Australian health authorities Thursday warned people against eating raw slugs after a man who reportedly ingested one as a dare became critically ill with a rare form of meningitis.

New South Wales health officials issued the warning following media reports that a 21-year-old man had been hospitalised with "rat lung worm" after a prank in which he swallowed a garden slug.

Normally found in Asia and the Pacific islands, the parasite was carried by and slugs which had eaten the faeces of infected rodents, and cases in Australia were rare, said communicable diseases chief Jeremy McAnulty.

"In the past, this sometimes has happened after a person has been dared to eat a slug or snail," McAnulty said in a public health alert.

"You should not eat raw slugs or snails and other animals, and ensure that you wash your hands after touching them."

Most infected people would only suffer mild, short-lived symptoms, but McAnulty said some could fall seriously ill.

"Even if infected, most people recover fully without treatment. However, it can sometimes cause severe meningitis," he said.

Because humans were not the natural host of the parasite, McAnulty said it eventually died without treatment and could not be passed from person to person.