Heartworm Symptoms That All Dog Owners Should Recognize

Updated on February 19, 2018
DrMark1961 profile image

Dr. Mark is a small animal veterinarian. He works mostly with dogs and exotic animals.

Recognize the symptoms of heartworm disease and protect your dog.
Recognize the symptoms of heartworm disease and protect your dog. | Source

When dogs are first bitten by mosquitoes infected with heartworm microfilaria (Dirofilaria immitis), they show no symptoms. That stage lasts for six months! By the time your dog is showing symptoms, things have been going on for a long time, so recognize these symptoms as soon as they start.

What are the symptoms in the different stages (classes) of heartworm disease?

  • Class 1: Your dog may not even have symptoms at this stage. He might have mild symptoms like an occasional cough.
  • Class 2: Things are getting a little worse. His symptoms are usually still mild, like an occasional cough, and he might be more tired than you would expect after very light exercise, like just running around the yard chasing a ball.
  • Class 3: At this point, your dog will start losing weight, be tired most of the time, and will cough more often. He will probably faint occasionally and show signs of congestive heart failure, like ascites (fluid on the abdomen).
  • Class 4: The heartworms are causing a blockage at this stage so the symptoms are severe. He will experience constant coughing, exhaustion, and weight loss because he will find it uncomfortable to eat. When your dog is at this stage, known as the caval syndrome, it might be too late to save him. You have no excuse to let a dog reach Class 4.

If your dog has any symptoms of heartworm, she should be taken to the vet for testing.
If your dog has any symptoms of heartworm, she should be taken to the vet for testing. | Source

What To Do Next

If you do recognize the symptoms of heartworm disease, the first thing to do is take your dog in to the vet for a heartworm test. Find out what to do next.

Her lungs and heart will be examined during her exam.
Her lungs and heart will be examined during her exam. | Source

Alternatives for a Heartworm Positive Dog

The first thing you need to do is take your dog in to your veterinarian and have his blood tested. If the antigen test is positive that indicates he has been infected with heartworms. He probably has at least fifteen, but maybe as many as several hundred adult worms in the heart.

If your dog is tested positive, do not start worrying; There are alternatives.

1. The first alternative, and the one suggested by most veterinarians, will be to give your dog injections of immiticide, an arsenic injection that goes into the muscles of the dogs back and causes the adult heartworms to die off. It is the quickest way to get rid of the problem and the worms cause less damage to the heart but is also expensive and can be dangerous. If you take your dog home and she runs around she can cause the dead worms to be broken off in a mass. The mass can cause a blockage in her lungs, and she can die.

2. The other alternative is to put your dog on a safe heartworm therapy. She is given ivermectin every month for several years. This does not cause the adults to die—they go on infecting your dog´s heart. It does keep them from reproducing, however, and when all the adults die your dog will be heartworm free.

This treatment is not recommended by most veterinarians since the adult worms are not killed. They will go on infecting your dog, and if she already has clinical heart disease most vets want those worms out of there as soon as possible.

3. The last alternative is to use safe herbal heartworm therapy. There is controversy on whether this therapy is effective, but if you are against giving your dog chemicals (like ivermectin) it is an alternative. Like safe heartworm therapy, this will not kill the adults.

How Long Will My Dog Live With Heartworm?

Your dog´s life expectancy after being diagnosed with heartworm is not really known. Some dogs will have a small burden and live for years. Smaller dogs can develop congestive heart failure with only a few worms in the heart and will die within a few months.

You will have to decide which of the alternative treatments to use based on the size of your dog and the degree of damage already done to your dog´s heart.

If her heartworm test is positive, you have several options.
If her heartworm test is positive, you have several options. | Source

How To Prevent Your Dog From Becoming Infected

You should have your dog on a heartworm preventative. Unfortunately some dog owners do not prevent heartworm disease because the manufacturers of heartworm preventative charge a big mark-up, and then the veterinarians that distribute this product charge another mark-up.

If you cannot afford the prices your vet charges, the alternative is to buy a large supply of ivermectin, the heartworm prevention available in Heartgard. You still need to dose your dog monthly, and the product is so cheap that I recommend you do so throughout the year. The chance of your dog getting infected in the winter is minimal, but so is the cost of the drug, and in my opinion it is not worth the risk.

You can buy a sheep formula online or purchase it from your local feed store. The doses are available in my other article on cheap heartworm prevention. If you have a Collie or other herding dog breed this may not be right for you. You can read more details about testing in the other article.

If you do not want to give your dog monthly ivermectin, there are also some holistic vets that recommend an oral herbal heartworm preventative. I do not recommend this and believe you are taking unnecessary risks with your dog´s health. If you want the various formulas you can speak to your holistic vet or look at another site.

Stray dogs are likely to become infected at an early age because they are outside all of the time, but even inside dogs can become infected.
Stray dogs are likely to become infected at an early age because they are outside all of the time, but even inside dogs can become infected. | Source

Will your dog become infected with heartworm?

If you keep your dog on heartworm preventative every month you do not need to pay for yearly testing. Some states and regions (like Georgia and the Mississippi valley), however, have reported an increase in heartworms resistant to the traditional preventatives, like ivermectin. If you live in Georgia, Alabama, or the lower Mississippi valley area, please read up on preventing resistant heartworm.

