Using museum specimens and field samples to examine the host range and divergence of a protozoan parasite across milkweed butterflies

This project examines the host range and evolutionary divergence of parasites, focusing on a debilitating protozoan Ophryocystis elektroscirrha (OE) that infects wild monarch butterflies (Danaus plexippus) throughout their worldwide range. The same or similar protozoan parasites also infect several other milkweed butterflies and noctuid moths. Because this parasite is prevalent in monarchs and can reduce monarch abundance, identifying the broader distribution of this parasite across different butterfly species is important. The REU student will summarize existing knowledge and new data on the host range and geographic distribution of OE-like parasites. Work in the laboratory will involve microscopy diagnostics of field-collected samples from neotropical butterfly species, together with analysis of samples archived from preserved museum specimens, and from a citizen science monitoring program. Methods will include scoring the infection status of butterflies, and digital image analysis to quantify differences in parasite spore morphology from different butterfly hosts. The student will learn computational approaches for data analysis and visualization, and will have the opportunity to participate in ongoing experiments with live butterflies and their parasites.

Mentors: Maria Luisa Muller-Theissen, Sonia Altizer, and Paola Barriga
Type of Project: Combination Empirical (lab-based) and Quantitative

Museum display of butterflies


Investigating phylogenetic differences of Dracunculus species in wildlife

Nematodes in the genus Dracunculus are large, subcutaneous parasites found in a variety of wildlife. In North America, Dracunculus insignis frequently infects raccoons (Procyon lotor), but has also been reported from domestic dogs and cats. In 2018, a novel Dracunculus species was recovered from a Virginia opossum (Didelphis virginiana) in Georgia, and is most closely related to a specimen recently recovered from a domestic dog in Spain. These findings highlight a knowledge gap in our understanding of the genetic diversity of dracunculids in wildlife in North America. The goal of this project is to evaluate the phylogenetic relationships of Dracunculus species recovered from retrospective and current samples collected from wildlife in Georgia. The student will be trained in and will perform molecular and phylogenetic analyses (involving DNA extraction, PCR, Sanger sequencing), as well as assisting with the development and optimization of a multiplex Real Time PCR to evaluate multiple species of Dracunculus. The student will gain valuable experience in laboratory procedures for molecular analyses of wildlife parasites, developing phylogenetic trees highlighting the relationships of parasites, and will contribute to a growing field of research with an understudied and intriguing genera of parasites. 

Host Lab: Dr. Chris Cleveland and Dr. Michael Yabsley
Type of Project: Emprircal (lab-based)

Image of Copepod infected with Dracunculus
Copepod infected with Dracunculus


OrNet: Spatiotemporal analysis of organelle morphology

The goal of this project is to develop and use a screening program to assess interactions between virulence factors secreted by intracellular bacterial pathogens and the target cellular organelles. The post-acquisition image processing software package, called OrNet, allows for analysis of tiny changes in organelle shape, spatial distribution, and mass over the course of infection. By examining changes in organelle dynamics during infections with bacterial mutants (each deficient in a single virulence determinant), we aim to determine which bacterial factors affect organelle processes and use that information to better understand bacterial virulence mechanisms and host cell control of organelle function.

Host Lab: Dr. Fred Quinn
Type of Project: Quantitative

Patterns of infectious disease in aquatic communities

The transmission of infectious disease occurs in a community context, with host species often interacting with their competitors and predators. These competitors and predators can in turn shape disease dynamics in populations of hosts. The ‘healthy herds hypothesis’ predicts that predators suppress epidemics in populations of their prey by selectively culling infected individuals, thereby inhibiting transmission from these infected hosts. In other words, predators may keep the herds of their prey healthy. While strongly supported by theory, empirical evidence of the ‘healthy herds hypothesis’ remains relatively weak. 

The proposed REU project will assess whether field patterns of infectious disease in aquatic communities are consistent with the healthy herds hypothesis. The focal host, Ceriodaphnia dubia is a zooplankton that often dominates grazer communities in shallow North American lakes. It suffers seasonal epidemics caused by the virulent bacterial parasite, Pasteuria ramosa. Planktivorous fish are predators that seem likely to suppress epidemics in C. dubia, because as visual predators, they are likely to target infected hosts. The host (C. dubia), parasite (P. ramosa), and predator (planktivorous fish) are all present in a set of four ponds located in Whitehall Forest, near UGA campus.

