Copepod survival in water bowls exposed to typical Chadian ambient temperatures

Zavier Eure, a junior from North Carolina A&T, worked with the lab of Dr. Michael Yabsley to study copepod survival in different types of water bowls.

Abstract:  Guinea Worm Disease (GWD), caused by the nematode Dracunculus medinensis, has been detected with increasing incidence among dogs in Chad, Africa. Cyclopoid copepods (freshwater crustaceans) are intermediate hosts for D. medinensis. Currently the route(s) of D. medinensis transmission to dogs is still unknown but drinking from unprotected water sources would pose a risk. Dogs have access to water dishes provided for domestic animals and depending on the source of water, these dishes could harbor infected copepods, thereby acting as a source of transmission. To determine how long copepods survive in water dishes when exposed to Chadian ambient temperatures (41.1ᵒC), copepods were placed in three different container types (plastic, glass, and metal) and heated to 40ᵒC. Our results indicate that under simulated Chadian temperatures, metal dishes result in the highest rate of copepods death in the shortest period of time (2hrs) and were the only container to reach 100% copepod mortality. Conversely, plastic dishes exhibited the lowest mortality of copepods. These results indicate that the type of dish used when supplying water for animals in Chad is an important consideration in terms of preventing or interrupting transmission of D. medinensis among dogs.

 

 

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Using long-term science data to examine relationships of wastewater infrastructure and water quality

Sarah Williamson, a junior from Baylor University, worked with Denzell Cross in the lab of Dr. Krista Capps.  They used community-collected data to examine spatial and temporal changes in water quality in a local watershed.

Abstract:  The integrity of freshwater systems throughout the world is threatened by increasing concentrations of gut bacteria, such as E. coli. In urban watersheds, increases in bacterial concentrations are associated with intentional municipal wastewater discharge and aging and obsolete wastewater infrastructure (e.g., sewage leaks and failing septic systems). Tracing sources of bacterial contamination in surface waters is often difficult due to the need for long-term monitoring. Moreover, long-term monitoring can be time intensive and costly.
Community science organizations can be a cost-effective way to collect large amounts of environmental data across broad spatial and temporal scales. However, data collected by community scientists are often criticized due to concerns about scientific rigor, data fragmentation, and inaccuracy. Other work has demonstrated that groups employing robust protocols can produce data that align with data collected by professionals, and can be used reliably in decision-making processes pertaining to environmental health and watershed management. The purpose of this study was to examine spatial and temporal changes in water quality using data collected by community scientists of the Upper Oconee Watershed Network, and use community data to investigate relationships between water quality metrics and wastewater infrastructure in Athens-Clarke County (ACC). Specifically, we wanted to ask if water quality metrics (i.e., conductivity and turbidity) correlated to fecal bacteria concentrations in ACC surface waters and if there are relationships between site- and watershed-specific concentrations of E. coli and the proximity and density of wastewater infrastructure. We found that turbidity may be a strong predictor in bacteria concentrations however, the relationship between bacteria and conductivity was not clear. Our data also suggests that there may be important links between wastewater infrastructure and reduced water quality.

What’s the buzz? An investigation on how urbanization impacts mosquito species distribution

Lilith South, a junior from the University of Georgia, worked with Mike Newberry in the lab of Dr. Courtney Murdock to study the relationship between urbanization and distribution of mosquito species.

Abstract:   Impervious surfaces, mainly paved roads and buildings, significantly impact microclimate by making an area hotter and less humid. For this reason, urban areas are warmer than less developed rural areas. Heat associated with high impervious surface coverage impacts mosquito development and decreases larval survival in Aedes albopictus. Although many species of mosquitoes are present in Athens, Georgia, the most prominent species and most important species for human health, Ae. albopictus, is one of few species that dominate the area. Ae. albopictus has shown potential vectoral capacity for diseases such as Zika, Dengue, and Chikungunya. Fortunately, it does not yet transmit these diseases in the south eastern United States, but with changing climate and urbanization these diseases have potential to spread. The impact that impervious surface coverage has on mosquito community composition was not previously known. To investigate this effect, sites were classified and selected by their impervious surface coverage. Rural sites had impervious surface coverage ranging from 0-5%, suburban had 5-55%, and urban had 55-100% coverage.  Larval samples from each site were identified to species and the proportion of occupied habitats for each species in each site was noted. Overall, species richness decreased in suburban and urban areas with higher impervious surface coverage. Diversity was highest and there was a more even spread of species in rural areas. Contrary to what was expected, the percentage of Ae. albopictus occupied habitats did not significantly change with impervious surface coverage. Although previous studies suggest that Ae. albopictus is sensitive to hotter urban areas, this species may be more resilient than other mosquito species to the effects of urbanization. Knowing how urbanization impacts mosquito community composition can help researchers better understand disease transmittance and develop solutions for potential viral outbreaks.

