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A Sample Lake Assessment Report

See exactly what a professional swimmer's itch assessment delivers — the same parasite identification, infection rates, and waterfowl analysis your association would receive.

Sample Report

What the Findings Look Like

Below are condensed versions of three actual 2025 assessments from Minnesota lakes. Full reports run nine pages and include maps, waterfowl survey data, and detailed qPCR tables.

Swimmer's Itch Assessment Report

Sample Lake 1, Otter Tail County, MN Sample

Assessment conducted July 14, 2025 · 10 collection sites · 4 lake system
● High Risk
16.4%
Snail Infection Rate
(lake-wide)
500+
Snails Examined
across 10 sites
6 of 7
Sites at
Epidemic Level
Key Findings
Dominant parasite
Trichobilharzia stagnicolae — confirmed dominant at 4 of 6 qPCR sites, at 10–100× the levels of any other species detected
Primary waterfowl host
Common merganser — at least 4 broods confirmed breeding on lake; hatch-year birds found infected and shedding high miracidia counts
Snail host
Stagnicola sp. — found at 7 of 10 collection sites; dominant snail species at most locations
Other species ruled out
T. szidati and A. brantae not detected; T. physellae and Avian Schistosome C present at trace levels only
Recommended action
Merganser brood relocation — targets the confirmed definitive host; documented 98% reduction on comparable lakes
Assessment Conclusion

"The lake-wide snail infection rate of 16.4% was the highest recorded on any lake in our dataset. Multiple independent lines of evidence — snail infection data, waterfowl samples, and qPCR water testing — all point to T. stagnicolae cycling through Stagnicola snails and breeding common mergansers as the source of the swimmer's itch problem."

Swimmer's Itch Assessment Report

Sample Lake 2, Becker County, MN Sample

Assessment conducted July 18, 2025 · 5 collection sites
● High Risk
12.5%
Snail Infection Rate
(lake-wide)
48
Snails Examined
across 5 sites
5 of 5
Sites Positive
for Cercariae
Key Findings
Dominant parasite
Trichobilharzia stagnicolae — confirmed dominant species; cercariae detected at all five collection sites
Primary waterfowl host
Common merganser — multiple adult females and juveniles observed along sampling transects during assessment
Snail host
Stagnicola sp. — predominant snail genus recovered at all sites; highest densities in 0.5–1.5 m depth zone
Other species detected
T. physellae present at trace levels at two sites; no T. szidati or A. brantae detected
Recommended action
Merganser brood management combined with targeted snail habitat assessment in the highest-density zones
Assessment Conclusion

"All five collection sites tested positive for cercariae, and T. stagnicolae was the overwhelming driver. The 12.5% infection rate combined with confirmed merganser presence indicates the same transmission cycle seen on other high-risk lakes in the region. The parasite load is sufficient to produce significant swimmer complaints."

Swimmer's Itch Assessment Report

Sample Lake 3, Becker County, MN Sample

Assessment conducted July 19, 2025 · 8 collection sites
● Moderate Risk
7.8%
Snail Infection Rate
(lake-wide)
129
Snails Examined
across 8 sites
3
Parasite Species
Identified
Key Findings
Parasite species detected
Trichobilharzia stagnicolae, T. physellae, and Avian Schistosome C — multi-species infection with no single dominant driver
Primary waterfowl hosts
Common merganser (T. stagnicolae) and diving ducks (T. physellae); both host types confirmed on-lake during assessment
Snail hosts
Stagnicola sp. and Physella sp. both present; distribution varied considerably across the 8 collection sites
Site variability
Infection rates ranged from 0% to 22% across sites — hotspots concentrated near aquatic vegetation beds on the east shoreline
Recommended action
Multi-species management plan needed; site-specific interventions at the two highest-density locations should be prioritized first
Assessment Conclusion

"The 7.8% lake-wide infection rate reflects a moderate but genuine swimmer's itch risk. The presence of three parasite species cycling through two different snail hosts makes this a more complex management case than a single-species lake. Targeted treatment of the eastern hotspot sites, combined with waterfowl monitoring, is the recommended starting point."

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