Climate Change Brings more Parasites like the brain-invading worms, spread by slugs and rats

Rat lungworm has been around for decades, but Climate Change has health officials worried.

There have been six cases of a rare parasitic infection called “rat lungworm” in Maui in the last

three months, health officials reported this week. The number is small, but it’s a dramatic jump

from the normal number of cases. In the decade before this period, the island had only seen two

other cases.

The surprising uptick has health officials and residents alike worried about the rise of the

worm, which can invade the human brain. In infected people, the infection may be

symptomless and resolve on its own. But for others, rat lungworm moves into the brain and

can cause inflammation, pain, and other neurological problems such as tremors. In those cases,

it can be fatal. In all cases, rat lungworm is very difficult to diagnose, and there is no treatment.

So far, at least three of the six cases have been confirmed by the state. There’s also a seventh

possible case. In April, one of the patients with a confirmed infection, 47-year-old Tricia Mynar,

told Honolulu Civil Beat: “The parasites are in the lining of my brain, moving around.” She

described the feeling as if “every once in a while somebody opens the top of my head, sets a hot

iron inside my brain, then pushes the steam button.”

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• Adult female worm of Angiostrongylus cantonensis recovered from rat lungs with

characteristic barber-pole appearance (anterior end of worm is to the top).

As the name suggests, rat lungworm is a parasitic roundworm (Angiostrongylus cantonensis)

that infects rats’ lungs as well as their blood and brains. Infected rats poop out worm larvae,

which can be picked up by snails, slugs, lizards, land crabs, and freshwater shrimp. These are

intermediate hosts that shed the worm. Humans can pick up the infection by handling or eating

any infected critter or by eating produce that has been contaminated by roaming infected snails

and slugs.

In Maui, the current uptick appears to be linked to a boom in the population of an invasive

“semi-slug” that is a particularly good carrier of the worm. While native slugs and snails may be

carriers around 25 percent of the time, the invasive semi-slug has a carriage rate of around 70

to 80 percent of the time, The Maui News reported.

Once alerted to the problem, residents reported seeing the semi-slugs in their yards and

gardens. They’re taking steps to knock back the population, as well as rein in the rats.

But, as The Atlantic noted, the rise of the rat lungworm has been a long time coming.

Researchers have noted that with climate change and increasing global travel, the parasite has

been spreading to new places and causing more cases.

The first human case was recorded in 1944 in Taiwan, and it was thought to be spread around

during World War II. Since then, rat lungworm has been prevalent in parts of Southeast Asia

and Western Pacific Islands, including Australia. In the past few decades, the parasite made its

way to the US, reaching Hawaii, California, Oklahoma, Alabama, Louisiana, Florida, and other

parts of the Gulf Coast.

In Hawaii at least, rat lungworm seems to be there to stay. “The problem isn’t going to go

away,” Maui Invasive Species Committee Manager Adam Radford told The Maui News. “Our

focus is on educating the public and determining the extent through social media and

potentially [a] survey.”