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How does the proportion of sugar fed Aedes albopictus mosquitoes vary across land use?

Alyssa Slicko, a junior from the University of Arkansas Little Rock, worked with Nikki Solano in the lab of Dr. Courtney Murdock to look at sugar-feeding and its relationship to land use in an invasive mosquito.

Abstract:  The Asian tiger mosquito, Aedes albopictus, is a non-native species to North America and is known to be highly invasive with an ability to vector up to 27 different arboviruses. Since female mosquitoes feed on both sugar and blood to survive, understanding the tendencies for sugar feeding could explain the differences in the abundance of invasive mosquito populations. Past studies have shown that temperature plays an important role in the distribution of vector borne diseases, but it has not been discovered whether other environmental factors such as sugar availability is a limiting resource for mosquito populations. Some species have evolutionarily adapted to low sugar resources, meaning they primarily feed on blood. However, little is known about the sugar feeding habits of Aedes albopictus. We collected A. albopictus from nine field sites classified as suburban, urban and rural based on percentage of impervious surface. A backpack aspirator was used to collect mosquitoes that were then frozen and identified by sex and species. A total of 90 female A. albopictus mosquitoes were collected, 30 from each land use type. Using homogenized solution of each individual mosquito, colorimetric sugar assays were performed with serial dilutions to determine relative sugar content per mosquito. The absorbance values of these solution were read through a spectrophotometer. At the 1:4 dilution values, urban sites have the greatest overall amount of sugar followed by rural and suburban land uses. There is evidence that mosquitoes in Aedes albopictus females do sugar-feed and that there are differences between sugar contents across land use types. However, a negative relationship was found between absorbance and concentration values across sites. This could be due to a potential chemical inhibitor formed with highly concentrated mosquito dilutions not allowing complete reading of absorbance values and determination of sugar content.

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The world’s smallest escape artists: manipulation of the host innate immune response by Bordatella bronchiseptica

Margaret Dedloff, a junior at Clarkson University, worked with Dr. Monical Gestal in the lab of Dr. Eric Harvill to study the role of a sigma factor by bacteria in manipulating host immune response.

Abstract:  During the course of infection, some pathogens are able to sense and respond to the host immune system. This can cause prolonged pathogenesis, high transmission rates, and vaccine failure. One group of bacteria known to manipulate the immune response in varied ways is the Bordetella spp. B. pertussis, B. bronchiseptica and B. parapertussis are able to inhibit complement and suppress B and T-cell functions [1].  The BvgAS two-component system is understood to be a regulator of many virulence factors and is known as the master virulence regulon, however this is most likely an oversimplification. We hypothesized that pathogens like bordetellae should be under strong selective pressure to sense and respond to signals in blood and serum, in order to modulate immune defenses. When studying blood and serum responsive genes, we identified a putative sigma factor up-regulated in both conditions, and we hypothesized that this might be a regulator that dictates adaptation to pressure from the immune system. Here we identified the role of this sigma factor, the Bordetella Sigma Factor, or bsr, in manipulating the immune response. Through the use of a B. bronchiseptica bsr knockout and in vitro assays, we have found that bsr interferes with the innate response. bsr inhibits survival in macrophages by changing the dynamics of phagocytosis, causing macrophage death, and causing bacterial death and replication within the macrophage by interfering with cytokine and chemokine expression as well as differentially interacting with TLR receptors. This suggests that subsequent cell recruitment will be different within the host. Our results demonstrate that the bsr gene plays a critical role in Bordetella interaction with the innate immune system. A better understanding of this gene and its function will be valuable in efforts to create successful vaccines and treatments not only for Bordetella spp. but also for other bacterial species.

