Acid-Coated, Brain-Bursting Alien Worms Invade Bangkok

A New Guinea Flatworm preys on a snail in Pathum Thani province. Photo: Nonn Panitvong

BANGKOK – Aliens appeared on Halloween in Bangkok with skin-burning acidic goo and deadly, brain-swelling parasites.

When Mongkol Utachai found 15 worms that looked like slimy slugs in his Bangkok backyard on Oct. 31, little did he know they were snail-eating New Guinea Flatworms, or nhon alien in Thai, one of the world’s most invasive species.

Environmental experts confirmed Tuesday that the specimens Mongkol found were indeed New Guinea Flatworms, said Nonn Panitvong, a researcher with environmental group Siamensis.

Nonn’s attention was drawn to pictures posted by Mongkol on social media of the nhon alien – sometimes called snail-eating worms – doing what they do best: eating snails.


“Sorry I didn’t take a lot of pictures. [I] was too excited,” Nonn wrote in response to an inquiry “From what I understand, they must have been in our country for some time now, given that they are so widespread. Some people claim to have seen them for more than two years.”

The species is listed by the Invasive Species Specialist Group as one of the world’s most invasive, because they pose a threat to the ecosystems by preying on the snails and earthworms that boost soil fertility and plant growth.

But that is not the only threat: Humans are warned to be alert too, since the New Guinea Flatworms can host a parasite known as the Rat Lungworm.

The good news: the lungworm is only transmitted between mollusks such as snails, slugs and rats. The bad news: the flatworm’s mucus and larvae can cause a severe type of meningitis. If the worm’s acidic goo contacts human skin, it can produce painful lesions. Its larvae – which can be infected with the parasitic lungworm – can be transmitted through contaminated water and cause fever, nausea, drowsiness, severe headaches and muscle pain.

According to Nonn, the invasive flatworms were found throughout the country including the provinces of Bangkok, Pathum Thani, Songkhla and Nakhon Ratchasima. But those discovered on Halloween by Mongkol were the first time Non saw that species of flatworm with his own eyes.

The hermaphrodite worm – native to New Guinea, as its name suggests – is mostly found on Pacific islands such as the Futuna Islands, Singapore, Solomon Islands, Philippines and Puerto Rico. It was found in Miami in 2015.


Nonn does not recommend killing the worm by cutting it, as he says it will only replicate into multiple copies. He suggests pouring hot water or salt on it.

If anyone finds the New Guinea Flatworm, they can report it to Siamensis on Facebook or via Line ID @Sde5284v.

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A New Guinea Flatworm in a yard in Pathum Thani province. Photo: Nonn Panitvong