A protozoan parasite weakens the stress reaction of monarch butterflies

Jovani Raya, a student from Abaraham Baldwin Agricultural College, worked with Dr. Sonia Altizer and Dr. Andy Davis to study the effect of infection on the stress reaction of monarch butterflies.

Abstract:  The protozoan parasite Ophryocystis elektroscirrha (OE) affects the adult mortality, longevity, body size, and flight ability of monarch butterflies (Danaus plexippus). However, very little research on how the parasite influences the stress response in monarchs has been conducted. We examined the effects of parasite infection and larval rearing densities on the monarch stress response. Monarch larvae were inoculated with parasite spores and reared in low (2 larva) or high (10 larva) densities. When the monarch larvae reached pupation, we assessed their stress reactions. To produce the stress response in the pupae, physical disturbance was applied for 20 seconds. After the disturbance, the pupa was placed on a device that detects movement within animal tissue and can record the movements of the heartbeat. This recording allowed us to count the number of beats per minute. The result showed that infection was a significant predictor of the magnitude and duration of pupa HR; infected monarchs had lower reactions. Lower reactions would negatively affect how well infected monarchs could cope with daily stressors, especially during the arduous fall migration.

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The Battle of the Sperm: Observations of Sperm Competition in a Wolbachia Infected Species

LaTrice Montgomery, a student from Hampton University, worked with Paul Ginsberg in the lab of Dr. Kelly Dyer to study sperm competition in an infected fly species.

Abstract:  Wolbachia, a maternally inherited bacterium, is broadly distributed among arthropod hosts. It is also capable of reducing viral load in its host, preventing the transmission of human pathogens and thus raising the possibility of its use as a biocontrol agent. In this study, we ask whether Wolbachia has any effects on the mating system of its host, specifically whether it affects patterns of male fertility and/or sperm competition. We conducted mating trials using the fly, Drosophila recens, which is naturally infected with Wolbachia. We utilized an infected, dark eye recessive mutant D. recens and uninfected, red eye wild type D. recens to assess paternity of infected and uninfected males. We found that there are no advantages or disadvantages of Wolbachia infection for male fertility or sperm competition.

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How does overall population density and temperature affect the fecundity of female Aedes aegypti mosquitoes?

Lindsey Jones, a student from Albany State University, worked with Michelle Evans in the lab of Dr. Courtney Murdock to look at fecundity of a mosquito vector species.

Abstract:  Dynamics of mosquito-borne diseases such as Zika, yellow fever, chikungunya, and dengue depend on the ecology of both the disease and vector. Past studies have shown that both abiotic and biotic factors, such as temperature and population density, influence mosquito population dynamics, but the relationship of their interaction is unknown. Here, we explore how abiotic and biotic factors interact to influence life history traits of the Aedes aegypti mosquito. Specifically, we explored how intra- and inter-specific population densities and environmental temperature affect the fecundity of female Ae. aegypti mosquitoes. We used a factorial design of twelve density and four temperature treatments, for a total of 48 treatments in this experiment. We reared 1st instar Ae. aegypti and An. stephensi larvae to adulthood in 250 mL RO water with 0.1 g Tetramin fish food in mason jars in Percival incubators. Following emergence, adult female Ae. aegypti mosquitoes were collected, blood fed, and individually placed into centrifuge tubes at 28oC. We collected and recorded the number of eggs laid for each individual emerging per day to estimate the mosquito per capita growth rate. We found that Ae. aegypti fecundity increases with decreasing temperatures. We also found that fecundity decreases as the overall population density increases, along with the density of the competitor. As an interaction, temperature, overall density, and density of the competitor, affected fecundity, suggesting the effects of biotic factors could quantitatively and qualitatively vary across different thermal environments. We found that the population growth rate of Ae. aegypti decreased with increasing density and decreasing temperatures. These results highlight the complexity of how environmental factors can shape disease transmission.

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The effects of land use and larval density on Aedes albopictus population dynamics

Carl Hintz, a student from North Carolina State University, worked with Emily Cook in the lab of Dr. Courtney Murdock to examine mosquito larvae dynamics.

