April is National Heartworm Awareness month. Spring is also the time of year when mosquitoes, the heartworm vector, become active. As the month winds down and the temperature goes up, the Texas A&M Veterinary Medical Diagnostic Laboratory, TVMDL, is addressing three common misconceptions related to heartworm disease and testing.
“Heartworm disease is serious issue,” said Catherine Campbell, DVM, veterinary diagnostician at the College Station lab. “Heartworm testing is important, and there are wonderful preventatives out there that provide great protection.”
Currently, more than 100,000 dogs in the U.S. test positive for heartworms each year. Although heartworm disease is less common in cats, they are still susceptible to infection. Despite the prevalence, there is some confusion regarding prevention and treatment approaches to the deadly disease, leaving pets vulnerable to heartworm infestation.
Campbell highlights a few common misconceptions associated with heartworm disease.
“It’s winter — dogs don’t need heartworm preventive.”
While it is true that mosquitoes — the carriers of heartworm larvae — thrive in warmer temperatures, their activity is not limited to summer or warm-weather regions.
“It’s been detected in non-native dogs in Alaska,” Campbell said. “There are mosquitoes up there too. Also, animals carrying microfilaria are transported all over the world.”
The travel or relocation of heartworm-positive dogs from high-risk areas is a concern, as it can introduce the parasite into regions where heartworm is not commonly found. Because heartworm transmission can occur year-round and sometimes in unexpected areas, maintaining a consistent prevention plan is the most reliable way for pet protection.
“Indoor pets do not need heartworm prevention.”
Some pet owners assume that heartworm prevention is not necessary for indoor pets.
“Mosquitoes can come indoors,” Campbell said. “It only takes one bite.”
If a mosquito carrying Dirofilaria immitis, the heartworm parasite, enters a home through a cracked door or window and bites a pet that is not on preventative medication, the risk of undetected infection increases. Neglecting preventative care can lead to severe heart and lung damage, potentially resulting in fatal consequences.
“Slicing and dividing the heartworm preventative tablets is an effective and cheaper alternative to giving the full recommended dose.”
Heartworm preventative prescriptions can be costly, so splitting up the tablets into smaller pieces seems like a sensible consideration at first; however, doing so is often counterproductive.
“It’s very important that you follow label directions and dose appropriately for that animal’s weight,” Campbell said. “Pets are not protected when they consume a portion of the tablet because the tablet may not be distributed evenly.”
Inconsistent or inadequate dosing can increase the risk of widespread resistance in heartworm populations within pets, leading to serious complications. Furthermore, treating heartworm disease in dogs costs thousands of dollars more than a 12-month supply of preventative medication. The FDA has not approved any medications for treating heartworm in cats, so proactive prevention is strongly advised to avoid serious health risks. Ultimately, sticking to a regular prevention routine is the best way to protect pets and prevent costly canine heartworm treatment.
What’s the impact of heartworm disease?
According to the FDA, the average worm count living inside an infected dog is 15, but that number can range from 1 to 250 with some worms stretching up to 12 inches in length. Cats have a much lower worm burden, but it only takes 1 to 6 heartworms to cause significant feline illness.
These parasites inhabit the heart, lungs, and surrounding blood vessels of dogs and cats, disrupting blood flow and triggering inflammation. Heartworm disease can lead to several health complications including heart failure and irreversible lung damage.
Fortunately, preventative medication coupled with diagnostic testing can help pet owners mitigate the disease’s threat.
The value of annual testing
Although a prevention care plan is effective in minimizing the risk of heartworm infection, the medication does not guarantee complete safety from the disease.
“Not every worm follows the rules,” Campbell said. “In addition to a prevention plan, I highly recommend conversations with your veterinarian about testing protocol and annual examinations. Work with your veterinarian and be on a team for the health of the animal.”
Heartworm disease is not exclusively a seasonal concern. Prevention is a year-round commitment. Regardless of whether a pet lives indoors or spends time outside, consistent use of preventive medication is essential for protection from D. immitis. Combined with annual testing, this proactive approach offers the best defense against a disease that is both dangerous and costly to treat.
Pet owners concerned about heartworm disease or who are interested in testing their pet should contact their local veterinarian for more information.
A helpful resource for understanding all concepts about heartworms is the American Heartworm Society.
For more information about TVMDL’s Dirofilaria immitis testing options, visit tvmdl.tamu.edu or call the College Station lab at 1.888.646.5623.
