What are the signs of heartworms in dogs? This article will certainly answer that question in detail; But first let us say up front that if you have a beloved canine companion that you are responsible for, it is not wise to wait until the signs of this debilitating disease manifest in your pet.
Heartworm disease is preventable and prevention is greatly preferable to treating this dangerous mosquito-borne canine condition; Also the internal organ damage caused by these heart-dwelling parasites can be permanent.
What Is Canine Heartworm Disease?
Canine heartworm disease is a serious and potentially deadly ailment of dogs that is spread by mosquitoes. Not every mosquito is a carrier of the disease, but the mosquito is the intermediate host of Dirofilaria immitis which is the scientific name for the dog heartworm.
Dogs are the most typical host mammal for heartworm disease. Heartworms that live inside an infected dog grow into adults (both male and female worms), which mate and produce offspring, all within the dog’s body. This puts the dog’s vital organs at serious risk.
Adult heartworms are long, spaghetti-like worms that live in an infected dog’s heart and pulmonary blood vessels. These internal parasites will eventually move into the lungs if left untreated. The adult female heartworms can grow to up to 14 inches (36 cm.) in length. The mature adult male heartworm is about half the size of the female.
Heartworms are of one the most dangerous parasites found in domestic dogs but they don’t just affect our precious pets. Wild canids such as wolves, coyotes, foxes, and jackals are also potential targets for this disease since it spreads from host to host by way of the ubiquitous mosquito.
You may be wondering how one little mosquito bite can result in a dog having worms of considerable length living in such a vital organ as the heart. It’s actually a cycle which takes several months to complete.
How are Heartworms Transmitted from Dog to Dog by a Mosquito?
The whole scenario begins with a dog already infected with heartworms and a hungry mosquito. We’ll call this dog “Buddy.”
- Buddy has adult heartworms in his heart. These heartworms mate and reproduce millions of microscopic offspring. These offspring, (or ‘baby heartworms’) are called microfilariae and they circulate freely in Buddy’s bloodstream.
- The hungry mosquito lands on Buddy for a blood meal and sucks up and ingests blood containing the microfilariae.
- Inside the mosquito, the microfilariae develop into an infective larval stage. This is why the mosquito is called the intermediate host of the heartworm.
- A couple of weeks later, this same mosquito lands on a different dog for a slurpy supper of canine blood. We’ll call this dog “Sophie.” She is healthy and heartworm free, but since she is not on heartworm prevention, she won’t be for long. When the mosquito begins feeding, the infective larvae enter Sophie’s body through the mosquito bite wound.
- Once inside Sophie’s body, the larvae begin to slowly migrate to the right side of her heart. Here they make themselves at home and are able to grow and develop into sexually mature adult heartworms.
- Within approximately 6 months time, Sophie’s heart is home to mature adult heartworms. These worms begin to mate and produce millions of microfilariae which circulate throughout her bloodstream. Soon another mosquito will land on Sophie for a meal.
- The cycle continues.
What are the Signs of Heartworms in Dogs?
A dog that has recently been infected with heartworm microfilariae by a carrier mosquito will typically not show signs of the illness right away. As the disease progresses however, the dog will begin to exhibit symptoms. It can sometimes take years for clinical signs to develop but it takes at least 6 months for the heartworms to mature and grow to a substantial size. Any time after that the worms begin clogging the right chamber of the dog’s heart, feeding off his blood, and affecting the pulmonary arteries and the dog’s lung capacity.
Signs of heartworms in dogs include:
- Uncharacteristic fatigue, even after moderate exercise
- A dry cough
- Decreased stamina
- Shortness of breath
- Lethargy
- Loss of appetite
- Loss of weight
These would be some warning signs that a pet parent might observe and most of them would be more noticeable following exercise. A veterinarian would likely hear abnormal heart and lung sounds when listening to the dog’s chest with a stethoscope.
The vet would need to draw a small amount of blood from the dog to test for heartworms. If the test(s) were to come up positive for heartworm disease, there is a treatment for it. Most infected dogs can be successfully cured but the treatment is expensive and intricate, and not without some risk. As mentioned earlier, heartworm prevention started early in the dog’s life (puppy hood) is by far the best option.
Heartworm Prevention for Dogs
All FDA approved heartworm prevention medications require an O.K. and a prescription from your veterinarian. Most veterinary clinics carry a variety of heartworm preventatives but you may be able to get them cheaper online.
There are 3 common kinds of heartworm preventative medications for dogs.
1.) The first is a monthly spot-on topical medication that the pet owner applies to the animal between the shoulder blades on the skin, rather than the fur. These medications are toxic if swallowed so the idea is to put the treatment on a place that the dog cannot reach to lick. The dog should also be isolated and kept away from other pets and children for a time after application and not allowed to try to rub the medicine off on furniture, or roll around in the grass immediately after.
Many of these topical monthly heartworm preventatives also have an active ingredient to eliminate fleas and ticks, as well certain intestinal parasites.
2.) There are also oral monthly heartworm prevention medications. These are available in tablet form or chewables. If you have a finicky eater you may be better off with the tablets that are small enough to hide in a bit of cheese or peanut butter. If you have a chow hound for a pet, he’ll most likely look forward to wolfing down his monthly “treat” with no trouble at all.
