Angiostrongylus vasorum – French Heartworm

A Deadly Parasite of Dogs in Europe, South America, and Canada

Jun 17, 2009

The roundworm Angiostrongylus vasorum infects members of the dog family in isolated places around the world. Dogs suffer chronic illness and sometimes death.

First discovered in France, A. vasorum may have spread from there to other places with infected foxes, dogs, slugs, or snails. Today it occurs in many European countries, including the United Kingdom, Brazil, Columbia, and Newfoundland, Canada. Domestic dogs acquire the parasite by eating a slug or snail.

Life Cycle of Angiostrongylus vasorum

The life cycle of A. vasorum is very similar to that of the closely related A. cantonensis, a parasite of rats and, sometimes, people. Angiostrongylus vasorum requires two hosts: an intermediate slug or snail host, where larvae mature to the stage that is infective for dogs; and a definitive canine host, in which adult female and male worms live and reproduce:

A dog or other canine is infected when it eats a slug or snail that hosts the larvae. Grass that infected slugs and snails have crawled on, and water that they have been in contact with are other possible sources of infective larvae.
Larvae that reach the intestine burrow through the intestinal wall and begin to mature to adult worms in the lymph nodes.
Immature adults travel to the liver in the blood stream and from there to the heart, where they establish themselves in the pulmonary artery – the artery that carries blood from the heart to the lungs. They arrive in the heart about ten days after being swallowed.
Male and female adult worms mate and eggs are released into the blood to be carried to the lungs.
Eggs hatch in the lungs and larvae break through into the air spaces.
The dog coughs, bringing larvae up from the lungs, then swallows them.
Larvae pass out of the dog’s intestine in droppings, One gram of dog droppings can contain hundreds of thousands of larvae.
Slugs and snails that come to feed on the dog droppings become infected, completing the life cycle.

Watch an animated video of the life cycle of A. vasorum.

Symptoms of Angiostrongylosis (French Heartworm infection)

Infection with A. vasorum may cause no symptoms, but some cases end with death. The first symptoms appear in one month to fifteen weeks. The most common symptoms include:

Labored breathing
Chronic cough
Gagging
Weight loss
Intolerance to exercise
Loss of appetite

Chronic (long term) or more serious infection may cause:

Damage to both blood vessels and lung tissue, possibly leading to pneumonia, bleeding into the lungs, and congestive heart failure.
Prolonged and abnormal blood clotting time.
Damage due to worms and/or larvae being carried to other parts of the body in the blood.
Sudden death.

Prevent Angiostrongylosis

Contact with the French heartworm is difficult to prevent with dogs that run free in areas where the parasite is found. Dogs should be prevented from eating slugs and snails if possible. Preventative antiparasitic drugs may protect them from infection if given regularly.

Routine stool examinations for larvae may detect an infestation that’s not causing obvious symptoms; however, a series of stool specimens may be necessary because shedding is sporadic and a single specimen might not yield larvae.

Other testing is available for dogs that are ill and angiostrongylosis is suspected.

Sources:

“Angiostrongylus vasorum or ‘French Heartworm.’” The Fenton Veterinary Practice.

"Canine Angiostrongylosis." Conboy, G. A. In: Bowman D. D. Ed. Companion and Exotic Animal Parasitology. International Veterinary Information Service (ivis.org). 2000.

“ ‘French Heartworm’ Infection of Dogs & Foxes in Newfoundland. Whitney, Hugh. Wildlife Diseases Fact Sheet: Newfoundland and Labrador Agriculture. 2004.

The copyright of the article Angiostrongylus vasorum – French Heartworm in Dogs is owned by Rosemary Drisdelle. Permission to republish Angiostrongylus vasorum – French Heartworm in print or online must be granted by the author in writing.