About the CLWA

Final report on 2018 swimmer’s itch control program

Swimmer’s Itch Control LLC, who carried out CLWA’s swimmer’s itch program during the summer of 2018, has now submitted its final report. The conclusions strongly support the preliminary results observed during summer activities, and point the way toward the continuing efforts that will be needed in the future. To read the full report, click HERE.

The 2018 program consisted of several components: trapping and relocation of all common merganser broods on Crystal Lake (a total of 16 broods, 143 birds); assessment of lake-wide snail infection by collection and analysis of 2112 Stagnicola emarginata snails; analysis of 40 lake water samples by qPCR technique to detect presence of swimmer’s itch-causing parasites; collection of avian schistosome worms from three breeding merganser hens; and training two local individuals in trapping and relocation techniques. This was the second year for trapping and relocation of all broods on the lake, and once again the riparian community proved to be extremely helpful by reporting sightings of broods.

The snail infection rate showed a 65% decrease from that found in the lake-wide snail assessment carried out in 2016. The qPCR analysis of the water samples detected the presence of the parasite species T. stagnicolae, suggesting that common mergansers are the only bird species responsible for swimmer’s itch infection on Crystal Lake. These tests also showed higher concentration of parasites at two specific locations on the lake.

While numbers of actual swimmer’s itch cases reported to the SIS website varied little from those reported in 2017, this can likely be ascribed to higher awareness of the availability of this feedback mechanism. Anecdotal evidence from all around the lake, including the detailed records kept at the Congregational Asssembly Beach, suggested that the number of cases was significantly reduced and seemed to be milder in impact.

In order to maintain the progress made to date, it will be necessary to continue the trapping and relocation of merganser broods into future summers. The two trained local individuals are now qualified to carry this out. CLWA will also continue to participate in various swimmer’s itch research projects, some under the auspices of the Michigan Swimmer’s Itch Partnership, so that swimmer’s itch will cease to be a problem on Crystal Lake.