Abstract:  The Asian Tiger Mosquito, Aedes albopictus, is nonnative to North America and is a vector of Dengue virus (DENV) and Chikungunya virus (CHIKV) in humans.  Like most other mosquito species, A. albopictus larvae develop in small pools of stagnant water and adult A. albopictus typically disperse less than 100 meters. Due to this life history, fine-scale variation in microclimate and larval habitat may have a substantial impact on population characteristics.  We use a semi-field study to examine the impact of land use and larval density on traits that are relevant for the population dynamics of A. albopictus. We examine larval development and adult characteristics at nine field sites in Athens-Clarke County, GA.  Sites are classified as urban, suburban and rural based on amount of impervious surface. Mosquito development rate (MDR) and probability egg to adult survival (PEA) are determined from daily adult emergence. The number of eggs per females per day (EFD) is inferred from wing length data. A. albopictus at urban sites have lower survival, faster development, and smaller body size than those at rural or suburban sites. This difference may result from substantially higher mean temperatures at urban sites. High density replicates have lower survival, slower development, and smaller body size, possibly due to limited food resources. Compared with differences in land use, larval density has a larger impact on A. albopictus population dynamics, but both factors have important consequences for mosquito population dynamics and could be incorporated to improve the accuracy of vector population models.

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Role of the bsr gene in the Intracellular Survival of Bordetella bronchiseptica

Hira Hasan, a student from Louisiana State University, worked with Monica Cartelle-Gestal in the lab of Dr. Eric Harvell to study the intracellular survival of Bordetella bacteria.

Abstract:  Bordetella pertussis and B. parapertussis are Gram-negative bacteria that cause a respiratory infection, known as whooping cough, in humans. Another member of the Bordetella species, B. bronchiseptica (BB), primarily infects mice, dogs, and horses.  The wild type strain of BB, RB50, contains a gene (bsr) encoding a putative sigma factor that is up-regulated when BB is exposed to blood. To test the role of this gene in pathogen-host interactions, a knock-out mutant called RB50Δbsr was made in our lab. Preliminary results showed that RB50Δbsr survives longer within macrophages than RB50. The mutant also confers sterilizing immunity against further BB, B. pertussis, and B. parapertussis infection in mice, which are excellent models for human infection. The aim of this study was to determine if there is a difference between how RB50 and RB50Δbsr are internalized by macrophages, specifically whether the latter survives longer intracellularly by inhibiting lysosome formation. Confocal microscopy and a lysotracker assay were used to determine the location of bacteria within macrophages, while electron microscopy and several internalization assays were conducted to quantify live bacteria within macrophages overtime. We found that there are higher levels of intracellular RB50Δbsr than RB50 over a 24-hour period, RB50Δbsr does not enter lysosomes readily, and RB50Δbsr infection results in less macrophage death. Based on the results of this study, bsr plays a vital role in macrophage response to BB infection. Since macrophages are involved in activating several other immune system components, manipulating bsr leads to an overall change in the persistence of Bordetella infections.

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The role of bacteria in mosquito development: a comparative study of distantly related species

Molly Hancuh, a student from University of Minnesota-Morris, worked with Bret Boyd and Ruby Harrison in the lab of Dr. Mike Strand to examine the role of bacteria in mosquito larval development.

Abstract: The digestive tract of a mosquito is home to bacterial community that is essential for normal development (1). In the larval stages, bacteria stimulate molting and growth (1). Some members of the larval gut community persist into the adult mosquito where they influence reproduction and ability to vector pathogens (2,3). Previous studies on the role of gut- bacteria in development have focused on the genus Aedes, including Aedes aegypti, which transmits the pathogens that cause Dengue fever and Zika virus syndrome. It is unknown if findings from Aedes species apply to all mosquitoes. Here, we address two important findings from Aedes in distantly related genus Anopheles by studying the malaria vectors An. gambiae and An. stephensi. First, we asked if Anopheles need bacteria to develop and if so, can we rescue development with individual bacterial species? Second, we assessed whether bacterial abundance in the guts of adult Ae. aegypti and An. gambiae differ before and after females blood feed. Like Ae. aegpyti, we find that bacteria free larvae cannot develop, however unlike Ae. aegypti some bacterial species cannot fully rescue larval development in Anopheles. Additionally the results were not equivocal between An. gambiae and An. stephensi. In adult mosquitoes, the bacterial community in the digestive tracts of Ae. aegypti and An. gambiae also responded differently to blood feeding. Collectively we find that that are commonalities between Aedes and Anopheles, however there were significant differences as well.

