Category Archives: 2022 Projects

How Various Feeding Rates Affect Pupation Rates in Anopheles stephensi Larvae

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Jacob Glover, a student at Franklin College, worked in the lab of Dr. Ash Pathak

Abstract Anopheles Stephensi are a dangerous vector for countless diseases without cures currently. If mosquitos could be contained or controlled, then this could eliminate these diseases they carry without having to find a vaccine or other types of cures for them. One of the best stages to control mosquitos is within their larval stage of life. In this stage, they are so fragile that minor changes in food or environment can kill them or stunt their growth. If mosquito larvae could be purposefully stunted or killed off, then there would be one less major vector for disease. Our experiment tests this hypothesis to see if manipulating the rate at which mosquito larvae are fed if that impacts their pupation rates.Within this experiment, we test to see if various feeding rates affect their pupation rates, ultimately testing if their growth stays the same under different feeding conditions. This was done by giving them different amounts of TetraFin pellets on Tuesdays and Wednesdays to see if there was a difference in growth rates. Overall, the results show that no significant changes occur in the pupation rates of mosquito larvae when feeding rates are altered.

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Modeling Fitness of Immune Evading Pertussis Mutants

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Gowri Vadmal, a student at Stanford University, worked in the lab of Dr. Pej Rohani

Abstract Pertussis was considered one of the great diseases of childhood with most people experiencing a bout of the infection by the age of 15.  The initial roll out of vaccines in the 1950s led to a marked decline in pertussis incidence, with optimism over its potential elimination.  Over the past 20-30 years, however, a clear increasing trend in pertussis cases has emerged.  A number of putative Pertussis (whooping cough) is caused mainly by the bacterium Bordetella pertussis. Many countries use acellular pertussis vaccines containing the antigen pertactin (PRN), which plays an important role in pathogenesis. In recent years, we’ve observed an increasing number of B. pertussis isolates that are PRN-deficient and able to infect people even in highly vaccinated countries. We used SIRV models to look at the fitness cost of the bacterium losing PRN and the advantage of being able to infect already vaccinated people. Strains can invade the population only if their leakiness (ability to infect vaccinated people) and transmission are above the threshold for invasion, which depends on vaccination coverage and the cost of immune evasion for the strain. At low vaccination coverage, strains with high leakiness dominate the system when the fitness cost to evade immunity is low, but as cost increases for the strains to infect people, there is bistability between the wildtype and mutant strains. However, at higher vaccination coverage, the wild type completely fades out and the strains with the highest leakiness dominate the system. Thus, the conditions for B. pertussis mutant invasion can change depending on a population’s vaccine coverage, the cost of losing the pertactin gene, and the advantage of being able to evade vaccine immunity.

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Designing and Evaluating the Need for Patient Based Clinical Prediction Rules for Influenza Triage Telemedicine

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Annika Cleven, a student at St. Olaf College, worked in the lab of Dr. Andreas Handel

Abstract Using data that was collected from a university health center where patients and clinicians were asked to report the presence of a list of respiratory-related symptoms, we analyzed the need for patient based Clinical Prediction Rules (CPRs).  We investigated inter-rater agreement between clinicians and patients on symptom reporting and found they often disagreed. A Bland-Altman analysis indicated that the disagreement on symptom reporting was enough to invalidate using patient reported symptom data on a CPR that was designed using clinician reported data. Further analysis determined that using patient versus clinician reported symptom data could lead to different risk category designations and advised care. In response, we built risk prediction models that were fit to patient reported data and they provided minimal improvement from the clinician based CPRs.  Our research indicates that clinician based CPRs cannot be effectively used with patient reported symptoms data, like in telemedicine. Our results also show that we can create a patient-based CPR, but because of the minimal improvement, a combination of at-home testing and a patient-based CPR would be the best approach to influenza triage telemedicine.

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Sensing Your Friends Getting Eaten is Stressful, Having a Parasite Makes it Worse

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Helen Gloege, a student in Mount Holyoke College, worked in the lab of Dr. Andy Davis

Abstract Daphnia and other animals face a multitude of different stressors in their daily lives. Parasites can cause various physiological changes in animals, yet few prior studies have looked at the combination of parasitism and stress in animal models. This study used Daphnia which are microscopic plankton that may have ectoparasite-like organisms attached to their surface. Vorticella, a single-celled ectoparasite, is one of these organisms that can be found attached to Daphnia. During this experiment, when Daphnia ambigua were exposed to a “stressor” the vorticella parasite led to an increased heart rate in the Daphnia. The “stressor” was made of macerated Daphnia and aimed to simulate a predation event. Daphnia without vorticella present appeared to have no discernable reaction to the stressor. While Daphnia with vorticella increase the heart rate and physiological stress reaction in Daphnia. When over twenty vorticella were present on the daphnia the heart rate continued to increase during the study period.

