What is Heartworm Disease in Dogs?

What is Heartworm Disease in Dogs?

What is it?

Heartworm is a parasitic disease that affects dogs, cats, and other animals. It is caused by a species of roundworm that is transmitted through the bite of an infected mosquito. Once inside the dog’s body, the heartworms can grow and multiply, leading to severe health problems over time.

How is it Treated?

The treatment of Heartworm in dogs typically involves a series of injections to kill the adult worms. This process can be risky, as the dead worms can cause severe inflammation and blockages in the blood vessels. After the adult worms are eliminated, additional medication may be necessary to kill any remaining immature worms in the dog’s body.

Breed Predispositions

Heartworm disease is a serious and potentially life-threatening condition that can affect any dog breed if they are bitten by an infected mosquito.


During a routine visit to the veterinarian, James was informed that it was time for his cherished Golden Retriever, Luna, to undergo her annual heartworm test. Expecting a routine, all-clear result, James was shocked when the veterinarian informed him that Luna had tested positive for heartworm disease, a potentially life-threatening condition caused by parasitic worms. In this blog post, we will explore the intricacies of heartworm disease in dogs.

Heartworms are parasitic worms that affect dogs. Only 20 percent of cats with heartworm infections have microfilaria (worms) in their blood, compared to 80 to 90 percent of infected dog owners. Mosquitoes spread these parasites and usually enter the body through the bite wound. Once inside, the larvae travel to the heart and lungs, where they mature into adult worms.

Dogs become infected when they eat mosquito larvae containing microfilariae, the immature form of the parasite. Infected mosquitoes then pass the worm onto another dog when biting. Because the parasite’s life cycle occurs within the mosquito, prevention involves eliminating breeding areas for mosquitoes.

There are two types of heartworms: adult heartworms and microfilariae. Adult heartworms grow larger than microfilariae. Microfilariae are smaller than 1mm long.

  • Adult heartworms are typically brownish-red in color, and Microfilariae appear white or yellowish. Both types of heartworms can infect dogs and cats; however, dogs are more likely to develop heartworm disease.
  • Microfilariae are transmitted via mosquito bites. Adult heartworms are transmitted from dog to dog during sexual activity. Microfilariae are immature larval heartworms that can be detected in a dog’s bloodstream. Microfilariae are spread by mosquitoes and can form the first stage of heartworm infection.

Causes of Heartworm Disease in Dogs

Heartworm disease is a parasitic infection caused by heartworms (Dirofilaria immitis) that affects domestic animals such as cats, dogs, ferrets, horses, pigs, rabbits, sheep, and cattle. Canine heartworm disease can be contracted from the bite of an infected mosquito. The life cycle of this parasite begins when a mosquito bites a dog, transferring microscopic heartworm larvae onto the dog’s skin. From there, the larvae develop for about six months until adulthood inside their canine host’s lungs and heart. As they mature, these worms reproduce and release microfilariae, another form of the parasite that infects other animals through new mosquito bites.

Unfortunately, many pet owners don’t realize that mosquitoes cause heartworm disease until their canine companions become symptomatic—treatment becomes much more difficult due to extensive damage to vital organs!

Causes of Heartworm Disease in Dogs

Though there are various preventative measures you can take to reduce your pup’s risk of heartworm disease, such as using medication specifically designed to kill existing parasites or avoiding areas where mosquitoes breed, it is essential to remember that reducing your pet’s exposure to mosquitoes is vital in preventing other vector-borne diseases as well.

What is Dirofilariasis Immitis?

Dirofilariasis immitis is the medical name for heartworm disease in dogs. This parasitic worm is spread by mosquitoes and can manifest itself inside your dog’s lungs and heart. The parasite will live inside the heart, consuming blood and eventually taking over the body if left untreated.

The primary symptom of dirofilariasis immitis is coughing and labored breathing, which is caused by many worms in the lung arteries. Other symptoms may include weight loss, a swollen abdomen often accompanied by a pot belly shape due to fluid build-up caused by cardiac worms, decreased exercise tolerance, and general lethargy or weakness.

Act quickly if you think your dog may be infected—the longer they go without treatment, the worse their prognosis can be. Your veterinarian can diagnose dirofilariasis immitis with simple tests such as an X-ray or physical examination to determine the size and number of parasites in your pet’s system. Treatment should begin immediately once diagnosed, as this disease can be fatal if left untreated.

What is Dirofilaria repens?

Dirofilaria repens is a species of roundworm that can cause heartworm disease in dogs. It’s found worldwide and is the only species to generate natural infection in dogs. Instead, it’s spread by mosquitoes, which pick up the adults from dogs during a blood meal and then transmit the parasites to other dogs through subsequent bites.

