What is it?
• Heartworms are parasites that live in your animal’s lungs.
• They primarily infest the lungs of dogs and wild canines, however cats are also susceptible to this condition.
• The changes that result from these parasites are different in cats than in dogs.

What causes it?
• Heartworms molt in mosquitos and are spread between animals as such.
• The heartworms then molt in the pet, and spread to the lungs where they develop into adults.
• Some of the parasites will die and irritate the lungs about 2-5 months after the pet is infected.
• Adult heartworms release substances that irritate the lungs and possibly other organs.
• In cats, heartworm disease is only a respiratory problem.
• Symptoms include coughing, heavy breathing, weight loss, sporadic vomiting, and lethargy.
• Sudden death may result from heartworms dying in the lungs and blocking major air pathways.

What tests are needed?
• Chest x-rays, routine lab tests, and testing for heartworm antigens and antibodies are typical for diagnosis.
• Sometimes the diagnosis of heartworm disease can be difficult in cats (false negatives or positives), heart ultrasounds (echocardiogram) and a radiologic contrast study of the lungs may be necessary.

How is it treated?
• Treatment is tricky, because if too many of the heartworms die at once, it could potentially kill the pet.
• Surgical removal of heartworms has proven only slightly successful, so often the recommendation is to treat the pet’s symptoms and allow 1-3 years for the heartworms to die on their own.
• Steroids may be prescribed to reduce lung irritation and vomiting. Bronchodilators have proven effective in relieving respiratory signs

What follow up care is needed?
• Periodic monitoring of the pet is necessary to evaluate any changes in their condition.
• Until the problem resolves, regular chest x-rays may be recommended to track progress once the pet has stabilized.
• Few pets continue to have chronic respiratory disease.


What is it?
• Heartworms are parasites that reside in the lungs of dogs and wild canines, and occasionally cats.
• They live in the pulmonary arteries, causing elevated pressure and thus strain on the right side of the heart.
• Eventually this may cause the right side of the heart to fail.
• The changes that result from these parasites are different in dogs than in cats .

What causes it?
• Heartworms are spread by mosquitos.
• They are passed on to dogs and cats in their infected form.
• Adult heartworms produce larvae which spread to different areas of the body.
• Heartworms take about 6 months to mature in the dog’s lungs.
• They produce a substance that irritates the lungs, and the presence of these parasites causes the lining of the pulmonary arteries to become thickened and stiff.
• If heartworms exist in the vena cava (large vein that carries blood back to the heart) it is called caval syndrome, in which a large mass of heartworms alters blood flow and damages red blood cells.
• Caval syndrome is very time sensitive, and if it goes untreated for too long can lead to death.
• Spreading of the larvae can cause irritation in other organs such as the kidneys and can lead to hypertensions in the lungs.
• Many dogs show no signs, but the disease can be detected with routine heartworm blood tests.
• Symptoms can include; lethargy, heavy breathing, coughing, and decreased activity.

What tests are needed?
• A Knott’s test will look for the presence of larvae in the dog’s blood.
• A heartworm blood test will determine the amount of heartworm antibodies and antigens.
• Chest x-rays may be done to look for heart and lung changes.
• A heart ultrasound (echocardiogram) may be performed to rule out other causes of heart trouble.

How is it treated?
• If heart failure, kidney or liver disease is present, the pet must be treated for that first to avoid problems with heartworm medication.
• Adulticide drugs will kill the heartworms, and are administered in one of two ways depending on the severity of the dog’s condition.
• Once the issue has been resolved, the dog will be treated with heartworm-preventative drugs.
• Any shock resulting from caval syndrome is treated aggressively with intravenous fluids and supportive care.
• Once the dog is stable, they will undergo surgery to remove the heartworms.

What follow up care is needed?
• When the adult heartworms die, they break up and can get lodged in smaller pulmonary arteries.
• Typically, the dead heartworms cause no significant problems, but sudden death may occur if a major artery gets blocked.
• Four to six months after treatment, a blood test should be performed to ensure all the heartworms have died.
• Preventative therapy should be given year-round. 

• Asymptomatic dogs have a very good prognosis.
• Dogs with right heart failure have a poor prognosis because significant lung changes may not reverse after treatment, but may improve with therapy.