[1] Gestal M.C., Whitesides L.T., and Harvill E.T. “Integrated Signaling Pathways Mediate Bordetella Immunomodulation, Persistence & Transmission”. In revision, Current Trends in Microbiology.

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Vive la resistance: the impact of antibiotic use in US livestock on emerging antibiotic resistance

Sydney Rentsch, a junior from Connecticut College, worked with Dr. JP Schmidt to examine the relationship between antibiotic use and resistance in US livestock.

Abstract:  The potential for livestock to spread antibiotic resistant pathogens to human populations is a cause for concern. This research focused on finding trends in data on US livestock antibiotic resistance, US livestock inventory and US livestock antibiotic consumption. Data was compiled from CDC, USDA and FDA reports and publicly available datasets. Data was analyzed in R and generalized additive models (GAMs) were used to test for increasing resistance as a function of time. We found that the tetracycline class of antibiotics had consistently high resistance over time. The antibiotic class lincosamides, had a sharp increase in resistance which was positively associated with the data from turkeys and chickens. Analyzes also found that poultry had the highest burden of antibiotic resistant pathogens. These results may lead future studies focused on antibiotic resistance in poultry and provide framework for future data analysis.

 

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Identifying bacterial pathogens in natural Drosophila populations

Kailene Richbow Dozier, a sophomore at Virginia Union University, worked with Dr. Kelly Dyer to examine the pathogens present in wild populations of Drosophila.

Abstract: An estimated 70% of the world’s insects are infected with the gram-negative bacteria, Wolbachia pipientis. Wolbachia is known to protect organisms against viral pathogens, however little is known about how it interacts with bacterial pathogens. The aim of this study was to isolate and identify bacterial pathogens within wild, mushroom feeding Drosophila. With this knowledge, we hope that we can aid future research studies trying to understand how Wolbachia increases host resistance to bacterial pathogens as compared to viral pathogens. Two species of flies, Drosophila Putrida and Drosophila Tripunctata were captured from Oconee State Park located in Athens, GA. The captured flies were separated by gender. Female flies were put aside to generate Iso-Female lines, while male flies were homogenized and streaked onto LB agar plates for bacteria growth. Once colonies began to grow after incubation, they were isolated and morphologically identified. 35 bacterial isolates were obtained from the 18 D. Tripunctata flies streaked. 20 bacterial isolates were obtained from the 20 D. Putrida flies streaked. A total of nine bacterial species were identified morphologically, seven of which were shared between the two species of wild flies. Similarities between the abundance of Micrococcus luteus and Enterococcus within both species of flies were observed. D. Tripunctata was seen to slightly differ from D. Putrida by carrying the bacterium Bacillus subtilis and Bacillus megaterium. For future exploration, 16S gene sequencing is needed to accurately confirm the identification of the bacterial pathogens discovered. Afterwards, testing for pathogenicity of the bacterial pathogens needs to be conducted as well as testing for Wolbachia’s interaction with the pathogens.

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Influence of mosquito gut microbiota on susceptibility to dengue infection

Robert Manuel, a junior from California State Polytechnic University, Pomona, worked with Ruby Harrison in the lab of Dr. Mike Strand to examine the relationship between mosquito gut biota and dengue infection.

Abstract: The mosquito Aedes aegypti is the primary vector of dengue virus (DENV). Prior studies report increased susceptibility of A. aegypti to DENV infection, and higher pathogen burden when adult females are treated with antibiotics. This suggests a role for the microorganisms that colonize the digestive tract of mosquitoes (gut microbiota) in susceptibility to DENV infection. We tested the hypothesis that microbe-depleted A. aegypti are more susceptible to DENV infection by comparing three treatments: axenic mosquitoes with no gut microbiota, gnotobiotic mosquitoes harboring only Escherichia coli, and conventional mosquitoes with a natural community of gut microbes. We validated the status of these mosquitoes using both culturing methods and PCR. We then assessed DENV presence/absence in each treatment fourteen days after feeding adult females an infected blood meal. Consistent with our working hypothesis, a larger proportion of axenic mosquitoes were infected with DENV than conventional mosquitoes. Proportions of axenic and gnotobiotic mosquitoes infected with DENV were nearly identical. However, our treatments had no effect on DENV dissemination among females that were infected. In summary, these results suggest A. aegypti with a more diverse gut microbiota are more resistant to DENV infection than axenic females but E. coli alone provides no increase in resilience.

