Quick Answer
Heartworm disease can cause a dog to vomit, but vomiting alone is rarely a sign of heartworms. More common signs of heartworm disease include coughing, lethargy, weight loss, and difficulty breathing. However, in severe cases, heartworms can cause damage to a dog’s lungs, heart, liver, and digestive tract, which may lead to vomiting. If a dog is vomiting and heartworm disease is suspected, it’s important to have the dog tested and treated by a veterinarian as soon as possible.
What are heartworms and how do dogs get them?
Heartworms are parasitic roundworms called Dirofilaria immitis that live in a dog’s heart and pulmonary arteries. Mosquitoes transmit heartworm larvae to dogs through bites. Inside a dog, the larvae develop into adult worms that can grow over a foot long and cause severe disease.
It takes about 6-7 months for larvae transmitted by a mosquito to develop into adult heartworms. During this time, the dog will not show any signs of illness. Once the worms reach maturity, they begin to reproduce and increase in number in the dog’s heart. This is when dogs may start showing symptoms.
How do heartworms cause vomiting?
In severe cases of heartworm disease, the worms can disrupt blood flow and cause inflammation and damage to a dog’s organs, including the:
- Lungs – Worms and inflammation block blood flow causing pulmonary hypertension. This puts stress on the right side of the heart.
- Heart – The heart has to work harder to pump blood through blocked arteries. Heart enlargement, heart failure, and circulatory shock can occur.
- Liver – Blockages and inflammation of the blood vessels impair liver function.
- Digestive tract – Malfunction of digestive organs leads to gastrointestinal issues.
The impaired functioning of these organs, especially the gastrointestinal tract, can lead to nausea and vomiting in some dogs with severe heartworm disease. The breakdown of organs over time due to restricted blood flow can also result in internal bleeding, which a dog may vomit up.
So while vomiting can be a symptom, it is not very common early in the disease. More significant and more common signs of heartworms include coughing, difficulty breathing, exercise intolerance, weight loss, and fatigue. As the disease progresses and organs begin failing, vomiting becomes more likely.
Can vomiting be the only sign of heartworms?
Vomiting alone is rarely the only clinical sign of heartworm infection. More commonly, the worms themselves and the damage they cause lead to pulmonary and cardiovascular symptoms first. However, in rare cases, a mass of heartworms can partially block blood flow to the liver and stomach, resulting in vomiting as the only symptom initially.
If vomiting is your dog’s only symptom, heartworms likely would not be at the top of a veterinarian’s list of initial diagnostic suspects. There are many more common causes of vomiting in dogs, including:
- Dietary indiscretion or food allergies
- Intestinal parasites
- Viral infections
- Pancreatitis
- Inflammatory bowel disease
- Abdominal obstruction
- Motion sickness
However, if heartworm disease is suspected, doing a blood test to check for the presence of heartworms is recommended.
Other signs and symptoms of heartworm disease
While vomiting may occasionally occur, the most common signs and symptoms of heartworm disease are related to the lungs, heart, and circulatory system. These include:
- Coughing – Caused by inflammation in the lungs and airways.
- Exercise intolerance – Difficulty breathing when active due to reduced oxygen; may cough or tire easily.
- Rapid breathing or panting – The body tries to compensate for impaired oxygen circulation.
- Lethargy and fatigue – Insufficient oxygen and circulatory impairment reduce energy.
- Weight loss – Appetite loss from nausea, vomiting, and reduced organ function.
- Congestive heart failure – Fluid buildup in lungs that causes coughing and difficulty breathing.
- Collapse or sudden death – In seriously affected dogs, worms can abruptly block blood flow.
Other less common signs that may develop over time include fluid accumulation in the abdomen or limbs, heart murmur, nosebleeds, and blood in the urine or feces.
Conclusion
While heartworm disease can sometimes cause vomiting in dogs, it is rarely the only symptom. More characteristic signs of heartworms are related to the lungs and heart, including coughing, exercise intolerance, fatigue, and weight loss. Vomiting is most likely to occur in advanced cases when the worms have already caused significant damage to organs like the liver and digestive tract. So vomiting alone is not strongly indicative of a heartworm infection. A heartworm test is needed to diagnose the disease, not just treatment of vomiting. With early detection and prompt treatment, many dogs recover well and avoid the most severe, life-threatening effects of heartworms.