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Date:   8/15/2008 11:19:59 AM ( 11 years ago ago)
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Parasite causing an itch for swimmers
By Denis Cuff
Contra Costa Times
Article Launched: 08/14/2008 08:16:58 PM PDT

It's a condition caused by a tiny water parasite with a barbed tail that will bore into your skin and cause welts and itching if it mistakes you for a duck or goose paddling in a lake or bay.

Swimmer's itch, rarely reported a decade ago in Contra Costa and Alameda counties, has become a rite of summer in several lakes in the East Bay Regional Park District in the last few years.

Complaints about the itch have prompted the park district this summer to post warning signs at Crown Beach in Alameda, Lake Anza at Tilden Park in Berkeley, and Quarry Lakes in Fremont.

In the last three or four years, Shadow Cliffs Reservoir in Pleasanton and Lake Temescal in Oakland also have been hit by the itch. Specific complaint numbers were not available Thursday.

Park officials said closing swimming areas is not warranted because the outbreaks and the itching are temporary.

The microscopic worm that causes the condition fails to penetrate the human body. But its attempts to dig in can trigger skin irritation for up to two weeks in the one in three people allergic to the parasite.

"There's no permanent effect, but it can be very unpleasant," said Neal Fujita, the regional park district's water resources manager. "We want to encourage people to enjoy the outdoor experience and use our lakes. We also want to inform people that, like mosquitoes and ticks, swimmer's itch can come with the territory."

The itch, also known as cercarial dermatitis, apparently is more prevalent in the Midwest and Northeast, but it is scratching out a hold in the West.

Greater awareness of the condition may be causing more people to complain about it, said Sara Brant, a parasite expert at the University of New Mexico in Albuquerque.

To cope with the problem, the park district has stepped up parasite monitoring and use of fliers and signs at lakes at which more than one person has complained, or where tests confirm the parasite's presence.

The signs advise swimmers to minimize infection risks by showering and drying off thoroughly.

Fujita said it is not necessary to post warning signs at all lakes at all times because the outbreaks can come and go in days as weather or environmental conditions change.

Unfortunately for swimmers, the parasite infections occur mostly in the summer months of heavy lake use.

Cathie Irwin of Berkeley was among the many bathers enjoying the sandy beach at Lake Anza on Wednesday afternoon as her sons, Tyler, 7, and Jake, 4, waded in the water and shoveled mud.

Swimmer's itch should not ruin a day at the beach, she said.

"Life is full of risk," Irwin said. "I think the opportunity to spend a nice day like this out in a beautiful natural setting outweighs the slight risk of getting swimmer's itch."

As she spoke, a heron glided over the blue lake and a pair of ducks swam by.

"You won't see that at a swimming pool," Irwin said. "Here my children can swim with the ducks."

Erik Andersen, 13, of Berkeley, said he contracted swimmer's itch two weeks ago at Lake Anza, but it didn't stop him from training in a junior lifeguard program.

"The rash on my arm and legs itched, but it was a small inconvenience," Andersen said. "On a scale of 5, I'd say it was a 2 for irritation."

Different people react very differently to the parasite that causes swimmer's itch. Most have no reaction at all, but a few experience moderate to extreme irritation, and end up seeking medicine for relief.

When lifeguards get swimmer's itch, the regional park district shifts them to a district pool or lagoon with chlorinated water, which kills the parasites.

Some 20 years ago, the park district used copper sulfate to treat water in at least one lake, but that would be unacceptable now because of lake ecosystem protections, Fujita said.

The swimmer's itch parasite initially burrows in a duck or goose and excretes its eggs into the water. The larvae seek out an aquatic snail to live in before transforming into the worm and starting the cycle over.

Lisa Bragato, a mother from Walnut Creek, said she had not heard about swimmer's itch until her visit to Lake Anza on Wednesday.

"It sounds unpleasant," she said. "I would come back here, though, as long as the children don't get the itch."


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