Zane Billings, a student at Western Carolina University, worked with Dr. Andreas Handel and graduate student Brian McKay in the UGA College of Public Health.
Influenza-like illnesses (ILIs) present with several of the same symptoms, including cough, fatigue, and weakness. However, ILIs can be caused by a range of different pathogens with vastly different treatments. Quantitative PCR is an incredibly specific and sensitive method to detect several ILIs, but until recently, qPCR methods were prohibitively expensive and required special training and equipment. Recent advances in qPCR technology have allowed for machines such as the Roche cobas Liat system to become available to point-of-care physicians. Using data collected from the University of Georgia Student Health Center, qPCR data was examined relative to patient and physician reported symptoms, as well as impacts and recovery from disease to determine if quantitative estimates of relative viral load are important for physicians to make informed decisions. While relative viral load estimates were found to be correlated to days since the onset of illness and patient temperature at diagnosis, no correlations were found between recovery or severity of illness and relative viral load. However, the study sample was very limited and more research should be performed on broader study populations.
Simran Budhwar from the University of Virginia, worked with Rachel Mercaldo, Brian McKay, and Dr. Andreas Handel to study shedding of Norovirus.
Abstract: Norovirus (NoV) is a common cause of acute gastroenteritis. Symptoms include vomiting and diarrhea, which can lead to complications such as dehydration and also serve to spread viral particles through bodily fluids. While some infections are asymptomatic, infected individuals shed the virus regardless of disease severity, primarily through stool. To understand the dynamics of viral shedding, previous studies measured viral load in healthy human subjects challenged with various doses of the virus. In the present analysis, data from these studies was combined to better describe NoV shedding over time. We calculated key variables such as peak viral titer, time to peak viral titer, and duration of shedding, in addition to estimating total shedding through the area under the curve (AUC) value of each participant’s total shedding time-series curve. On average, patients shed the virus for 22 days, with the peak viral titer appearing on day 5 following challenge. Peak viral titers were 10.551 (log10) genomic equivalence copies per gram of stool, while AUC averaged at 11.58 (log10) genomic equivalence copies per gram stool. Though these are key variables that are necessary to understand viral shedding, future work should focus on exploring the drivers of variation in viral load and shedding, such as symptoms or other patient-specific factors.
Lutchie M. Carrasquillo, a student at the University of Puerto Rico at Arecibo, worked with Christian Hurd and Dr. Andy Davis to study the effects of parasitism on Daphnia heart rate using a new methodology.
Abstract: Daphnia are a model organism often used in investigations of chemical toxicity, and for biology classes. Measuring changes in heart rate is a commonly-used approach to assess responses to toxins. However, these assessments are usually done manually, which is time consuming and tedious. We developed a novel apparatus for monitoring changes in Daphia heart rates in real-time, without harming the animals. We used this approach to investigate how heart rate changes in response to naturally-occurring parasites (epibionts) and a natural Daphnia predator (glassworms). Our results showed Daphnia heart rates were not greatly affected by these, but we did discover an unusual diurnal effect, where the heart rate response differed between the morning trials and the evening trials.
Kareena Collins, a students at the University of Maryland Eastern Shore, worked with Paul Ginsberg and Dr. Kelly Dyer.
Abstract: Wolbachia is a maternally inherited
intracellular endosymbiont that can manipulate reproduction in many different
species of arthropod hosts, enabling its invasion into novel host populations.
The most common types of reproductive manipulation is cytoplasmic incompatibility
(CI), where mating between an uninfected females and infected males results in
embryonic mortality. Two Drosophila species, D. recens and D. subquinaria, were used to investigate whether Wolbachia can affect mating preference
in a native versus non-native host species. D.
recens is the infected species of Wolbachia
with a frequency ~ 98%, while D.
subquinaria is the uninfected host of Wolbachia.
