environmental predictors of schistosome parasite production in michigan lakes thomas r. raffel,...
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![Page 1: Environmental predictors of schistosome parasite production in Michigan lakes Thomas R. Raffel, Ph.D. Madelyn Messner Department of Biological Sciences](https://reader034.vdocuments.net/reader034/viewer/2022051516/56649e3f5503460f94b30973/html5/thumbnails/1.jpg)
Environmental predictors of schistosome parasite production in Michigan lakes
Thomas R. Raffel, Ph.D.Madelyn Messner
Department of Biological SciencesOakland University
Rochester, MI
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Raffel Lab Approach:• Spatial & temporal surveys• Experiments at large & small scales• Pollution effects on parasite communities• Temperature & parasitism
• Statistical & predictive models
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Her
bici
deFe
rtiliz
er
Pollution & trematodes example: (2008 Study with Jason Rohr Univ. S Florida)
+Snails
+Cercariae
Eutrophication
Cattle tank experiment:
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• Trematode biology is temperature-dependent̶5 Snail growth & reproductive rates̶5 Trematode development rate̶5 Cercaria production rate**
• BUT most studies ignore:
Temperature & trematodes: (Ongoing collaboration with Piet Johnson’s lab Univ. Colorado)
Nonlinearities Variability
Day
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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:
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Temperature & trematodes: (Ongoing collaboration with Piet Johnson’s lab Univ. Colorado)
• Predictive model:̶5 Based on metabolic theory & dynamic energy budget theory̶5 Parameterized by measuring temperature-dependence of
host food assimilation & respiration
13°C Acclimation22°C Acclimation28°C Acclimation
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Temperature & trematodes: (Ongoing collaboration with Piet Johnson’s lab Univ. Colorado)
• Predictive model:̶5 Based on metabolic theory & dynamic energy budget theory̶5 Parameterized by measuring temperature-dependence of
host food assimilation & respiration
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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)
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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
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What determines swimmer’s itch exposure?
Snail population density
Percent snails infected
Cercariae produced per snail
Bird infection
Temperature variation
Nutrient loading (Eutrophication)
Cercariaein water
SWIMMER’S ITCH!
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Potential Management Strategies• Snail control– Copper sulfate– Mechanical removal
• Bird control– Hunt, relocate, treat
• Pollution control• Protective skin creams• Public education• Predictive modeling
Management decisionsReal-time alerts
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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.
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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 AlgaeSnail population
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Snail densitiesNutrients Land Use
2. Spatial surveyWhat 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
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MethodsLake 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
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MethodsRaffel 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
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Quantitative/Real-time PCR
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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
Spatial survey 2015:
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TimetableMonth 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