ZAHRA AHMED
PROFESSOR DANIEL RUBENSTEIN
THE EFFECTS OF ENVIRONMENTAL, SOCIAL AND BEHAVIORAL CONTEXTS
ON THE MULTIMODAL COMMUNICATION PATTERNS OF PLAINS ZEBRA
(EQUUS QUAGGA)
The ability to communicate efficiently and effectively with other
individuals plays a critical role in the lives of all animals as communication
mediates reproduction and survival. And, therefore, context specific
correlations are useful, if not essential, in suggesting how conspecific
patterns in animal behavior and communication evolve and progress. In
this this study we seek to better understand how Plains zebra (Equus
quaaga) manage trade-offs between signal efficacy and the variable
factors in which signaling may be specific to. We explore three such
contexts, namely environmental and ecological, social and behavioral
contexts and look at the posterior components of behavior, such as the
frequency and length of behavior are impacted by these contexts. Based
on these results we then look to see if flexibility in the multimodal
communication systems of Plains zebra (Equus quagga) can explain the
patterns we see. Preliminarily, we found that (1) zebra groups prefer some
habitats to others, (2) zebra are located in different sized groups but
group size doesn’t vary with habitat and (3) the occurrence rate of sexual
and agonistic interactions do not decrease in dense habitat but the
duration of the interaction is shortened, while the occurrence rate of
social behavior decreased in dense habitat, in part perhaps because
there is no significant difference in the length. This may imply inflexibility in
how social behavior is communicated and signaled. We also found that
the presence of stallions dampened the length of behaviors, perhaps due
to the need of stallions to manage time and efficiency trade-offs. With
these analyses in mind we looked at how these three contexts interact to
modify behavior and allow Plains zebra to signal information across a
wide range of situations and conditions. We found that woody vegetation
buffers wind and that wind speed only affects the acoustic signaling of
Plains zebra and no other modality, in two very interesting ways. The rate
of contact calls increases in dense habitat but if variable in open habitat
depending on wind and the time of day. Differences in group size did not
affect how multimodal patterns of signaling change. And finally, we
found that the occurrence rate of visual and tactile signaling decrease in
dense habitat, while the occurrence of olfactory signaling increased
almost 6x in dense habitat – the implications of which are that the
communication systems of zebra have redundancies in signal content,
especially in olfactory communication, that allow sexual and agonistic
behavior to persist and social behavior to not in different environments.
MICHELANGELO BALL VAN ZEE
PROFESSOR DAVID WILCOVE
LACK OF HATCH DATE ADJUSTMENT IN RESPONSE TO WEATHER IN FOUR
ARCTIC-BREEDING SHOREBIRDS
Many species of shorebirds breed in the Arctic. Even in summer, severe
weather events can result in decreased growth rates and mortality for
chicks, both through exposure and decreased prey abundance,
affecting chicks’ fitness. An earlier study suggested that shorebirds could
delay hatch dates in the case of inclement weather to minimize chicks’
exposure; this could explain observed variation in incubation length. In this
paper I look for statistical evidence that hatch dates can be brought
forward or delayed in response to weather. I looked at data collected in
Barrow, AK, during the summers 2003 to 2014 on 12 meteorological
variables and four shorebird species: pectoral sandpiper (Calidris
melatonos, n=388), dunlin (Calidris alpina, n=226), semipalmated
sandpiper (Calidris pusilla, n=203), and red phalarope (Phalaropus
fulicarius, n=503). I compared the average weather on nest hatch dates
to the previous and subsequent days for each variable and species.
Though there was substantial variation in incubation length, no
meteorological variable differed significantly between the hatch dates
and the surrounding days for any species; this implies that shorebirds do
not adjust hatch dates in response to weather. Even if shorebirds do
possess this ability, delaying hatch dates could have detrimental effects,
including leaving less time for development and causing parents to
incubate for longer. This suggests that shorebirds may be less adaptable
to the more frequent extreme weather expected as a result of climate
change.
TYLER BEAUCHAMP
ASSISTANT PROFESSOR CORINA TARNITA
MEDICAL INNOVATIONS AND THEIR IMPLEMENTATION CHALLENGES
IN THE UNITED STATES
There is a large disconnect between the amount Americans spend on
healthcare and their relatively poor health outcomes. In this thesis, I
explore the reasons for this disconnect and offer potential solutions. After
discussing healthcare waste reduction strategies, I outline medical
innovations that could improve healthcare quality, with a focus on
innovations in the rapidly changing fields of genetic testing, regenerative
medicine, and big data. I discuss the often-hyped promises of these
innovations, and consider the scientific, logistic, political, economic,
social, and ethical challenges that need to be solved before they can be
implemented. I end by analyzing the reasons for the successful
implementation of a now-ubiquitous medical innovation, the CT scanner,
and apply insights from this analysis to innovations that I outline earlier in
the paper.
KARLOS BLEDSOE
ASSISTANT PROFESSOR BRIDGETT VON HOLDT
MANGE IN YELLOWSTONE NATIONAL PARK WOLVES: THE ROLE OF
MICROSATELLITE VARIATION IN A NOVEL HOST-PARASITE RELATIONSHIP
The grey wolf (canis lupis) was reintroduced to Yellowstone National Park
(YNP) in 1995. Reintroduced wolves were selected for good health and
low parasite burden. Upon introduction to the park, wolves were
vaccinated for local diseases and they benefitted from low infection
rates. The disappearance of this induced immunity initiated novel hostparasite relationships. This study examines one such relationship between
the wolf and the sarcoptic mite (sarcoptes scabiei). Infection by s. scabiei
leads to sarcoptic mange, which is characterized by inflammation and
hair loss. Inflammation is the result the host’s immunological response to
mite infestation. Scratching and biting of the inflamed epidermal regions
leads to hair loss. Wolf immune systems must balance resistant and
tolerant mechanisms to maintain fitness during mite exposure without
producing detrimental immune responses. Prior studies have associated
genetic variation with optimization of the host immune response. Variable
canine genes associated with resistance to mange are therefore subject
to new selection pressures from s. scabiei. This study uses 26 microsatellite
loci from intergenic and intronic regions of the canine genome to test for
an association between disease progression and genetic variation. This
study uses simple regression and multiple regression models to analyze the
effect of microsatellite allele length and heterozygosity on the wolf’s
response to mange. Certain microsatellite loci show a statistically
significant relationship to the severity and duration of mange infection.
Allele length of microsatellite loci was associated with disease outcomes,
but not heterozygosity. This indicates that attenuation of the wolf immune
response to s. scabiei happens in part through the contraction and
expansion of non-genic microsatellite regions.
EMILY BOBRICK
ASSISTANT PROFESSOR C. JESSICA METCALF
VARIABILITY IN ESTIMATES OF THE BASIC REPRODUCTION NUMBER AND THE
UTILITY OF THE POLYMOD DIARY STUDY
The basic reproduction number, R0, represents the number of secondary
infections caused by one typical individual in a susceptible population.
R0 is considered one of the most important parameters for the study of
infectious diseases because it quantifies a threshold below which disease
spread is controlled. Estimates of R0 are highly variable, mostly because of
differences in the mathematical models used for estimation. A major
source of uncertainty in these models is how patterns of social contacts
are represented. Mixing patterns in models generally depend on poorly
substantiated, a priori assumptions and not on data. The Polymod diary
study, conducted in 2005-6 in eight European countries, is the first largescale, representative study aimed at quantifying social contacts relevant
to the transmission of respiratory infections in an effort to substantiate
mixing assumptions. However, there is some uncertainty as to whether the
Polymod data properly captures social mixing patterns relevant to disease
transmission.
This research reveals that Polymod-based models measles, mumps, and
rubella seroprevalence data poorly in a systematic way. Across different
settings and data collection methods, the Polymod data seems to
underestimate transmission-relevant contacts in infants and overestimate
them in schoolchildren. Potential reasons for the data's shortcomings and
how they relate to R0 estimation are explored through the lens of
demographic features and through examination of different subsets of
the Polymod data. This work suggests that much more research needs to
be done before the impact of social mixing patterns on disease
transmission is properly understood.
COLLEEN BOYCE
PROFESSOR DANIEL RUBENSTEIN
THE BEHAVIORAL, ASSOCIATIVE, AND SEXUAL EFFECTS ON YOUNG BULL
AFRICAN ELEPHANTS IN RESPONSE TO THE REMOVAL OF THE DOMINANT
BULL FROM PONGOLA GAME RESERVE, SOUTH AFRICA
It has been determined that dominant bulls are social and ecological
repositories of information for the younger bulls (Evans & Harris, 2008).
Other reserves have learned that without this dominant bull the younger
bulls do not learn how to properly interact socially or copulate with
females (Slotow & van Dyk, 2001). Instead, they engage in abnormal
social behavior such as killing rhinoceros and entering musth, their sexually
reproductive period, at too early an age making them pursue females
when they are inexperienced (Slotow & van Dyk, 2001). This study looks at
a herd whose dominant bull was hunted and therefore removed and how
that has affected the younger bulls within the herd. It was expected to
see extreme social upheaval among the younger bulls and a strong
change in the dominance hierarchy. While there was a change in the
dominance hierarchy it was only among males that were very similar in
age and the dominant male kept his position, losing no dominance
interactions. Every other form of behavior did not see any change after
the dominant bulls’ removal. The bulls at Pongola were all given
vasectomies as a population control measure except the dominant bull
that was too big for the procedure so he was given gonadotropinreleasing hormone (GnRH). This resulted in the dominant bull not going
into musth and therefore not attempting to copulate with females or be
aggressive toward the younger bulls to keep his dominant position. By
doing this, Pongola Game Reserve was unintentionally creating an
opportunity for the beta bull to transition into the dominant position while
the dominant bull was still present. Using GnRH to help make a smooth
transition between dominant bulls in other game reserves looking to
remove the dominant bull is a proactive and preemptive management
method.
