Local vet talks heartworms in canines

KYLE  — According to Companion Animal Parasite Council, one in 50 dogs tested positive for heartworms in Hays County in 2024. In honor of National Heartworm Awareness Month,  Guy Mathews, DVM, of Kyle Animal Hospital explained the risk factors of the disease. “Heartworms are actual worms. If you could get them out of the heart, you could fish with them,” said Mathews. “They’re a parasite that lives inside the heart, inside the chambers of the heart … and they obstruct blood flow.” The parasite is primarily found in the canine species, but has occasionally been reported in other species, such as cats and horses. The worms live a specific life cycle, first beginning in the bloodstream of an infected dog as microscopic babies — microfilariae — which a mosquito picks up when it takes a blood meal from an infected dog. After the microfilaria enters the mosquito, they mature inside of the mosquito for two weeks, where they will then be transported to another dog when it is bitten. The larva migrates through tissues and bloodstream as they evolve into young adults. Once into the major organs, primarily the heart, worms develop sexual maturity, creating more microfilaria, which will appear within six months. The most important aspect of this cycle is the time inside of the mosquito. Heartworms do not spread through social interactions or feces, only through the bite of an insect; otherwise, they would not grow into adults to begin the cycle once more. “They attach to the walls of the heart and the blood vessels, sometimes going into the blood vessels of the lungs,” Mathews explained. “As the blood flow slows down around the worms, they start to have blood clots and we all know the problems with blood clots in our bloodstream. If one of those blood clots breaks loose and hits into a big pulmonary vessel or cardiac vessel, the dog will die.” Mathews continued by stating that when looking at a dog’s heart who was a victim of the disease, it can occasionally look like “a mass of spaghetti.” If left untreated, the disease is almost certainly fatal, leading to heart failure. But sometimes, due to the worms traveling to other vital organs, additional problems can arise. There are four stages that veterinarians categorize each dog when infected with heartworms, which range from mild to heart failure. Typically, the only signs an owner would see to recognize that their dog has been infected are the signs of heart failure, when it is too late to save the animal, explained Mathews. To preserve quality of life, a veterinarian can provide support for the heart for the remaining months of the dog’s life. “[Heartworms] are very preventable,” he said. “There are quite a few different ways to do [heartworm preventative medication]. You can do it as a monthly oral, a monthly topical or there is even a 12-month shot … Heartworm preventative medications are one of the most effective medications that we have.” Although the definition of low-cost varies from person to person, medications can be found at many veterinarian offices and on multiple online websites, such as www.chewy.com, where heartworm pills, depending on the weight of the dog, can range from $5 to $20 monthly. Some owners feel as though heartworm preventative isn’t needed to which Mathews stated: “All dogs are considered susceptible to them. We’ll even see heartworms occasionally in indoor cats … There’s no place that doesn’t have mosquitoes, some have more than others, but there’s no place that doesn’t have them … Every heartworm positive dog is spreading heartworms to the rest of the community.” If caught early enough, heartworms are treatable, but it is often difficult for the pet because the primary medication used to treat an infected dog is a derivative of arsenic. the veterinarian noted that the worms dying while being treated also poses potential problems because as they die, they break loose from the heart and float in the bloodstream, which can still create a form of a blood clot. Mathews recommends testing dogs every year, whether they are on medication or not. “It’s disturbing to see a dog that’s already in heart failure and the owner really cares about the dog, but they just didn’t get it tested and there’s really nothing to do at that point. So, early detection so that we can still treat them when they’re in those early stages [is important],” he said. “It’s like anything else in life, if they don’t have a dog on heartworm preventative, they’re taking a risk,” Mathews stressed. For more information on treatment, visit www.kylevet.com or a local veterinarian. To learn more about heartworms, visit www.capcvet.org/guidelines/heartworm .