In the geographic region where both species overlap there is gene flow between
species. We introgressed Wolbachia
from D. recens into D. subquinaria in the laboratory. Both
species show the CI phenotype in the lab when there is a cross with an
uninfected female and an infected male. We conducted no choice mate trials for
all crosses among infected and uninfected individuals for each species (all
intraspecific crosses), and watched for mating for a three hour observation
period. We found that Wolbachia had
no effect on mating preference in the native host, D. recens. However, in the non-native host, D. subquinaria, Wolbachia
had a huge effect on mating preference, with a significant reduction of mating
rate in the cross between an uninfected female and an infected male ( the
“incompatible” cross). Because Wolbachia
had such a significant effect on mating preference only in the non-native host
of D. subquinaria, it has potential
implications for Wolbachia’s
inability to become established as a native host in the population and/or
Jillian Dunbar, a student at the University of Alabama, worked with Ellen Martinson and Vincent Martinson in the lab of Dr. Michael Strand.
Reproduction and immunity are metabolically expensive systems; therefore, organisms with a limited amount of resources have to invest carefully (Schwenke et al. 2016). With the goal of producing offspring, organisms must invest resources into reproduction, yet also reserve resources for protecting themselves. In many cases reproduction and immunity are not directly linked. However, it has been shown in Aedes aegypti mosquitoes that, in addition to inducing egg production, a blood meal also increases the number of circulating immune cells called hemocytes (Castillo et all. 2011; Castillo et al. 2006). These findings elicit the question, does reproduction (blood-feeding) result in lower immunity for the mosquito? Through a variety of bacterial injections into blood-fed and non-blood-fed mosquitoes, this project worked to understand the possible tradeoffs between immunity and reproduction. We found an inverse relationship between immunity and reproduction, in that mosquitoes laid fewer and smaller eggs when injected with both live and heat-killed bacteria, but only for the more virulent species and higher doses. Interestingly, the results also showed that blood-fed mosquitoes were more successful in clearing or tolerating less virulent bacterial infections, suggesting resources gained from a blood meal are used to produce an anticipatory immune response. These preliminary findings are essential for continuing research and strengthening our understanding of the A. aegypti immune system with hopes of controlling or preventing diseases propagated by A. aegypti in the future.
J, Brown, MR and Strand, MR (2011) Blood feeding and insulin-like peptide 3
stimulate proliferation of hemocytes in the mosquito Aedes aegypti. PLoS pathogens 7: e1002274.
Castillo, J, Robertson, A and Strand, M (2006)
Characterization of hemocytes from the mosquitoes Anopheles gambiae and Aedes
aegypti. Insect biochemistry and
molecular biology 36: 891-903.
Schwenke, RA, Lazzaro, BP and Wolfner, MF (2016)
Reproduction–immunity trade-offs in insects. Annual Review of Entomology 61:
Callie Effler, a student at Lee University, worked in the lab of Dr. Eric Harvill.
survival is a common trait among human pathogenic bacteria that has advantages
for the bacteria’s protection from the host immune response, persistence, and
dissemination within the host. Bordetella pertussis, the gram-negative
bacteria that causes whooping cough in humans, is commonly regarded as an
extracellular pathogen. However, it has been recovered from macrophages in in
vitro experiments, and reported anecdotally in clinical samples. It is
unknown what contribution to pathogenicity the intracellular population has, if
any, on the host. In this work, our broad objective was to evaluate the impact
of B. pertussis’ intracellular survival and its role in pathogenicity.
To do so, we planned to identify mutants similar to the wild type in general
measured aspects of virulence, but that failed to survive inside of
macrophages. A transposon library of B. pertussis UT25 was screened, resulting
in the identification of several putative mutants that were deficient in
intracellular survival. These strains were further screened for intracellular
deficiency as a confirmatory measure, and went through further in vitro assays
screening for cytotoxicity, hemolytic activity, resistance to serum
complementation, and general fitness (growth). Based upon these assays, mutant
strain G4 was the best candidate among those tested for an
intracellularly-deficient mutant with similar virulence-related characteristics
to the wild type. Preliminary C57 mouse infection studies suggest that the
mutant strain behaves similarly to the wild type in vivo, indicating
that intracellular survival may not be contributing to virulence. It is
hypothesized that intracellular survival may be a phenotypic remnant of an
ancestral strain of B. pertussis that transitioned from the environment
to a become a human pathogen using this trait.