CATHERINE BREEN
PROFESSOR STEPHEN PACALA
CARBON STOCK AND PHYSIOLOGICAL TRAIT VARIATION ACROSS A
RAINFALL GRADIENT IN ROCKY MOUNTAIN FORESTS
The Rocky Mountains are the second largest carbon sinks in the western
U.S., yet how carbon stock and the traits that affect carbon stock change
over a rainfall gradient needs further investigation. I will look at carbon
stock and the functional traits affecting carbon, including 13C:12C isotope
ratio, leaf-to-shoot ratio, and specific leaf area in four forest types: piñon
pine (Pinus edulis) – juniper (Junis osteosperma), ponderosa pine (Pinus
ponderosa), trembling aspen (Quercus gambelii), and Engelmann spruce
(Picea engelmannii). I will test how these traits and carbon stock vary
across gradients of mean annual precipitation. I found that the forest’s
carbon stock and functional traits respond on a community level rather
than a species-specific level to rainfall changes. Only spruce forests show
variation of carbon stock to rainfall, and only ponderosa forests show
strong trait variation over the precipitation gradient. Performing a
comprehensive analysis on the carbon storage and the traits that affect
the carbon storage in the Rocky Mountain ecosystem indicates that
climate extreme events are affecting one of the largest carbon sinks in
the United States.
NICOLE BUNYAN
PROFESSOR JANET MONGE
SUBSISTENCE STRATEGIES AND BONE RIGIDITY: A STUDY COMPARING THE
RELATIVE FEMORAL RIGIDITY OF THE HASANLU AND PRE-HOLOCENE HOMO
Until agriculture was invented roughly 12 000 years ago, humans survived
by practicing a hunting/gathering subsistence strategy. This less efficient
food-acquisition mechanism imposes a great amount of physical stress on
the skeleton through biomechanical loading, which results in greater
bone rigidity. This study examines the relative femoral rigidity (femoral
rigidity: humeral rigidity) within the agricultural Hasanlu population, and
compares their values to those of pre-agricultural Early African Homo
erectus (EAHE), Homo neanderthalensis (Neanderthals), and Anatomically
Modern Homo sapiens (AMHS). A greater relative femoral rigidity is
indicative of high levels of lower limb loading, which could be caused by
extensive amounts of walking or running. In this study, the Hasanlu
exhibited no significant differences in relative femoral rigidity between
sexes, age groups, distinct topographic locations, or time periods within
their population. In contrast, the Hasanlu did exhibit significantly lower
levels of relative femoral rigidity compared to some Neanderthals and
some Anatomically Modern Homo sapiens specimens, but did not differ
significantly from the two Early African Homo erectus skeletons. While a
larger and more diverse sample size of pre-agricultural Homo is necessary
for a more complete analysis, these results suggest that relative femoral
rigidity is influenced to a greater extent by subsistence strategies (ie.
hunting/gathering vs agriculture), than it is by age, sex, topographic
location, or time period.
NICOLE BYL
ASSISTANT PROFESSOR C. JESSICA METCALF
MODELING CHAGAS DISEASE PERSISTENCE: THE INFLUENCE OF HOUSEHOLD
GUINEA PIGS AND DOGS IN AREQUIPA, PERU
Chagas disease, one of the world’s 13 most neglected tropical diseases,
affects 6- 7 million people worldwide and causes 14,000 deaths per year
(Hotez et al., 2007). It is a vector borne disease transmitted via Triatoma
infestans and harbored in many animal species. It has an incredibly low
transmission rate, but continues to persist in many poor regions throughout
Latin America (Clayton, 2010). The goal of this study was to examine a
particular transmission system in the region in Southern Peru—a household
with dogs and guinea pigs—and uncover how the different components
of the system influence persistence over time. The main findings of this
study are that the only necessary components for persistence are those
that can spark the infection in the short term (the guinea pigs) and those
that can sustain it over longer periods of time (the humans); the
intermediate lifespan (dogs) is not necessary for persistence.
CHRISTINA CARANO
PROFESSOR ADEL MAHMOUD
THE RISKS OF VACCINE HESITANCY AND REFUSAL: A CASE STUDY OF
MEASLES OUTBREAKS IN SWANSEA, WALES, AND KNOX COUNTY, OHIO
Vaccine hesitancy and refusal, a growing trend in recent years, hinders
the elimination and eradication of diseases. This thesis looks investigates
the extent to which the anti-vaccine movement impacts vaccine
coverage and creates opportunities for epidemics to occur. Measles virus
has been controlled globally and especially in the developed world
through vaccination programs with the MMR vaccine, which when
administered as a two-dose regimen has 95-100 percent efficacy.
However, in recent years, the U.S. and U.K. have seen increases in
incidence of the disease. A case study of two recent measles outbreaks,
a 2012-2013 outbreak of 1,202 notified cases in Swansea, Wales and a
2014 outbreak of 383 cases among the Amish in Ohio, serves as the basis
for investigating the role of vaccine refusal on outbreak. In both
outbreaks, low vaccine coverage rates associated with vaccine
hesitancy and refusal compromised herd immunity and allowed for the
spread of disease among communities where measles is no longer
endemic. The reintroduction of eliminated viruses into these
undervaccinated populations represents a new challenge to public
health control teams. Therefore, this thesis looks at reactive responses to
this sort of outbreak with low routine vaccination coverage. The potential
efficacy of vaccination and behavioural interventions is investigated using
a parameter sweep of a theoretical SIR model. The model shows that
both interventions can be used to reduce incidence given a sufficiently
significant intervention with time constraints post onset of outbreak. The
case study shows the consequences of vaccine refusal in communities,
and provides insight into a changing risk-benefit analysis in deciding
whether or not to vaccinate.
JONATHAN CHOI
PROFESSOR DAVID WILCOVE
TROPICAL FOREST RESTORATION ON CATTLE PASTURES IN THE GUANACASTE
PROVINCE OF COSTA RICA
Ecological restoration has demonstrated huge potential in slowing and
ultimately reversing the tide of species extinction and land use change.
Trends in urbanization and globalization have led to the widespread
abandonment of cattle pastures which have the potential to be restored
to forest. Unfortunately, the perception of restoration as expensive and
contrary to economically “useful” land use has precluded efforts to
regrow forests. The use of agricultural waste generated from orange juice
manufacturing, namely pulp and peels, in Área de Conservación
Guanacaste offers a unique opportunity to explore the restoration of
tropical forests from cattle pastures in Mesoamerica.
After the supervised application of 1,000 truckloads of orange peels in
1998, soil surveys in 2000 and 2014 recorded large scale differences in soil
properties. Vegetation surveys in 2014 recorded a 3 fold increase in
species richness for trees larger than 5 cm in DBH and a 2 to 4 fold
increase in aboveground biomass. Invertebrate pitfall traps revealed a
large difference in number of individuals between the two sites, but was
unable to discern a difference in family-level diversity. Vertebrate audio
surveys using passive audio recorders provide a hint into the vertebrate
community using the restored habitat, including howler monkeys
(Alouatta palliata) and white-faced capuchin monkeys (Cebus
capucinus).
The potential for the use of orange peel-based restoration is immense.
Studies of the exact mechanisms for orange-peel catalyzed regeneration
and the potential for the use of other agricultural waste would help to
improve policy recommendations for restoration. The uniquely costeffective nature of this restoration method makes it a particularly
attractive method for further research.
LAURA COOPER
PROFESSOR BRYAN GRENFELL
POWER LAWS FOR HETEROGENEOUS BITING AND MALARIA
EXPOSURE IN UGANDA
Malaria is a threat to global health and wellbeing and control remains a
significant epidemiological challenge. The biting patterns of anopheline
mosquitoes, which transmit falciparum malaria, are influenced by a
variety of environmental, population dynamic, and behavioral factors. As
a result, human exposure to malaria is significantly heterogeneous
between individuals and over time. Heterogeneity in exposure increases
disease persistence and amplifies transmission because those individuals
most likely to be infected by infectious mosquitoes are also most likely to
infect uninfected mosquitoes. Knowledge of the nature of heterogeneous
transmission is essential to reducing or eliminating the global malaria
burden.
Mosquito biting patterns are explored using mosquito catch data from
three communities in Uganda between October 2011 and March 2013.
Heterogeneity in exposure, as measured by the Pareto index, the
coefficient of variation, and the dispersion parameter, 𝑘, decreases with
mean biting intensity. Biting patterns are well described by a power law
with a gradient greater than one, suggesting significant over-dispersion in
the distribution of bites. Significant associations between seasonal and
environmental variables and heterogeneity are also observed, but these
may be confounded by seasonal and environmental differences in mean
biting intensity.
The relevance of the observed mean-heterogeneity relationship to basic
epidemiological parameters is explored. The force of infection saturates
at high biting intensities, but not as quickly as predicted by models that
assume constant levels of heterogeneity across the spectrum of biting
intensity. Likewise, transmission efficiency declines less rapidly than fixedheterogeneity models predict. The basic reproduction number increases
with biting intensity and the coefficient of variation, and a global
minimum value exists such that at certain points, decreases in mean biting
intensity lead to increases in the basic reproduction number. As a result,
elimination may be more difficult than originally thought and may require
new control strategies. From these findings it is apparent that a precise
understanding of the dynamics and drivers of heterogeneity are essential
to successful malaria control.
