Baylisascaris procyonis prevalence and dynamics in a rodent population in Georgia

Ian Buchta, from Tulane University, worked with Dr. Michael Yabsley and members of his lab to study parasites in a local racoon population.

Ian Buchta1,2, Amanda Holley1, Kayla Buck1,3, Sarah Sapp1,4, Michael Yabsley1,3

Baylisascaris procyonis, the common roundworm parasite of raccoons, is a well-recognized zoonotic parasite. It utilizes small vertebrates as intermediate hosts and undergoes migration through the central nervous system which can lead to behavioral modifications or death. Previous studies on rodents have been conducted in Indiana where the prevalence of B. procyonis in raccoons is very high and only focused on a single species, the white-footed mouse (Peromyscus leucopus). In Georgia, the prevalence is low in raccoons, possibly due to its recent emergence. Our study was conducted to determine if rodents in Georgia are infected and investigate if other rodents are involved in the life cycle. Additionally, we tested if habitat disturbance impacted prevalence. Rodents were trapped at five sites with variable disturbance. After human euthanasia, brains were removed, pressed between glass slides, and microscopically analyzed for larvae. The remaining tissues, other than the skin, were digested in a 0.3% pepsin and 1% hydrochloric acid and the resulting liquid was analyzed for larvae. Infections were noted at two sites in Jackson and Clarke counties. Of 71 P. leucopus tested, seven (10%) were infected, although only one had larvae in the brain. None of the cotton rats (n=10), cotton mice (n=3), brown rats (n=4), or chipmunks (n=2) were infected. No difference in prevalence was noted for P. leucopus from sites with low or high levels of disturbance. Our finding of B. procyonis in P. leucopus is the first to document the parasite in a non-raccoon host in Georgia and of the parasite in Jackson Co., Georgia. Because this parasite causes disease in numerous avian and mammalian hosts, wildlife with neurologic disease should be considered suspects for B. procyonis infection



  1. Southeastern Cooperative Wildlife Disease Study, Department of Population Health, College of Veterinary Medicine,  Athens, GA 30602
  2. Tulane University, New Orleans, LA 70118
  3.  Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602
  4. Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA 30602

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Spore persistence in the environment drives infection dynamics of a butterfly pathogen

Mary-Kate Williams, from the University of Arkansas at Little Rock, examined parasites of Monarch butterflies with Dr. Sonia Altizer, Dr. Richard Hall and graduate student Dara Satterfield.

Mary-Kate Williams1, Sonia Altizer2, Richard Hall2, Dara Satterfield2

1University of Arkansas at Little Rock, 2Odum School of Ecology, University of Georgia

Environmentally transmitted parasites commonly infect humans and wildlife. Environmental transmission is particularly important for insect pathogens, yet the factors affecting the persistence of infectious stages in the environment are poorly understood. Monarch butterflies are commonly infected by Ophryocystis elektroschirrha (OE); recent years have seen an increase in pathogen prevalence at the same time monarch populations in eastern North America have declined. OE is transmitted both vertically (from infected females to their progeny) and environmentally (when infected adults scatter spores onto milkweed leaves that are consumed by unrelated larvae). By using a combination of a mathematical modeling and an experimental study, we examined (1) how environmental conditions affect persistence of a free-living stage pathogen and (2) how pathogen shedding rate and environmental persistence time affect pathogen prevalence and host population size during the summer breeding season. We found that increased time spent fully exposed to environmental conditions (sun, rain, heat) reduced average infection severity induced by parasites, but did not reduce the fraction of monarchs infected by spores; therefore, parasites were able to remain viable after 15 days outdoors. Consistent with the experimental results, modeling findings showed that, parasite spores must persist for at least 20 days, in combination with a high shedding rate onto host plant leaves, for predicted prevalence to match the minimum prevalence observed in prior field studies.

