Happy Spring, Happy Heartworm Prevention!
Greetings, fellow dog and cat lovers!
Spring is in the air, and that means it’s time to start thinking about heartworm prevention. Heartworm (HW, scientifically known as Dirofilaria immitus) is carried by mosquitos, and it’s only possible for your dog to contract HW if they are bitten by a mosquito that is carrying HW larvae. In southeast Pennsylvania, our mosquito season is typically late spring through late fall. But that can vary, and mosquito season will likely become longer as climate change causes our climate to grow warmer.
Let's talk about the worms themselves for a minute. Heartworms are long, thin, spaghetti-shaped worms that can grow to over a foot in length 😳 Adult heartworms live in the pulmonary artery, right ventricle and right atrium of the heart. A heavy infection (meaning many adult worms) can clog the pulmonary arteries and heart, and, if left untreated, cause severe heart and lung damage, and ultimately, heart failure and death. That’s the bad news. The good news for those of us who live in southeast PA is, we do not have a high HW incidence at this time. Again, this may change as our climate continues to warm, but all of the HW patients that I have been aware of over the past three decades were rescued dogs who were brought up from the south, who were not on HW prevention prior to being rescued. Heartworms thrive in prolonged heat and humidity, which is why there's a ton of HW in the south, and why it’s not uncommon for rescued dogs who are brought up from the south to be HW positive. (Check out this incidence map from the American Heartworm Association: https://www.heartwormsociety.org/veterinary-resources/incidence-maps.)
There’s concern that between the climate warming and HW positive rescues from warmer climates being brought north for adoption, more mosquitoes in our area will become infected with HW, transmitting HW to more dogs in our area—unless said dogs are treated with HW prevention during mosquito season. HW disease can usually be treated, but the treatment (killing the adult worms) is painful, expensive and dangerous. HW prevention, on the other hand, is effective, relatively inexpensive, and best of all, safe.
As an integrative veterinarian, my goal is to use conventional pharmaceuticals minimally and mindfully. Unfortunately, there are no natural substances, such as herbs or homeopathic remedies, that are reliably effective at preventing HW infection. But parasiticides (anti-parasite drugs) such as milbemycin, selamectin and ivermectin (which gained a lot of attention during the pandemic, and does not prevent Covid, but does prevent heartworm disease), are all effective at preventing HW, and are relatively safe. Preventing HW requires very small doses of parasiticides, and side effects are uncommon. In fact, if side effects occur, they are more often due to the flavoring of the chewable HW medications rather than the drug itself. For this reason, if your dog has severe food allergies or sensitivities that show up in the form of dermatological or gastrointestinal issues, you may want to use a topical product, rather than oral.
Part of the reason the HW preventatives are so safe is that, unlike flea and tick products, which stick around for months, HW preventatives only stay in the bloodstream for one to two days. They work by killing the microscopic larvae that have been deposited by mosquitos, preventing the larvae from growing into adult heartworms. So, you want to be sure to give HW prevention monthly, starting within the first month of seeing mosquitos in the spring, and ending AFTER you’ve seen the last mosquitos in the fall. Occasionally, folks will see a mosquito inside their home in the middle of winter. Since we have such a low HW incidence in the Philly area, even if that single mosquito bites your dog, the chances of your dog getting HW from it are low. Not zero, but low. That said, many of my clients prefer to follow the American Heartworm Society guidelines and keep their dogs on monthly HW prevention year-round, just to be on the extra safe side.
HW prevention is very good at preventing HW disease, but not 100% effective. (Especially if, like me, every now and then you forget to give your dog their monthly dose on time.) For this reason, and also because it can be dangerous to give HW prevention to dogs if adult heartworms are already present, I recommend testing all dogs annually for HW, using an in-clinic (or in my case, in-your-home) blood test test that checks for HW, along with three of the most common tick-borne diseases—Lyme, Anaplasmosis and Ehrlichia. I’m a big fan of this test; it gives me reassurance that my patients are HW negative, and it also tells me if they’ve been exposed to any of the tick-borne diseases.
If, for any reason you, choose not to give your dogs HW prevention, please do your best to minimize their exposure to mosquitos. Try to avoid having your dog spend time outside when mosquitos are most active, such as at dusk and dawn. Unfortunately, there are no great mosquito repellants for dogs that I’ve found. If any of you have found any that are safe and effective, feel free to let me know.
That’s all for now. Wishing you and your canine companions a safe, happy and heartworm-free spring! 🐾🌷
~Dr. Kassell
PS: Cats can get HW, too, but the incidence is far lower than in dogs, and I don’t recommend HW prevention for most cats at this time. That said, if you have a cat that spends time outside, please try to avoid letting them out during high mosquito times, especially dawn and dusk. And if your cat does frolic with the mosquitos, consider using Interceptor, NexGard Combo, Revolution Plus for Cats or another parasiticide that kills HW larvae in cats.
PPS: Un-fun fact: Humans can get HW, too! Not that I’ve ever heard of anyone who ever has—it’s even rarer in humans than in cats, thank goodness.
PPPS: Many of my clients are finding ticks on their dogs year-round now, even during those most frigid February days. But spring fever is real for all of the animal kingdom—birds, bees, dogs, cats, humans, fleas and ticks. And the ticks are WILD right now! And most concerning is that we have loads of Lyme Disease and other tick-borne diseases, such as Anaplasmosis and Ehrlichia. So please keep on top of your tick prevention.