HELEN DAIFOTIS
PROFESSOR SIMON LEVIN
A MULTIPLE FIRST-LINE THERAPIES MODEL FOR PLASMODIUM FALCIPARUM
MALARIA: FACTORS INFLUENCING THE SPREAD OF ARTEMISININ RESISTANCE
IN HIGH AND LOW TRANSMISSION REGIONS
Malaria is a parasitic, vector-transmitted, febrile illness endemic to nearly
100 countries and responsible for more than half a million deaths in 2014.
Following the advent of highly efficacious antimalarials in the post-World
War II era, some began to plan for worldwide eradication of the disease.
However, these goals were thwarted by political instability, administrative
issues, and, most importantly, the spread of drug resistance. Starting in
2001, artemisinin combination therapies (ACTs) became the
recommended first-line treatment for uncomplicated P. falciparum
infections. Shortly thereafter, resistance to artemisinin was detected in the
Greater Mekong Subregion, threatening recent gains in malaria mortality
and morbidity and mimicking the prior emergence of resistance to
chloroquine and sulphadoxine-pyrimethamine in the latter half of the 20th
century. Unlike these historical examples, there is no non-artemisinin based
substitute expected to enter the marketplace for at least five to ten more
years should resistance continue to spread. In light of this concern, this
research utilizes a multiple first-line therapies (MFTs) based evolutionaryepidemiology model to examine what factors about the Greater Mekong
Subregion foster the emergence of antimalarial resistance. Though the
original hypothesis of this research focused on modeling high versus low
transmission areas and comparing their difference in population-level
immunity and drug pressure, it ultimately became clear that the true
segregating factor is the level of disease endemicity. The models
demonstrate how in areas of high endemic disease, rapid transmission
and immunity work together to minimize the amount of drug pressure
exerted on the parasite population. Without a high level of drug pressure,
the fitness of resistant parasites is decreased and the trait is less likely to
spread throughout the population. In the future, drug deployment and
distribution strategies should focus on alleviating the level of drug pressure
in areas of low disease endemicity to mitigate the emergence and
spread of resistance.
RENATA DIAZ
ASSISTANT PROFESSOR ROBERT PRINGLE
HERBIVORE‑MEDIATED EFFECTS OF ECOSYSTEM HOTSPOTS ON THE
DEMOGRAPHY OF A WIDESPREAD EAST AFRICAN SAVANNA TREE
In African savannas, ‘ecosystem hotspots’ – nutrient)enriched grazing
sites that increase system-wide productivity for many taxa – feature
specific patterns of tree population density and age structure. Some
hotspots have edge effects, the specific extent and nature of which
depend on the spatial distribution of the hotspots. The changes to
tree populations in and around ecosystem hotspots contributes to the
long)term maintenance of the hotspots themselves, and defines the other
ecological impacts of hotspot edges. When hotspots occur close
together, their edge effects reduce habitat quality for large herbivores
and may further bush encroachment. The mechanisms maintaining
distinctive tree populations associated with hotspots are an open
question, and it is yet unknown whether hotspot edge effects persist over
long time scales. Of the possible mechanisms regulating trees in and
around ecosystem hotspots, seed predation remains under)explored. I use
seed removal experiments to test whether seed predation is a
possible mechanism maintaining variation in tree demography in and
around ecosystem hotspots. I find that seed predation is only likely to
significantly affect tree demography in hotspot edges. I then use a
mathematical model to project the long)term persistence or decay of
hotspot edge effects, and the relative contributions of seed predators
and large mammalian herbivores to this outcome. I find that edge effects
can persist for centuries, and suggest that land managers take steps to
avoid creating edges with long)lasting detrimental effects. Edge effect
persistence depended on all parts of the system, including both
edge-edge interactions and a complete network of plant)herbivore
interactions. I suggest that predictions regarding the long)term
development of edge effects can be made more accurate by taking
into account specific edge effects, including edge)edge interactions,
and the basic ecology of the system in question. Seed predation is a
potentially quite widely overlooked process regulating savanna
vegetation, especially in naturally-occurring contexts where large
herbivores are at lower-than-normal density.
EMMA GLENNON
ASSISTANT PROFESSOR C. JESSICA METCALF
CLIMATE, CONTACT, AND CHOLERA: A DISCRETE-TIME APPROACH TO
REVEALING SEASONAL PATTERNS OF VIBRIO CHOLERAE O1TRANSMISSION
IN DHAKA, BANGLADESH
When ingested by humans, the bacterium Vibrio cholerae causes
cholera, a diarrheal disease that afflicts 3–5 million people annually.
Though often considered a primarily waterborne (i.e., indirectly
transmitted) disease, cholera may also be transmitted via more direct
fecal-oral routes. The dynamic roles of these pathways are not well
understood.
We investigated the relative dynamic roles of these two pathways of
cholera trans- mission—direct and indirect—by constructing a two-path
SIR-derived model in discrete time. We fit this model to fourteen years of
data (2000–2013) on a total of 5,939 patients testing positive for V.
cholerae O1 at the International Centre for Diarrhoeal Disease Research,
Bangladesh (icddr,b) in Dhaka, Bangladesh, one of the largest cities
affected by endemic cholera. We used the fit model to infer a seasonallyvariable growth/decay rate (χ) for aquatic V. cholerae as well as
temporal variations in the proportions of cases attributable to each
transmission pathway.
The aquatic bacterial growth rate χ peaked preceding each biannual
outbreak, with incidence starting to climb as χ was at or near its local
maxima. In general, the proportion of cases attributable to indirect
transmission was especially high as total incidence increased. In
combination with the known effects of climatic factors on V. cholerae
growth, these predictions suggest a possible critical period during which
initial transmission via the aquatic reservoir sparks outbreaks subsequently
fueled by bacterial shedding and even later by direct transmission.
Generalized linear models predicting the chance of each case being
attributable to indirect transmission, using case exposures as covariates,
support our predictions about the roles of different pathways over time.
We discuss the implications of model assumptions as well as the value of
future research to test these assumptions and extend applications of our
model. We also discuss potential implications for public health, especially
the targeting of water and sanitation interventions to a critical period of
environmental transmission and the potential for climate change to
extend and intensify endemic cholera outbreaks.
SANDRA GOLDLUST
PROFESSOR BRYAN GRENFELL
MALARIA CONTROL IN VIETNAM: IMMUNE DYNAMICS AND
ARTEMISININ RESISTANCE
Objective: The purpose of this study was to investigate the association
between artemisinin-based case management and the incidence of
malaria in Vietnam between 1991 and 2010. Moreover, the study aimed
to evaluate how this relationship was modulated by host immune
dynamics and transmission intensity. Understanding these interactions is
critical to mitigating the threat of artemisinin resistance and working
towards malaria elimination in the Greater Mekong Subregion.
Methods: In the first part of this thesis, data on reported malaria
cases, antimalarial treatment requests, vector control measures, and
urbanization metrics from all provinces in Vietnam between 1991-2010
were collected from annual reports of the National Malaria Control
Program. Generalized estimating equations were used to investigate the
factors associated with malaria incidence. A mathematical model was
then developed to evaluate the effects of ACT case management and
artemisinin resistance on malaria transmission in hypothetical populations.
A subsequent model was fit to malaria case data from Vietnam and used
to predict malaria incidence following increased rates of treatment failure
as a result of artemisinin resistance.
Results: Statistical analysis revealed a significant (P <0.001) inverse and
spatially consistent association between the incidence of malaria in
Vietnam and the proportion of antimalarial treatments that contained
artemisinin. The dynamic models revealed that decreasing the treatment
failure rate reduced the number of asymptomatic cases in both high and
low transmission settings, while the number of symptomatic cases
increased in the high transmission setting and decreased in the low
transmission setting. Increasing the rate of treatment failure increased the
number of asymptomatic cases in both transmission settings, while
symptomatic cases decreased in the high transmission setting and
increased in the low transmission setting. Moreover, the fitted model
provided a reasonable picture of the decline of malaria in Vietnam by
varying the rate of treatment failure. The model predicted that increased
rates of treatment failure in subsequent years would lead to an epidemic.
Conclusions: Artemisinin-based case management was significantly
associated with the decline of malaria in Vietnam between 1991 and
2010. However, the population-level effects of ACT case management on
incidence may be greater in low transmission settings in populations with
low levels of acquired immunity. In particular, reduced immune protection
in Vietnam heightens the threat posed by artemisinin-resistant P.
falciparum.
CRICKET GULLICKSON
PROFESSOR BRYAN GRENFELL
THE TRUE BURDEN OF MEASLES: THE ASSOCIATION BETWEEN MEASLES
INCIDENCE AND NON-MEASLES INFECTIOUS MORTALITY IN CHILDREN
IN BRAZIL, 1980-1995
Infectious disease is a major driver of global mortality, particularly in
children. Despite the impact of vaccination campaigns, measles remains
endemic in much of the developing world and recent outbreaks in the
developed world – due in part to the misconception that measles is a
benign infection – have raised concern of measles resurgence. In addition
to being a primary cause of childhood mortality, measles also causes a
profound immunosuppression that predisposes infected individuals to
secondary infection, making measles an important underlying cause of
non-measles infections as well; however, the extent and etiology of the
contribution of measles to all non-measles infectious mortality has not
been well-characterized. Here, epidemiological data for 1-9 year olds in
Brazil is used to show that measles explains more than 60% of the
decrease in childhood infectious mortality observed to coincide with the
introduction of nationwide measles vaccination. These results suggest a
much greater role for measles vaccination as a driver of reduced
childhood mortality – particularly respiratory and diarrheal mortality – than
had previously been described, and indicate that measles vaccination
should continue to be emphasized in global health today.
JOSHUA HAMILTON
PROFESSOR STEPHEN PACALA
CARIBBEAN REEF SHARK DECLINE AND MESOPREDATOR RELEASE
IN THE TROPICAL ATLANTIC
Removal of apex predators has been demonstrated to have lasting
negative effects on the community structure of many ecosystems in the
form of trophic cascades, specifically through the release and resultant
superabundance of mesopredators.