This is a preventable disease. Do something about it today.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

Questions & Answers

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    • LongTimeMother profile image

      LongTimeMother 

      3 years ago from Australia

      Thanks for your response, Mark. Local vet says it is poisoning, probably from eating a baited mouse, with no mention of heartworm. I've written more to you in the forum. Thanks for being such a helpful vet.

    • DrMark1961 profile imageAUTHOR

      Dr Mark 

      3 years ago from The Atlantic Rain Forest, Brazil

      LTM, dont you live in an arid part of Australia? You may not even have endemic HW there. Before you go in, try to catch some sputum in a plastic bag (in case the dog will not cough during the exam!). It may be some sort of lungworm, not sure what is a problem in your area.

      If the dog is old it may be a tumor. Hope everything goes all right.

    • LongTimeMother profile image

      LongTimeMother 

      3 years ago from Australia

      Hi Mark, I have been minding one of my adult kid's dogs while she's working overseas ... and it is coughing (or more like loud panting) up blood. Waiting for the local vet to open. Does this sound like heartworm?

    • barbat79 profile image

      B A Tobin 

      5 years ago from Connnecticut

      Thank you for clarifying that! Yes, I hope it does help her help her dogs..but I can't impose my opinion, so informational material is just the right way to go about it. :) I will lead her to your site, but I can't make her drink.

    • DrMark1961 profile imageAUTHOR

      Dr Mark 

      5 years ago from The Atlantic Rain Forest, Brazil

      Sorry I misunderstood your post and thought you were asking about the once a month preventative. It does not have any arsenic in it, just the treatment, which is given deep in the back and is very painful. (The safe therapy is much better, in my opinion).Some people do not like to give their dog the prevention every month, as it is a chemical, but I think it is the worse of two evils! Thanks for sharing this with your acquaintance, I hope it helps.

    • barbat79 profile image

      B A Tobin 

      5 years ago from Connnecticut

      It was mainly to confirm my previous understanding of prevention..did I read correctly that arsenic is in the medicine?? That would be unusual in my mind ...poison to give once a month, but if I did read correctly, it would be the lesser of two evils in a minute dose.

      What are the properties in immiticide or the treatment? Do I have that right?

      Wow thank you for your information and response to my inquiries!

      Your article makes a reader SEE the disgusting and horrible possibilities! I voted thumbs up and useful for this and will refer to an acquaintance who does not believe in medicine for her dogs...recall I stated "acquaintance" Perhaps if she saw this she may change her mind.

    • DrMark1961 profile imageAUTHOR

      Dr Mark 

      5 years ago from The Atlantic Rain Forest, Brazil

      Yes, in almost all parts of the US monthly heartworm preventative is recommended. Some areas (like northern Montana) may be okay, but the prevention is so safe, and so cheap, that it is really a good idea about everywhere. Since you have several dogs (I don't know how much your JRTs weigh) the sheep product is probably the best for you.

      Be sure to read that article when you get a chance and leave me a note if you have any questions about it. Was your question about the heartworm prevention or another product? The other worms are really not much of a concern in an adult dog, but the heartworms are something that should be prevented.

    • barbat79 profile image

      B A Tobin 

      5 years ago from Connnecticut

      Wow Dr Mark1961, this article is a real eye-opener. You don't realize the impact of not giving your dog the once a month wormer the vet recommends even without any sign of worms until you see the pictures of a dog's heart with the worms! Ugh! and the symptoms, so sad. Thank you for your thorough article.

      By the way, is that traditional of a Vet to tell you to give a monthly wormer even for my dogs without heartworm?

    • DrMark1961 profile imageAUTHOR

      Dr Mark 

      5 years ago from The Atlantic Rain Forest, Brazil

      Thank you, Thelma, I appreciate your visit.

    • ThelmaC profile image

      Thelma Raker Coffone 

      5 years ago from Blue Ridge Mountains, USA

      Thanks for another informative article. I enjoy reading your hubs very much!

    • WillStarr profile image

      WillStarr 

      5 years ago from Phoenix, Arizona

      She's nine months.

    • DrMark1961 profile imageAUTHOR

      Dr Mark 

      5 years ago from The Atlantic Rain Forest, Brazil

      The dose for a 3 pound dog is really, really small, so if you can afford the commercial product it is a better idea.

      How old is she now? 3 pounds. Wow. That makes my Maltese look like a Giant Dog Breed.

    • WillStarr profile image

      WillStarr 

      5 years ago from Phoenix, Arizona

      My only concern is that our chihuahua is so tiny. She weighs just three pounds, so I guess we'll stick to the commercial dosage.

    • DrMark1961 profile imageAUTHOR

      Dr Mark 

      5 years ago from The Atlantic Rain Forest, Brazil

      If you have any financial worries and the Heartgard is too expensive, be sure to click on the hyperlink to the sheep formula. It is ivermectin, the same drug, but you can buy a 3 year supply for about what 6 months of Heartgard costs. The dosing rate is in the other article.

      I live on the beach (lots of mosquitoes) and have to give heartworm prevention year round so it is worth it to me, but since my dog is big I just bought a bottle of the cattle formula at my local feed store.

      Thanks for reading and commenting!

    • ellesvoice profile image

      Elizabeth Hanks 

      5 years ago from Queen Creek

      Another great article! Both of my pups are getting on Heartgard sometime next month. Things have been hard for my fiancé and I financially for a while, but like I've been telling him for months, that's no reason to neglect our dogs' health!

      Prevention is definitely the best way to go with just about any infectious disease in the pet world, whether by monthly meds, vaccinations or even feeding them higher quality food!

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