Parasitism and Stress

Research in the Davis lab is broadly focused on animal “ecophysiology”, with study subjects ranging from birds, to butterflies, to beetles. REU students can make many contributions to these ongoing projects, with a combination of field work and laboratory experiments.  A recent thematic area involves asking, how can animals cope with the daily stressors in their lives while being parasitized? A useful study subject for these experiments is a common forest-dwelling beetle (horned passalus, pictured), which is naturally-parasitized by a seemingly benign nematode (pictured). This parasite appears to cause little outward harm to its host, but during times of duress or heightened activity, there is in fact an observable cost to being parasitized.

In the summer of 2020, an REU student will conduct an experiment that tests the behavioral and physiological reactions of parasitized and unparasitized beetles to a mild, non-lethal stressor, to further understand how parasites impact their hosts. The details of this project will depend in part on the interests of the student. The ideal applicant for these projects is someone who is OK with traipsing through chigger-infested forests, is able to work with (handle) bugs, and who is not squeamish about icky dissections.

Mentor: Andy Davis
Type of project: Empirical, Lab- or field-based

Understanding hydrogen peroxide employment by honeybees as an anti-parasitic social immunity tool

Hydrogen peroxide has immunological function across a broad suite of life on earth, and is still used in the US as a common antiseptic. Honeybees are another self-medicating social animal also known to use hydrogen peroxide manipulation – mostly in honey production; this in part makes it the only naturally occurring foodstuff to never spoil and underpins part of its medical applications in wound healing. Previous undergraduate work with UGA and Emory University investigated whether hydrogen peroxide content in honey poses a toxicity risk to a macroparasite, the small hive beetle, in addition to its antimicrobial effects. Dr Lewis Bartlett is currently trialling novel small hive beetle control methods, and this project will integrate with that work to further establish: ranges of hydrogen peroxide content in naturally occurring honey across different nectar sources, honeybee tolerance of hydrogen peroxide consumption and whether it exceeds that of other insects, and toxicity of hydrogen peroxide to juvenile and adult small hive beetles with the potential for it to be employed as a parasite control agent. The study will further be framed in the context of floral diversity and pollinator health, by determining whether different plants favour the production of honey with different antiparasitic or antiseptic properties through. The student will undertake empirical entomological toxicity trials and basic entomological rearing at the UGA honey bee lab, as well as data analysis and visualisation focussed on assessing survivorship, with the aim to produce a concise scientific publication; they will also have the opportunity to learn field skills in apicultural research if they wish. The student will also be given the option to attend (for free – including transport from Athens, meals and accommodation) a leading honeybee conference in North Georgia (https://bees.caes.uga.edu/yhc-uga-beekeeping-institute.html) as an introduction to the system in the week of May 11th – 16th, prior to the official REU start date of May 18th.

Mentor: Lewis Bartlett
Project Type: Empirical, lab- and field-based

Specific Requirements: Student cannot have a known allergy to honeybees, and must have no objection to euthanasia or experimental destruction of live insects for research purposes.

Honeybees in a hive

How parasites influence ecosystems: studying the varied effects of a trematode parasite on its environment

Historically, parasites have been primarily studied for their negative effects on human and animal health. However, the scientific community is becoming increasingly aware that parasites can have complex effects on their ecological communities (Dunn et al. 2012, Mischler et al. 2016), and in some cases can benefit the ecosystem (Davis and Prouty 2019). How parasites alter ecosystem processes and nutrient cycling remains relatively unexplored, despite calls to address this question (Raffel et al. 2008, Hatcher et al. 2012). However, this question is vital because such research could provide novel insights into both human and ecosystem health.  In addition to the direct impacts of parasites on host mortality and population growth, parasites can indirectly impact their communities and environments in subtle, but equally important ways (Buck and Ripple 2017). For example, parasites can alter ecosystem processes through changes in host physiology (Bernot and Lamberti 2008), nutrient excretion stoichiometry (Bernot 2013) and behavior (Lafferty and Ecology 1996) that have population and community-wide effects. For this project, we will investigate how a trematode parasite influences its snail host, Helisoma trivolvis, in terms of various host changes such as nutrient excretion, metabolism, respiration, foraging and behavior. The REU student will investigate these effects by comparing infected and uninfected snails in the lab. The majority of the work will be done in the lab, but there is possibility for field work and field manipulations given time and interest.

Mentors: Emlyn Resetarits and Jeb Byers
Type of project: Empirical, lab-based

Who is at risk of getting infected in structured contact networks?

Human immunodeficiency virus transmits through networks of people linked through a
range of contacts, including sexual contact and intravenous drug use. SARS and Foot
and Mouth Disease are spread through long-distance movements of infected people
and livestock, followed by local transmission. These outbreaks demonstrate the
important role of networks to transmission of pathogens. Networks can be quantified in
many ways, and an individual’s “importance” to the population can be described with
node “centrality” statistics. Identifying which centrality statistics indicate an individual
has high vulnerability to infection could greatly enhance surveillance and prevention.
However, pathogen transmission routes and human social networks are highly variable
in their structure. For example, sexual contact networks for HIV tend to be assorted by
race. This project will investigate our ability to predict the vulnerability of individuals to
infection when networks are structured in space or social groups. These results could
help us understand when it is worthwhile to estimate node centrality for surveillance
and prevention systems.

The student selected for this project will work closely with Paige Miller (PhD student) to
write computer code (R and python) for disease simulations on networks. The project
will be supervised by Dr. John Drake (Odum School of Ecology, Director of the Center
for the Ecology of Infectious Diseases) and Dr. Chris Whalen (College of Public Health,
Director of the Global Health Institute). This is a quantitative and simulation-based
project; we will not be collecting our own data. Long hours of learning how to code and
manage data in R will be required. An interest in mathematical modeling of infectious
diseases, ecology, and human sociology is encouraged. The student is free to tailor
this project to their own interests by focusing on specific pathogens or populations!

Mentors: Paige Miller, John Drake, Chis Whalen