Project 2: The ecology of Lyme
disease risk
Images, left-right: a landscape fragmented by development (www.pinchot.org); black-legged ticks
(www.des.umd.edu) ; Borellia burgdorferi (CDC).
Introduction
For this project, imagine that you are a biologist who has been asked to make a presentation to the
town council of a rural-suburban town in New Jersey. The town council is drafting a development
strategy for the town and wants the input of a biologist familiar with Lyme disease ecology, since the
incidence of Lyme disease has been on the rise in their area. You will make a scientific poster
summarizing your points and supporting your arguments with data for your presentation to the town
council.
Schedule and basic description of parts:
Part 1 – Background/History (5 pts)
Answer some questions on the basic ecology of Lyme disease, based on a reading. Due printed
in recitation the week of 11/12
Part 2 – Data graphing and interpretation (5 pts)
Create and interpret a figure from a dataset. Due printed in recitation the week of 11/26
Part 3 – Implications of fragmentation (5 pts)
Create a diagram illustrating the effects of fragmentation on the community interaction network
and spread of Borrelia burgdorferi. Due printed in recitation the week of 12/3
Part 4 – Poster (25 pts)
Create a publication quality poster summarizing your finding and conclusions. Due uploaded to
Blackboard by 12/13.
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Project 2 – Part 1
Due printed in recitation the week of 11/12.
Read the article “The Ecology of Lyme-Disease Risk” by Richard Ostfeld (1997). Answer the following
questions; all the information you need to answer the questions can be found in the article. Just be sure
not to plagiarize the article in your answers, and do not use direct quotes from the article – your goal is
to demonstrate your understanding of Lyme disease ecology in your own words.
1. Briefly describe Lyme disease. What causes it? What are some of the most common symptoms?
2. For each of the following organisms, provide the common name and match each organism to its role
in the spread of Lyme disease.
a. Borrelia burgdorferi
i. reservoir host: organism that chronically harbors
the disease agent while showing no to little illness
b. Ixodes scapularis
ii. disease agent: organism that causes disease
iii. disease vector: organism that transports the
c. Odocoileus virginianus
disease agent from one host to another
iv. vector host: organism that is host (harbors) the
d. Peromyscus leucopus
vector organism
3. Below is the life-cycle of the black-legged tick. Answer the following questions about the life stages
(egg, larva, nymph, adult) of the black-legged tick.
a) On what organism(s) does the black legged tick feed at each life stage?
b) At what life stage(s) is it possible for the tick to acquire Borrelia burgdorferi? During which life
stage is it most likely?
c) B. burgdorferi can be transmitted from the tick to which organism(s)?
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4. What is a good predictor for the abundance of tick nymphs in a given year? According to Figure 6,
which habitats have the most ticks and which habitats have the least? Why might this be?
5. a) Refer to Figure 7. When do you see peaks in the mouse population in oak dominated forests?
b) What dispersal patterns from these oak forests have been observed for mice at peak abundance? See
Figure 9.
c) What relationship is there between mice population densities and risk of Lyme disease to humans?
Where are these high populations found?
6. Describe how the following factors found in Figure 8 are related to Lyme disease risk and explain
why.
a) Number of predators
b) Number of mice & chipmunks
c) Number of deer
d) Number of ticks
7. On page 8, Ostfeld describes the use of a computer model to predict Lyme disease dynamics. What
do these results suggest are important ecological factors related to risk from Lyme disease?
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Project 2 – Part 2 Background
Your presentation was requested because the town council learned that you’d recently conducted some
research on the relationship between Lyme disease risk and forest fragmentation in Dutchess County,
NY, the county with the highest incidence of Lyme disease in the United States (Orloski et al. 2000).
In preparation for your presentation to the town council, you need to analyze a dataset you recently
collected. You were interested in whether forest fragmentation (reduction in forested areas – for
example, through clear-cutting, development, or conversion to agriculture - resulting in smaller patches
of forest surrounded by non-forested areas) would affect the risk of Lyme disease. You designed an
experiment to test the hypothesis that Lyme disease risk is related to forest fragment size. You decided
to measure Lyme disease risk as the density of Ixodes scapularis tick nymphs infected with Borrelia
burgdorferi and followed the following methods to collect your data:
1. You selected 14 forest fragments of various sizes (measured as area in hectares) throughout Dutchess
County. All sites were maple-dominated forests, to control for the effects of acorn abundance. You
visited each site during peak tick activity.
2. At each site, you collected ticks using a standardized protocol which allowed you to record the
number of ticks per area. You counted only tick nymphs, since that is the life stage most likely to infect
humans (Barbour and Fish 1993).
3. You brought the collected tick nymphs back to your laboratory and tested each one for the presence
of B. burgdorferi. You pulverized each tick and then added rabbit antibodies to B. burgdorferi which
were labeled with a fluorescent marker. If the antibodies found and associated with B. burgdorferi in
the tick, the sample appeared to glow under immunofluorescence microscopy. Using this method, you
were able to determine which of the ticks you collected were infected with B. burgdorferi.
