Project Title:
Encounter filters that determine host preference in ticks

Project Description (short):
Tick species show preference in what host they choose to parasitize but there is little information to understand why they have preferences. The specific objective of this project is to determine if encounter mechanisms are an important filter in establishing host preference of ticks in the small mammal community of northeast Missouri. We will address this objective by determining the habitat preferences and patterns of activity of a common host, Peromyscus (white-footed mouse), and the two possible tick parasites, Dermacentor variabilis and Ambylomma americanum. Students involved in this research will learn a variety of field, laboratory and statistical methods. (Longer description here.)

Skills needed:
Both students will need to demonstrate the following:

• The ability to conduct field work under arduous environmental conditions.
• Willingness to handle and sacrifice small mammals, ticks and other parasites of small mammals.
• Willingness to engage problems and issues outside their discipline.
• Willingness to follow directions and execute independently.
• Willingness to work as a member of an interdisciplinary team.

Biology:

• Required Coursework:, STAT190 (Introduction to Statistics)
• Preferred Coursework: BIOL 301 (Introduction to Ecology)
• Preferred Experience: Handling and sacrificing insects and small mammals

Mathematics Students:

• Required Coursework: STAT 290 (Introduction to Statistics)
• Preferred Coursework: STAT 378 (Regression), STAT 375 (ANOVA), STAT 570/571 (Mathematical Statistics), BIOL 100 (General Biology)
• Preferred Experience: SPSS, C language, R, Excel

Start Date:
January 2008

End Date:
Ongoing

Mentors:
Prof. Laura Fielden-Rechav (Biology) lfielden@truman.edu
Prof. Stephanie Foré (Biology), sfore@truman.edu
Prof. Hyun-Joo Kim (Statistics), hjkim@truman.edu

Current RLC Students:

• None.

About Prof. Foré:
Dr. Foré has resided in Kirksville for eleven years, the longest she has lived in any one place or state. She received her B.S. in Biology from St. Andrews Presbyterian College, a very small liberal arts school, a M.S. in Plant Pathology from North Carolina State University and a Ph. D. in Botany from Miami University. Before coming to Truman she did postdoctoral work in the Department of Zoology at Miami University and was a Research Ecologist at Savannah River Ecology Laboratory. She is transitioning from primarily plant population biology to animal population/community ecology and is enjoying her collaboration with Dr. Fielden and Dr. Kim and many wonderful students. She loves to take long walks in wild, unpopulated places, spin and dye her own yarn which she then knits, and eat richly spiced food and therefore has learned to cook ethnic food.

About Prof. Kim:
Dr Kim was born and raised in Seoul Korea. She completed her M.S. (1998) and Ph.D.(2000) in Statistics department at the University of Missouri-Columbia. Her research emphasized model building and model selection criteria in linear and nonlinear regression models. Recently, she is interested in Statistical application in Biology including logistic regression model, logit model, discriminant analysis, spatial statistics, and longitudinal analysis.

She has a two and a half year old daughter (Juni) and a four month old son (Minu) who claims most of her free time. She enjoys doing yoga, walking, eating Korean food and cuddling with her kids.

About Prof. Fielden:
Dr Fielden was born, raised and educated in Southern Africa. She completed her Ph.D in Zoology at the University of Natal , South Africa. She considers herself first and foremost an ecophysiologist and is currently interested in water balance and energetics of ectoparasites specifically ticks and fleas. She has been teaching at Truman for seven years and has particularly enjoyed her research activities with undergraduate students. She loves to travel (with her family), sample fine cuisine and watch great movies.

Project Description (long):
Small mammals often serve as reservoirs for microparasites that cause disease in humans and domestic animals (for example Rocky Mountain Spotted Fever). Ticks are one ectoparasite of these small mammals that are important vectors of microparasites to other animals. Host-parasite associations range from generalist, feeding on many hosts, to highly host specific, feeding on only one host (Poulin 1992, Combes 2001). Combes's filter concept (Euzet and Combes 1980; Combes 1991, 2001) postulates that the host specificity of a parasite is determined by host-encounter and host-compatability filters. Encounter filters exclude all hosts that a parasite cannot meet for behavioral or ecological reasons. Compatibility filters exclude species on which a parasite cannot survive and develop for morphological, physiological or immunological reasons. The long term goal of our research is to examine factors that are important in determining host specificity in ticks parasitizing small mammals and the consequences of this specificity for both host and parasite individuals.

The specific objective of this Math-Bio project is to determine if encounter mechanisms are an important filter in establishing host preference of ticks in the small mammal community of northeast Missouri. Previous work in our lab has shown that there are variety of small mammals in our study sites at the Truman State University farm. The most common species is Peromyscus leucopus, but the communities also include other rodents and shrews. We have collected two species of ticks, Dermacentor variabilis and Ambylomma americanum, living off-host. However, we have found the larval and nymphal stages of only one of these species, D. variabilis, on rodents. No ticks have been observed on shrews. Encounter mechanisms that could give rise to this preference for rodent hosts by D. variabilis but not A. americanum may relate to a) habitat usage by ticks and rodent species and b) daily and seasonal activity patterns of ticks and rodent species.

The specific questions that we seek to address include. What are the habitat preferences of the most common rodent P. leucopus and its close relative P. maniculatus? What are the habitat preferences of D. variabilis and A. americanum? What are the seasonal and daily patterns of activity of rodents and ticks?

Methods:
To address these questions we will use mark-recapture to determine habitat usage of Peromyscus over short periods (days) and longer periods (months) of time. Seasonal and daily patterns of activity of ticks off host will be assessed by drag sampling and/or bait stations. Vegetative habitat will be assessed by determining cover of physiognomic categories (i.e., trees, shrubs, herbs, grasses). Meterological variables, such as temperature and humidity, will be assessed at the regional and microhabitat scale.

First, the ''hot spot'' for small mammal and tick activity will be determined. Hot spots for each species and the relation among them will be visualized and analysed in the GIS environment. In addition to understanding the species' geographical preference, this will provide us better insights for the study of how the abundance of each species is affected by the vegetative habitat and metrological variables. For this research, various statistical techniques will be used including logistic regression, logit modeling, repeated measure, and time series analysis. Seasonal and spatial factors will also be considered. Computer software such as GIS, SPSS, and R will be used for the analysis.

References:

• Combes, C. 1991. Evolution of parasite life cycles. Pp. 62-82 in: Parasite-host associations: Coexistence or conflict? (eds. C. A. Toft, A. Aeschlimann & L. Bolis). Oxford Univ. Press: Oxford.
• Combes, C. 2001.Parasitism. The ecology and evolution of intimate interactions. Univ. Chicago Press: Chicago.
• Euzet, L. & Combes, C. 1980. Les problemes de léspece chez les animaux parasites. Bull. Soc. Zool. Fr. 40: 239-285.
• Poulin, R. 1992. Determinants of host-specificity in parasites of freshwater fishes. In. J. Parasitol. 22: 753-758.