12) Influenza A Viruses in North American Wild Birds

Anas platyrhynchos, one of many important waterfowl species in the IAV system.

Mentor: Dr. Rebecca Poulson
Abstract: Wild birds serve as the natural reservoir for influenza A viruses (IAV). Though we know a lot about low pathogenicity (LP) IAV in wild bird hosts in North America, our understanding of the influenza landscape was abruptly altered with the introduction of highly pathogenic (HP) H5 viruses via wild birds late in 2021 into Canada and then across the United States. HP IAV has now been detected in over 100 different avian species in the United States alone and is leading to significant mortality events in some taxa. The long term effects of this introduction, and how it will change the wild bird influenza A system are yet to be fully understood, but we can gain glimpses into what the future may hold for certain species by using serological tools aimed at assessing potential exposure to both LP and HP IAV. The REU scholar will learn both virologic and serologic techniques related to IAV in wild birds and it is anticipated that they will help in screening a subset of serum samples for antibodies to IAV, to better understand the role immunity might play in modulating infection and disease.
Is the project computational, empirical, or both? Empirical

9) Evaluating the transmission mode of a nematode parasite within horned passalus beetles, Odontotaenius disjunctus

Horned passalus beetles live in decaying logs, where they excavate cavities for rearing young. They are commonly parasitized by a nematode, Chondronema passali

Mentor: Dr. Andy Davis
Abstract: Horned passalus beetles are a common forest insect in the eastern United States, and are host to a variety of naturally-occurring parasites, including a nematode that lives in the abdomen (Chondronema passali). Beetles can be heavily parasitized, sometimes with thousands of these worms, though there are many questions about how these nematodes transmit to other beetles. Ongoing work in the Davis lab has sought to determine the impact of these parasites to the host physiology and behavior. Recent projects have revealed how female beetles can be affected more so than males, including influencing their willingness to explore. This implies that the nematode could be causing a behavioral change to its host, to promote its own transmission during oviposition activities. This will be the focal question that will be explored in summer 2023.
A student will be tasked with conducting one or more lab-based experiments designed to help elucidate this question. This will include collecting beetles from local forests, housing them in the lab, overseeing behavioral experiments, and performing dissections to determine parasite loads. The details of the projects will be fleshed out when the program starts.
The ideal student for this project is someone who is interested in insects, animal behavior, parasites, and who is completely fine with looking for icky, squiggly worms in soil samples or within beetle carcasses.
Is the project computational, empirical, or both? Empirical.

2) How do predators affect disease dynamics in their prey? Experimental tests of the healthy herds hypothesis with fish predators, zooplankton hosts, and a fungal parasite

The host, Daphnia dentifera. The top and second from bottom are infected by the fungus Metschnikowia bicuspidata, turning the host darker.

Mentors: Dr. Robbie Richards and Dr. Alex Strauss
Abstract: Food web members can dramatically impact host-parasite dynamics through a wide variety of mechanisms. The “healthy herds hypothesis” posits that predators can substantially decrease parasitism in their prey by directly consuming infected individuals. However, experimental tests of this idea remain rare. Moreover, the few experiments that have been attempted have yielded inconsistent results, with predators sometimes decreasing disease, increasing disease, or having no effect on disease in their prey. Reconciling these divergent outcomes is increasingly important as prey species serve as reservoirs for many diseases of concern for spillover into human populations. In this project you will have the opportunity to conduct a large-scale manipulative experiment to test the healthy herds hypothesis. We will use a replicated mesocosm (i.e., artificial pond) system of mosquitofish predators, fungal parasites and their shared host/prey, the water flea, Daphnia dentifera. Finally, we will measure several key traits (e.g., preference of fish for infected vs. healthy hosts) and ask whether they explain why predators increase, decrease, or have no effect on disease in the experiment.
Is the project computational, empirical, or both? Mostly empirical, but with opportunities to learn computational skills such as model fitting and parameterization.

1) Quantifying and characterizing the Chagas disease parasite burden in kissing bug vectors across land use change gradients

Rhodnius pallescens, principal vector of Chagas disease in Panama

Mentors: Dr. Nicole Gottdenker and Juliana Hoyos
Abstract: Anthropogenic environmental change has been associated with the emergence of zoonotic vector borne pathogens. In this project, the REU scholar will investigate how parasite burden with the Chagas disease agent Trypanosoma cruzi varies in kissing bug vectors collected across different gradients of deforestation and reforestation in rural areas of central Panama. The student will learn laboratory methods in molecular detection of trypanosomes in kissing bugs and will also apply statistical methods to investigate how land cover, bug abundance, microclimate, stage, and bug population characteristics relate to parasite burden in the bugs. 
Is the project computational, empirical, or both? Both.

