Another emerging infectious disease issue for the Ontario dog population appears to be lungworms. As you’d probably guess, lungworms are parasites that live in (or near) the lungs. A variety of different types of lungworms exist, but most concerns around here relate to two.
In Canada, both the fox lungworm (Crenosoma vulpis) and the French heartworm (Angiostrongylus vasorum) have been found in the Atlantic provinces for a while. However, this seems to be a new situation in Ontario, with a small but increasing number of reports of Crenosoma vulpis in dogs that have not been outside of the province. I haven’t heard about any Angiostrongylus cases in the province yet (and hope it stays that way – see why below).
Foxes are the natural reservoir of both of these lungworms. Like many parasites, lungworms have a rather bizarre life cycle. Adult Crenosoma worms live in the lungs and lay eggs. The eggs are then coughed up, swallowed and passed in feces. After being pooped out, the lungworm larvae infect snails. Dogs get infected by eating infected snails, as the larvae move from the intestinal tract and through the body to the lungs, where they mature and the whole cycle starts again.
It’s similar with Angiostrongylus, although the larvae can also infect frogs (when they feed on infected snails), and dogs can be infected by eating infected snails or frogs. After a dog swallows the larvae, they migrate into the bloodstream and make their way to the heart and arteries of the lung.
Typical signs of Crenosoma infection in dogs include a chronic or intermittent cough that’s not responsive to common treatments directed at bacterial or inflammatory diseases. Fortunately, Crenosoma infections are usually treatable with anti-parasitics, with a good outcome.
Angiostrongylus vasorum is a bigger concern, because infection can result in more severe lung disease, blood clots, heart failure and a few other bad things. Adult worms can also head to other parts of the body and cause more problems (but fortunately that’s pretty uncommon).
If one or both of these parasites are established in the fox population in the province, lungworm is not going away. Understanding where it is present will be important for prompt diagnosis and to determine the best preventive medicine programs. As it stands now, lungworms have to be considered as a potential cause of chronic cough in dogs in Ontario. It’s still probably rare but is potentially treatable and something of which to be aware.