A sharp rise in infections stemming from a parasitic worm that invades the human brain has health officials in the Hawaiian island of Maui worried.

Six cases of rat lungworm disease have so far been confirmed in Maui in the last three months, with more episodes currently being investigated. Given the island had only experienced two documented cases of rat lungworm in the decade before this outbreak, the sudden increase is causing concern.

Rat lungworm disease is caused by the parasitic roundworm Angiostrongylus cantonensis, with the adult form of the parasite found only in rats.

The infection is spread when rats carrying the parasite excrete the larvae of the roundworm in their faeces. From there, it can be picked up by other animals, such as snails, slugs, freshwater shrimp, crabs, and frogs.

If people handle or consume any of these infected animals – or come into contact with them on contaminated food sources, such as raw fruit and vegetables – they too can become infected.

For many, there are no symptoms, and most people recover from the infection on their own. But in some cases, the worm moves into the brain and nervous system, resulting in a parasitic form of meningitis that can cause intense headaches, tremors, numbness, and fever symptoms – and which can ultimately turn out to be fatal.

…

The Hawaiian Islands on the whole usually average about 10 cases of rat lungworm per year, according to state epidemiologist Sarah Park, who says the symptoms are as random as they are terrifying.

“If you could imagine, it’s like having a slow-moving bullet go through your brain and there’s no rhyme or reason why it’s going to hang out in this part of the brain or that part of the brain,” she told Associated Press.

As for what’s caused such a spike in Maui recently, nobody’s entirely sure, but there are concerns the parasite is being spread by a rise in numbers of an invasive semi-slug in the region, with as much as 80 percent of the species carrying the roundworm.