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Tricks Not Treats: Wolbachia’s Manipulation of Sex in Infected D. subquinaria Offspring

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Madeline Sheppard, a student at Eckerd College, worked in the lab of Dr. Kelly Dyer

Abstract Wolbachia is a bacteria that is found in up to 60% of all insects, which is transmitted exclusively from mother to offspring through the egg. In many host species Wolbachia infection does not Wolbachia are gram-negative maternally transmitted bacterial endosymbionts that are found in upwards of 60% of arthropods. Here, we aimed to determine the phenotype expressed in D. subquinaria when they are infected with a strain of Wolbachia originally found in a closely related species, D. recens. Wolbachia infection is expressed as one of two phenotypes: Cytoplasmic incompatibility (CI), which causes the deaths of most infected offspring, and Male Killing (MK), which causes the death of the sons of infected males. Additionally, we tested how Wolbachia interacts with the varied genetic backgrounds of D. subquinaria populations, as well as how that would influence which phenotype is displayed in infected offspring. We tested a total of 15 lines of D. subquinaria by taking 2 to 3 infected females and crossing them with 1 uninfected male. The F1 offspring from those crosses were collected, and the sex distribution per line’s offspring was determined. Ten lines produced a significant number of flies (n>10). We tested for Wolbachia infection by using PCR, and determined the F1 generation was positive for Wolbachia. All lines expressed evidence of the MK phenotype, and four lines showed nearly complete MK (98-100% female). The remaining six expressed partial MK (60-84% female). In the future, we aim to determine whether there is a genetic suppressor of the MK phenotype in D. subquinaria, as well as to generalize the results of this project to further understand the population dynamics of Wolbachia-infected flies.

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Temperature fluctuation on disease transmission in multi-host communities

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Jenavier Tejada, a student at Denison University, worked in the lab of Dr. Alex Strauss

Abstract The dilution effect seeks to explain disease transmission in environments with multiple species. Essentially, the dilution effect predicts an increase in diversity will lead to a decrease in disease transmission. In zooplankton communities, the resistant diluter, Ceriodaphnia dubia can lessen disease in the host Daphnia dentifera caused by the parasite Metschnikowia bicuspidata. However, dilution is only effective when diluters and hosts co-exist; because when they compete, competitive exclusion can occur. Fitness of both D. dentifera, and C. dubia depend on temperature. Specifically, C.dubia benefits in warmer temperatures and D. denifera in cooler temperatures. Therefore, in environments where temperatures fluctuate,  this may lead to co-existence, greater abundances of the diluter, and less disease transmission. We are testing whether the dilution effect reduces infection prevalence when a diluter is present, and how dilution effects differ at a constant 20˚C versus a fluctuating temperature around the same mean. We designed a multi-generational mesocosm experiment with communities that contained the host and parasite, and communities that contained the hosts, parasites, and diluters at both constant and fluctuating temperatures. We hypothesize that the changing environmental conditions caused by fluctuating temperature will lead to more diluters, causing a greater dilution effect via co-existence of the host and diluter. This project will help us learn more about the possible effects of climate change – especially variable temperature – on disease dynamics in communities with multiple species.

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Approximating abundance of Daphnia dentifera using environmental DNA (eDNA) samples

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Emily Landolt, a student in St. Norbert College, worked in the lab of Dr. Alex Strauss

Abstract Freshwater zooplankton, such as Daphnia dentifera, are helpful model organisms for studying infectious disease dynamics and are ecologically important because of their role in food webs. They are consumers of primary producers like algae and are prey for other organisms such as fish. However, field sampling of freshwater zooplankton can be costly in terms of time and effort. The use of eDNA to estimate species abundances rather than an assessment of presence/absence in aquatic ecosystems is an exciting concept because it allows for more efficient and potentially more accurate field sampling. eDNA sampling methods for this study system can also be important for monitoring populations and epidemics in the field to ensure ecosystem health. This methodology has been studied in fish but is not yet well understood for invertebrates. We explored this idea by generating artificial mesocosm populations of Daphnia. Sampling for species abundance was done in two ways: using a traditional observational method of taking a subsample and counting the number of Daphnia, and a novel molecular method to quantify the amount of eDNA using a qPCR assay. Our results are a correlation between the observed species abundance and the molecular quantification of eDNA. Preliminary results show insignificant relationships indicating complexity that needs to be explored. Possible factors that affected the amount of eDNA in the water include water chemistry (i.e. pH), age structure, time since introduction, and water replenishment from evaporation/sampling. In the future, more research will be needed to explore the factors of eDNA persistence and how it can be used to better approximate species abundances of aquatic invertebrates like Daphnia.

