Here is a list of signs, symptoms, and transmission of canine heartworm infection

Throughout their lives, canines are exposed to many infections. Some of these infections become life-threatening if not rapidly diagnosed and treated. Heartworm infection is one such example. This article discusses heartworm infection, its signs and symptoms, and transmission in dogs.

What Is Heartworm Infection?

  • Heartworm disease or dirofilariasis is a potentially life-threatening disease caused by a blood-borne parasite. The parasite responsible for causing heartworm infection is known as Dirofilaria immitis. When fully matured, Dirofilaria immitis takes on the appearance of long hair like worms.

Adult heartworms reside in infected dogs’ hearts, pulmonary arteries, and large blood vessels. Female heartworms are about 6 to 14 inches long and 1/8 inch wide. Adult male heartworms are about half the size of females. As many as 300 heartworms can live and reproduce inside a dog. They can live up to 5 years.

Transmission Of The Parasite

  • The parasite is transmitted in canines through the bite of an infected mosquito. The parasite develops and reaches its infective stage inside the mosquito. The parasite is transferred to the dog’s blood when this infected mosquito bites the dog.

The mosquito is the intermediate host, while the dog is the final host for this parasite. Once the parasite is inside the dog’s blood, it continues to grow and develop inside the dog for the next 3 months.


  • When the parasite is fully developed, it moves bodily tissues into the heart. This migration from blood to the heart occurs about 3 to 4 months post mosquito bite. The deadly parasite begins to reproduce after 6 to 8 months.

The offspring of Dirofilaria immitis are called microfilaria. They are detected in the bloodstream during the diagnostic test. Heartworm infection cannot be transmitted from one pet to another.

Signs Of A Potential Heartworm Infection

  • The symptoms vary from mild to severe depending on the individual dog and the severity of the infection. The symptoms are outlined below.

Mild Signs Of Infection

  • The infected dog may have a mild cough. In case of a mild infection, the dog may not show any outward symptoms.

Moderate Signs Of Infection

  • The infected dog cannot run and tires quickly. The dog displays a moderate cough, has difficulty breathing, and may become exercise intolerant.

Severe Signs Of Infection

  • In case of severe infection, the dog shows signs of labored breathing. The dog may not tolerate any exercise due to difficulty in breathing. In addition, the dog begins to show signs of heart failure.

Caval Syndrome

  • canine heartworm infectionThis is the most severe stage of heartworm infection. In caval syndrome, the blood flow throughout the heart becomes obstructed because of the heavy burden of worms in the blood. This is a fatal condition; the dog suffers from extreme breathing difficulties and may collapse. Surgical removal of the worms becomes crucial; otherwise, death may occur.


  • Mild to severe heartworm infections can be treated with the help of an injectable medication. The medication is designed to kill adult heartworms residing in the canine heart. It is highly effective when combined with the product used for killing baby heartworms. The treatment is lengthy and requires multiple injections. The injections are painful and require a lot of cage rest before and after the treatment.

If your dog shows heartworm infection signs, consult a veterinarian immediately. At Autumn Trails and Veterinary Center, we provide life-threatening disease. We have the experience and technology to handle all types of healthcare needs of your pets. We are located in Charlottesville, VA. Appointments are conveniently available. Call us at 434-971-9800.