The large number of ducks in Topsail Pond in Paradise is causing a skin infection in some swimmers.

It's called 'swimmer's itch' or 'water rash', and is a temporary skin irritation swimmers can get after taking a dip in ponds that contain a common worm that ducks can pass to humans.

Mayor Ralph Wiseman said the town decided to investigate why swimmers were developing rashes after receiving complaints from parents a few weeks ago.

"Some of the children (who) were swimming in the pond developed sort of a rash, an itchy rash," said Wiseman.

He said the town took some water samples to provincial officials who did an investigation.

What they found, he said, was that the rash comes from a worm that is present in ponds across North America, but is predominant in bodies of water where there are lots of ducks.

He said Topsail Pond has had up to 200 ducks in the past.

Wiseman said the larvae that cause the irritation lives in the stomach of the duck. The worm in the feces then attaches itself to plants and snails.

"And in this particular case of course, it mistakenly attaches itself to humans," said Wiseman.

He said the town has posted signs warning people of the danger.

"This is an area where this worm actually exists," he said.

He said if people continue to go Topsail Pond for a swim they they should keep moving in the water, not to stay in too long, and to dry off with a towel.

If a swimmers develops the rash, he said they shouldn't scratch it and if it lasts longer than two or three days to seek medical attention.