Final PS: The American Heartworm Society has lots more good info on HW: https://www.heartwormsociety.org/
Greetings, fellow dog and cat lovers!
Spring is in the air, and that means it’s time to start thinking about heartworm prevention. Heartworm (HW, scientifically known as Dirofilaria immitus) is carried by mosquitos, and it’s only possible for your dog to contract HW if they are bitten by a mosquito that is carrying HW larvae. In southeast Pennsylvania, our mosquito season is typically late spring through late fall. But that can vary, and mosquito season will likely become longer as climate change causes our climate to grow warmer.
Let's talk about the worms themselves for a minute. Heartworms are long, thin, spaghetti-shaped worms that can grow to over a foot in length 😳 Adult heartworms live in the pulmonary artery, right ventricle and right atrium of the heart. A heavy infection (meaning many adult worms) can clog the pulmonary arteries and heart, and, if left untreated, cause severe heart and lung damage, and ultimately, heart failure and death. That’s the bad news. The good news for those of us who live in southeast PA is, we do not have a high HW incidence at this time. Again, this may change as our climate continues to warm, but all of the HW patients that I have been aware of over the past three decades were rescued dogs who were brought up from the south, who were not on HW prevention prior to being rescued. Heartworms thrive in prolonged heat and humidity, which is why there's a ton of HW in the south, and why it’s not uncommon for rescued dogs who are brought up from the south to be HW positive. (Check out this incidence map from the American Heartworm Association: https://www.heartwormsociety.org/veterinary-resources/incidence-maps.)
There’s concern that between the climate warming and HW positive rescues from warmer climates being brought north for adoption, more mosquitoes in our area will become infected with HW, transmitting HW to more dogs in our area—unless said dogs are treated with HW prevention during mosquito season. HW disease can usually be treated, but the treatment (killing the adult worms) is painful, expensive and dangerous. HW prevention, on the other hand, is effective, relatively inexpensive, and best of all, safe.
As an integrative veterinarian, my goal is to use conventional pharmaceuticals minimally and mindfully. Unfortunately, there are no natural substances, such as herbs or homeopathic remedies, that are reliably effective at preventing HW infection. But parasiticides (anti-parasite drugs) such as milbemycin, selamectin and ivermectin (which gained a lot of attention during the pandemic, and does not prevent Covid, but does prevent heartworm disease), are all effective at preventing HW, and are relatively safe. Preventing HW requires very small doses of parasiticides, and side effects are uncommon. In fact, if side effects occur, they are more often due to the flavoring of the chewable HW medications rather than the drug itself. For this reason, if your dog has severe food allergies or sensitivities that show up in the form of dermatological or gastrointestinal issues, you may want to use a topical product, rather than oral.
Part of the reason the HW preventatives are so safe is that, unlike flea and tick products, which stick around for months, HW preventatives only stay in the bloodstream for one to two days. They work by killing the microscopic larvae that have been deposited by mosquitos, preventing the larvae from growing into adult heartworms. So, you want to be sure to give HW prevention monthly, starting within the first month of seeing mosquitos in the spring, and ending AFTER you’ve seen the last mosquitos in the fall. Occasionally, folks will see a mosquito inside their home in the middle of winter. Since we have such a low HW incidence in the Philly area, even if that single mosquito bites your dog, the chances of your dog getting HW from it are low. Not zero, but low. That said, many of my clients prefer to follow the American Heartworm Society guidelines and keep their dogs on monthly HW prevention year-round, just to be on the extra safe side.
HW prevention is very good at preventing HW disease, but not 100% effective. (Especially if, like me, every now and then you forget to give your dog their monthly dose on time.) For this reason, and also because it can be dangerous to give HW prevention to dogs if adult heartworms are already present, I recommend testing all dogs annually for HW, using an in-clinic (or in my case, in-your-home) blood test test that checks for HW, along with three of the most common tick-borne diseases—Lyme, Anaplasmosis and Ehrlichia. I’m a big fan of this test; it gives me reassurance that my patients are HW negative, and it also tells me if they’ve been exposed to any of the tick-borne diseases.
If, for any reason you, choose not to give your dogs HW prevention, please do your best to minimize their exposure to mosquitos. Try to avoid having your dog spend time outside when mosquitos are most active, such as at dusk and dawn. Unfortunately, there are no great mosquito repellants for dogs that I’ve found. If any of you have found any that are safe and effective, feel free to let me know.
That’s all for now. Wishing you and your canine companions a safe, happy and heartworm-free spring! 🐾🌷
~Dr. Kassell
PS: Cats can get HW, too, but the incidence is far lower than in dogs, and I don’t recommend HW prevention for most cats at this time. That said, if you have a cat that spends time outside, please try to avoid letting them out during high mosquito times, especially dawn and dusk. And if your cat does frolic with the mosquitos, consider using Interceptor, NexGard Combo, Revolution Plus for Cats or another parasiticide that kills HW larvae in cats.
PPS: Un-fun fact: Humans can get HW, too! Not that I’ve ever heard of anyone who ever has—it’s even rarer in humans than in cats, thank goodness.
PPPS: Many of my clients are finding ticks on their dogs year-round now, even during those most frigid February days. But spring fever is real for all of the animal kingdom—birds, bees, dogs, cats, humans, fleas and ticks. And the ticks are WILD right now! And most concerning is that we have loads of Lyme Disease and other tick-borne diseases, such as Anaplasmosis and Ehrlichia. So please keep on top of your tick prevention.
Final PS: The American Heartworm Society has lots more good info on HW: https://www.heartwormsociety.org/