Many of these oral medications also serve more than one function. Some will not only eliminate the heartworm larvae but certain intestinal parasites as well and they contain an active ingredient for flea control.
3.) Injectable heartworm preventative is effective for up to six months with one injection. A licensed veterinarian must administer the dose to your dog. He or she should explain to you any warnings, possible adverse reactions, or side effects of the drug.
In any case, the good doctor should be able to advise you as to what heartworm prevention would be best for you and your dog. Whichever medication you choose, be sure to follow all label directions and let the vet know if your pet shows any aftereffects or sign of illness. To protect your dog even further from this unwanted disease, it’s always recommended having your dog tested for heartworms annually.
And if you are considering purchasing or adopting a puppy, be sure to get him or her started on heartworm prevention at an early age to prevent future heartache and heartbreak! Thanks for visiting and learning about canine heartworm disease. Please leave any questions or comments or relevant experiences you may have in the comment section below. Thank you for visiting My Geriatric Dog!
Sue, I can’t say I’ve ever heard of this. Thanks for the education. The symptoms you describe sound similar to what I’ve heard in dogs I know. I can only wonder if they have heartworm disease. The fact that it takes so long for symptoms to appear is scary. I will definitely keep this in mind if and when I hear or see the symptoms you described and be sure to tell the owner what I read here. Keep up the good work.
Bob
Hi Bob, and thanks so much for your comments. For pet owners, awareness of certain diseases and symptoms is key in protecting their health. I’m glad you learned from the article. Thanks for your interest and input and for visiting My Geriatric Dog!
Well I am a cat owner, but I have had dogs before, so this is good information for my brother and his two dogs. They love to be outside, but the dangers of mosquitos and how that can be spread from dog to dog is a little scary for me. I am pretty sure that my brothers dogs are up dated on all there shots and heartworm medicine, but I will be informing them of the dangers of the mosquito and how it relates to heartworms. Thanks for this website, very informative and loaded with very good info.
Hi Bobby and thanks for visiting and commenting on my article. I’m glad you learned from it even if you are a cat lover (I am too) and I appreciate you spreading the word about the dangers of mosquitoes as the vectors for heartworm disease.
I’ve often wondered myself if there is anything at all good about the mosquito, since they can also be blamed for spreading malaria, West Nile virus, and dengue fever. Turns out there is. If anyone cares to read about it, here’s the link: https://www.npr.org/2016/02/19/467395225/mosquitoes-what-are-they-good-for
I’m happy that you enjoy my website Bobby and thanks for visiting My Geriatrc Dog!
I never realized that heartworms came from mosquitos. That’s interesting. It’s something that I need to consider for my dogs. We’ve used the topical ointment for fleas though, which works great.
I love your site, it’s great to see the focus and articles. And as a detailed person, the level of information is exceptional. Keep up the good information.
Thanks
Hi JB and thanks so much for your comments and compliments on my website. Yes, if you have dogs but were unaware of heartworms and how they are spread, I would definitely recommend getting your dogs tested. As the article states, prevention is much more preferable to treating this debilitating disease but you won’t be able to start heartworm preventative until you have your dogs tested.
Good luck and thanks for visiting My Geriatric Dog!
There are so many afflictions that could affect our furry loved ones. I’m really glad I now know the associated symptoms to keep an eye on Tobby. Thanks a lot for this post.
Is this FDA preventive medication having any type of side effects?
Have you used the oral medication before? Can you give me a recommendation?
Thank God none of the symptoms is present at the moment on Tobby; he’s not as active as he used to be, but he has been with us for nine years so far. In any case, I’ll definitely ask his vet about the diagnostic blood test just to make sure everything is O.K.
Hi there Juan, and thanks so much for your comments and questions. If Tobby has never been tested for heartworm disease, I do think it would be a very good idea to do so soon. You don’t mention where you live but mosquitoes are present on most all continents of the world, so if Tobby is not on preventative, there is a chance that he could have the disease.
Since your veterinarian will need to do a blood test, the good doctor is the one you should ask to recommend the right heartworm preventative for Tobby, should his blood test turn up negative. Yes, some of the medications do have side effects, especially for certain breeds. But after the vet does a thorough examination of Tobby’s health status, ask him or her to advise you as to which type of prevention would best suit your dog.
Thanks for visiting My Geriatric Dog!
Thank god that I now live in NYC, we only get mosquitoes in the summer time and I make sure that those mosquitoes won’t come near me and my Shiro, a husky. I take my Shiro to the vet and get his injections regularly so far he is as healthy as a horse. Yet again, he could have had the parasite and the symptoms don’t show up yet. I will get him a throughout check up soon for peace of mind.
Thanks!
Hello Nuttanee, thank you for your comments and input. It’s true that canine heartworm disease is less prevalent in colder areas of the world because the mosquitos are not year round; However, the incidence of the disease increases every year so it’s not safe to assume that just because you live in a northern climate that Shiro cannot contract the disease.
I definitely think that it would be a good idea to have him tested by your veterinarian if the vet doesn’t routinely do it when Shiro gets his inoculations. As you say, for peace of mind; For even greater peace of mind, you should get Shiro started on a heartworm prevention program if he tests negative for the disease.
Thank you Nuttanee, for visiting My Geriatric Dog!