Floyd “Morty” Morton was throwing a cast net for bait fish 300 yards east of the Cape Henlopen State Park Fishing Pier last Friday when he felt an odd tingling at his ankles and feet.

When the veteran fisherman stepped out of Delaware Bay, there was a peculiar gnawing sensation below his knees.

The 49-year-old Morton rushed to his truck and wiped antiseptic solution on his hands and his feet. He then hurried home to Georgetown wash off whatever was irritating his skin.

"And I thought, 'Oh God, please no,'" he said.

When red, itchy, pimplelike blisters appeared on his legs and feet the next morning, Morton knew — it was the third time he had contracted "swimmer's itch."

Known medically as cercarial dermatitis, swimmer's itch appears when a microscopic parasite burrows under the skin, according to the Centers for Disease Control and Prevention.

A trip to the doctor on Tuesday confirmed his self-diagnosis. Morton knew he would have to deal with the swelling, tingling and burning pain for seven to 10 days.

He reached out to Delaware park officials, pleading with them to warn people about the possibility of parasites in the water.

On Wednesday, swimmer’s itch advisory signs appeared at bay access points, Michael Globetti, spokesman for the Delaware Department of Natural Resources and Environmental Control, wrote in an email Thursday.

The signs alerted swimmers and waders of the possibility of swimmer's itch.

“After swimming or wading, towel off promptly and vigorously,” the sign cautioned.

The CDC also suggests showering immediately after leaving shallow, still water near the shore. Those are the conditions in which the parasites leave their host mud snails, possibly in pursuit of sunlight, scientists say.

Symptoms can begin minutes — or days — after swimming in contaminated water. The CDC said all bathers are equally at risk if conditions are right for the parasites to leave their host, but it affects children more because they typically play in shallow water.

All reports of swimmer’s itch have been on the bay side near the state park area, with the first report coming from the point on Cape Henlopen, Globetti said.

The free-swimming trematode parasites that trigger swimmer's itch typically experience a three-host life cycle — starting with a mud snail, then a crab or a fish that will eventually be eaten by a bird.

The trematode parasites first takes form in a larval stage called cercariae then work their way out of the snail on their own, said Jonathan Cohen, assistant professor at the University of Delaware's School of Marine Science and Policy, who has studied marine life in the area for nearly six years.

"So the snail is basically leaking parasites," he explained. "This is called 'shedding.' A human can come into contact with cercariae once they are shed into the water."

Although these types of parasites are commonly found in environments like the Delaware Bay, contracting swimmer’s itch is rare, Cohen said.

“For student labs, we collect snails all the time and look for parasites," he said. "We always find parasites, the snails are laden with parasites — but they’re not always the ones that cause swimmer’s itch.”

Cohen said Morton’s case is not surprising. Friday’s high of 79 degrees fits conditions when these types of parasites could leave the snails, he said.

Because the conditions have to be just right for humans to come into contact with the parasite, the CDC says swimmer's itch is not an ongoing problem. There is also no way to know how long the water may be unsafe, but larvae generally survive 24 hours once released from a snail, according to the CDC.

“What’s happening in the swimmer’s itch case is that parasites are presumably leaving the snail and trying to find their next host, but instead they get a swimmer’s leg,” Cohen said.

Floyd made his own attempts to warn others. He posted a warning on his Facebook page, “Delaware Brethren of the Coast,” a group of area fisherman who share fishing techniques, closings and safety warnings.

The initial post, which included two photographs of his legs, attracted more than 1,000 likes, 8,800 shares and 930 comments.

A handful of Facebook users claimed they, too, have swimmer's itch from swimming in the bay.

Morton said the widespread reaction to his posts have caught the eye of some Cape Henlopen State Park employees and a few area businesses.

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Jon Siddons, a Lewes resident and bartender at Irish Eyes Pub and Restaurant, said he and his co-workers aren't worried about Morton's claim and view it more as an isolated event.

Siddons noted an incident in 1992 involving Milford high school students, as the only other time he has heard of swimmer's itch.

"It's not something I've heard of frequently — or ever since then," Siddons said.

For Dave Beebe, lifetime Lewes resident and owner of Lighthouse View Bait and Tackle, the consensus among fishermen in his shop this week was that there is not much to be concerned about.

“I’ve been in that water every day for four straight weeks catching mullet, I catch all the mullet for our tackle shop," he said. "I don’t have a single thing on my legs.

"All the people around here that do the same thing, they don’t have any problems.”

Beebe said he has fished in Lewes since the mid-1960s, and in addition to catching bait, he teaches clamming classes in the area Morton said he encountered the parasites.

“I’ve seen his pictures — he got nailed hard by something, so I don’t dispute that he got it," Beebe said. "But to say that it’s common is a huge stretch.”

To Beebe, jellyfish and crabs pose a bigger threat than the type of parasites found in these waters.

“I’m up to my waist every day in that same water,” he said. “You can take a look at my legs and they’re perfect – that’s what my wife says at least.”