As the name suggests, Lungworm is a parasitic roundworm (or nematode) that lives in the lungs of infected dogs. Its technical name is Angiostrongylus vasorum, and is not to be mixed up with the Heartworm (Dirofilaria immitis), despite the fact that some older books (and vets!) still refer to Lungworm as the French Heartworm (an old-fashioned and rather confusing name!).
How does this parasite live its life?
The life cycle of the Lungworm is sometimes called “indirect”; this is because (unlike most worms), an intermediate host is required. So, we’ll start with the larvae (baby worms) being passed out of your dog in their faeces. Once outside, they burrow through the skin of slugs and snails, infecting them, and continue to develop inside.
If the dog eats a slug (some dogs seem to love the taste!), or even licks the slime trail (over a bowl or a toy that’s been left outside), the more mature infective larvae burrow their way out of the dog’s gut and into the bloodstream. Once there, they make their way to the pulmonary artery (running out of the heart and into the lungs).
Here they grow up into adults, mate and lay eggs. The eggs hatch almost immediately, and the larvae make their way into the airways of the lungs, where they are coughed up, swallowed, and then passed in the faeces, to start all over again.
What dogs are at risk?
The distribution of Lungworm across the UK is very patchy; it is traditionally thought that there are higher concentrations in the South West and Wales. We have seen a few cases at Animal House Vets, so albeit at a low level for the practice, it’s definitely around Bristol. However, some towns and villages even in high-risk areas very rarely see cases, and others in supposedly low-risk areas (like the South East) seem to see a lot, so there’s no way to know for certain if your dog is at risk of exposure or not.
If there aren’t any dogs around, the parasites can also reproduce in foxes, so areas with a high fox population (particularly towns and cities) are a particular risk.
Of course, dogs who like eating slugs, snails or frogs are putting themselves in danger by doing so!
So, what does it do to the infected dog?
Some dogs appear to show few clinical signs, at least initially; however, a heavy infestation will always cause disease. The common symptoms include:
- Coughing (65% of cases)
- Reduced ability to exercise, shortness of breath or puffing (43% of cases)
- Abnormal bleeding, such as bruises, nosebleeds, vomiting blood (35% of cases)
- Sudden collapse (26% of cases)
- Heart failure (causing difficulty breathing, pulses in the jugular vein and fluid in the abdomen) – rarely apparent.
- Very rarely, the worm larvae may “get lost” and end up in a different organ, such as the eye, brain, or liver. Here they cause damage to those organs, such as blindness, seizures, or liver failure and jaundice.
The “gold-standard” test has long been considered finding the larvae in the dog’s faeces. This is done by a special test (a Baermann Test); however, even in heavy infestations, dogs may not pass larvae every day, so usually at least five sets of faeces are required. In addition, some dogs may be severely affected before the worms in the arteries are sufficiently mature to lay eggs.
More recently, a Lungworm Snap Test has become available, that tests the dog’s blood for Lungworm proteins. This is much faster – we can do it in the practice in about 15 minutes! If the result is positive, it is highly likely that the dog has an active Lungworm infestation.
Can it be treated or prevented?
Fortunately, there are treatments available; these are also effective as preventative measures. Prevention, or treatment, require a combination medication containing imidacloprid and moxidectin, available as a “Spot-On” that is dropped onto the skin at the back of your dog’s neck.
Reduction in the numbers of slugs and snails in your garden can also be valuable – but be careful never to use metaldehyde-based slug pellets, as they are lethally toxic to dogs.