There are a range of different lungworms in Ireland – the Fox Lungworm (Crenosoma vulpis), the Cat Lungworm (Aelurostrongylus abstrusus) and the Dog Lungworm (Angiostrongylus vasorum). However, it is the Dog Lungworm that is the most dangerous, and that’s the one we’ll be talking about in this blog.

Does it live in the dog’s lungs?

Actually, no – the adult worms live inside the large blood vessels leading to the lungs and in the right side of the heart. It’s other name is the French Heartworm, but don’t get it mixed up with the “true” Heartworm (Dirofilaria immitis) which is a different species (and, to confuse you even more, actually does live in France!).

Then why is it called a lungworm?

Because the eggs laid by the adults hatch out in the bloodstream, and the larvae then crawl into the airways of the lungs. These wriggling creatures in the lungs stimulate a cough, so they are coughed up, and then swallowed.

How is it spread?

Once in the intestine, the larvae don’t stop – they keep moving through until they are passed in the dog’s faeces. Once out in the environment, the larvae infect passing slugs or snails, and inside their bodies, the worms develop into their infective stage (the “L3” larval form).

If a dog eats a slug or snail (which some do!) they swallow the larvae, which then burrow into the gut wall, enter the blood, and crawl to the heart, where they grow into adults and start to breed. However, even if the dog doesn’t devour the mollusc, just licking an object (such as a food bowl or toy) which the slug or snail has crawled over, can lead to them becoming infected, because the infective larvae are secreted in the slime trail.

What does it do to a dog?

Many dogs tolerate a lungworm infestation relatively well, at least if there are only a few worms. However, the more there are and the longer they’re there for, the worse affected the dog will be.

Lung symptoms are most common, as the presence of the larvae in the lungs causes irritation and may lead to difficulty breathing.

More dangerous, though, are the worms own defence mechanisms. The presence of a foreign body in a blood vessel would normally result in a blood clot forming to immobilise it. However, the worms don’t want that to happen and so secrete a biological blood thinner, to prevent the dog’s blood from clotting around them. This severely damages the dog’s ability to clot their blood. Eventually, if untreated, the dog may deteriorate to the point where they lose weight and condition due to anaemia, or even bleed to death.

How would I know if my dog was infected?

In many cases, there are no obvious symptoms. However, possible signs include a chronic cough, difficulty breathing, pale gums (due to anaemia), bleeding from the nose, mouth, anus or genitals, or internal bleeding. In some cases, this may be life threatening; occasionally, the worms can also trigger seizures or other brain damage.

However, all these symptoms are fairly non-specific – there are hundreds of possible causes. If our vets suspect lungworm, however, we have a very fast in-house blood test that we can use to test for the presence of lungworm proteins in the blood. It takes about 10 minutes and can be done while you wait – if the result is positive, we treat the dog!

Can lungworm in dogs be prevented or treated?

Yes – the same medications are generally used for both, either killing the larvae before they reach adulthood (for prevention) or killing the adults (treatment).

The most commonly used treatment is a spot-on medication containing two drugs called moxidectin and imidacloprid that kill the worms at all stages of development. This drug combination also kills fleas, intestinal roundworms, mange mites and a range of other parasites, so it is a good broad-spectrum preventative treatment!

The other option is to use a tablet wormer that contains milbemycin oxime and praziquantel; if given monthly, this kills lungworms, roundworms and tapeworms too. The exact choice of drug will depend on your dog’s lifestyle and what other threats they are exposed to, although it is unusual to use the combination tablet to treat an infection (it’s only licensed for prevention).

Is my dog at risk?

Sadly, yes. All dogs in Ireland must be considered at risk, and we have seen a number of cases in recent years. Most infected dogs survive, but there are always some fatalities, which is why we strongly recommend regular treatment against this horrible, and lethal, parasite.

If you are worried about lungworm in your dog or would like to discuss lungworm treatment in dogs, make an appointment to see one of our vets.