Carcharhinid sharks such as
Carcharhinus perezi (Caribbean Reef Shark) are important apex predators
on coral reefs and have suffered massive population declines over the
past century. In order to assess how C. perezi population density affects
overall reef trophic structure, I surveyed fish biomass and biodiversity
across six reef sites in the Turks and Caicos Islands. I found a significant
negative correlation between mesopredator biomass and C. perezi
sighting frequency. This suggests C. perezi plays an important regulatory
role in maintaining healthy coral reef populations, and has important
implications for reef conservation.
SARAH HANNA
ASSOCIATE PROFESSOR ANDREA L. GRAHAM
HELMINTH INTERACTIONS WITH THE HOST IMMUNE SYSTEM: A COMPARATIVE
STUDY OF MICE IN LABORATORY AND NATURAL SETTINGS
The motivation for this study rests on the biome depletion theory, an
extension of the hygiene hypothesis that posits that the increase in the
prevalence of inflammatory diseases seen in developed countries is a
result of the loss of coevolutionary partners from the human internal
ecosystem. Specifically, the removal of intestinal helminths through
improved sanitation measures and/or anthelmintic treatment has been
suggested as a primary cause of the problem. This raises public health
questions about which human populations might benefit from chronic
helminth infection. However, experimentally investigating the potential
benefits of helminths in human populations is fraught with ethical
concerns because helminths have the potential to cause negative health
outcomes as well (malnutrition, anemia, fatigue, etc.). Laboratory studies
on animal models have frequently been used, but the laboratory setting is
so inherently different from the natural environment that it is unclear to
what extent these results will be generalizable. This study aims to provide a
new protocol for studying immune mechanisms. Namely, this study runs
parallel experiments on inbred mice in a laboratory and in a semi-natural
environment, measuring various cytokine levels to characterize immune
responses. This methodology enables an examination of the effects of
heterogeneous environments on uninfected control mice and direct
comparisons of the effects of helminth infection in the lab and in more
natural environments. Our results indicate that the immunological effects
observed in the lab are largely generalizable to the natural environment,
but that effect size and/or absolute levels of cytokine expression vary by
location. However, our results also suggest the presence of some immune
effects associated with exposure to a natural environment. These effects
are inherently missed by laboratory studies. Finally, the results indicate that
the semi-natural environment methodology is a viable methodology for
examining immunological mechanisms in a more natural setting.
REBECCA HAYNES
PROFESSOR DAVID WILCOVE
FOREST COVER CHANGE IN COSTA RICA'S PROTECTED AREAS
AND BIOLOGICAL CORRIDORS: 2000-2010
Following decades of rampant deforestation, Costa Rica gave birth to a
political framework and a system of protected areas devoted to the
preservation of the country’s ecosystems and wildlife. Forest regeneration
seen across the nation in recent years has led to its international
recognition as a conservation success story. Is this praise justified,
according to recent forest cover trends? This study uses ArcGIS to analyze
land cover maps from 2000, 2005, and 2010 in order to assess forest losses
and gains in Costa Rica. The analysis revealed that forest cover increased
by 13.4% across the country from 2000 to 2010. In the biological corridors
that link protected areas, net forest regrowth was 17.1%. Net deforestation
of 4.7% in the national parks and 5.8% in the biological reserves occurred,
but further examination revealed that these two figures are at least
partially due to error. Forest cover was stable in the buffer zones
surrounding the parks, with net forest regrowth ranging from 0.20% to
12.0%, but net forest loss occurred in the buffer zones surrounding the
reserves, at rates ranging from 4.8% to 6.9%. Loss of forest in areas
surrounding the reserves indicates cause for concern because these
buffers are critical to preventing the isolation of ecosystems within
protected areas. However, these results reveal general trends towards net
reforestation in Costa Rica, concentrated in the biological corridors,
which may positively contribute to wildlife conservation.
VICTOR HSIAO
PROFESSOR BRYAN GRENFELL
THE IMPACT OF SCHOOL CLOSURE AND VACCINATION ON HAND-FOOTAND-MOUTH DISEASE TRANSMISSION DYNAMICS IN CHINA
Background: Hand-foot-and-mouth disease (HFMD) has been an
increasing concern in China since HFMD outbreaks began there in 2008.
HFMD became a national notifiable disease in China in 2008 and up to
2012, there were 7.2 million cases of probable HFMD cases reported to the
China CDC. A number of public health guidelines including school
closures have been implemented to minimize HFMD transmission and
incidence in China. However, there is little evidence-based consensus
about whether these school closures have effectively reduced HFMD
incidence. A proposed, and potentially more effective, public health
intervention is an HFMD vaccine. Different enterovirus serotypes have
been shown to cause HFMD, with Enterovirus 71 (EV71) and Coxsackievirus
16 (CA16) being the predominant ones in China. Recent phase 3 clinical
trials showed that inactivated monovalent EV71 vaccines effectively
reduced EV71-related HFMD incidence. We use mathematical models to
compare the impact of school closures and vaccination in reducing
HFMD incidence in the cities of Beijing, Chongqing, Shanghai, and Tianjin,
and thereby better inform future HFMD-related public health policy.
Methods: We used the time-series susceptible-infected-recovered (TSIR)
model to estimate average weekly seasonal transmission rates as well as
the basic and effective reproductive number (R0 and RE) for HFMD in
China from 2008 to 2012. These seasonal transmission rate estimates were
used to fit the TSIR model to China’s HFMD epidemic time-series data.
School closures were modeled by lowering the transmission rates at
different times during the year. Vaccination campaigns were modeled by
reducing the effective number of susceptible individuals entering the
population. Lastly, the invasion of an HFMD-causing pathogen was
simulated by increasing the proportion of the population susceptible to
the pathogen.
Results: RE peaked above 1 twice in southern cities and only once in
northern cities, thus matching the number of peaks of HFMD incidence
per year observed between 2008 and 2012. There was a minimal
decrease in the seasonal transmission rates corresponding to the summer
holidays, with this decrease being more pronounced in cities located in
southern China. Single-week school closures at the calculated week of
onset of the HFMD epidemic caused short-term decreases in incidence
but had insignificant effects on long-term, annual HFMD incidence. Singleweek school closures only caused the epidemic to slow down with the
overall seasonality staying the same. Multiple-week school closures
caused greater reductions in annual HFMD incidence as the number
of weeks of school closure increased. However, even when schools were
closed for the whole year, reductions in annual HFMD incidence did not
drop below 94% relative to the
noclosure annual HFMD incidence scenario.
In comparison, with vaccination, HFMD incidence decreased as the
proportion of newborns vaccinated increased and as the length of
vaccination campaigns increased. Even at low vaccination coverage
rates of 50%, incidence was reduced to below 90% in all cities that were
studied. At 90% vaccination coverage, incidence was reduced to below
20% in all selected cities. Vaccination-related reductions in incidence
were also less pronounced in southern cities. HFMD epidemic seasonality
increased when invasion occurred during the winter months or when
there was a lower proportion of the population that was susceptible to the
given pathogen. Meanwhile, seasonality decreased when invasion
occurred nearer to the summer months or when there was a higher
proportion of the population that was susceptible to the given pathogen.
Discussion: The possibility of the invasion of a new HFMD-causing virus
strain is concerning, especially if a large proportion of the population is
susceptible to the pathogen and if the invasion occurs during the summer
months. School closures, however, are relatively ineffective for reducing
annual HFMD incidence. As such, other public health interventions should
be explored. Vaccination is a promising solution to dramatically
reducing HFMD incidence especially because an EV71 vaccine is
expected to be released in China this year.
DAMARIS IRIONDO
PROFESSOR DANIEL RUBENSTEIN
ZEBRA STRIPES: THEIR ROLE IN MODULATING BITING FLY LOADS
AND BODY TEMPERATURE
The function of zebra stripes is analyzed by testing two major theories –
thermoregulation and protection from ectoparasites – on individual plains
zebras and control species on Ol Pejeta Conservancy. This study
significantly supports the thermoregulation theory: plains zebras exhibit a
lower body surface temperature compared to control species. In fact,
striped surfaces have reduced counts of flies compared to solid surfaces.
Moreover, body surface temperature follows a normal curve pattern with
time of day, peaking during hot afternoon hours and lowering with
high wind speeds. Zebras were observed in the hot open habitats more
often because their ability to stay cool for longer, confirming that they
can regulate their temperature and heat loading. The ectoparasite
hypothesis is analyzed by measuring the level of harassment and
concentration of biting flies for its differences on solid versus
striped colored coats. It is found that flies concentrate more on solid
coats, specifically dark colors, and on smaller groups more than larger
ones. Moreover, fly concentrations are highest on sunny hot days, bushier
habitats, and low wind conditions. The zebras respond to increasing fly
harassment by increasing tail swish and comfort movements.
JAKOBI JOHNSON
PROFESSOR STEPHEN PACALA
QUANTIFIABLE ANALYSIS OF CONCUSSION SYMPTOMS
AND SYMPTOM RELATIONSHIPS
Recently, concussions have been one the largest public health problems
for healthcare professionals. They are a seemingly unpreventable aspect
of many different sports. A concussion can be defined as a complex
biological process that results from biomechanical forces acting on the
head that can affect normal brain functioning. If not treated properly and
carefully, concussions may lead to prolonged symptoms and a higher risk
of developing brain disorders later in life. Some of the most easily
recognizable symptoms of concussions include: dizziness, loss of
consciousness, and headache. Finding a viable treatment, and a way to
evaluate concussion severity and future effects, presents a major
challenge for healthcare providers. Presently, most treatments consist of
rest from cognitive and physical activity. Healthcare professionals decide
how and when patients can gradually return-to-play and return to other
activities based on how symptoms are displayed. Since most of what we
can see from concussions is based on symptoms reported by concussed
individuals and their healthcare professionals, this study takes a deeper
look at concussion symptoms and post-concussion syndrome.