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Impact of patient non-compliance on tuberculosis treatment regimens

Kylie Balotin, a student at Rice University, and Dr. Andreas Handel, in the UGA Department of Epidemiology and Biostatistics, worked together to model the effect of patient compliance on the effectiveness of tuberculosis treatments.

Kylie Balotin1 and Andreas Handel2

1 Rice University, Houston, TX, 77005, USA1

2 Department of Epidemiology and Biostatistics, College of Public Health,

University of Georgia, Athens, GA 30602, USA

Tuberculosis is a leading cause of death in the world today and infects about one third of the world’s population. WHO currently recommends a standard treatment for TB consisting of multiple drugs. Alternative drug combinations are also being investigated as possible regimens. Although the current standard treatment is fairly effective, due to factors including the long treatment time of tuberculosis, many patients do not follow the entire treatment regimen. This noncompliance could lead to the relapse of the patient and the emergence of resistance to anti-TB drugs. The objective of this study is to use a mathematical model that simulates TB drug treatment and patient non-compliance in order to investigate the effect of patient compliance with three TB treatment regimens (the standard regimen, Remox 1, and Remox 2) a percentage of the time. We show that Remox 2 is generally more forgiving towards patient non-compliance than the other two regimens.


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Development of deterministic and stochastic models for a T7 phage-E. coli system with vaccination strategy implementation

Abigail Smith, from Carnegie Mellon University, worked with Reni Kaul in the lab of Dr. John Drake to develop models to study the effectiveness of vaccination strategies.

Abigail L. Smith1, RajReni B. Kaul2 and John M. Drake2

1Carnegie Mellon University, 2Odum School of Ecology, University of Georgia

Vaccination is widely considered the most effective method of preventing the spread of infectious disease.  Pulse vaccination strategy, the repeated application of a vaccine over a defined population at a set time interval is gaining prominence as a strategy for the elimination of diseases such as measles, hepatitis, and smallpox. In order to study the effectiveness of this strategy, a bench experiment will be designed using E.coli bacteria and T7 bacteriophage, and studying the interactions and mechanisms in a chemostat. Using this system allows us to study the spread of infectious disease in laboratory setting. To test vaccination in system, a concentration of IPTG will be used to induce expression of the rcsA gene (immunity) in E. coli. Results can be generalized from an experimental bench system (E. coli bacteria and T7 phage) by developing a deterministic compartmental model, and then factoring in noise to form a stochastic model. Additional classes were added to track phage populations and experiment with vaccination strategy.  Preliminary studies were designed to study early warning signs for approaching a bifurcation point and critical slowing down, by examining the phage being driven to extinction.


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Photo credit: School of Life Sciences, Gibbet Hill Campus, The University of Warwick, Coventry, CV4 7AL

Effects of pH and Temperature Variability on Fungal Pathogen Development and Population Survival in Daphnia

For this project, based in the lab of Dr. John Drake, Trianna Humphrey worked with Tad Dallas to study the effect of changing environmental conditions on a host-parasite relationship.

Trianna Humphrey, Tougaloo College

Tad Dallas, Odum School of Ecology, University of Georgia

 Extreme environmental conditions can have an influence on host-parasite relationships and capable of altering interactions. Extreme conditions on Daphnia dentifera, also known as water fleas, and it’s fungal pathogen (Metschnikowia bicuspidata), can alter disease dynamics and population dynamics. This study was designed to answer the question, “Does the influence of temperature variability have an effect on the host-parasite relationships within Daphnia.”  Also we wanted to answer the question ”Does a change in pH have an effect on the host-parasite relationships or an effect on the population?” We show that we exposed half the population to the pathogen. A temperature of 20C was used as a control and 12C and 28C were the two extreme temperatures, with time variations of either 0,1,2, or 4 hours. This study is ongoing and data are still being collected. To alter the pH, we added a HCL solution to the populations and exposed half the populations to the pathogen to answer the question ”Does pH have an effect on infection and spores within Daphnia?”  After examining the data, we didn’t find any useful data to answer our big question.

