This year’s GSS was a major success! This year, Odum hosted its largest Graduate Student Symposium in history, with a record number of both graduate student presenters (40) and undergraduate posters (28). To top it all off, there was a wonderful presentation by this year’s keynote speaker, an Altizer Lab alum, Dr. Cecilia Sánchez.
Big thanks to all who participated, visited, presented, and put in valuable time and effort to make such an event possible! Let’s make future GSS events live up to this one!
OSE graduate students congregate on a red cedar (Juniperus virginiana) branch at the Wormsloe Historic Site.
During the fourth weekend of April 2022, 25 OSE graduate students embarked on the inaugural OSE Graduate Student Retreat in Savannah, Georgia. Envisioned by our Graduate Program Representatives, Cali Wilson and Daniel Suh, the retreat fulfills a recent initiative by UGA Graduate School’s to promote retention and inclusion. And, in the wake of two COVID-19 pandemic years with remote learning and canceled school traditions, the OSE graduate students were keen to connect in the outdoors.
UGA’s Center for Research and Education at Wormsloe (CREW) hosted the students in their cabin facilities on the Wormsloe Historic Site. This site is rich in cultural and environmental history. First constructed as a fort to protect from Spanish invasion, then operating as a plantation worked by enslaved people, the 800+ acres are now managed as a State Historic Site.
Building on several diversity, equity, and inclusion initiatives hosted by OSE, this weekend presented an opportunity to engage with the issues of environmental justice and racism in coastal Georgia. Students visited the Pin Point Heritage Museum to learn about the settlements and lives of freed slaves who were forced off Skidaway Island, and the role of oystering as an industry for Gullah/Geechee people. Then, led by OSE graduate candidate Jeff Beauvais, students toured downtown Savannah, on a 2.5 mile loop hearing about the human migrations and politics that have occurred in this historic port city.
Of course, ecology nerds can’t visit the marsh without some outdoor activities. Andrew Nagy led a fishing expedition and Anna Willoughby took kayakers out on the Skidaway River. Laura Kojima and friends herped in the dead of night, and Jeff Beauvais taught crabbing techniques. Our Saturday ended with a boat ride with dolphin sightings and lots of sea bird squawks.
The weekend ended with a tour of Wormsloe, led by Wormsloe Foundation President and UGA librarian Dr. Sarah Ross. We discussed the importance of heirloom seeds, the abundance of fresh water on the Isle (the tastiest on earth!), and the strength of tabby as a building material.
Experimental gardens at the CREW site used by Ania Majewska for her dissertation research. Figure borrowed from Majewska et. al. 2018.
Several OSE alumni have collaborated with CREW for their graduate research as Wormsloe Fellows, including Ania Majewski (Ph.D 2019), Alyssa Gehman (Ph.D 2016), and Jennifer Pahl (M.S. 2009). These alumni researched diverse systems including butterfly gardens, mud crab parasites, and wetlands. CREW is growing, with new facilities planned to expand opportunities for teaching and research on Isle of Hope.
What a successful weekend! Special thanks to Dr. Sonia Altizer, Dr. Craig Osenberg, Mica Turner, Laura Leachman, Jennifer Mathews, Amberly Tankersley, Leslie Sitz, Joanne Greenway, and the Retreat Planning Committee: Jeff Beauvais, Daniel Suh, Cali Wilson, Matt Pierce, Alyssa Quan, and Anna Willoughby.
Black Girls Create is an after-school program directed by Dr. LaShawnda Lindsay, highlighted in the article by Scott-Elliston, Arnold, and Pittman.
PhD Student Kaylee Arnold co-authored, “A Call to Address Disparities in K-12 Education for Black Youth“, published by the American Society for Microbiology. In this piece, Arnold and co-authors discuss the history of science education for Black children in the United States and highlight programs that are effectively engaging Black youth.
Congratulations, Anecia! As part of this scholarship, she will utilize a variety of field and laboratory methods to understand the ecology of Malagasy fruit bats. She will characterize viral dynamics of Malagasy fruit bats through antibody analysis of bat tissue types. She will determine seasonal resource use through isotope analysis of bat hair. Lastly, she will deploy GPS trackers on bats to delineate the extent of seasonal fruit bat overlap in home range.
In an *UNPRECEDENTED* year, a delayed Ecology and Evolution of Infectious Diseases meeting reformulated into an “Animal Crossing”-esque virtual conference extravaganza. Check out the amazing work OSE students and graduates presented while navigating a complex map full of disease experts, habitat boundaries, and french paraphernalia.