This study analyzes data from twenty-three different studies using multiple
statistical tests (t-test, ANOVA Chi-Squared) to determine which
concussion symptoms are statistically significant. This thesis shows that
most of the common concussion symptoms are found at high enough
frequencies to reject the null hypothesis of a frequency of zero. This study
also revealed that some symptoms occur at a higher frequency in the
general population than in the concussion samples. Moreover, the
ANOVA test showed that many of the symptoms had complex
interactions. Future studies should investigate these associational
relationships to identify the mechanisms. This thesis also provides support
for the testing of blood for endocrine and hormone levels to get a more
complete measurement of the severity and proper treatments that should
follow concussions.
MEGAN KENNEDY
ASSOCIATE PROFESSOR ANDREA GRAHAM
THE ROLE OF THE MICROBIOME IN TRANS-GENERATIONAL
IMMUNE PRIMING OF T. CASTANEUM
Trans-generational immune priming is a phenomenon recently
documented in insects in which the offspring of previously infected
mothers inherit a survival advantage over larvae from uninfected mothers.
This form of immunological “memory,” analogous to adaptive immunity in
vertebrates, has provided the scientific community with an important
mechanistic puzzle: in the absence of heritable antibody-conferred
resistance, how is this survival advantage transmitted from parent to
offspring? Despite a proliferating scientific literature that has revealed
much about the immunogenetic manifestations of immune priming, the
mechanistic basis by which immune advantage is imparted transgenerationally in insects remains poorly understood. I approached this
question through a framework that identified two potential sources of
inheritance: maternally provisioned immune factors (i.e., immune factors
supplied within the egg) and socially inherited microbial flora (i.e., gutcolonizing bacteria found on the egg). In this thesis, I used Tribolium
castaneum, the red flour beetle, and Bacillus thuringiensis (Bt), an
entomopathogenic bacterium, to perform a cross-fostering experiment in
which I controlled and manipulated the bacterial exposures of larvae
from primed and unprimed mothers. This allowed me to parse out the
influences of maternal inheritance and microbial inheritance on survival
and immune gene expression as they relate to the primed larval
phenotype. From my survival analysis, I found that maternal egg
provisioning plays a more predominant role in producing the primed
phenotype, but that the microbial inheritance may still have a modulatory
influence that varies depending on maternal priming status. Although my
analyses of gene expression patterns across maternal and microbial
exposures revealed few conclusive trends, my combined investigations
into survival and gene expression have provided testable conceptual
explanations for observed patterns, and pave the way for continued
investigation of the role of the microbiome in trans-generational immune
priming.
ABRAHAM KIELAR
PROFESSOR LARS HEDIN
FACTORS AFFECTING TART CHERRY ORCHARD BLOOM DATE, HARVEST
DATE, AND YIELD IN DOOR COUNTY, WISCONSIN
Door County, Wisconsin, is a small landmass forming a peninsula that
extends into Lake Michigan. The moderating effect of the lake on regional
weather makes it possible to grow tart cherries and other crops at
latitudes that would otherwise be too cold for such agricultural practices.
Growing up on an orchard in this community, I knew that orchards in the
northern part of the county tended to ripen later, and this inspired me to
investigate the evidence for a ripening gradient based on latitude. I also
set out to identify the factors that most strongly influence bloom date,
harvest date, and yield per acre of tart cherry trees in Door County. An
additional goal was to identify which orchards were the most successful in
terms of yield and determine why.
I concluded that the factor with the highest impact on bloom and
ripening time was average temperature in the months preceding bloom
and harvest. Warmer temperatures in April translated to earlier bloom and
warmer temperatures in April through July resulted in earlier harvest dates.
Temperature also had an impact on yield, but the implications were less
clear since there was not a known optimum temperature for producing
the highest yield. I concluded that orchards in the south and on the bay
side of the county do indeed tend to bloom and ripen earlier in the spring,
but there was no clear gradient and many orchards that deviated from
this trend. I did not find evidence for a yield pattern in terms of latitude or
distance from Lake Michigan. Door County’s yield was comparable to the
national average for tart cherry growing states.
ELIOT LINTON
ASSISTANT PROFESSOR ROBERT PRINGLE
IS AN EYE TO A BIRD WORTH TWO IN A BUSH? BOTH EYESPOTS
AND OBSCURED BRANCH PLACEMENT REQUIRED FOR
PROTECTION IN MODEL CATERPILLARS
Many moths, butterflies, caterpillars, and pupae exhibit small paired
symmetrical circular markings commonly called eyespots, which are
hypothesized to provide significant protection by mimicking the eyes of a
deadly predator. A growing body of experiments has demonstrated that
these markings do confer protection, in adult as well as larval lepidoptera,
against predation from birds. Eyespots are thought to be particularly
effective in combination with a startle effect, meaning that they are more
effective when displayed suddenly to exploit a predator’s immediate
reaction. It has been hypothesized, though never tested, that eyespots
are more prevalent in caterpillars which spend most of their time in
obscure microlocations, due to this startle effect. To investigate the
protective effects and interaction of eyespots and obscure microlocation,
four treatments of artificial clay caterpillar were placed in a 2x2 factorial
design and exposed to predation by wild birds in the Area de
Conservacíon Guanacaste, in Costa Rica. The survival of each model
caterpillar was monitored for 96 hours in four trials. The data showed that
both eyespots and obscured microlocation were both required to see a
major reduction in hazard rate, suggesting that caterpillar eyespots are
more effective when a caterpillar is not plainly visible from far away.
Furthermore, for a subsample of these models, branch size and caterpillar
placement along the branch were correlated and led to increased
predation rates. These results support the hypothesis that eyespots are less
effective when constantly displayed and more effective when displayed
suddenly, and that an effective means of generating this effect for
caterpillars is to live in an obscure microlocation.
VERONIKA LIPKOVA
PROFESSOR SIMON LEVIN
SPATIAL PATTERNS OF MULTIDRUG-RESISTANT TUBERCULOSIS DISTRIBUTION
IN CAPE TOWN AND PORT ELIZABETH, SOUTH AFRICA
Objectives: To carry out a spatial clustering analysis of multidrug-resistant
tuberculosis incidence (MDR TB) in South Africa on the global and regional
levels and to use multiple linear regression to find socioeconomic
predictors of the distribution using data from the Cape Town and Nelson
Mandela Bay (Port Elizabeth) local municipalities.
Methods: National Health Laboratory Service data between 2009 and
2011 were used along with South African Census 2011 data to find spatial
distribution of MDR TB incidence. The Getis-Ord Gi* statistic tool of ArcGIS®
10.2 was used to compute the location of significant hot and cold spots
on the level of South Africa, Cape Town and Port Elizabeth (Nelson
Mandela Bay municipality). Lastly, the regional datasets were examined
by the means of a non-spatial multiple linear regression in STATA 13.
Results: MDR TB incidence data points were significantly clustered on
thenational as well as regional levels. The Getis-Ord Gi*statistic yielded
significantresults, showing the hot and cold spots of the disease on the
level of South Africaas well as the Cape Town (CT) and Nelson Mandela
Bay (NMB) loca lmunicipalities. A multiple linear regressions selection
revealed that in the CT municipality the MDR TB incidence variable was
significantly negatively correlated with education (p=0.002) and positively
with income (p=0.015) and TB incidence (p<0.001). Port Elizabeth MDR TB
incidence showed a
significant positive relationship with TB incidence (p<0.001).
Conclusions: The distribution of multidrug-resistant tuberculosis is
significantly non-random on at least two levels of resolution, the national
and the municipal. In general, the spatial distribution of MDR TB and
socioeconomic variables suggests higher incidence in economically
disadvantaged areas, which was confirmed by analysis of data from CT
and NMB. Nevertheless, further research is required to understand the
socioeconomic predictors of the disease and to find
additional variables that may be associated with the spatial distribution of
MDR TB both locally and globally.
DANIELLE MARTIN
ASSISTANT PROFESSOR CORINA TARNITA
ANGIOSTRONGYLUS CANTONESIS: HOST POPULATION DYNAMICS
AND THE INFLUENCE OF SEASONALITY
The aim of this paper is to determine the dynamics of Angiostrongylus
cantonensis in its host populations, focusing particularly on the effects of
seasonality. Fieldwork in Jamaica, noting a decreased prevalence of A.
cantonensis in the test species Thelidomus Aspera, culminated in a
hypothesis that seasonality influences prevalence. Specifically,
prevalence drops during the dry season. An SI model was created to
describe rat lungworm dynamics first without and then with
seasonality. The first model illustrates the stability of this parasite’s life
cycle, which requires few definitive hosts to maintain significant
prevalence in a system. It also indicates that areas of human disturbance
are likely to carry higher prevalence. This model also provides evidence
showing that infection from rats to snail by means of infected snail mucus
and by means of consumption of the snail yield similar equilibriums. This
provides evidence supporting the possibility of infection through
consumption of snail mucus even though no study has yet to detect
larvae in this medium. Finally seasonality was added using cosine function
to simulate the wet and dry seasons of tropical environments. Simulations
of this model show that snail populations are impacted more significantly
by seasonality. This model also seems to reject the initial hypothesis
developed based on fieldwork. In almost all cases prevalence of infection
in the snail was higher during the dry season. At very high contact rates or
transmissions rates prevalence seemed to shift toward the wet season.