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Behavioral and environmental determinants of parasite transmission in a butterfly host

Chastity Ward, a sophomore from Fayetteville State University, worked on a project with Dr. Sonia Altizer, Dr. Richard Hall and Dr. Paola Barriga to examine how parasites of the Monarch butterfly are transmitted.

Abstract:  Many pathogens can be transmitted when infectious stages shed into the environment are later encountered by susceptible hosts. Environmental transmission is common among insect parasites, and also occurs for human diseases such as cholera and polio. Understanding how host behavior and environmental variables affect the shedding of infectious stages is crucial for predicting patterns of infection risk. Monarch butterflies Danaus plexippus are commonly infected by the protozoan Ophryocystis elektroscirrha (OE); this parasite is transmitted environmentally when infected adults deposit spores onto host plants (milkweed) that are consumed by monarch larvae. To quantify host contact with milkweeds as an estimate of parasite transmission, we set up outdoor flight cages with adult monarchs and milkweed plants. Cages varied in the number of adult monarchs and milkweed plants, and were assigned to one of two milkweed species. We used captive-raised monarchs from several genetic lineages, and marked the monarchs with unique number and color codes to track activity. We observed cages for replicate intervals over a week-long period, during which we noted observed monarch contacts with plants, and recorded monarch and plant identity, activity type, temperature, weather, and time of day. Our results showed strong heterogeneity in plant visitation rates among monarchs that was best explained by monarch sex (females had 4.7 times higher visitation rates than males, owing to frequent oviposition on milkweeds).  We also found wide variation among individual plants in the number of visits by monarchs. Milkweed species, plant flowering status and plant leaf number did not affect visitation rates, but plants in cages with a higher number of monarchs were visited more frequently. In sum, our findings provided evidence for individual monarch’s serving as superspreaders of infection, and for some milkweed plants serving as hotspots of infection. This study provides a starting point for estimating environmental parasite transmission in wild milkweed patches, and suggests that individual-level heterogeneity might be more important than environmental variation in driving parasite transmission in this system.

 

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Age-structured model for Tuberculosis intervention planning

Kennedy Houck, a junior from Ursinus College, worked with Paige Miller in the lab of Dr. John Drake to study age-based interventions for Tuberculosis.

Abstract:  Tuberculosis (TB) represents a widespread public health concern.  The World Health Organization’s “End TB Strategy” has set the goal for global TB eradication by 2050.  Previous studies have suggested that current public health intervention strategies may not achieve this goal in many parts of the world that experience high TB incidence rates.  The goal of this project was to determine whether age-based interventions could enhance current interventions, which are currently implemented.  A standard TB model, which includes five state variables (Susceptible, Latent, Infectious, Noninfectious, and Removed), was modified to include 16 different age classes, and parameterized with previously published information for India and South Africa.  The model was run for 500 years until equilibrium was reached.  Once equilibrium was reached, 18 different interventions, all simulating faster rates of testing and treating, or shorter infectious periods, among active TB cases, were tested by calculating the rate of decrease of TB cases in each population over time.  A “baseline” scenario where the rate of treatment was held constant was compared to interventions where the infectious period was reduced by 10, 50, 70, and 90% independently for either a specific age class or overall (i.e. a “blanket strategy”).  To test the validity of model predictions, we calculated the correlation between the stable age distribution of cases at equilibrium and WHO TB prevalence data.  In general, age-targeted interventions were found to be more effective at reducing TB cases than the “blanket” strategy.  In India, targeting 15-19 year olds was predicting to result in the greatest overall decline in incidence of both latent and active TB at all intervention levels.  In South Africa, targeting 10-14 year olds was predicted to result in the greatest overall decline of latent TB at all intervention levels; however, targeting 10-14 year olds at lower intervention levels and a blanket strategy at higher intervention levels, were more effective at reducing infectious TB burden.  These results suggest that age-based interventions may complement current public health interventions by further reducing TB burden to achieve WHO eradication goals.  Future studies should utilize a more detailed model for TB dynamics to generate a more realistic prediction.

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