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Parasite Sharing in Marine and Terrestrial Mammals

Keri-Niyia Cooper, a student from Savannah State University, worked with Drs. John Drake and Andrew Park over the summer to investigate parasite sharing in mammals.

Abstract: After a literature review was performed to compile a list of parasites that infect marine mammals, we created a database of parasite-host pairings found in the articles.  We then merged this database with information gathered from the GMPD and CLC Life Cycle, after subsetting certain traits.  We used the resulting database to examine three questions: (1) Is parasite generalism greater in marine environments or terrestrial environments? (2) Is parasite sharing greater when hosts are grouped by taxonomy (cetacean/ungulate v carnivore) or habitat (marine v terrestrial)? (3) Are parasites that infect hosts of both environments drawn disproportionately from some parasite taxonomic groups? It was noted that parasite generalism is greater in terrestrial environments. Hosts have a higher chance of being infected by the same parasite if they are found in the same environment. There is a higher chance of helminth species being more commonly found in a single environment.

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Resource shifts and infectious disease dynamics in urbanized bird popualtions

Katie Adkins, a student from Clemson University, participated in an ongoing study of infectious disease dynamics in urban bird populations, supervised by Dr. Sonia Hernandez and Dr. Michael Yabsley.

Many wildlife species benefit from novel resources – especially supplemental food – offered in human-altered habitats. Shifts in wildlife ecology in response to intentional or accidental feeding can dramatically alter infectious disease dynamics. If hosts aggregate near resources and interact with novel species, provisioning can increase contact rates and exposure to pathogens. Concentrated resources could also improve host immune defenses, and dietary changes might alter the host’s microbiome, with downstream effects on pathogen invasion. Depending on the strengths of these relationships, provisioning could cause some pathogens and parasites to increase and others to decline. The goal of the overarching project is to examine how host use of anthropogenic resources influences pathogen and parasite dynamics across organizational scales. Specifically, our research explores interactions between an enteric pathogen, Salmonella, and the American White Ibis in South Florida, a recently urbanized species, to understand how resource shifts in urban habitats alter host ecology and pathogen dynamics.

Inoculum Dose and Infection Outcome

Annaliese Wiens, a student from Tabor College, worked with Dr. Andreas Handel to examine the relationship between inoculum dose and infection outcome.

Abstract:  Dose-response models describe how different inoculum doses of a pathogen alter the probability of infection with a host. It is generally assumed that higher amounts of inoculum increase infection rates, but the exact relationship has yet to be determined. We performed a meta-analysis of systematically-reviewed influenza challenge studies in which the exact inoculum dose and proportion of people infected were given. This data was used to fit several models, including an exponential model and an approximate Beta-Poisson model. These models were also stratified by different covariates, such as the strain of influenza and preparation of the virus. We used the exponential model to show that viruses prepared by different methods (wild-type, cold-adapted, etc.) have differing levels of infectivity, implying some loss of fitness during passaging through human or non-human cells.

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Research and Design of Biomedical Telemetry Device using Light Transmission

Mauricio Gallegos, a student from Clemson University, along with Austin Mesa from Florida International University, worked in the lab of Dr. Juan Guttierrez to design an implantable biomedical sensor.

Abstract: The goal of this project was to design and miniaturize an implantable biomedical telemetry sensor that provides continuous, long-term telemetry data that could, in turn, be used with predictive algorithms to pre-diagnose disease or predict the severity of an oncoming disease. Current sensors that accomplish the same goal are power-hungry due to radio transmission and bulky due to a large battery, making them poor implants. Our team designed a proof-of- concept device for telemetry data transmission that uses visible light instead of radio waves, which should theoretically reduce overall battery consumption and minimize size. The system features two components, one for data collection and transmission, and the other for data reception. These components work simultaneously to provide real-time telemetry data that can be analyzed further. For our particular transmission device, the sensors used were a 3-axis accelerometer, which detects the overall activity of the subject being studied, and a temperature sensor which provides a general measurement of biological health. This hardware along with code loaded to the microcontroller allows the system to transmit live data through an LED, which is instantaneously received by the photoresistor on the receiving end. By parsing and interpreting the binary data, it can be organized and plotted for further analysis.

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