SHANNON MCGUE
PROFESSOR SIMON LEVIN
GUT FEELINGS: THE POTENTIAL FOR INCREASED INTUSSUSCEPTION WITH THE
INTRODUCTION OF ROTAVAC INTO INDIA’S UNIVERSAL IMMUNIZATION
PROGRAM
Though the introduction of a new rotavirus vaccine, Rotavac, into India’s
universal immunization program would prevent diarrheal morbidity and
mortality, it may also increase the incidence of a rare intestinal obstruction
called intussusception. Current rotavirus vaccines carry a risk of
intussusception on the order of 1-2 excess cases per 100,000 vaccinated
infants, while a previous rotavirus vaccine was withdrawn after being
associated with an excess risk of 1 intussusception per 10,000 vaccinated
infants. The number of intussusception cases that could be seen in India if
Rotavac is added to the universal immunization program is assessed using
the average baseline intussusception incidence seen in countries with
comparable under-5 mortality rates and the average relative risk
observed after vaccination with current rotavirus vaccines. Assuming that
Rotavac doses are administered at the same levels as diphtheria-tetanuspertussis doses currently are, then there will be 5,906 excess cases of
intussusception due to rotavirus vaccination per year in India, representing
an increase of 20% over baseline number of intussusceptions. Only 12-500
will be reported as adverse events through the standard reporting system,
with 15-700 potentially reported through a web portal. The number
reported decreases when the state-by-state vaccine coverage and
surveillance data are used. The government is recommended to either
strengthen both the AEFI surveillance system and existing knowledge
about intussusception or focus on self-controlled case series analyses.
Rotavirus vaccination risks are outweighed by potential benefits for Indian
society, provided that the intussusception risk is monitored.
PALLAVI MISHRA
PROFESSOR SIMON LEVIN
COMMUNITY-BASED CARE FOR MATERNAL HEALTH
AMONG PASTORALISTS IN LAIKIPIA, KENYA
Morbidity and mortality related to pregnancy and childbirth are major
priorities in the field of global health today. In the year 2013, nearly
300,000 women died as a result of obstetric complications, most of which
are preventable with proper diagnosis and treatment. 99% of maternal
deaths occur in low-resource settings and over half in sub-Saharan Africa,
starkly reflecting global disparities in the distribution of resources and
health services.
This study focuses on maternal healthcare utilization in a rural and
historically underserved population, the Mukugodo Maasai pastoralists of
Laikipia County in the Rift Valley Region of Kenya. Access to healthcare in
these communities is remains low for a number of reasons, from the limited
availability of transportation in the area to the continued prevalence of
traditional birth practices and the semi-nomadic lifestyle of the Maasai. In
recent years, a variety of initiatives intended to improve maternal health
have been initiated, including the removal of user fees for maternity care,
training of community health workers, training of traditional birth
attendants, and provision of hygienic birth kits.
Quantitative and qualitative methods were used to analyse women’s
reported experiences with healthcare during pregnancy and childbirth.
Additionally, a mathematical model was created to explore the dynamics
of the uptake of a health-promoting behaviour in this community under
conditions representing different interventions. The model shows that
delivery in a health facility will eventually be accepted as a norm by the
majority of the population. In reality, this outcome will also depend on
factors that are slower to change, such as building the capacity of the
health system in the area. Survey responses show that while interventions
aimed at education for behaviour change have made an impact on
women’s attitudes towards maternal healthcare, their actual rates of
skilled attendance at birth have not significantly increased as a result.
Overall improvement of maternal health in this region will call for a
nuanced, context-dependent approach that addresses people’s
practical needs as well as their deeply held beliefs.
NANA OWUSU-NYANTEKYI
PROFESSOR JANET MONGE
STAND UP TALL: THE POSITION OF THE FORAMEN MAGNUM
IN BIPEDAL AND QUADRUPEDAL PRIMATES
.
In human paleontology, the position of the foramen magnum has been
widely used as an indicator of locomotion pattern in bipeds and
quadrupeds. Regardless, previous studies have failed to comprehensively
show a functional connection between an anteroposterior foramen
magnum position, a shortening and broadening of the cranial base and
bipedalism. Many have argued that early Pliocene primates, for example
Sahelanthropus, Ardipithecus ramadis and Australopithecus are in fact the
earliest known hominids, as they exhibit a relatively anterior foramen
magnum and a short and wide basicranium. Metrical and morphological
comparative analyses were conducted, using 3D computerised
tomography scans, of the cranial base of 46 extant Homo fossils (one
species: Homo sapiens) and 28 extant non-habitually bipedal primates
fossils (four genera: Papio, Pongo, Macaca, Gorilla). Measurements of the
two auricular points, the two carotid foramina, basion to the opisthion and
the lateral tympanic length were taken on all samples. The data were
then used to test the hypothesis that an anteroposterior position of the
foramen magnum, deduced by a shortening and widening of the cranial
base, is correlated with facultative bipedal locomotion. The results show
that in bipeds, as represented by the Homo sapiens sample, the cranial
base is shorter and broader than that of quadrupeds. Additionally, the
carotid foramina has shifted laterally and the mediolateral tympanic
length has shortened, indicating a relatively anterior position of the
foramen magnum in Homo sapiens compared to the non-habitually
bipedal primates. These changes to the cranial base are associated with
hominid status and bipedalism but conclusions must be made with
caution.
DANIEL PAOLILLO
PROFESSOR BRYAN GRENFELL
COMPARATIVE DYNAMICS OF PERTUSSIS AND THE IMPACT OF CONTROL
Pertussis is an infectious disease with incidence resurging over the past
two decades despite high levels of vaccine coverage. Incidence in
adolescents and adults noticeably increased, which raises questions
about pertussis transmission dynamics. Resurging incidence in adolescents
and adults has been prevalent in developing countries and developed
countries across North America, Europe, Africa and Asia, which is why
pertussis is a global health problem. Pertussis still is a major killer in
developing countries. This literature review will primarily synthesize sources
in order to critically examine and evaluate the problems with
understanding pertussis dynamics, the focus on pertussis in developed
countries, where resurgence is best documented, and hypotheses that
propose why pertussis incidence resurged. It includes an introduction,
which will provide background on the bacteria, symptoms, and clinical
stages. It includes a methods section to describe the process of reviewing
the literature and, additionally, to describe the summer research that led
up to this literature review. This synthesis of the literature can serve as a
blueprint that could be a useful resource for future research on pertussis
dynamics and transmission.
SUNNY PATEL
SENIOR RESEARCH SCHOLAR RAMANAN LAXMINARAYAN
ANTIMICROBIAL SUSCEPTIBILITY AND MOLECULAR DIVERSITY OF
ESCHERICHIA COLI: THE EVOLUTION AND ESCALATION OF AGRICULTURAL
ANTIMICROBIAL RESISTANCE AND ESBLS IN PUNJAB, INDIA
Bacterial resistance to antibiotics is increasing, in part because of the
inappropriate use of antibiotics in human medicine but also due to
unregulated practices in the agricultural industry. Livestock animals are
given large quantities of antibiotics to promote animal health, growth,
and productivity. But, in addition to these benefits, agricultural use
promotes the selection of resistance genes in bacterial populations.
Resistant bacteria from agricultural environments may be transferred to
pathogens in human communities where they can universally spread and
cause disease. This study surveyed the bacterial populations of broiler
chickens in Punjab, India to assess the abundance of antibiotic resistance
and determine the diversity and dominance of resistant bacterial strains.
The study found E. coli isolates to contain resistance genes and detected
an elevated presence of ESBL-producing bacteria. These results
corroborated previous findings in India and are comparable to those in
other nations as well. Also, plasmid profiles of bacterial isolates
demonstrated that individual farms possess immense strain diversity. This
study reveals the widespread prevalence of antibiotic resistance within
the agricultural industry of a developing country and stresses the need to
control and monitor the use of antibiotics in food animal production.
TAYLOR PEARSON
ASSISTANT PROFESSOR ROBERT PRINGLE
ECOSYSTEM ENGINEERS: A STUDY OF THE COMMON HIPPOPOTAMUS
(HIPPOPOTAMUS AMPHIBIOUS) AND ITS IMPORTANCE IN SUB-SAHARAN
AQUATIC ECOSYSTEMS THROUGH AN ANALYSIS OF THE AFRICAN
SHARPTOOTH CATFISH (CLARIAS GARIEPINUS)
The common hippopotamus (Hippopotamus amphibious) has long been
implicated as a driver of connective dynamics between aquatic and
terrestrial Sub-Saharan ecosystems. Hippos are semi-aquatic in nature and
spend the majority of their day in pools of water but are known to emerge
at night and graze heavily on terrestrial grasses. This nocturnal feeding
behavior provides a unique scenario where the majority of hippo feces
are submitted as an allochthonous input directly into the water. Aquatic
inputs are hypothesized to increase trophic production in rivers by
creating nutrient hotspots, whose effects can ripple throughout a food
web. To assess the validity of this claim, a population of hippos on the
Ewaso Ngiro River in Laikipia, Kenya were studied to assess the effects
hippo nutrients could have on the growth of local fish species. Two
species of fish were surveyed: an air breathing catfish called the
Sharptooth Catfish (Clarias gariepinus) and Ripon barbel (Barbus
altianalis); both of which were measured for their health and 13C/15N
stable isotope. All catfish were found in areas of high hippo density, and
should in theory have more nutrients available to them than the barbel
caught in low hippo density areas. The population of Sharptooth Catfish (n
= 21) was found to scale isometrically (b = 3.1358) with an average
condition factor of 0.3665; where the population of Ripon Barbel (n = 24)
was also found to scale isometrically (b = 2.8409) and have an average
condition factor of 0.9533. Scaling constants indicate both species were
growing in proportion based off their length and weights with catfish
having slightly higher growth parameters but lower overall health. Stable
isotope analyses indicate catfish operate at multiple trophic levels
depending on age but adults operate as an upper level consumer that
feeds on various species. The data on fish species in this study does not
provide conclusive evidence toward the beneficial role hippo inputs play
in Sub-Saharan ecosystems; however, previous research and theory
suggest there is an important contribution being made to aquatic
ecosystems and hippos are an essential species in connecting African
habitats.