How Various Feeding Rates Affect Pupation Rates in Anopheles stephensi Larvae

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.


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

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.


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

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.


Temperature fluctuation on disease transmission in multi-host communities

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.


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

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.


Roadkill as sentinels for parasite detection in a wild squirrel population

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.


Spatial Variation in Oyster Macroparasites Across the Georgia Coast

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. 


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

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.


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

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.


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

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.


Infection and Spore Yield of Daphnia Microsporidian

Hannah O’Grady, a student at Mount Holyoke College, worked in the lab of Dr. Alex Strauss.

Abstract An important part of understanding how diseases spread and impact a community is understanding the tradeoffs that occur when a parasite generalizes. While sampling ponds in Whitehall Forest we discovered a potentially novel microsporidian that was able to infect at least five zooplankton in the Cladocera superorder at relatively high infection prevalence. We designed an experiment to investigate the potential costs of its generalism. We exposed isoclonal lines of two different species of Daphnia, each from two different lakes, to spores gathered from the dominant host in each lake to test whether the microsporidian was 1) more successful at infecting Daphnia of one species over the other or 2) whether it was more successful at infecting Daphnia from the same lake or 3) the same species from which the parasite spores were gathered. We also counted spore yield (a metric of parasite fitness) from the six infected species gathered from the field to test for differences across species, lakes or time. None of the Daphnia exposed to the spores in the lab became infected, leading us to hypothesize that there is an intermediate host for this parasite. Spore yields from field-collected hosts did differ significantly among host species, with higher spore yields in D. laevis (mean=446,415.55±412,977.53) and Diaphanosoma (mean=253,888.83±78,085.34) than in D. ambigua (mean=40729.12±41,396.68), D. parvula(mean=46250.06±49,432.78), and Simocephalus (mean=17083.17±13,025.14). There were no significant differences in spore yield across lakes or days. More research will be needed to find the intermediate host for the microsporidian as well as to determine its exact genus and species.


Royally Split: Morphological divergence of parasites in milkweed butterflies

Katie Yan, a student from Skidmore College, worked in Dr. Sonia Altizer‘s lab.

Abstract Ophryocystis elektroscirrha (OE) is a protozoan parasite found in Monarchs (Danaus plexippus). Same or similar OE-like parasites have been found in Queens (D. gilippus) and other Danaus butterflies. Experimental cross infection provided evidence of parasite specialization on natal host species via low infection rates on novel hosts, motivating in-depth analysis of parasite morphometric and genetic variation across host species from different locations. To examine OE and OE-like spore morphology across Danaus species, we looked at five host species from previously curated museum samples including: Jamaican Monarch (D. cleophile), Plain Tiger (D. chrysippus), Queen (D. gilippus), Common Monarch (D. plexippus), and Lesser Wanderer (D. petilia). Analysis of wild-collected museum spores showed that on average, Jamaican Monarchs and Common Monarchs had larger spores than other species. This relationship is consistent with the phylogenetic relationships of host similarity within the Danaus genus and further supports the hypothesis of parasite specialization on hosts. We then examined the influences of host and environmental factors on parasite morphology by analyzing spores from a cross-infection experiment involving Monarchs and Queens. Hosts in this experiment were fed either tropical milkweed (Asclepias curassavica) or swamp milkweed (A. incarnata). Monarchs and Queens were infected at a high rate by their natal parasites, some Monarchs were infected by Queen parasites, and no Queens were infected by Monarch parasites. Morphometric analysis of spores showed that Monarch parasites from Monarch hosts were largest, and that Queen parasites from Queen hosts were smallest; Queen parasites from Monarch hosts were intermediate in spore size. Other spore traits (shape, hue, density) were similar across treatments. Additionally, we found that spore size positively correlated with host wing area, suggesting that larger spores are found on larger butterflies. Milkweed species, sex, and final spore load did not predict variation in spore morphology. In summary, we found strong evidence for parasite specialization on different host species based on differences in spore size; further work should ask whether molecular genetic divergence of OE parasites across host groups matches differences in spore morphology and host phylogeny.


Scared stiff: Effects of a nematode parasite on fearfulness in bess beetles

Anna Shattuck, a student from Tulane University, worked in the lab of Dr. Andy Davis.