Once a dog is infected, the adults colonize the pulmonary arteries of the lungs and eventually make their way into the chambers of the heart. As they settle in these areas, they can impede blood flow, causing coughing and exercise intolerance. Over time, this can also lead to permanent damage or death if not treated aggressively and promptly. To protect your pup against Dirofilaria repens, speak with your vet about getting on a preventative regimen such as monthly heartworm medication or fending off mosquito exposure with an EPA-registered repellent!

Symptoms of Heartworm Disease in Canine

While most infected dogs never develop symptoms, others experience mild to severe illness. In addition, symptoms vary depending on the severity of the infection, and some dogs may also exhibit signs of congestive heart failure.

Dogs infected with heartworms may develop symptoms such as:

  • coughing
  • wheezing
  • difficulty breathing
  • vomiting
  • diarrhea
  • fever
  • weight loss

If these symptoms occur, your vet will test whether your dog has heartworms. Clinical signs of heartworm disease can vary but may include a persistent cough, exercise intolerance, fatigue after moderate activity, weight loss, or an enlarged abdomen. In more severe cases, dogs may experience seizures, fainting episodes, or difficulty breathing. It’s essential to consult a veterinarian if your dog displays any of these symptoms, as they could also indicate other severe health conditions. Treatment of heartworm infection requires aggressive drugs and close monitoring for potential side effects.

Diagnosis of Heartworm Disease in Dogs

Veterinarians diagnose heartworm disease in dogs through a variety of methods. The most common are physical exams, blood tests, and x-rays.

Physical Exam

If your veterinarian suspects your dog might have heartworm disease, they will perform a physical exam and order additional diagnostic testing. The vet will examine your dog’s gums and teeth, examine their eyes, ears, nose, throat, abdomen, and skin, and check for signs of coughing, sneezing, diarrhea, vomiting, lethargy, weight loss, fever, or swollen glands. Approximately 20% of dogs do not test positive even though they have heartworms because of acquired immunity to this stage of the Heartworm. Your vet may also take a sample of your dog’s feces (poop) to test for eggs. If your dog has heartworm disease, the eggs will usually appear in the stool.

Blood Test

An antigen-testing blood test can help determine if your dog has been exposed to heartworm larvae. All dogs should also have a heartworm blood test at around seven months of age and then be retested annually (according to your veterinarian’s recommendations). It looks for the presence of specific antigens that adult female heartworms can only produce. If these antigens are detected, this is confirmation that an infestation has occurred, and a more invasive procedure may be necessary.


X-rays of your dog’s chest will reveal any obstructions like fluid build-ups or the worms living around their heart or lungs. This can help vets plan the best treatment option for your dog, such as surgery or medication prescriptions. Your vet may also use ultrasounds to measure any damages caused by heartworm infestations, such as enlargements around certain heart chambers or random clots that could have developed due to parasite migration throughout the body.

Treatment of Heartworm Disease in Canine

Treatment of heartworm disease in canine

Treatment for heartworms in dogs is done to prevent or manage the disease. Treatment depends on how advanced the disease has progressed. It also considers factors such as your pet’s lifestyle, allergies, and potential side effects due to treatments for the disease.

The two primary treatment options for heartworms in dogs are prevention and elimination. Prevention is done with monthly medications administered orally or topically to reduce the risk of future infections. Eliminating Heartworm involves using a combination of drugs to kill the parasites.

Anthelmintics are medicines that kill adult heartworms. These drugs are given orally or intravenously. Some anthelmintics are effective against multiple species of heartworms. Others are specific to one type of worm. Some common anthelminthic medications used to treat heartworm disease include ivermectin, milbemycin oxime, moxidectin, selamectin, pyrantel embonate, febantel, and imidacloprid.

These drugs are typically given orally once per month, although some veterinarians recommend giving them twice monthly. Some dogs require higher doses of medication to achieve effective treatment.

Heartworm Treatment Steps 

Treating heartworm disease in a dog begins with diagnostic testing and assessing the severity of the condition. Then, a physical examination and laboratory tests, such as a complete blood count, enzyme-linked immunosorbent assay (ELISA) to test for antigens from adult worms, x-ray imaging to visualize lung changes, and chest ultrasound to detect worm movement should be performed. According to the American Heartworm Society standards of care, dogs should also be treated with quality broad-spectrum heartworm preventives that contain at least macrocyclic lactones (MLs).

Once the patient is diagnosed with heartworm disease, deworming injections can be administered every two weeks for up to six months to kill the adult worms. These injections are typically ivermectin, moxidectin, or milbemycin oxime. Additionally, supplemental treatments may include antibiotics, exercise restrictions, and anti-inflammatory medications. Heartworm treatment can be difficult and strenuous, so close monitoring of the pet’s health must occur throughout this period through regular vet visits and blood work. Prednisone may also be prescribed as part of the treatment plan in cases with severe signs or extensive damage due to inflammation caused by Larva migration.