GABRIELLE RAGAZZO
PROFESSOR IAIN COUZIN
THE EFFECT OF TURBIDITY ON GROUP SIZE DISTRIBUTION OF GOLDEN SHINER
(NOTEMIGONUS CRYSOLEUCAS) FISH SCHOOLS
Understanding how and why organisms form groups in nature is an
essential aspect of collective animal behavior, but the influence of
environmental conditions on group formation is an area of comparatively
little exploration . This research seeks to determine the effect of turbidity,
or the scattering of light by suspended particles in water, on the group size
distribution of golden shiner fish (Notemigonus crysoleucas). The large tank
experiments compared the group size distribution of 75 experimental fish
in water of 0 NTU and 30 NTU over the course of two hours. It was found
that a 30 NTU turbidity level increased the fragmentation of the fish,
leading to a greater number of small, dispersed groups in 30 NTU water
compared to 0 NTU water. For water of a 30 NTU turbidity level, the
probability of an individual fish existing in a small or intermediate group
increased, the median group size decreased, and the median group size
expected for an individual decreased. The small tank experiments
investigated whether this change in group size distribution observed in the
large tank experiments was due to simply a decrease in the visual
information available to the fish, or the presence of an additional
behavioral response. Results suggest that raising water to a turbidity level
of 30 NTU induced a repulsive behavioral response between groups of fish,
and that this behavior was not present with fish in water at a 0 NTU and 15
NTU turbidity level. The probability of a fish avoiding the group increased
as turbidity increased, as did the frequency of time that an individual fish
spent avoiding a group. If turbidity does induce a repulsive effect
between groups and individuals, then existing models used to predict
group size distribution must quantify and incorporate this repulsion in
conditions where the water is turbid. The impact of turbidity on group size
distribution of fish schools will become an increasingly important area of
research as climate change continues to increase the turbidity of earth’s
surface water.
SCOTT RUSHTON
PROFESSOR ANDREW DOBSON
DATING THE FIRST PITCH: THE EVOLUTION OF THROWING IN PRIMATES
The evolution of throwing behavior influenced many other aspects of
human development. Published research associates the behavior with the
development of human language, motor coordination, and highly
improved hunting ability. Because most early hominin species are extinct
and the fossil evidence is limited, non-human primates are currently the
most useful and readily available option for research on fundamental
hominin behavior. However, even in chimpanzees, the most advanced
non-human thrower, the behavior is undeveloped and inaccurate. The
majority of modern research compares living primate throwing tendencies
to that of modern humans, but very few have analyzed throwing within
the primate phylogeny. The current study expands on the already rich
library of primate throwing research by analyzing anatomical changes
that occurred during primate evolution that may have contributed to the
evolution of throwing. Preliminary data collection was based on e-mails to
primate sanctuaries and published literature to identify which species
throw and how they do so. Non-human primates were placed into one of
three groups based on their throwing tendencies and posture: Thrower,
Tosser, or Non-Thrower. Resources provided by the Smithsonian Institute
were used to make measurements of two anatomical structures, the
scapula and relative arm length, ulna to humerus, which literature
indicates are indicative of
throwing. Results revealed a significant
difference in both anatomical features between Throwers and NonThrowers. Tossers possess scapula similar to Throwers and relative arm
lengths similar to Non-Throwers, which exposes a potential evolutionary
relationship between quadrupedalism, throwing, and scapular anatomy.
Results confirmed Calvin et al.’s original hypothesis that human throwing
originated in underhand tosses, and adds additional detail regarding the
anatomy and identity of the first throwers. The first pitch was thrown
underhand by a quadrupedal primate. As evolution brought about new
anatomical features to cope with a challenging environment, a “true”
throwing ability evolved to allow for a more precise delivery. Future
analysis should focus on the anatomical differences between the different
quadrupedal primates to identify which features allowed underhand
tosses to develop into overhand throws.
KATHERINE SMITH
PROFESSOR LARS HEDIN
NUTRIENT CYCLING IN THE LOWER MISSISSIPPI RIVER FLOODPLAIN: ROLE OF
BACKWATER ENVIRONMENTS IN NITROGEN AND PHOSPHORUS UPTAKE
The Mississippi River watershed encompasses more than a third of the
nation’s land area, and is home to much of the nation’s agricultural
production. As a result of generous fertilizer application, the watershed
has incredibly high nitrate and phosphate concentrations. This study
investigates the role of backwater environments (backwater lakes,
flooded forests, and secondary channels) in nitrogen and phosphorus
uptake in the Lower Mississippi River over a two month period in the
summer of 2014, using biweekly sampling and analysis for chlorophyll,
anion and cation concentrations, membrane inlet mass spectrometry,
and stable isotope analysis of nitrate. It asks which environments serve as
the largest sink for nitrogen and phosphorus and by which mechanisms
the uptake occurs. Our findings indicate that backwater lakes and
flooded forests have the highest uptake of nitrate via denitrification, but
that over the study time, they did not take up phosphorus. We also
present evidence to support that the main channel and secondary
channels are sites of denitrification, but not over the short distances
measured in this study.
KATHRYN STACK
ASSOCIATE PROFESSOR ANDREA GRAHAM
THE IMPACT OF TRICHURIS MURIS INFECTION AND ENVIRONMENT ON THE
DIVERSITY AND COMPOSITION OF THE GUT MICROBIOTA OF C57BL/6 MICE
A single soil-transmitted helminth species, Trichuris trichiura, infects
between 795 million and 1.05 billion individuals [1]. Public policymakers
have recently begun to contemplate mass dewormings in regions where
T. trichiura is endemic [1]. However, the interaction between helminths
and the gut microbiota is not well understood. Given this potential policy
shift, a critical need exists for a deeper understanding of the interaction
between helminths and the gut microbiota and whether this interaction is
environment-dependent. This study seeks to characterize the gut
microbiota of mice and to analyze how the composition and α-diversity of
mice’s gut microbiota change with Trichuris muris infection and relocation
to a semi-natural environment. Specifically, this study analyzes V4 region
16S rRNA sequencing data isolated from 256 stool samples collected from
48 specific-pathogen free C57BL/6 mice at six time intervals. In this study,
T. muris infection induced significant changes to the composition of the
gut microbiota of C57BL/6 mice during two of the five observation time
points. Additionally, relocation from the lab to a semi-natural habitat
induced significant changes to the composition of the gut microbiota of
C57BL/6 mice. The bacterial families with relative abundances that were
significantly altered by T. muris infection were environment-dependent.
The results of this study reinforce the need to conduct long-term gut
microbiota mouse studies in semi-natural habitats. This will enable the
scientific community to understand better how environment shapes the
composition of the gut microbiota and whether the impact of helminth
infection on the gut microbiota is environment-dependent.
KALIN STOVALL
PROFESSOR LARS HEDIN
CARBON STORAGE, FOREST STRUCTURE, AND FISH BIODIVERSITY ACROSS
HUMAN-IMPACTED MANGROVE ECOSYSTEMS IN TELA BAY, HONDURAS
Tela Bay's mangrove ecosystems provide vital resources for the local
Garifuna communities. Specifically, mangroves support wood production
and fisheries, and may provide more economic benefits with the
development of Reduced Emissions from Deforestation and Degradation
(REDD+) certification schemes. Tela's mangroves continue to be
threatened by human activities, and the effects that these anthropogenic
disturbances are having on Tela are unclear and require investigation. This
study aims to discern the effects that anthropogenic disturbances have
on four different mangrove ecosystems by comparing carbon storage,
forest structure, and fish biodiversity. The relationship between carbon
storage and forest conditions including pollution, salinity, fern density, soil
water content and soil organic matter are examined to help explain how
anthropogenic disturbances are affecting mangrove productivity.
Additionally, fish biodiversity of the mangrove ecosystems was accessed
using information from a study that interviewed local fishermen.
Results from this study indicate that anthropogenic disturbances have a
clear effect on Tela's mangroves. More anthropogenically disturbed
mangrove forests had lower carbon storage from biomass. These
differences might be explained by anthropogenic disturbances leading to
increased organic and oil pollution, increased salinity fluctuations, and
increased fern sizes. Moreover, more anthropogenically disturbed
mangrove forests had lower fish biodiversities than less disturbed forests.
This is most likely explained by disturbed mangroves serving as poorer
habits to fish communities because of their reduced structural complexity
and heterogeneity. Lastly, carbon storage in soils was comparable
between all mangrove forests, possibly because of the differences in
autochthonous and allochthonous organic matter inputs. These findings
represent valuable information that local officials should consider when
deciding how to sustainably use Tela Bay's mangrove ecosystems.
