Merganser Control Out: No Plan B For Controlling Swimmer's Itch

By Anne Stanton

During these hot days of summer, the lakes get warm and swimmer's itch literally gets under people's skin. Caused by a flatworm parasite, swimmer's itch resembles a bad case of mosquito bites that itch like crazy. A few years ago a lake association in Leelanau County figured out a way to rid itself of the parasite. But the DNR has stopped the program and lake associations are left with no good options to deal with the problem.

Scourge of summer

At the Prescription Shop in Glen Arbor, William Dean is in line to buy Benadryl to help ease the pain of swimmer's itch. Dean says both his grandkids got hit swimming in Glen Lake.

"The 14-month-old just got it today. The other is getting it for the second time, I believe today. He's been screaming bloody murder."

Swimmer's itch is caused by a parasitic worm that cycles between snails and ducks. Sometimes the flatworm happens to find a human instead of a duck. The worm burrows in and dies, but the itch remains. Lake owners across the state historically battled swimmer's itch using copper sulfate, which kills the snails. The only problem is that it didn't work, says Rob Karner. Karner, a Leelanau School ecology teacher, was asked to use copper sulfate in Glen Lake in the early 1980s, when he was first hired by the Glen Lake Association.

"The people were still getting swimmer's itch and we hit an all-time high of spending upwards of forty to fifty-thousand dollars using aerial crop dusters to put copper sulfate into the water."

The chemical is only effective for two hours. After that, the surviving snails simply move back into the treated area. Karner thought there had to be a better way.

Glen Lake pioneers control program

In 1982, the Glen Lake Association hired Dr. Harvey Blankespoor, a Hope College professor and one of the world's leading experts on swimmer's itch. Blankespoor discovered that mergansers—not mallards, as long thought—carry the parasite in Glen Lake. To stop the parasite's life cycle, he moved the mergansers a mile away to Lake Michigan. That caused the infection rate in snails to drop dramatically.

In 2004, Blankespoor formed a company called SICOM. For six years, he and his research team were paid by the Glen Lake Association to trap the merganser broods and move them to Lake Michigan.

But in 2010, Blankespoor retired and wanted to sell the company. The state Department of Natural Resources refused to issue the necessary permit. It objected to the fact that the project had become a business proposition. Blankespoor said his fees were simply to cover the cost of the $30,000 trap and his time.

"It wasn't a money-making thing at all, but we thought we were doing an environmentally very friendly thing"

The DNR worried that issuing a permit would set a precedent with other lake owners. What worked for Glen Lake might not work for an inland lake farther from Lake Michigan. And wildlife officials didn't want property owners moving mergansers without knowing what they were doing.

The DNR also worried about the survival rate of the mergansers after they were moved. DNR Waterfowl Specialist Barbara Avers says there might be unintended consequences of relocating the birds.

"On Lake Michigan we've had this type E botulism outbreaks for a number of years now and so you may be exposing them to a disease that otherwise they might not have been exposed to," Avers explained.

When the DNR denied the permit to trap mergansers, the agency suggested copper sulfate instead. It is still legal, but rarely used today. Ironically, the DEQ—the permitting agency for copper sulfate—discourages the use of copper sulfate because it's toxic and not all that effective.

No Plan B

So for now, lake associations around the state are left with no good solutions.

On Glen Lake, property owners scare off migrating mergansers by shooting pyrotechnics with a shotgun in early spring and fall. Some lake associations like Walloon and Crystal Lake have hired sharp shooters to kill mergansers in the fall.

Although it's legal to shoot common mergansers during hunting season, Karner said he doesn't want to kill birds. He wants to move them off the lake. Karner argues that if he were allowed to transplant the broods to Lake Michigan, he would do no harm to the environment and solve the swimmer's itch problem.

The DNR plans to meet with lake associations this summer to see what more can be done. Meanwhile, swimmers can protect themselves with a relatively new product called Swimmer's Itch Guard. It's available online and in some area drug stores—perhaps near the Benadryl.