Michael Lansford, a student at the University of Rochester, worked with Dustin Dial and Dr. Gaelen Burke
are sap-sucking insects that contain bacterial endosymbionts to help them synthesize
essential amino acids. The adelgid life cycle alternates between sexual
generations that parasitize spruce as a primary host and asexual generations
that parasitize a secondary host plant species. The adelgid family consists of
five lineages each with a different secondary host plant: Douglas fir, fir,
hemlock, larch, and pine. Each adelgid lineage has a different pair of symbionts,
a primary symbiont that was acquired by the adelgid first and a secondary
symbiont that was acquired second. Vallotia is
a symbiont shared between the Douglas fir lineage, where it is the secondary symbiont,
and the larch lineage, where it is the primary symbiont. To determine the nutritional
roles of Vallotia in different species,
genomic data were searched for genes involved in amino acid synthesis. FastQC
was used to evaluate the quality of raw adelgid read data. The Georgia Advanced
Computing Research Center (GACRC) cluster was used to assemble and annotate
genomes from the raw reads. After running scripts to assemble raw reads into
scaffolds, BLAST was used to identify which scaffolds were from symbionts.
Symbiont genes were annotated using PROKKA and Geneious Prime and biochemical
pathways were reconstructed with help from BioCyc. The results showed that Vallotia
is primarily responsible for synthesis of all essential amino acids
except cysteine in the Douglas fir lineage species A.
the primary symbiont in the Douglas fir lineage, works together with Vallotia
in lysine and aromatic amino acid synthesis. In both larch lineage
species, Vallotia is only responsible for
the final steps in tryptophan synthesis and depends on the secondary symbiont Profftia
in A. lariciatus and probably A.
abeitis for most steps in aromatic synthesis. These results suggest that Vallotia
was acquired by the Douglas fir lineage to account for the loss of
most synthesis genes in Gillettellia and Profftia
was acquired by the larch lineage to account for the loss of
aromatic synthesis genes in Vallotia.
Courtney Schreiner, a student at the University of Idaho, collaborated with fellow REU student Taryn Waite, along with Nicole Solano, Dr. Courtney Murdock, and Dr. Craig Osenberg.
Abstract: We were interested in studying the effects of larval density on the fitness of the Asian tiger mosquito (Aedes albopictus). Aedes albopictus live all around Georgia and in various types of habitats that can support varying amounts of larvae. This creates competition which can effect downstream traits like fitness and disease transmission. Our experiment took place in a semi-field enclosure. We had 7 different larval density treatments that ranged from 5 to 240 larvae in each jar, for a total of 92 jars. Daily emergence, sex ratio and wing size were all recorded for all emerged mosquitoes. Overall we found that the proportion that survived, proportion female, fecundity, and wing size all decreased as density increased. We calculated the intrinsic growth rate using these estimates and found that lower densities have a higher intrinsic growth rate than those at lower densities. This told us that mosquitoes have a higher fitness at lower densities. Which also means that higher disease transmission would also be found in lower densities.
Clara Tucker, a student at Stony Brook University, worked with Justine Shiau, Ashutosh Pathak, Courtney Murdock
Lily Tanner, a student at New College of Florida, worked with Denzell Cross and Dr. Krista Capps.
Abstract: Urbanization often compromises the
diversity and abundance of native species living in watersheds (Rodrigues et
al., 2015). Research has shown that riparian spiders are susceptible to land
use change associated with urbanization (Sanchez-Ruiz et al., 2017). We conducted a spider density survey in riparian habitats in
and around Atlanta as a metric to assess the impact of urbanization on regional
spider populations. We hypothesized that if overhanging vegetation was
important web-building substrate for some taxa and vegetation provided
cover for ground-dwelling species, then the highest density of spiders would be
found in transects with vegetation hanging over the stream. Our results indicate that overhanging vegetation was related to
higher densities of web-weaving species. Increasing amounts of overhanging
vegetation was also related to increasing bank slope, suggesting there may be
potentially important interactions between physical and biological
characteristics of riparian areas that mediate spider population structure.
