the Haskell Valley Veterinary Clinic team to learn more about heartworm disease, get started with heartworm prevention, or schedule your pet’s next wellness visit and heartworm test.