After completion of treatment, reexamination after four months is essential. This allows veterinary professionals to confirm that all worms have been eliminated through assessment findings on physical exam patterns and antigen ELISA tests that measure adult-stage infestation density levels compared with their initial readings before r starting any therapy efforts. Reevaluation after one year is also recommended since mortality continues 6-8 months post-treatment completion when unresponsive infections rebound due to delayed medical attention in prolonged exposure circumstances before accurate diagnosis occurs.

How to Prevent Heartworm Disease

You can do several things to prevent your dog from getting heartworms.

  1. Vaccinate your dog against the canine distemper virus. This vaccine protects your dog from most diseases caused by viruses.
  2. Protect your dog from mosquitoes. Please ensure your yard has no standing water, and remove weeds and debris near your house.
  3. Clean your dog’s bedding regularly. Remove old bedding and wash bedding in hot water.
  4. Avoid feeding raw meat to your dog. Raw meat carries parasites that can infect your dog.
  5. Make sure your dog only goes outdoors with protection. For example, you can use insect repellent when going outside.
  6. Use flea and tick prevention products. Fleas and ticks carry heartworm parasites, and preventing these insects from biting your dog helps protect them from contracting heartworms.
  7. Could you talk to your vet about heartworm prevention? Heartworm prevention medicines are available for dogs.
  8. Watch for signs of illness. Please contact your veterinarian immediately if your dog develops a cough, fever, or weight loss. Contact your veterinarian immediately

Frequently Asked Questions

No, Heartworm is not a mosquito larva. The mosquito solely acts as the vector which transfers parasites from one animal to another via its bite. Therefore, the only way for heartworms to infect an animal is if they are ingested by their host directly or indirectly through the bite of an infected mosquito. This means that while a mosquito can transmit heartworms between animals, it doesn’t have any kind of larvae stage responsible for this transfer of parasites.

Mosquitoes transmit many dog diseases, including West Nile Virus, Dengue Fever, Chikungunya fever, Malaria, Yellow fever, Japanese encephalitis, etc.

Mosquito larvae in water can be dangerous for dogs if they are ingested. Mosquito larvae contain proteins and bacteria that can cause gastroenteritis, an inflammation of the gastrointestinal system, in dogs and other animals. Eating large amounts of these proteins and bacteria can result in electrolyte imbalances and dehydration, leading to severe vomiting and diarrhea.

Additionally, consuming contaminated water can increase a dog’s risk of contracting diseases such as heartworms, life-threatening conditions caused by larval worms that invade the heart muscle.

  1. Ensure the water bowl is in a sunlit or well-ventilated area. This will help keep mosquitoes less likely to linger or breed near the bowl.
  2. Regularly change or top off the water in the dog bowl with fresh, clean water twice a day (morning and night). Keeping a new supply of clean water daily eliminates many mosquito eggs and larvae that might otherwise thrive in stagnant pools of standing water.
  3. Using plant-based products such as citronella oil to line the inside of the bowl can also help repel mosquitos away.
  4. If you live in an area with high populations of mosquito species, try covering up your pet’s outdoor bowls at night so mosquitos can’t get into them. This will be especially necessary during peak mating seasons when female insects are particularly voracious for blood meals from humans and animals.

By taking these proactive measures against pesky insects, you can enjoy peace of mind knowing that your pup always has access to clean drinking water without unwanted mosquito visitors!

The average lifespan of a dog infected with heartworms is approximately three years. The disease causes severe damage to the heart muscle, which results in congestive heart failure. Dogs who develop this condition usually die from complications associated with their weakened hearts. However, some dogs live longer than expected because they do not show symptoms until the later stages of infection.

Yes! A dog can live with heartworms if they receive proper treatment. The worm lives in the blood vessels of dogs and cats, and it causes inflammation and blockage of the arteries, leading to decreased blood flow to the organs and tissues of the body. If left untreated, this condition can cause death.

Dogs do not necessarily poop worms. Therefore, the dog’s feces could contain worm eggs passed through the stool when the dog defecates. If these eggs hatch into larvae, the dog might become infected with heartworm disease. However, this is very unlikely because most dogs need to pass more worms to infect another animal.

Heartworms look like white worms in your dog’s stool and are parasites inside your dog’s blood vessels. The worm itself doesn’t cause any problems, but if you don’t treat them, they can grow up to 7 inches long!

The treatment of heartworm disease costs approximately $1,000 per year. Today’s most common treatments include monthly injections of ivermectin (IVM) and diethylcarbamazine (DEC). In some cases, DEC alone is effective at killing adult worms. However, if you’re treating dogs who live outdoors, there’s no guarantee they won’t pick up another infection from mosquitoes. On the other hand, if the other hand, if your dog is indoors only, then DEC should work just fine.