The project will include a field survey of the ponds located in Whitehall Forest, which will encompass one full day of field work per week for ~8 weeks (sampling the four ponds from kayaks) along with a substantial amount of dedicated microscope work. Time at the microscope will be spent identifying host species (different zooplankton taxa), visually quantifying infection prevalence in the focal host, and quantifying body size of hosts as an index of fish predation intensity. The REU will also learn appropriate statistical approaches to analyze the data, and will have the opportunity to participate in complementary lab-based experiments.

Mentors: Alex Strauss & Kate Galbraith
Type of project: Empirical, lab-based

Image of Ceriodaphnia dubia
A healthy Ceriodaphnia dubia, the focal host (photo credit: Meg Duffy)


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.

Mentor: Emlyn Resetarits
Type of Project: Empirical (lab- and field-based)


Temperature effects on parasite transmission: investigating key parameters to inform management of shrimp black gill disease on the Georgia coast

It is widely accepted that temperature influences the interactions between hosts and parasites, however, the effects of temperature on host-parasite relationships is often complex and nonlinear. Increasing temperature is thought to increase the rate of transmission of Hyalophysa lynni, the ciliate that causes shrimp black gill disease. The mechanism behind this potential increased rate, whether it is through increased replication of H. lynni or through weakened host defenses, is unclear. Evidence suggests that shrimp infected with the ciliate have increased mortality and reduced ability to escape predation. Therefore, understanding the factors shaping the transmission of H. lynni is a top priority for the management of Georgia’s shrimp fishery. This project will continue investigating temperature effects on H. lynni transmissionby measuring natural transmission rates in the field and conducting temperature-controlled experiments in the lab. The REU student will help with shrimp husbandry and experimental design and execution on the Georgia coast. Additionally, the student will learn molecular techniques such as DNA extraction, PCR amplification and gel electrophoresis. The information gained from this project will be used to parameterize a future model describing shrimp-H. lynni interactions and to later provide management recommendations to stakeholders.

Mentor: Jeb Byers
Type of project: Empirical (field-based) and Quantitative

two shrimp


Parasite effects on behavior and stress responses in beetles

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 2021, an REU student will conduct an experiment that tests the behavioral and physiological reactions of parasitized and unparasitized beetles to one or more mild, non-lethal stressors, to further understand how parasites impact their hosts. The details of this project will depend in part on the interests of the student. Students who enjoy handling insects, collecting beetles under logs in forests, recording behaviors, and dissecting insects for parasite infection are well-suited to this project.

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 may, if the conference is running, 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.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

Mammalian host biodiversity and filovirus spillover risk in Africa

Ebola and other filoviruses are multi-host pathogens that can infect a wide variety of species, and filovirus emergence presents a pressing threat to human health.  Presumably areas that contain large numbers of host species that are susceptible to filoviruses or that contain key reservoir species (such as bats) in high abundance are also areas where the risk of transmission from wild animals to humans is high.  However, this hypothesis has rarely been tested.  Using data on the location of past spillover events of Ebola, Marburg virus, and other filoviruses in Africa, the goal of this project will be to test what aspects of mammalian host biodiversity (e.g., variation in  mammalian species richness, phylogenetic diversity, or ecological diversity) have the greatest impact on spillover risk.  Mammalian host data will be drawn from a variety of published sources such as PanTHERIA (a species level database of mammalian trait data) and species range data compiled by the International Union for Conservation of Nature. The project will involve compiling large data sets and analyzing them using the R programming language. 

Project Mentor: Patrick Stephens
Type of Project: Quantitative/Computer-based

Development of infectious disease research and teaching software

Using computer models to study infectious diseases can be challenging for students and researchers who are not trained as modelers. To make this process easier, we have developed several software packages, implemented in the popular R language, to help individuals learn about and analyze infectious disease models both at the individual and population level. The goal of this project is to further advance this software by implementing new features, making tutorials, testing existing features, adding new features, and more. This will increase the usefulness and power of the software and will give future students and researchers better tools to learn about and analyze different infectious diseases. This project is quantitative. We will make use of the R language for all parts of this project. The project is offered by the Handel group.

Host Laboratory: Andreas Handel
Type of project: Quantitative/Computer-based