You see a slug on the path. Maybe one on your lettuce. Or maybe your kid dares their friend to eat, because children are agents of chaos.It’s just a slug… right?
Well, mostly, yes. But sometimes that slug is carrying a parasite with a surprisingly dramatic life story.
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Let’s talk about Rat Lungworm Disease.
How do slugs pick up the parasite?
Some slugs and snails carry the parasite Angiostrongylus cantonensis, better known as rat lungworm. The adult worms live in rats’ lungs (hence the name), and rats pass parasite larvae in their feces. Snails and slugs then eat the contaminated droppings and pick up the larvae.
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The parasite grows inside the snail or slug, but it doesn’t become an adult yet – that only happens when a rat eats the infected snail. So, this neat life cycle goes rat, to slug, to rat. But sometimes, humans accidentally end up involved.
So how do people get infected?
Short answer: by eating the wrong thing. Most infections happen when someone eats a raw or undercooked snail or slug carrying the parasite. It’s more common in places where snails are eaten as food.
But the weird cases tend to get the headlines. Kids sometimes swallow slugs for ‘reasons’ (please don’t), and some people are exposed accidentally if a tiny snail or slug is hiding in raw food, like lettuce.
There’s also some evidence that certain animals – like freshwater shrimp, crabs, frogs or prawns – can carry the larvae if they’ve eaten infected snails, though this route is less clearly established. Fish, thankfully, are off the hook.
Importantly, the infection isn’t contagious, so you can’t catch it from another person.
What happens if someone gets infected?
Often, not much, thankfully. Many people have mild symptoms or none at all, and the infection eventually resolves itself without treatment.
But in some cases, the parasite reaches the nervous system and causes a form of meningitis called eosinophilic meningitis. That can mean headaches, stiff neck, nausea, vomiting, fever, strange tingling or painful skin sensations and sometimes sensitivity to light or confusion.
Unpleasant, yes. Common, no.
Is it deadly?
Usually not. Most people recover fully, even when meningitis develops. The parasites die over time, and the body clears the infection.
Treatment typically focuses on managing symptoms – things like pain relief for headaches or medications that reduce inflammation – rather than trying to kill the parasite directly.
In other words, your immune system ends up doing most of the work.
Should we panic about slugs now?
Definitely not. Rat lungworm disease is still relatively rare, and simple precautions go a long way:
- Wash your fresh veg properly
- Don’t eat raw or undercooked snails or slugs (this feels like common sense…)
- And maybe discourage children from eating garden wildlife as a party trick
Because yes, it’s just a slug, but sometimes that slug has been hanging out with rats.
