1. Department of Biological Sciences
Environmental predictors of schistosome parasite production in Michigan lakes
Thomas R. Raffel, Ph.D.
Madelyn Messner
Department of Biological Sciences
Oakland University
Rochester, MI

2. Raffel Lab Approach: Spatial & temporal surveys
Experiments at large & small scales
Pollution effects on parasite communities
Temperature & parasitism
Statistical & predictive models

3. Pollution & trematodes example:
(2008 Study with Jason Rohr Univ. S Florida)
Cattle tank experiment:
Herbicide
Eutrophication
Fertilizer
+Snails
+Cercariae

4. Temperature & trematodes:
(Ongoing collaboration with Piet Johnson’s lab Univ. Colorado)
Trematode biology is temperature-dependent
Snail growth & reproductive rates
Trematode development rate
Cercaria production rate**
BUT most studies ignore:
Nonlinearities
Variability
Day

5. Temperature & trematodes:
(Ongoing collaboration with Piet Johnson’s lab Univ. Colorado)
Thermal Stress Hypothesis
Depletion of host energy reserves at stressful temperatures
Lower cercaria production following excessively warm periods
Temperature-shift experiment:
Predictions:
Observations:

6. Temperature & trematodes:
(Ongoing collaboration with Piet Johnson’s lab Univ. Colorado)
Predictive model:
Based on metabolic theory & dynamic energy budget theory
Parameterized by measuring temperature-dependence of host food assimilation & respiration
13°C Acclimation
22°C Acclimation
28°C Acclimation

7. Temperature & trematodes:
(Ongoing collaboration with Piet Johnson’s lab Univ. Colorado)
Predictive model:
Based on metabolic theory & dynamic energy budget theory
Parameterized by measuring temperature-dependence of host food assimilation & respiration

8. Swimmer’s Itch Research Needs
Better monitoring & detection methods
Filtration + microscopy; Slide samplers (short-term)
Quantitative PCR (DNA detection; medium-term)
Electronic biosensors? (longer-term)
Control measure effectiveness & impact
Track & model population-level impacts of snail/bird removal
Test ecosystem-level impacts of copper sulfate & alternative molluscicides (surveys/mesocosms, medium-term)
Improve predictive models for snail density, trematode prevalence, and cercaria production
Spatial & temporal surveys (short-term)
Lab & Mesocosm experiments (medium-term)
Predictive modeling (medium-term)
DEVELOPMENT OF ALERT SYSTEMS (long-term)
Test and validate predictions of Aquatox models, used by regulators to help make decisions.

10. Swimmer’s itch Trematode infection (avian schistosomes)
2-host life cycle (SNAILS)
Discourages recreational water use (economic impact)
Difficult to manage
Limited research literature
Limited funding opportunities

11. What determines swimmer’s itch exposure?
Snail population density
Percent snails infected
Cercariae produced per snail
Bird infection
Temperature
variation
Nutrient loading (Eutrophication)
Cercariae
in water
SWIMMER’S ITCH!

12. Potential Management Strategies
Snail control
Copper sulfate
Mechanical removal
Bird control
Hunt, relocate, treat
Pollution control
Protective skin creams
Public education
Predictive modeling
Management decisions
Real-time alerts

13. 2015 Summer Research Aims:
1. Temporal surveys: Obtain field data that can be used to validate models predicting short term fluctuations in swimmer’s itch exposure
2. Spatial Survey: Collaborate with volunteers to obtain data from 8 lakes to determine predictors of schistosome cercariae abundance across a region.

14. 1. Temporal survey
What are the best predictors of daily abundance of avian schistosome cercariae?
Core hypothesis– cercaria production is driven by the thermal biology and dynamic energy budgets of the snail host
Alternative predictors– water temperature, wind direction/speed, snail population dynamics, algal growth (food)
Temperature
Wind speed
Snail population
Algae

15. 2. Spatial survey
What determines patterns of schistosome cercariae production across a broad landscape?
Potential predictors:
lake size/depth/hydrology
Land use & soil/rock types
Climate (temp, precipitation, wind)
Snail & invertebrate densities
Pollutants (pesticides & nutrients)
Algae/vegetation growth
Bird visitation
Nutrients
Snail densities
Land Use

16. Methods Lake Volunteers
Sample from water surface using 1 liter, 35 µm mesh filters
50 filter scoops along shore  one sample
Rinse filters with ethanol to preserve cercariae
Sample between sunrise and noon each day
Store samples in cool, dark place

17. Methods Raffel Lab Survey snail populations Pipe-sampling PCR methods
qPCR to quantify schistosome DNA in water
Regular PCR & sequencing to identify species
ELISA kits to detect pollutants
Herbicides: triazines & metabolites, glyphosates
Insecticides: organophosphates and carbamates
Periphyton growth
Ceramic tiles chlorophyll extraction
Land use characterization
GIS software and datasets
Water temperature, wind velocity, precipitation
HOBO loggers and weather databases

18. Quantitative/Real-time PCR

19. Spatial survey 2015: Raffel Lab commitments: Organize survey
Provide training and sampling materials
Survey snail & invertebrate populations
Measure environmental variables
Process cercaria DNA & water chemistry samples
Statistical analysis, reports, and presentations
Lake Association participation:
Recruit at least 1 volunteer to collect daily filter samples for 2-4 weeks during July/August
Provide financial support to analyze cercaria DNA and water chemistry samples ($500 per site)
Help select sampling sites

20. Timetable Month Goals April
Sampling schedule, refine methods, identify study sites
May/June
Monthly visits to sites to survey and collect data
July/August
Daily cercaria sampling from lakes known to harbor swimmer’s itch
September
Process samples, compile data
Oct/Nov/Dec
Follow-up experiments & analysis