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Do Parasite Infections Effect Fighting Ability in Beetles

David Vasquez, a student from Virginia Tech, worked with Andy Davis in the Odum School of Ecology to examine the effect that parasite infections have on the fighting ability of beetles.

David Vasquez1, Andy Davis2

1Virginia Polytechnic Institute and State University,

2Odum School of Ecology, University of Georgia

Parasites, by definition, subsist off their host’s resources, which can drain energy. This can have negative consequences for the host, especially during energy-intensive activities. Fighting is common in most animals that are territorial, or that are protective of young. Few studies have examined the effect of parasites on fighting capacity in animals. The bess beetle (Odontotaenius disjunctus) is a saprolytic insect common in forests within the eastern United States, and it is susceptible to a naturally-occurring nematode parasite (Chondronema passali). We examined the effect of infections on the outcome of staged fights in this beetle. Beetles were selected based on weight (so that each pair contained similarly-sized individuals), then placed in a small wooded arena to observe fighting behavior. A video camera recorded 3 minutes of fighting. Afterwards, beetles were killed and dissected to determine gender and parasite status. From the videos, an external observer recorded the number of bouts, wins and losses for each pair, and the overall winner. A total of 78 beetles were used in the experiment; 40% were infected with C. passali. 31 infected beetles were the overall winner in 52% of their matches, while uninfected beetles won 48% of fights (this was not significantly different X2 test). However, when fights were grouped by infection severity, we found that beetles with the highest infection score (thousands of nematodes) won 71% of their battles, while the least-infected beetles only won 25% of the time. This is counter-intuitive to the idea that infection has a negative energetic effect on host fitness.

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Host Breadth of Parasites in Ungulates and Carnivores

Emili Price, a student from Winthrop University, worked with Drs. Patrick Stephens and John Gittleman in the Odum School of Ecology to look at host breath of parasites in ungulates and carnivores.

Emili Price1, Patrick R. Stephens2, John L. Gittleman2

1. Winthrop University, Rock Hill, South Carolina

2. Odum School of Ecology, University of Georgia, Athens, Georgia

Most parasites infect multiple hosts, but few studies have focused on characteristics of hosts and parasites that may cause differences in the host breadth. We investigated two facets of host breadth: variation in the number of host species different parasite species infect and the similarity of parasite communities among host species (i.e., overlap in the parasite species that infect different pairs of host species).  We first tested for the effects of parasite transmission mode and taxonomic identity on host breadth among parasites of ungulates and carnivores using a number of definitions of host breadth, and using several methods to try and correct for differences in sampling effort among parasite species. We found that viruses and sexually transmitted parasites infect significantly more hosts than other types of parasites in ungulates regardless of the estimate of host breadth considered.  We also found that viruses and vertically transmitted parasites infect significantly more hosts than other types of parasites among ungulate parasites that infect at least two hosts.  Finally, among carnivore parasites with two or more hosts, we found that parasites transmitted via feces infect significantly more hosts than other types of parasites.  We next investigated the effect of phylogenetic distance, differences in mass, and the geographic overlap among ungulate host species on parasite community similarity. All three variables showed statistically significant correlations with parasite overlap regardless of whether Jaccard’s or the corrected Jaccard’s index was used to measure parasite overlap among hosts.  However, geographic range area overlap and phylogenetic relatedness explained much more variation than differences in body mass among hosts.  Our results were almost identical when we restricted consideration to viruses, save that mass was an even weaker predictor of overlap.  Finally, we tested to see whether carnivore species that prey on ungulates are infected by more ungulate parasites than those that do not. We found that carnivore species that prey upon ungulates were infected by on average twice as many ungulate parasites than carnivores that specialize on different prey items.

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Quantifying the Performance of Spatial and Temporal Early Warning Signals of Disease Elimination

Dominic Gray, a student from Norfolk State University, and Dr. John Drake from the Odum School of Ecology examined the use of temporal early warning signals in disease dynamics.

