What Are the Symptoms of Late-Stage Heartworm Disease in Dogs?

Symptoms of late stage heartworm in dogs
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It is our responsibility as responsible pet owners to keep our beloved pets safe. Heartworm disease is one of the most pernicious threats hiding in the shadows. While prevention is essential, it is also critical to be aware of the symptoms of late-stage heartworm disease in dogs. In this blog post, we will discuss the signs and symptoms that may suggest late-stage heartworm disease in dogs. By recognizing these symptoms, you can seek prompt veterinarian care and possibly save the life of your cherished friend.

Understanding Heartworm Disease

Heartworm disease is a serious and potentially fatal condition caused by the parasitic worm Dirofilaria immitis. It is spread by the bite of an infected mosquito. The larvae move through the circulation after being bitten, finally settling in the heart and lungs, causing severe damage. A heartworm infection may not display noticeable symptoms at first, making it difficult to identify. Regular heartworm testing and treatment are required to keep the disease from advancing to its late stages.

The Value of Early Detection

When it comes to heartworm disease, early detection is critical. In the early stages, dogs may show no symptoms or have mild symptoms such as a persistent cough or decreased appetite. This is why it is critical to have annual heartworm testing and preventive treatments. Early detection of heartworm infection provides for more effective therapy and a better likelihood of success.

Symptoms of Late-stage Heartworm in Dogs

Unfortunately, if left untreated, heartworm disease advances and symptoms worsen. Significant damage to the heart, lungs, and other organs distinguishes the late stage of heartworm disease. The dog’s overall health and quality of life are seriously harmed at this time. Recognizing late-stage heartworm disease symptoms in dogs is critical for quick care. Here are the symptoms of the late stage of heartworm disease in dogs:

#1. Respiratory Distress

Heartworms restrict blood flow via the heart and lungs as they multiply and expand, causing respiratory difficulty. Dogs with heartworm disease may cough violently, particularly after activity or when they are excited. Wheezing or gagging may accompany a persistent cough. Dogs may also exhibit breathing difficulties, fast or shallow breathing, and exercise intolerance.

#2. Weakness and Fatigue

Heartworm disease puts a substantial strain on a dog’s circulatory system, resulting in decreased oxygen flow to tissues and organs. Dogs with late heartworm disease may experience significant fatigue and weakness as one of its symptoms. They may feel apprehensive about engaging in physical exercise, become lethargic, and lose interest in their environment. Even simple actions like walking or climbing stairs can be difficult for them.

#3. Appetite Loss and Weight Loss

As heartworm disease advances, dogs may lose weight and lose their appetite. The parasites affect the digestive system’s natural functioning and impede the dog’s capacity to absorb nutrients appropriately. Dogs may lose muscular mass, appear gaunt, and refuse their usual meals as a result. The combination of weight loss and reduced appetite is a concerning sign in the late stages of heartworm disease.

#4. Swollen Abdomen and Fluid Retention

Dogs with severe heartworm disease may have a large or bloated belly. A fluid buildup in the abdominal cavity is what causes ascites. Heartworms’ impeded blood flow can create increased pressure within the blood vessels, leading to fluid leakage into the abdomen. Weight gain, discomfort, and trouble lying down may accompany an enlarged abdomen.

#5. Collapse and Fainting

Late-stage heartworm disease can cause serious cardiac damage and impair the heart’s capacity to pump blood adequately. Syncope is a condition that can cause fainting or collapse in dogs. These crises occur when the brain does not receive adequate blood and oxygen as a result of a weakened cardiovascular system. Fainting and collapsing are both concerning symptoms of late-stage heartworm disease in dogs that necessitate prompt veterinarian attention.

#6. Pale Gums and Jaundice

The presence of heartworms in blood vessels can impair normal blood circulation and oxygenation. As a result, dogs with advanced heartworm disease may have pale gums, indicating anemia and limited oxygen-carrying capacity. Additionally, heartworm disease’s liver damage can cause jaundice, which is characterized by yellowing of the skin, gums, and eyes. Pale gums and jaundice are early warning signs and symptoms of late-stage heartworm disease in dogs.

#7. Neurological Symptoms

Late-stage heartworm illness can cause neurological problems in certain cases. Heartworms in the blood vessels can cause obstructions in the circulatory system, resulting in decreased blood supply to the brain. Seizures, disorientation, difficulty coordinating movements, and even paralysis can occur in extreme cases. Neurological symptoms are a dangerous indicator of late-stage heartworm disease in dogs that necessitates rapid medical intervention.

#8. Irregular Heartbeats and Heart Murmurs

Heartworms impair the proper functioning of the cardiovascular system by invading the heart and blood vessels. Heart murmurs, which are aberrant sounds heard during a veterinary examination, may be present in dogs in the late stages of heartworm illness. The presence of heartworms causes turbulent blood flow, which causes these murmurs. Arrhythmias, or irregular heartbeats, can also occur, limiting the heart’s capacity to pump blood adequately.

#9. Hemoptysis (Blood Coughing)

Hemoptysis, or the coughing up of blood, can occur in dogs with advanced heartworm illness. Heartworm damage in the lungs can cause blood vessel rupture, resulting in the presence of blood in the respiratory system. Hemoptysis is a severe symptom that necessitates emergency veterinarian care.

#10. Distended Jugular Veins

Heartworms in the heart can create increased pressure in the circulatory system, resulting in dilated jugular veins. These veins, which are located in the neck, can become engorged and visible. Distended jugular veins are an indication of late-stage heartworm illness that indicates substantial cardiovascular damage.