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Deforestation alters spillover risk of multi-host pathogens

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Annalise Cramer, a student at Westfield State University, worked in the lab of Dr. Richard Hall

Abstract Deforestation alters landscape configuration resulting in novel contacts between host species, which can promote pathogen spillover from wildlife to domesticated animals and humans. Given heightened awareness of zoonotic spillover, studies are urgently needed to understand how the rate of deforestation interacts with host abundance and distribution to shape pathogen transmission across habitats and human exposure risk. In this study, we derive a mathematical model coupling land use change with pathogen transmission between hosts in forested and deforested habitats. We explore how deforestation rate and host relative abundance across habitats influence the dynamics, peak and cumulative number of infected hosts in deforested habitats as a proxy for human spillover risk. We find that the number of infected hosts in deforested habitats peaks sooner under faster deforestation rates. When the deforested hosts are less abundant, most transmission occurs in mixtures of forested and deforested habitats where large habitat boundaries maximize contacts with the more abundant forest hosts. This results in a hump-shaped relationship between deforestation rate and short- and long-term spillover risk. These results suggest that surveillance and interventions at habitat boundaries are crucial to reduce the risk of zoonotic spillover.

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Roadkill as sentinels for parasite detection in a wild squirrel population

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Jonah Giermann, a student at College of St. Scholastica, worked in the lab of Dr. Sonia Altizer

Abstract Disease surveillance of wild populations is difficult, as capture and release techniques can be time-iRoadkill is an excellent display of human-wildlife conflict. Carcasses can inform ecologists about population trends, species distribution, and behavior. Carcasses can be inspected for parasitic infection, but data obtained is subject to bias from a variety of factors. We chose rock squirrels as our study system because their behavior makes them host to a variety of parasitic species. I asked questions regarding the factors influencing measures of infection (richness, abundance, diversity) in roadkill, and how those measures compare in live-trapped samples.Samples were collected in Zion National Park from 2020-2022. Roadkill intestines were dissected, and whole worms were counted. Fecal samples were obtained from live trapped squirrels. Fecal flotation using sodium solution was conducted and any resulting eggs were counted. We found that squirrels collected in autumn host more parasites than the other two seasons. Male squirrels are collected as roadkill more frequently than females. Males display exploratory and dispersal behavior, likely causing more vehicle collisions. Parasite richness was higher in the roadkill population than it was in the livetrap population.  We used the Shannon diversity index to get a parasite diversity value for each sample type. The diversity index factors in both richness and abundance to analyze diversity. Roadkill had higher diversity, but livetrap had a similar value. Microparasites were found in live-trapped samples but could not be seen using our roadkill sampling method. Based on these results, roadkill seems to be an effective indicator of parasitic infection in wild populations, provided biases are accounted for.

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Spatial Variation in Oyster Macroparasites Across the Georgia Coast

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Sofia Markiewicz, a student at Scripps College, worked in the lab of Dr. Jeb Byers

Abstract Oysters are a key coastal foundation species that have declined drastically across the US coasts due to the combined effects of overharvesting, pollution, and disease. With climate change, there The eastern oyster (Crassostrea virginica) is a keystone species and ecosystem engineer that stabilizes sediments, cycles nutrients, improves water quality, and provides habitat for fish and crustaceans. Oysters are prone to several macroparasites, including pea crabs (Zaops ostreum), mud blister worms (Polydora websteri), and boring sponge (Cliona spp.), all of which can damage their gill tissue and shells. Although oyster populations have been widely studied in other areas of the eastern United States, the geographic and environmental factors that influence macroparasite infection in Georgia’s oyster population are still largely unknown. In this study, we sampled oysters from 24 reefs across eight distinct sites along the Georgia coastline and examined them for macroparasite infection. The relationships between macroparasite prevalence and geographic location and environmental conditions (specifically reef complexity, reef shell density, dissolved oxygen, water temperature, and salinity) were examined. We found no correlation between location and macroparasite prevalence for any of the macroparasites examined. However, increased prevalence of blister worms was correlated with low salinity and low reef complexity. Prior research has also shown that shellfish infected with blister worms exhibit decreased shell strength, and are therefore more vulnerable to damage and predation. Understanding what conditions affect blister worm prevalence and how they may be altered by by climate change (e.g. changing salinity) is important for evaluating locations where oyster reefs are likely to have low macroparasite infection and be less prone to damage, in order to better maintain high-quality reef habitat. This is especially crucial in a relatively understudied environment such as Georgia, where the effects of these conditions are less well known. 