Yes, you can! There are many ways to test your dog for Heartworm Disease. The most common way is to use a fecal test kit. You can purchase these kits online or through your vet. Both methods require a trip to the veterinarian. If you decide to do this yourself, follow all instructions carefully. Also, if you suspect your dog has heartworm disease, contact your vet immediately so they can perform a blood test.

Treating your pet’s heartworm infection at home is not recommended due to the risk of complications. Instead, veterinarian-prescribed medications are the best way to treat a heartworm infection. These include specially formulated anti-parasitic medicines and additional support treatments such as antibiotics and steroids. Your veterinarian will provide specific instructions for administering these medications depending on your pet’s condition.

Vaccinating young animals for Heartworm begins at six weeks and should continue every three months until the animal is 12-18 months old. The American Heartworm Society recommends year-round prevention of heartworm disease with environmental management and preventive medications.

This includes regular preventative care, such as controlling mosquitos in and around your home and giving your pup monthly preventative medications designed to target heartworms. Additionally, they recommend yearly blood tests to check for adult heartworms and microfilariae presence.

The answer is it depends. While some over-the-counter (OTC) options exist, many heartworm preventives have active ingredients that require a prescription from your veterinarian. Additionally, prescription-only products often offer more excellent protection against parasites than OTC versions.

Regardless of what type of heartworm prevention product, a vet visit is always recommended as part of your pet’s overall preventive care program. During the appointment, the doctor will evaluate your pet’s health and lifestyle to determine which product best meets their needs.

Your vet may recommend a particular type of medication depending on how frequently it needs to be taken or if other pets in contact with yours use a different preventive treatment. It’s also essential for your vet to assess the risk posed by the environment in your area and make sure that the appropriate dosage of active ingredients is chosen before making any pharmaceutical recommendation.

Studies have shown that some types of heartworm medication are more effective in dogs younger than eight, while others are more effective in older dogs. However, any treatment plan’s effectiveness depends on several factors, including your dog’s weight and health condition.

Dogs are infected with heartworms when an infected mosquito bites them. These mosquitoes carry immature larvae that enter the dog’s body after biting and grow into adult worms inside its heart and lungs. As the adult worms mature, they produce more larvae which can be passed along when another mosquito bites that dog. Heartworm disease can spread quickly since many mosquitoes can feed on an infected dog in one day and spread those larvae to other animals or even humans who come in contact with them.

Heartworm disease can be transmitted from one pet to another by contact with the blood or feces of an infected animal. Heartworm disease can also be transmitted through the bite of an infected mosquito.

There is no vaccine available for heartworm disease. However, preventive measures can be taken to reduce the risk of contracting the infection, including using an insect repellent and checking your dog’s blood work regularly for signs of heartworm disease.

A dog can die from heartworm disease if the disease is severe and untreated. The most common cause of death in dogs with heartworm infection is a blockage or narrowing of the arteries that supply blood to the heart muscle, leading to cardiac arrest.

Heartworm testing in dogs is an essential part of preventive care. It involves testing for the presence of heartworm disease-causing parasites, also known as Dirofilaria immitis. A positive result indicates that the dog has been infected and must receive treatment to prevent serious health problems.

Testing for heartworms in dogs is vital because it allows veterinarians to diagnose them early and provide appropriate treatment. Left untreated, heartworms can cause various cardiovascular issues, including painful inflammation and severe blockages in the veins and arteries leading to the vital organs. Early detection makes all the difference in treating and preventing further damage caused by this disease.

The most common heartworm test performed on dogs involves taking a blood sample from your pup and having it examined under a microscope or sent away for further study at a lab to look for evidence of infection. The results are usually available within a few days. If your dog tests positive, further diagnostics will be needed to determine if any treatments are necessary.

The life cycle of Heartworm in dogs can be complex and long-lasting. First, a type of roundworm causes it, Dirofilaria immitis, transmitted through an infected mosquito’s bite. The larvae migrate through the dog’s body and eventually reach the right side of the heart and lungs, maturing into adult heartworms over six to seven months.

Once established in the animal’s pulmonary arteries, it takes about five months for these worms to reach adulthood and start reproducing within the host dog; hence, signs of heartworm infection only usually appear at least six months since the initial infection occurred. During this time, adult worms mate and produce offspring in large quantities – sometimes tens of thousands or more – which are then carried away in thickened clots of infected dog’s blood or otherwise released back into the atmosphere via coughing up drops of respiratory fluid contaminated with infective organisms.

Disclaimer: The information provided on this veterinary website is intended for general educational purposes only and should not be considered as a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a licensed veterinarian for any concerns or questions regarding the health and well-being of your pet. This website does not claim to cover every possible situation or provide exhaustive knowledge on the subjects presented. The owners and contributors of this website are not responsible for any harm or loss that may result from the use or misuse of the information provided herein.

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