Abstract Freezing is a defensive behavior seen in many different animals as a response to extreme threats such as predators. While research on freezing behavior is widespread, there is little known about how parasites may influence it. A non-lethal nematode parasite, Chondronema passali, can be found in the hemocoel cavity of bess beetles, Odontotaenius disjunctus. A single beetle can carry the burden of hundreds of these nematodes. Previous research has shown that parasitized beetles eat more and are more active, suggesting they are bolder and may be less prone to freezing. This experiment tests whether the nematode parasite influences fearfulness in beetles by exposing a population of bess beetles to different stressors and observing their freezing behavior in response to each. Following the trial period, beetles were dissected, and parasite load and sex were assessed. Out of 161 beetles, 14% were unparasitized by C. passali. We found that heavier parasite loads increase freezing durations in males and decrease freezing durations in females in response to a stressor. We suspected that female beetles experienced greater energy loss from being parasitized and laying eggs, making them more inclined to move and forage. To test this idea, we deprived 22 beetles of food for 48 hours in hopes they would display freezing behavior less when responding to a stressor. After being starved, only 4 beetles displayed freezing behavior, indicating fearfulness is tied to hunger.  Further investigation is needed in order to elucidate this relationship.


The Community Effects of Trematode Parasites on Species Interactions

Kailah Massey from the University of Georgia worked with Dr. Emlyn Resetarits.

Abstract Trematode parasites have a complex life cycle that infects and castrates snails as their initial host. (Wood et al., 2007). The snails our team observed were Elimia type snails. These snails have top-down control over algae in aquatic ecosystems. Snails have total control over algae and influence lower trophic organisms that feed on algae. Changes done by top-down organisms have an inverse effect on the lower trophic level organisms. High levels of parasite infections can alter the resilience of an ecosystem. Furthermore, research has shown that trematode parasites can influence host consumption, potentially creating more of a strain and impact on ecosystems (Rosemond et al., 1993). To assess this claim, we conducted location surveys to quantify infection prevalence within snails at each site. We then constructed a chlorophyll consumption trial consisting of a blind experiment to determine if infected snails consumed more algae on average than uninfected snails. Our results indicate that a trematode infection can increase the consumption of chlorophyll in their snail hosts. Trematode parasites were responsible for up to twenty percent of chlorophyll consumption across our sites. Further research will include the differences between visceral and gonadal infections on the consumption of Elimia snails. 


The Tradeoff of Nutrition in Malaria Transmission

Nathan Garcia-Diaz, a student from Willamette University, worked in the lab of Dr. Ash Pathak.

Abstract The effects of nutrition on malaria transmission was studied by collecting the most influential components of Vectorial Capacity. Vectorial Capacity (C) measures the Anopheline mosquito’s efficacy at transmitting the Plasmodium berghei parasites, and the largest factors impacting C are Extrinsic Incubation Period (EIP) and Vectoral Survival Probability (VSP). In order to force the mosquito to decide where to allocate nutrients, four conditions were created by combining two different treatments: Low Nutrient Treatment (1% Dextrose) and High Nutrient Treatment (10% Dextrose); Gravid (No Oviposition Site) and Not Gravid (Oviposition Site). Data was collected for EIP by examining sporozoite prevalence, and VSP was measured by mosquito mortality at fixed intervals after the infectious blood meal. To gain a more comprehensive notion on mosquitoes’ infectiousness, sporozoite density was measured alongside the other variables. The results from VSP data indicate that mosquitoes were most likely to survive if given the high nutrient treatment, and less likely to survive if the mosquitoes had the not gravid status. Additionally, when comparing EIP data between Gravid and Not Gravid statuses in the low nutrient treatment, gravid mosquitoes were infected sooner and at a higher rate than the not gravid counterparts. This pattern was seen again in the parasite density, gravid mosquitoes being more infectious than not gravid mosquitoes. It can be concluded that when infected mosquitoes are in a nutrient deficient state, gravid mosquitoes prioritize caring for its progeny rather than assembling an immunological response.


Assessing the impacts of Hyalophysa lynni infection on oxygen consumption of commercial shrimp

Roland Berg, from Lewis & Smith College, worked with Megan Tomamichel and others in the lab of Dr. Jeb Byers.

Abstract Shrimp black gill disease (sBG), caused by the parasite Hyalophysa lynni, may be contributing to the recent declines in commercial shrimp populations off the Southeastern US coast. H. lynni attaches to shrimp gill tissue, triggering an immune response that causes gill melanization characteristic of sBG. While effective at killing the parasite, this immune response also deteriorates surrounding gill tissue; thus, sBG is speculated to alter host respiration. To address the impact of H. lynni infection on host oxygen uptake, we isolated individual shrimp in containers filled with artificial seawater and monitored the changing dissolved oxygen (DO) concentrations of their water over the course of five days. Afterwards, we diagnosed shrimp with sBG by pulling their gill tissue and performing a DNA extraction and PCR assay to identify the presence of H. lynni DNA. Although our results suggested that H. lynni infection did not impact host oxygen consumption, several other factors were significant predictors of a system’s DO concentration (most significantly time, shrimp length, water temperature, and shrimp gill color). Further research is needed to determine shrimp black gill’s effects on other gill functions, such as acid-base balance and ammonia excretion, as well as H. lynni’s impact on host respiration outside of restful experimental conditions.