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Seeing What Floats: Comparing Fecal Diagnostic Techniques for the Detection of Zoonotic Cestode Eggs

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Sierra Felty, a student at Radford University, worked in the lab of Dr. Christopher Cleveland

Abstract Coyotes (Canis latrans) are an anthropogenically abundant and increasingly widespread species, Members of the genus Echinococcus are parasitic cestodes that pose a zoonotic threat to wildlife, livestock, domestic animals, and humans. They utilize wild canids, such as coyotes and foxes, as their definitive hosts. Two species of interest are E. multilocularis and E. granulosus given their impacts on native wildlife, agriculture, and human health. E. multilocularis uses rodents as intermediate hosts, and E. granulosus utilizes cervids as intermediate hosts. As the rate of urbanization continues to rise, humans and domestic animals are at greater risk of infection through more frequent interactions with wild canid hosts. Given the increased risk of infection, especially in non-endemic regions, it is important to have reliable detection methods in place. Our study sought to test the sensitivity and detection limits of three different fecal flotation methods (centrifugal, passive, and Mini-FLOTAC) in recovering Echinococcus spp. eggs. For each method, fecal samples were spiked with a known concentration of eggs (25, 40, and 60 eggs per gram of feces) and zinc sulfate was used as the flotation solution. Our findings indicated that the centrifugal flotation and Mini-FLOTAC were the most sensitive for detecting Echinococcus spp. eggs and the Mini-FLOTAC had the highest egg recovery. Therefore, the Mini-FLOTAC appears to be the most reliable fecal flotation method in detecting Echinococcus spp. eggs.

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A Blast to the Past: Multi-decadal Trends in Parasite Diversity in Plethodon Salamanders

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Samantha O’Keefe, a student at Jacksonville University, worked in the lab of Dr. Sonia Altizer

Abstract Climate change is rapidly impacting our planet and its ecosystems at immense scales, and many of the future impacts are unknown. One consequence of climate change seen in nearly every ecosystem type is loss of biodiversity, including parasitic organisms. To investigate whether parasite communities infecting Plethodon salamanders are changing over time, we utilized formalin fixed natural history collections (mostly Plethodon shermani) collected from Macon County, NC from 1943-2017. Additionally, a collection of surveys of parasites infecting Plethodon salamander species from 1937 was used as a baseline to compare the museum specimens’ sample parasite diversity changes over time. Salamander digestive tracts were surveyed at the 5x magnification using a dissecting scope, and any parasites found were counted and identified to the species level based on morphological traits. We noted that macroparasite aggregation was common, where 80 percent of the parasites were found in 20 percent of the hosts. The findings of this study revealed that the infection prevalence of two parasite taxa were stable, while 4 other gastrointestinal parasite species found were decreasing significantly in prevalence over time, specifically Cosmocercoides dukae, Capillaria inequalis, Crepidobothrium cryptobranci, and an undescribed subcutaneous nematode. These changes in infection prevalence over time may indicate different climate sensitivity between parasite species. Additionally, diversity and parasite richness were found to be gently decreasing, which may indicate overall reduction in parasite transmission. Future directions for this work consists of molecular confirmation of parasite taxa, and the continuation of surveys of preserved salamanders to increase temporal resolution in time chunks.

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Predictors for SARS-CoV-2 Seropositivity in Owned and Feral Cats in North Georgia

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Sarah Blankespoor, a student at California Polytechnic University, worked in the lab of Dr. Mark Tompkins

Abstract Little is known about the epidemiology of SARS-CoV-2 in animal populations. Cats are a host for the virus, with cat-to-cat transmission demonstrated in lab settings. Both feral and owned cats interact with many species and could drive interspecies transmission. This project investigates dynamics of SARS-CoV-2 by evaluating seropositivity predictors in cats. Serum samples were taken from owned cats brought to the University of Georgia Veterinary Teaching Hospital from 08/2021-06/2022 and feral cats captured locally from 01/2022-06/2022. Samples were tested for anti-SARS-CoV-2 antibodies using indirect ELISAs. For feral cats with n=33, none of the samples were positive. For owned cats with n=193, 10 of the samples were positive (5.2%). There is preliminary evidence for lasting antibodies with two repeat positive cats, with samples taken up to 3 months apart. Binary logistic regression models for the owned cats were determined in R through multi-model inference. Two terms were present in the 3 equivalent best models: cumulative human COVID-19 cases by county, with a positive coefficient; and days since the pandemic started, with a negative coefficient. These results suggest that cats acquire SARS-CoV-2 infections from humans rather than other cats or wildlife. The negative coefficient for time in the models can be explained by the delta and omicron surges at the beginning of the study period. SARS-CoV-2 surges in humans have a ripple effect into the larger ecosystem, particularly for cats owned by humans with COVID-19. Future research should continue to investigate this impact over a larger time scale and expand feral cat sample size to confirm observed trends.

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