#11. Secondary Organ Damage

Heartworm disease not only affects the heart and lungs, but it can also harm other organs. Heartworms can cause liver and kidney damage by impairing blood flow and causing inflammation. Increased thirst and urine, decreased appetite, weight loss, and abdominal pain are symptoms of late-stage heartworm disease in dogs. These symptoms reflect subsequent organ involvement and the severity of the disease.

Diagnostic Tests for Late-Stage Heartworm Disease

Veterinarians use a mix of tests to confirm the presence of heartworms and determine the extent of organ damage in dogs with late-stage heartworm disease. These diagnostic tests are critical in selecting the best treatment approach for the sick dog. Let’s take a look at some of the most frequent diagnostic tests for late-stage heartworm disease:

#1. Blood Tests:

Blood testing is an important diagnostic tool for heartworm illness. They aid in the detection of adult heartworms or antigens in the dog’s bloodstream. For this purpose, ELISA (enzyme-linked immunosorbent assay) assays are routinely used. These tests can identify specific proteins produced by adult female heartworms.

#2. Microscopic Examination:

Another diagnostic procedure is a microscopic study of a dog’s blood sample, known as a microfilaria test. This test is designed to detect the presence of microfilariae, the larval stage of heartworms that circulate in the bloodstream.

#3. Chest X-Rays:

Chest X-rays, commonly known as radiographs, are necessary for determining the extent of heartworm damage in the lungs and heart. X-rays can detect changes in the lung pattern, heart enlargement, and symptoms of pulmonary hypertension.

#4. Ultrasound:

Ultrasound imaging is a non-invasive imaging technique that enables veterinarians to see the heart and blood arteries in real-time. It is especially beneficial for detecting heartworms and determining the level of damage.

#5. Electrocardiography (ECG):

Electrocardiography is a diagnostic procedure that assesses the electrical activity of the heart. ECG can reveal irregularities in the heart’s rhythm and electrical conduction in cases of late-stage heartworm illness.

#6. Complete Blood Count (CBC) and Chemistry Panel:

A complete blood count and chemistry panel are normal blood tests that can reveal more about the dog’s overall health and the impact of heartworm illness on various organs.

Treatment Options for Late-Stage Heartworm Disease

Treating late-stage heartworm disease is more difficult and dangerous than treating the disease in its early stages. A combination of medications to destroy adult heartworms and supportive care to control symptoms and problems may be used in the treatment procedure. The treatment approach will be influenced by the dog’s overall health, the severity of the condition, and the presence of secondary organ damage. In some circumstances, surgical eradication of heartworms is required. However, prevention is still the best approach because treatment for late-stage heartworm disease can be costly, time-consuming, and unsuccessful in certain cases.

Is it serious?

Yes, late-stage heartworm disease in dogs is a serious condition with substantial health consequences. Heartworm illness advances through multiple phases when left untreated or undiscovered, with the late stage being the most progressed and severe.

Late-stage heartworm disease can harm the heart, lungs, and other organs severely. Adult heartworms can cause heart failure, pulmonary hypertension (high blood pressure in the lungs), and respiratory distress if they are present in the heart and blood vessels.

What should I do if my dog has late-stage heartworm disease?

If you fear your dog has late-stage heartworm disease, seek emergency veterinary attention. Late-stage heartworm illness is a dangerous condition that necessitates immediate treatment. The following are the steps you should take:

  • Contact your veterinarian
  • Veterinary examination and diagnostic tests
  • Treatment options
  • Follow the veterinarian’s recommendations
  • Monitor your dog’s condition
  • Preventive measures

How do you know if heartworms are getting worse?

Heartworm Warning Symptoms:

  • A mild, dry cough that worsens after exercise or play.
  • Breathing too quickly or experiencing respiratory trouble.
  • Lethargic demeanor.
  • Unexplained weight loss and appetite loss.
  • A swollen chest.
  • Collapse

What is Stage 4 of heartworms in dogs?

Heartworms have severely damaged the animal’s heart, lungs, liver, and kidneys in Stage 4. Caval syndrome is likely at this point. Caval syndrome occurs when a significant number of worms obstruct blood flow to the heart, resulting in a sudden life-threatening issue that requires immediate surgical intervention.

Can Stage 3 heartworm be treated?

If the dog already has caval syndrome, the mature worms must be removed surgically as soon as possible. There is a procedure that involves only two melarsomine injections rather than three; however, it is not advised as the first line of treatment.

How long can a dog live with stage 4 heartworms?

In this condition, a dog’s lifespan is most certainly restricted to a few weeks or months. Depending on the severity of your dog’s infection, your veterinarian will advise you on the best course of treatment. After contracting heartworms, dogs can survive for at least six to seven months.


Late-stage heartworm disease is a serious threat to dogs’ essential organs and overall health. Recognizing the signs is critical for early intervention and enhancing treatment outcomes. If you detect any of the signs mentioned in this blog post, you must seek immediate veterinarian assistance. When it comes to heartworm illness, remember that prevention is always preferable to cure. Regular heartworm testing, administering preventive drugs as directed by your veterinarian, and keeping an eye out for any potential signs of infection are critical to protecting your dog’s health.

Understanding the symptoms of late-stage heartworm disease in dogs allows you to be proactive in obtaining medical care, potentially sparing their lives. Together, we can tackle this quiet threat and protect our cherished canine companions. Let us all work together to avoid heartworm disease and give our four-legged pals a long, healthy, and heartworm-free existence.

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