For the last 30 years, controlling Swimmer’s Itch used to be more simple – one duck, one snail, one parasite. Break the life cycle of the parasite that uses Common Mergansers and Stagnicola snails and you’re on your way to having a respectable lake-wide control of Swimmer’s Itch.  

Unfortunately, based on last summer’s outbreak of itch despite our efforts, we now fear that itch on Glen Lake it is no longer that simple.
Key Questions:
– Are other ducks, geese or swans contributing to the itch by serving as hosts to multiple species of itch causing worms?  
– Are migrant waterfowl in the spring and fall contributing to the itch that undermines the effort of trapping and relocating resident merganser broods?

In order to unravel the mystery of the complex issues surrounding Swimmer’s Itch, we need to conduct weekly waterfowl surveys on Big and Little Glen lakes.
Waterfowl Survey Defined:
What does a waterfowl survey entail? Our surveys include weekly boat rides around the shoreline where we record the numbers and locations of any ducks, geese, and swans. Also, we attempt to collect fresh fecal samples of the waterfowl on docks, analyze the samples in the lab, and determine which parasite is in what bird (there are at least five different parasites that cause itch in our lake).  

Three surveys have been completed so far. The surveys will continue throughout the summer and end the first week in November. GLA has developed a three-member waterfowl survey team that includes Rob Karner, Watershed Biologist along with our summer intern Cecelia Denton and our GLA assistant for water quality studies Laura Wiesen. 

It is our hope that the waterfowl survey, together with the water sampling program that was mentioned in the last email blast, along with the help and expertise of Freshwater Solutions, the mysteries of Swimmer’s Itch will be solved. Stay tuned in December of 2019 for a full report of our findings and what it may all mean for managing Swimmer’s Itch in the future.

For more information, contact Rob Karner at


Cecelia Denton and Laura Wiesen are part of survey team.