4. You recorded your data (below) for each site as density of infected nymphs / m2 (DIN).
Area (ha)
0.57
0.89
1.16
1.20
1.21
2.93
3.05
3.65
3.71
4.00
4.04
4.61
7.09
7.43
DIN
0.107
0.075
0.027
0.081
0.054
0.017
0.019
0.027
0.006
0.005
0.019
0.021
0.008
0.004
Methods and data for Part 2 adapted from Allan et al. 2003.
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Project 2 – Part 2 Assignment
Due printed in recitation the week of 11/26.
Open up a blank worksheet in Excel and enter the data above.
1. Make a scatterplot of the dataset. (If you need a reminder of how to do this, see the detailed
instructions for making a scatterplot with a trendline in HW5.)
2. Add a power function trendline by selecting “Power” from the “More Trendline Options” box.
You do not need to display the equation for the trendline on your figure.
3. Don’t forget to label the axes of your figure!
4. Include a figure caption/legend that briefly explains what is shown by the figure.
Answer the following questions:
1.
You used maple-dominated forests to control for the effects of acorn (produced by oaks)
abundance. Why is this important? (Recall what you learned about oaks in Part 1.)
2.
What hypothesis was tested in this experiment? Do the results support the hypothesis?
3.
What ecological factors do you think might be influencing the pattern you see in your data?
You can refer back to Part 1.
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Project 2 – Part 3 Background – DISCUSSED IN LECTURE/RECITATION
In order to suggest a mechanism for the results you graphed in Part 2, you did a thorough search of the
scientific literature on Lyme disease ecology and the species involved. Copied below are some of the
figures you found most useful.
The figure to the left is from a
paper investigating the effects of
fragmentation on white-footed
mice (Nupp and Swihart 1996).
1. A) What methods were used to collect the data in Figure 1 from Nupp & Swihart 1996?
B) What is the relationship between mice density and woodland size?
C) How does this relate to your Part 2 results?
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2) Use Table 1 from Rosenblatt et al. 1999 to sketch a graph of the relationship between species
richness (number of mammal species present) and area.
A) What is the overall relationship between fragment area and mammal species richness?
B) Which species were found in large forest fragments?
C) Which species were found in small forest fragments?
D) How does this relate to the previous figure on p. 6?
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Species
White-footed mouse
Eastern chipmunk
White-tailed deer
Raccoon
Virginia opossum
Gray squirrel
Body burden
Mean (SE)
N
27.8 (3.3)
28
36.0 (11)
57
239 (99)
12
127 (30)
12
254 (115)
21
142 (58)
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Reservoir competence
Mean % (SE)
N
92.1 (2.9)
15
55.0 (6.4)
20
4.6 (2.3)
19
1.3 (0.6)
12
2.6 (1.1)
18
14.7 (5.1)
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Table 1. Species parameters relevant to NIP (nymphal infection prevalence). All data were collected in
forest fragments in Dutchess County, NY. Body burden is defined as the mean number of engorged
black-legged tick larvae collected during a 72-h captive period. Reservoir competence is a measure of
the infection prevalence (% infected with B. burgdorferi) of the nymphs that resulted from feeding on
the host species as larvae.
The table above adapted from LoGuidice et al. 2003.
3) Using the Table 1 above from LoGuidice et al. 2003
A) Which species have the highest body burden? Which have the lowest? What might explain this
pattern?
B) Which organisms have the highest reservoir competence? Which have the lowest? What factors
may influence the reservoir competence of different mammal species?
C) Is body burden of ticks correlated with reservoir competence?
D) How might body burden and reservoir competence together affect Lyme disease risk in a forest
patch? Explain.
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The figure to the left is not based
on field data. The data were
derived from running a
mathematical model predicting
overall nymphal infection
prevalence (NIP) under various
scenarios. The model
parameters were determined
using data collected in the field,
including the data in Table 1
above.
The figure above was excerpted from LoGuidice et al. 2003.
4) Using Figure 2 from LoGuidice et al. 2003:
A) What does this figure show?
B) What ecological factors do you think affect the ability of an organism to dilute the effect of whitefooted mice?
5) Consider all the previous figures and tables and the figure you produced for Part 2. Why do you
think the density of infected nymphs is highest in small fragments?
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Project 2 – Part 3 Assignment
Due printed in recitation the week of 12/3.
Create a two-part figure showing the effects of forest fragmentation on the community of small
mammals relevant to Lyme disease in eastern forests. Figure A should depict the interaction network of
a large forest patch with higher species diversity. In Figure B, illustrate how the interaction network and
transmission of Borrelia burgdorferi are different in a small forest fragment with low species diversity.
As you know, eastern forests are diverse communities in which many species interact with one another,
but your figure will be a simplified interaction network showing some of the most important species
related to the ecology of Lyme disease. Remember that your goal is to illustrate how increasing
fragmentation affects forest mammal communities in a way that increases Lyme disease risk (as you
found in Part 2).
•
•
•
•
•
Choose from the following species for your figure: black-legged tick, white-footed mouse,
raccoon, eastern chipmunk, gray squirrel, white-tailed deer, Virginia opossum, coyote, fox. You
do not need to include all these species. You can find extra resources on these organisms online.