Aedes aegypti outcompetes Anopheles stephensi across a range of larval temperatures MV Evans, JM Drake, L Jones, CC Murdock
Anopheles stephensi, the primary vector of malaria in urban centers in India, has recently expanded its range across the Middle East and North Africa, raising concern it may become established and contribute to urban malaria transmission in sub-Saharan Africa. In its invasive range, An. stephensi interacts with resident mosquito species, and understanding how these interactions can affect An. stephensi population dynamics is necessary to predict transmission risk at the species’ invasive edge. Further, mosquito life-history traits are extremely sensitive to temperature and competition between mosquito species may be dependent on temperature as well. Here, we explored temperature-dependent competition between An. stephensi and Ae. aegypti across five temperatures (16 – 32 C). We measured traits relevant for population growth from which we estimated each species’ per capita growth rates and derived each species’ competitive ability at each temperature. Ae. aegypti emerged as the dominant competitor at all temperatures, primarily due to differences in larval survival and development times across the two species. Our results suggest that competitive interactions with resident mosquito species, such as Ae. aegypti, could shape the distribution of An. stephensi, and therefore the human population at risk of urban malaria, across its invasive range.
Community composition, abundance, and environmental coditions may synergistically enhance transmission of a ranavirus in larval amphibian communities
Daniel Suh and Andrew Park
Communities of hosts can change through space and time, altering the transmission potential of parasites. We investigated how changes in host composition, total host abundance, and environmental conditions affect a ranavirus in larval amphibian communities. We developed a dynamical model for ranavirus in a 2-species community and manipulated this model in terms of community composition, host abundance, and viral half-life. Next, we measured community competence, diversity (richness, evenness, phylogeny), and overall composition using previously collected amphibian community data. Community competence is the propensity for a community of hosts to support a parasite and was calculated as the sum of the products of each species’ mean viral load and their relative abundance in a community. After calculating these metrics, we used data visualization and correlation tests to detect patterns between our variables of interest (composition, abundance, and environment) and transmission potential of ranavirus.
Our transmission model showed that manipulations of community composition, host abundance, and viral half-life can all enhance a community’s ability to support a parasite, and that when combined, the effects of these variables resulted in communities highly susceptible to ranavirus. Analysis of real host communities confirmed that similar host compositions (according to PCA ordination) had similar community competence, but dissimilar compositions could still result in similar community competence. In our diversity analysis, we found patterns across an evenness gradient but not across richness. We also saw that high competence species appeared intermediately dispersed throughout the phylogeny. Further analysis showed that communities with high community competence were often the most abundant and occurred in months with lower temperatures, resulting in communities highly susceptible to ranavirus. Finally, in univariate correlation tests, community competence, host abundance, and water temperature were all significantly correlated with infection prevalence in host communities.
Parasite and host traits predict the zoonotic risk of protozoa
Joy Vaz, Barbara A. Han, John M. Drake
Protozoan zoonoses such Chagas disease and leishmaniasis remain endemic in large parts of the world, exacerbating social inequity and contributing heavily to the global burden of infectious disease. Novel protozoa species which have emerged from wildlife to humans in the recent decades (e.g., Plasmodium knowlesi, a causal agent of malaria) have proven difficult to control. Our ability to anticipate and prevent future emerging disease threats relies on identifying the characteristics of zoonotic pathogens and targeting surveillance efforts accordingly. While several studies have profiled the traits of zoonotic viruses, protozoa have received limited attention. We compiled a dataset of protozoa species which incorporates both parasite and host traits, including information on community structure and importance within a host-parasite bipartite network. Using a machine learning algorithm, extreme gradient boosting, we distinguished zoonotic from non-zoonotic protozoa with 85% accuracy. Our model found that traits of generalist protozoa (e.g., broad tissue tropism, high network centrality, multiple transmission modes) were most useful for predicting zoonotic status, compared to intrinsic biological traits (e.g., morphology), environmental traits (e.g., temperature), or host-related traits (e.g., life history). We ranked the zoonotic potential of protozoa species currently not known to be zoonotic based on their trait similarity to known zoonotic protozoa. Here we report parasitic protozoa species of wild mammals which are most likely to be undiscovered sources of current or future zoonoses, identifying them as priority targets for surveillance.
Urbanization, food provisioning, and transmission-relevant behaviors in Florida white ibis
Cali A. Wilson, Julia N. Weil, Sonia M. Hernandez, Sonia Altizer, Richard J. Hall.