ANNEMARIE WAMSTED
PROFESSOR ANDREW DOBSON
THROWING IMAGEJ TO THE (GRAY) WOLVES: AN EXPLORATORY STUDY OF
IMAGEJ’S APPLICABILITY IN A NON-LABORATORY SETTING
ImageJ is an image processing program originally created for use in
medical microscopy but, due to its users’ ability to add any plugins they
create, it has a theoretically unlimited set of functions. However, few
studies have taken ImageJ out of its traditional lab setting, and even
fewer (potentially none) have looked at when it is and isn’t an effective
program to use in non-lab settings. The hypothesis of this project was that,
in addition to its traditional use in medical microscopy and other
laboratory projects, ImageJ could also be used as an effective tool for
field studies. Specifically, it was hypothesized that ImageJ could be used
to more easily track and quantify the outbreak of sarcoptic mange in
Yellowstone gray wolves. This application of the program would be useful
because it would allow researchers to more fully explore resources they've
already gathered. If ImageJ could be shown to be useful in this context
researchers could expand the data available to them by using pictures to
track and quantify mange outbreaks instead of using more labor-intensive
methods. In addition, if the program's use was shown in this context,
further applications could include tracking the spread of mange in other
species, or potentially tracking other diseases that have a visual
manifestation. This study did not find clear-cut evidence that ImageJ can
be used to track and quantify the outbreak of sarcoptic mange in
Yellowstone gray wolves. The project did, however, examine a promising
alternative to its main method in the form of a thermal picture. Using
thermal pictures with ImageJ to track and quantify mange in Yellowstone
gray wolves appears to be the most promising avenue for any future
projects interested in this potential application of ImageJ.
SARAH WASZKEWITZ
PROFESSOR STEPHEN PACALA
THE VARYING FUNCTIONAL ROLE OF CTENOCHAETUS STRIATUS:
AN ANALYSIS OF BEHAVIOR & MORPHOLOGY IN TOP-DOWN VERSUS
BOTTOM-UP REEF ENVIRONMENTS IN PALAU
The Ctenochaetus striatus (common name: Striated Surgeonfish) is an
herbivorous reef fish found on most Pacific reefs. They are considered to
be detritivores in the guild of herbivorous fish as they are best adapted to
sweeping their food off the reefs’ epithelial algae matrix (EAM) with their
bristle-like teeth. Much is known about their role in sediment removal on
the reef. During feeding they ingest sediments coating the reef algae and
carry and excrete the sediment off the reef making the algae more
palatable to other herbivores that feed on and remove the large algal
turfs. This cleaning function is extremely important to maximizing reef
resilience and coral larva settlement. Beyond understanding this general
relationship not much else is known about the life of the striated
surgeonfish even though they are a dominant population on many reefs.
As such they are believed to be a vital component of the energy and
nutrient flows between primary reef producers and primary reef
consumers. C. striatus may play an important role in most, if not all “reef
ecosystems,” but each system is different and it may not be valid to
generalize the life cycle and function of even the same species in
different environments. Various complex dynamics and interactions
impact the arrangements of a reef ecosystem. Coral reefs are one of the
world’s most productive ecosystems harboring vast numbers of species
resulting in extreme biodiversity. Not surprisingly the significance of even
small variation between these ecosystems is not well understood. This lack
of understanding can only be remedied by the further study of species
ideally in a presently stable and controlled reef environment currently best
approximated by marine protected areas. In order have and create
effective marine protected areas the target goal of the area and the life
cycle and functional niches of species vital to this goal must be well
understood. This study identifies multiple behavioral and morphologic
adaptations of C. striatus in nearby, but different reef environments and
survival stresses. Specific characteristics and functional roles of C. striatus
populations existing on a top-down predator dominated environment are
compared with fish living in a bottom-up resource limited one. It is hoped
the study’s findings of these varied roles will have implications for the
future planning of marine protected areas by providing a more detailed
analysis of varying reef environments and the varying roles a single
species may play in them.
LEAH WORTHINGTON
PROFESSOR IAIN COUZIN
WISDOM OF THE CROWD AND CHEMOTAXIS IN FREE-LIVING
PLACAZOA (TRICHOPLAX ADHAERENS)
The wisdom of the crowds hypothesis describes the way in which larger
groups of animals contribute to increased accuracy of decision-making
and collective behavior. Recently, interesting parallels have been drawn
between the highly coordinated patterns of behavior observed in animal
collectives and cellular collectives, raising questions about the role of
crowd wisdom in multicellular groups. In this project I studied Placozoa
(Trichoplax adhaerens), the simplest known multicellular organisms, which
are characterized by their high degree of intercellular organization
despite the lack of a central nervous system. I investigated their patterns
of movement in order to determine whether isotropic cellular groups can
migrate collectively towards a target and how size may affect the
accuracy and coordination of this behavior. Here, using an
unprecedented in vivo experimental set-up, I show that starved Placozoa
are able to chemotax, or respond to chemical cues, towards an algal
food source in their local environment through the collective motion of all
of their cells. Though the size of the animals did not seem to play a
significant role in measures such as the directedness or speed of
chemotaxis, it was positively correlated with accuracy (chemotactic
index). Their initial proximity to the food source was also a strong factor in
foraging success. These results suggest that detection of an appropriate
chemoattractant can initiate coordinated and accurate multicellular
movement towards the source. In addition to describing a previously
unexplored area of Placozoan behavioral ecology, this study also
addresses questions about the robustness of the wisdom of the crowd
hypothesis in more complex environments. These findings have important
applications that will advance current knowledge about the dynamics of
coordination and migration in multicellular aggregations.
EMILY YU
PROFESSOR ANDREW DOBSON
BARTONELLA SPP. INFECTION IN MALAGASY RODENTS:
A STUDY ON BARTONELLA SPP. PREVALENCE, STRAIN DIVERSITY, AND
DYNAMICS IN R. RATTUS IN MADAGASCAR
Rodents have been recognized to carry a wide diversity of Bartonella
genetic variants which have the potential for human zoonosis. However,
little is known on how rodent individuals of different location, sex, and age
might be affected by Bartonella and different Bartonella strains. This study
collected kidney samples from two species of invasive rodent (Rattus
rattus and Mus musculus) from the Ankazobe and Ranomafana regions in
Madagascar for Bartonella testing. R. rattus was found to carry two
variants of B. elizabethae (1 & 2), B. phoceensis, and B. rattimassiliensis.
Bartonella was not detected in M. musculus. Increasing age in male and
female R rattus showed increasing prevalence of Bartonella spp. in both
regions, likely explained by increasing social behavior and risk of infection
with increasing age. Increasing age in R. rattus showed increasing
prevalence of B. phoceenis in both regions, and decreasing prevalence
of B. elizabethae, indicating possible strain replacement dynamics in
Bartonella spp.. Finally, this study aimed to find a transmission model to
predict likelihood of infection of rodents in certain ages. With numerous
recently described species and current research, Bartonella research can
be further developed and used to understand zoonotic disease dynamics
in vectors, reservoirs and humans in future studies.
NICOLE ZENES
PROFESSOR STEPHEN PACALA
EFFECTS OF PIPELINE CONSTRUCTION CLEAR-CUTTING ON WATER QUALITY
AND NITROGEN LOADING IN NORTHEASTERN HEADWATER STREAMS
Clear cutting in hardwood forests has been shown to increase the
concentration of nitrates in stream water. Studies of gap size have been
done to determine the size of disturbance necessary for nitrate losses. My
study was designed to test whether the deforestation from natural gas
pipeline construction was sufficient to cause an increase in nitrate levels. I
took water samples above and below fifteen streams across Northeast
Pennsylvania and North New Jersey. I found that the below pipeline
concentration of nitrate was significantly higher than the above stream
concentration. On average, there was a 63% increase. There was not a
significant effect of dominant tree species on the amount of nitrate
increase. Temperature above and below the pipeline was also taken.
Contrary to other studies on clear cutting, there was not a significant
impact on water temperature. Current methods of pipeline construction
should be reevaluated to limit impact on water quality.
DEANNA ZHU
PROFESSOR BRYAN GRENFELL
BACTERIAL INTERACTIONS IN THE HUMAN NASOPHARYNX:
THE IMPACT OF HIV COINFECTION IN CHILDREN
Bacterial disease is a leading cause of morbidity and mortality in children
globally. Invasive bacterial disease occurs only after asymptomatic
colonization by an invasive strain in the nasopharynx, which is influenced
by bacterial interactions and host immune responses. Nasopharyngeal
colonization is also a platform for bacteria to evolve and spread within
populations. To explore the effects of immunity and interventions on
bacterial interactions in the nasopharynx, I analyze nasopharyngeal
colonization of three disease-causing bacteria, Streptococcus
pneumoniae, Haemophilus influenzae, and Staphylococcus aureus, in a
cohort of HIV infected and uninfected children. S. pneumoniae was
associated with 30% less S. aureus colonization and 150% greater H.
influenzae colonization. By controlling for immune response and
considering only HIV infected individuals, both associations were
strengthened. However, the consumption of prophylactic antibiotics was
associated with colonization by antibiotic-resistant bacteria, suggesting
that these effects were confounded by antibiotic use. When the
interaction in HIV infected individuals was assessed using methicillinresistant S. aureus, removing the confounding effect of antibiotic use in
addition to prophylactic antibiotic consumption, S. pneumoniae was
associated with 70% less S. aureus colonization. This effect was strongest in
vaccine serotypes of S. pneumoniae and in colonization by new serotypes
in hosts colonized previously by a different S. pneumoniae strain. These
results suggest that bacterial interactions may be mediated by innate
immune responses and nuance the role of interventions in the care of HIV
infected children.
John T. Bonner Senior Thesis Fund
Porter ’52 EEB Research Fund
Mountlake Field Research Fund
Leslie K. Johnson Senior Thesis Fund
H. Hamilton Hackney ’53 Senior Thesis Research Fund
Anthony B. Evnin ’62 Senior Thesis Fund in Ecology & Evolutionary Biology
Colvin Family and the Becky Colvin ’95 Research Fund
Dean of the College
Community Based Learning Initiative
Princeton Environmental Institute
Program in Latin American Studies
Program in Global Health
Adel Mahmoud Global Health Scholars Program
Grand Challenges