There are images posted on Blackboard for you to use if you like, or feel free to create your own.
If hand-drawn, figure must be publication-quality and submittable as a pdf file.
There is no single right way to make this figure - be creative! Use the examples of food webs
and interaction networks from lecture as inspiration. Color-coding, arrows, and relative size of
images are suggestions of ways to convey information visually. Make a key that explains your
use of symbols, colors, or other visual graphics.
You may choose not to include all possible species in the interest of highlighting those you feel
are most important, use Table 1 from Rosenblatt et al. 1999 to guide you.
Don’t forget to include a legend/caption for your figure!
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Project 2 – Part 4 Assignment
Upload a .pdf of your poster to Blackboard by Thursday 12/13.
Throughout this project, you have been acting as a biologist interested in the relationships between
forest fragmentation and Lyme disease risk. You designed an experiment to test a hypothesis about this
relationship and generated a graph of the data you collected.
Now you have been asked to advise a town council about how their future development strategy might
influence the Lyme disease risk in their community. You will make a poster, such as those displayed at
scientific conferences, to illustrate the main points of your presentation. Your poster should include a
graph of the data you collected on forest fragment area and DIN (from Part 2), a figure depicting the
effects of fragmentation on the community interaction network and the transmission of Lyme disease
(Part 3), and written text describing the a) context for your experiment, b) how your data were
collected, c) your explanation for the patterns you observed, d) what changes you predict in the
community overall if their proposed development strategy leads to increased forest fragmentation, and
e) your recommendations for future development plans in their town.
Posters presented at scientific conferences are usually assembled using PowerPoint. Researchers design
a single slide and then print it at the appropriate dimensions for a poster. Posted on Blackboard is a
PowerPoint slide that you can use as a template for your own poster. It also includes a brief description
of the type of information that should be included in each section of the poster. The second slide of the
posted PowerPoint file is an example of a completed poster. For this example, I used an experiment
from a paper about invasive pigs leading to declines in foxes in the Channel Islands as the subject –
please note that you are not required to know any of the information from the example! The final
poster (submitted as a .pdf – save your Powerpoint slide as a pdf when you are finished) will be graded
according to the rubric below.
Do not use direct quotations from any of your sources. Be sure to cite your references for the
information you write about within the text of the poster using whatever format you prefer (for
example, using numbers or parentheses). Most of these references can be found at the back of the
packet. Use APA or MLA style for full references in Works Cited (minor formatting errors will not be
penalized).
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Project 2 - Part 4 Rubric
Possible Points
Fig. 1: DIN vs. area Graph
Well-labeled, correct figure
2
Caption describes content of graph well
1
Fig2: Interaction Network Figure
Well-labeled, correct figure showing ecological interactions
1
Caption describes content of graph well
1
Visually conveys community changes & Borrelia burgdorferi transmission
2
Text - Intro
Brief intro to Lyme disease ecology
2.5
Hypothesis of research experiment
1
Text - Methods
Brief description of methods for DIN vs. area study in own words
2
Text - Results
Brief description of results of DIN vs. area study
2
Refer to diagram in text (Fig. 1)
0.5
Text - Discussion
Statement summarizing research & results
1
Brief description of proposed explanation of results
2
Refer to diagram in text (Fig. 2)
0.5
Brief description of the potential consequences if development strategy increases
fragmentation
1
Recommendation for development strategy
1
Text - Works Cited
Formatted reference list
1
In-text citation
1
Format
Neat/clear organization
2
Title
0.5
For all categories, full credit reserved for well-done work. Points will be deducted for lateness or
plagiarism.
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Literature Cited
Allan, B. F., F. Keesing, and R. S. Ostfeld. 2003. Effect of forest fragmentation on Lyme disease risk.
Conservation Biology 17:267-272.
Barbour, A. G., and D. Fish. 1993. The biological and social phenomenon of Lyme disease. Science
260:1610-1616.
LoGuidice, K., R. S. Ostfeld, K. A. Schmidt, and F. Keesing. 2003. The ecology of infectious disease: effects
of host diversity and community composition on Lyme disease risk. Proceedings of the National
Academy of Sciences 100:567-571.
Nupp, T. E., and R. K. Swihart. 1996. Effect of forest patch area on population attributes of white-footed
mice (Peromyscus leucopus) in fragmented landscapes. Canadian Journal of Zoology 74:467–
472.
Orloski, K. A., E. B. Hayes, G. L. Campbell, and D. T. Dennis. 2000. Surveillance for Lyme disease: United
States, 1992–1998. Morbidity and Mortality Weekly Report 49(SS03):1–11.
Ostfeld, R. S. 1997. The ecology of Lyme disease risk. American Scientist 85:338–346.
Rosenblatt, D. L., E. J. Heske, S. L. Nelson, D. M. Barber, M. A. Miller, and B. MacAllister. 1999. Forest
fragments in east-central Illinois: islands or habitat patches for mammals? American Midland
Naturalist 141:115–123.
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