As urban areas expand and natural habitats shrink, many wildlife species have shifted into cities. In urban areas, animals often aggregate at higher density, move less, encounter anthropogenic stressors, and alter their diets by consuming human-provided food, all of which can affect the transmission of infectious diseases. American white ibis (Eudocimus albus) in South Florida are well-suited for studying the consequences of urbanization on pathogen transmission. Ibis naturally reside in wetlands but now commonly forage in urban parks and consume human-provided food. In this study, we investigate how transmission-relevant ibis behaviors change between urban and natural sites, across urban sites along a gradient of provisioning, and when urban ibis are fed. We find that ibis in urban parks spent less time actively foraging relative to those in natural wetlands. Within urban sites, foraging, preening, and vigilance behaviors differed across the sites observed. Ibis at two urban sites foraged less, on average, than those at other sites, but spent significantly more time preening or being vigilant. Lastly, during feeding intervals, ibis density increased by over 20 times each time food was thrown. These results suggest that urbanization and provisioning alter wildlife behavior in ways that can influence exposure to parasites. Specifically, in ibis, food provisioning can increase local density and contact rates for transmission of directly-transmitted parasites, while decreasing exposure to environmentally-transmitted parasites due to lower active foraging time. Further studies of how urbanization and recreational feeding influences wildlife behavior can inform management strategies to benefit both wildlife and human health.
Heterosporis sutherlandae is an invasive microsporidian parasite in the Great Lakes region of North America that infects the skeletal muscle of numerous fish species, rendering the fillet unfit for human consumption. Although H. sutherlandae has been identified as a pathogen of concern by state management agencies, there is little information to inform regulation and intervention. We sampled fishes over 1 year from three lakes in northern Minnesota with known infected populations to determine the importance of host demographic and environmental variables for influencing H. sutherlandae infection prevalence. Heterosporis sutherlandae was present during all sampling periods, ranging in prevalence from 1% to 11%. The prevalence of H. sutherlandae among Yellow Perch Perca flavescens varied significantly according to season, with winter having the lowest prevalence (1%) and summer having the highest prevalence (11%). For other fish species, the prevalence of H. sutherlandae also varied significantly with season: the lowest prevalence occurred during spring (1%) and the highest prevalence occurred in fall (9%). Rates of pathogen transmission were estimated by exposing Fathead Minnows Pimephales promelas in the laboratory. Transmission rates were 23% when naïve fish were fed infected tissues and only 2% when naïve fish were held in cohabitation with tissue-fed fish. Exposure method and exposure duration (d) increased the probability that a fish was infected with H. sutherlandae. These findings suggest that H. sutherlandae transmission is greater when a susceptible host consumes infected tissue than when the fish is exposed to spores present in the water column. The current rates of infection in wild fishes are in stark contrast to the prevalence documented in 2004 (28%), suggesting a reduction in H. sutherlandae prevalence within at least one Yellow Perch population in the Laurentian Great Lakes region since the early 2000s.
Tomamichel MM, Venturelli PA, Phelps NB. Field and Laboratory Evaluation of the Microsporidian Parasite Heterosporis sutherlandae: Prevalence, Severity, and Transmission. Journal of Aquatic Animal Health. 2020 Dec 28. https://afspubs.onlinelibrary.wiley.com/doi/full/10.1002/aah.10122
A CDC Miniature Light Trap used in the fieldwork for López et al. 2021. Photo provided by Juliana Hoyos.
