What is Swimmers’ Itch?

Swimmers’ itch is a fairly common skin irritation caused by the larval from of a specific flatworm. These flatworms are a parasite found in snails and waterfowl. The larva burrows into a human’s skin and dies as humans are not the correct host, causing an itching sensation. While not dangerous, swimmers’ itch can cause immense discomfort. See the report from freshwater solutions of the page for more information.

Comprehensive Assessment Research Initiative

Elk-Skegemog Lake Association (ESLA)
2020 Final Report
20 November 2020
Submitted by: Ron Reimink, M.A. Freshwater Solutions, LLC & Patrick Hanington, Ph.D. University of Alberta

Hear It From Us

Swimmers’ Itch ESLA Update

Swimmer’s Itch, and the dilemma ESLA’s board has faced amid growing SI concerns form our members has been an enormous challenge. AS we have learned from Covid-19, simple solutions are elusive.

Consider the unknowns: Why do some people get SI, while others do not? Why do some lake shave success reducing the infections by removing Common Mergansers, while others do not? Why does Elk lake have the highest level of cercariae (the ‘worms’ that cause the SI rash) of any lake in northern Michigan, but has relatively few common mergansers, a critical link in the SI life cycle?

In 2018 and 2019, ESLA hired Ron Reimink, found and owner of Freshwater Solutions, LLC (FWS) to collect data as complaints from our riparians were increasing. Reimink’s expertise and experience working with the lake associations to combat SI and out interest in establishing a database to better understand the problem and potential solutions drove the board’s decision. In 2018, data gathering was required to apply for a permit from the State to trap and relocate Common Mergansers.

In 2019, we also contacted with Curt Blankenspoor of Swimmer’s Itch Solutions (SIS) to trap and relocate Common Merganser broods. Two lakes, Higgins and Crystal, had reported significant success reducing the SI with this method. Blankenspoor successfully removed four broods from Elk Lake last summer and said the benefits of his work would be apparent this summer or nest year.

What We Learned

Freshwater Solutions concluded that its assessment of the three lakes in northern Michigan definitely showed that migrating ducks, previously though to be inconsequential, were part of the problem. It’s still unclear to what degree. Also, Reimink found that a new snail species was contributing to SI. The SI life cycle in northern Michigan previously had been linked only to Common Mergansers and the T. stagnicola snail. Based on his findings last summer, Reimink concluded there was a new contributor, tiny SI-causing worms that used Helisoma snails and Canada geese as their hosts. FWS also found significantly more Helisoma snails in some northern Michigan lakes in 2019 than in 2018.

Meanwhile, Blankenspoor last summer attached tacking devices to the Common Mergansers he trapped to help locate trees where the hens make their nests with the though the holes they used could be blocked. While this method had technical success, it was not practical to implement as it was time consuming and expensive. In addition, SIS banded six female Common Mergansers and moved them to state-approved sites on Lake Michigan, Lake Huron and two impoundments. At least three of the hens dies and the signal was lost on a forth. One hen from Elk Lake was relocated to Suttons Bay and made its way back to Elk Lake. SIS determined that the hens stayed with their broods and moved many miles
from their relocation release sites.

Research on Elk and Skegemog Lakes in 2019 supported similar findings in 2018 – our lakes have some of the highest cercariae levels among northern Michigan lakes, even though we do not have large numbers of Common Mergansers. Some experts believe that only one or two broods of Common Mergansers could cause the numbers of SI infections on our lakes, while others believe the high cercariae numbers suggest other waterfowl are likely a vector.

Our 2019 research showed twice as many geese on our lakes in 2019 as 2019. This could be significant, considering Reimink’s findings linking a new snail and Canada geese to SI. In 2018, few Helisoma snails were in Elk and Skegemog, and none were infected with the SI larvae. In 2019, we did not collect snails, but the DNA analysis showed most of the cercariae coming from T. stagnicola snails (with Common Mergansers co-host) and Helisoma snails (Canada Geese co-host). Although more water samples showed cercariae from T. stagnicola, the count of the ‘worms in the water’ showed more from the Helisoma snail.

Where ESLA’s SI Strategy Is Headed?

ESLA’s budget cannot sustain perpetually spending for the same services it hire two contractors to perform in 2019. Consider, too, that in 2019 we were reimbursed about $8,000 from the Michigan Swimmers Itch Partnership for our contractor costs. That money, from a state grant, is no longer available.

The board, meeting from homes via Zoom, overwhelming voted April 17 not to trap mergansers this summer. In a separate vote, the board voted to continue discussions on research with FWS to better understand issues such as the role of migratory birds and resident geese, as well as risk reduction strategies for riparians.

At its next meeting May 21, the ESLA board expects to finalize its 2020 approach following further discussion with Reimink, as well as other lake associations with the Elk River chain of lakes.

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