Taryn Waite, a student at Colby College, collaborated with REU student Courtney Schreiner, Nicole Solano, Dr. Craig Osenberg, and Dr. Courtney Murdock.
Conspecific density in larval habitats is an important factor affecting adult
fitness in Aedes albopictus mosquitoes, as it drives competition for
food and space. We conducted a larval density experiment wherein mason jars
containing leaf infusion and varying numbers of larvae were placed in a field
enclosure, developmental stage was recorded daily, and emerged adults were
collected. Nonlinear regressions were performed on the data for survival to
adulthood, sex ratio of adults, and wing length of females, and fecundity was
inferred from wing length. Using these regressions, an equation was created to
predict short-term population dynamics in habitats with varying conspecific
densities. What determines the densities that will actually occur in various
larval habitats is where females choose to lay their eggs. Female mosquitoes
have the ability to skip-oviposit, which entails spreading their eggs out among
multiple habitats instead of dumping them all in one habitat. The population
dynamics equation was used to evaluate the theoretical consequences of skip-
versus non-skip- oviposition, using scenarios with varying numbers of
egg-laying females and a fixed number of available larval habitats. We found
that at low densities of ovipositing females, skip-oviposition produces more
short-term population growth than non-skip-oviposition. At higher densities,
non-skipping becomes more productive than skipping, though there is less
divergence between the outcomes. This simulation demonstrates a way in which
patterns of density-dependence could act as a link between oviposition behavior
and population dynamics. Due to the effects that we found of density dependence
in larval habitats, individual females’ oviposition behavior could have
consequences for short-term population dynamics.
Juliana Taube, a student at Bowdoin College, worked with Paige Miller and Dr. John Drake.
Abstract: Transmission trees contain valuable
details about who infected whom in infectious disease outbreaks. We created a
database with 81 published, standardized transmission trees consisting of 12 directly-transmitted
pathogens (mostly viruses). We also demonstrated how the database could be used
to help answer research questions in infectious disease epidemiology. First, we
analyzed overall and pathogen-specific patterns between tree parameters (R0 and
variation in secondary infections). We found that outbreak size is nonlinearly
associated with R0 and the dispersion parameter, but emphasize
that pathogen-specific patterns and intervention efforts may alter theoretical
relationships between these variables. Second, we examined how superspreader
contribution to onward transmission, either directly or through their tree
descendants, varies across pathogens. Superspreaders were responsible for most
cases via their descendants and the number of superspreaders varied across
pathogens. Additional database exploration matched theory1 about
how the proportion of superspreaders increases at intermediate levels of
dispersion, an idea that should be further explored. We hope that our database
will assist both theoretical and applied infectious disease epidemiology
research in the future.
1. Lloyd-Smith, JO, Schreiber, SJ, Kopp, PE, & Getz, WM (2005)
“Superspreading and the effect of individual variation on disease emergence.”Nature, 438(7066):
Maya Sarkar, a student at the University of Minnesota, worked with Isabella Ragonese, Dr. Sonia Altizer and Dr. Richard Hall.
It is important to understand the consequences
of a warming climate, especially in organisms that are more sensitive to
temperature changes and where the outcome of warming may not be intuitive. This
project used the Monarch-OE system to study how temperature may affect
host-parasite interactions. The monarch butterfly (Danaus plexippus) is
an iconic North American migratory species and the specialist protozoan
parasite OE (Ophryocystis elektroscirrha) is present in all monarch
populations. It has been shown that monarch development proceeds faster with
increasing temperatures and that increased temperature exposure lowers OE spore
infectivity over time. However, the effect of temperature on the host and
parasite during active infection is not known. This project examined how
temperature affects the monarch-OE system, focusing on the interaction between
monarch immune function and parasite replication. Monarchs were inoculated with
strains of OE parasite and placed in different temperature treatments. Three
lineages (B,F, and D) of migratory monarch were used to test genetic effects,
while 2 spore lines (E3 and E10) were used to study virulence effects within 5
different temperature treatments (18, 22, 26, 30, and 34°C). The results of
this study provide novel insight to how extreme temperatures affect the fitness
of a host and its parasite.