The Leishmaniases are a group of neglected tropical diseases caused by different species of the protozoan parasite Leishmania, transmitted to its mammalian hosts by the bites of several species of female Phlebotominae sand flies. Many factors have contributed to shifts in the disease distribution and eco epidemiological outcomes, resulting in the emergence of Cutaneous Leishmaniasis outbreaks and the incrimination of vectors in unreported regions. New research development is vital for establishing the new paradigms of the present transmission cycles, hoping to facilitate new control strategies to reduce parasite transmission. Hereafter, this work aims to model and infer the current transmission cycles of Cutaneous Leishmaniasis in Colombia defined by vector and mammal species distributed and interacting in the different regions and validate them by performing sand fly and mammal collections. Vector-host co-occurrences were computed considering five ecoregions of the Colombian territory defined by the World Wide Fund for Nature (WWF) and downloaded from The Nature Conservancy TNC Maps website. Four validation sites were selected based on Cutaneous Leishmaniasis prevalence reports. Sand flies and mammals captured in the field were processed, and species were defined using conventional taxonomic guidelines. Detection of infection by Leishmania was performed to identify transmission cycles in the selected areas. This study uses predictive models based on available information from international gazetteers and fieldwork to confirm sand fly and mammalian species’ sustaining Leishmania transmission cycles. Our results show an uneven distribution of mammal samples in Colombia, possibly due to sampling bias, since only two departments contributed 50% of the available samples. Bats were the vertebrates with the highest score values, suggesting substantial spatial overlap with sand flies than the rest of the vertebrates evaluated. Fieldwork allowed identifying three circulating Leishmania species, isolated from three sand fly species. In the Montane Forest ecosystem, one small marsupial, Gracilinanus marica, was found infected with Leishmania panamensis, constituting the first record of this species infected with Leishmania. In the same locality, an infected sand fly, Pintomyia pia, was found. The overall results could support the understanding of the current transmission cycles of Leishmaniasis in Colombia.
López, M., Erazo, D., Hoyos, J. et al. Measuring spatial co-occurrences of species potentially involved in Leishmania transmission cycles through a predictive and fieldwork approach. Sci Rep11, 6789 (2021). https://doi.org/10.1038/s41598-021-85763-9.
Check out the new book chapter on mosquito virus development by OSE students Mike Newberry and Nikki Solano-Asamoah, and recent OSE graduate Dr. Michelle Evans!
Reitmayer CM, Evans MV, Miazgowicz KL, Newberry PM, Solano-AsamoahN, Tesla B, and CC Murdock. Mosquito- virus interactions. InPopulation Biology of Vector-Borne Diseases. Drake JM, Bonsall M, Strand M, editors. Oxford University Press; 2020 Dec 30. Section 3; Chapter 11.
Figure 2 from the paper. Predicted probabilities of OE infection are plotted over the range of experimental temperatures for the three exposure durations: 2 weeks (purple), 35 weeks (blue), and 93 weeks (green). Provided by Isabella Ragonese.
Many parasites have external transmission stages that persist in the environment prior to infecting a new host. Understanding how long these stages can persist, and how abiotic conditions such as temperature affect parasite persistence, is important for predicting infection dynamics and parasite responses to future environmental change. In this study, we explored environmental persistence and thermal tolerance of a debilitating protozoan parasite that infects monarch butterflies. Parasite transmission occurs when dormant spores, shed by adult butterflies onto host plants and other surfaces, are later consumed by caterpillars. We exposed parasite spores to a gradient of ecologically-relevant temperatures for 2, 35, or 93 weeks. We tested spore viability by feeding controlled spore doses to susceptible monarch larvae, and examined relationships between temperature, time, and resulting infection metrics. We also examined whether distinct parasite genotypes derived from replicate migratory and resident monarch populations differed in their thermal tolerance. Finally, we examined evidence for a trade-off between short-term within-host replication and long-term persistence ability. Parasite viability decreased in response to warmer temperatures over moderate-to-long time scales. Individual parasite genotypes showed high heterogeneity in viability, but differences did not cluster by migratory vs. resident monarch populations. We found no support for a negative relationship between environmental persistence and within-host replication, as might be expected if parasites invest in short-term reproduction at the cost of longer-term survival. Findings here indicate that dormant spores can survive for many months under cooler conditions, and that heat dramatically shortens the window of transmission for this widespread and virulent butterfly parasite.
Ophryocystis elektroscirrha, the brown football shapes depicted above, is an obligate, neogregarine protozoan parasite that infects monarch butterflies
Sánchez CA, Ragonese IG, de Roode JC, Altizer S. Thermal tolerance and environmental persistence of a protozoan parasite in monarch butterflies. Journal of Invertebrate Pathology. 2021 Feb 11:107544. https://doi.org/10.1016/j.jip.2021.107544
Figure 9.1 Life-cycle of a mosquito, from egg to larvae to pupae to adult. Environmental carry-over effects of the larval environment and the relevant adult life history traits discussed in this chapter are labeled. Source: Eric Marty.
Check out the new book chapter by OSE student Mike Newberry and recent OSE graduate Dr. Michelle Evans!
Evans, M., Newberry, Philip M., and Courtney C. Murdock. “Carry-over Effects of the Larval Environment” inPopulation Biology of Vector-Borne Diseases. Editors: Drake JM, Bonsall M, Strand M. Oxford University Press; 2020 Dec 30. 155-174.