Dominic Gray, Norfolk State University

John Drake, Odum School of Ecology, University of Georgia

Early warning signals of disease emergence and elimination seek to forecast changes of state in infectious disease system. Most such signals are a result of critical slowing down and other universal patterns near bifurcations. Most work to date has focused on temporal early warning signals, which are known to be statistically inefficient and discard information contained in the spatial pattern of cases. We sought to quantify the performance of spatial indicators and compare them to temporal indicators by simulating a spatial SIR compartmental model with vaccine induced immunity over a spatially homogenous environment. We found that spatial indicators greatly outperform their temporal counterparts, suggesting that additional gains in statistical efficiency could be achieved by adopting these newer methods.

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Using the power ratio as an early warning signal to detect critical transitions for disease emergence and eradication

Paige Miller, from Gustavus Adolphus College, and Dr. John Drake in the Odum School of Ecology, examined early warning signals in disease systems.

Paige Miller, Gustavus Adolphus College

John Drake, Odum School of Ecology, University of Georgia

 Infectious diseases have ravaged the human population since the beginning of time. Eradication of human infectious diseases has been a public health initiative for more than a century. Emerging and re-emerging infectious diseases, such as Ebola, multi-drug-resistant TB, and pertussis, continually threaten lives of people across the world. Predicting when eradication of a disease is almost achieved or when emergence events are likely to occur could give policy makers specific evidence to stop the disease emergence or continue eradication efforts. Early warning signals (EWS) have been studied in many systems such as fishery collapses, economic market fluctuations, and global climate change. In the case of infectious diseases, however, EWS are difficult to use because of inherent periodicities (seasonality or multi-yearly cycling) and under-reporting issues in the datasets along with violations of normality, independence, and stationarity assumptions. We evaluate wavelet-based methods, which make fewer assumptions and allow us to specify which periodicities to study. Wavelets are a method for representing a time-series in terms of coefficients that are associated with a particular time and a particular frequency. The power ratio, the ratio of low frequency waves to high frequency waves, is calculated using wavelet-based analysis. Here, we determine if the power ratio can be used as a more reliable early warning signal for detecting infectious disease emergence and eradication.

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Identifying Chagas Disease Reservoirs with PCR and Next-generation DNA Sequencing

For this project, students Nicolas Means from Oklahoma State University and Darlisha Owens from Grambling State University, teamed up with Dr. Travis Glenn in the Department of Environmental Health Science and Dr. Nicole Gottdenker in Veterinary Medicine to use next-generation DNA sequencing to identify disease reservoirs.

Nicolas J. Means1, Darlisha Owens2, Troy Kieran3, Travis C. Glenn3, Nicole Gottdenker3

1Oklahoma State University, 2 Grambling State University

3University of Georiga

American trypanosomiasis (Chagas Disease) is a zoonotic vector-borne disease caused by the protozoan parasite Trypanosoma cruzi,  and is an important cause of morbidity and mortality in Latin America. T. cruzi circulates between reservoir hosts (wild and domestic mammals) and hematophagous triatomine insect vectors. Humans are susceptible to the disease once infected with the parasite by contact with the infected insect vector, ingestion of food or drink contaminated with the pathogen, transplacental transmission, or by transfusion with infected blood or tissue transplants. Research has shown that blood meal analysis, via standard PCR and sequencing, are capable of identifying host reservoirs down to the species level, but these techniques are limited because: 1) they often cannot identify multiple blood meals within a vector, 2) they cannot be used to simultaneously detect vector infection with trypanosomes or coinfection with other pathogens, and 3) they may require a relatively large amount of vertebrate reservoir DNA, which may be degraded in the insect vector. The objective of this study is to standardize next generation sequence methodologies for simultaneous blood meal species identification and trypanosome infection within kissing bugs, Rhodnius pallescens, a triatomine vector of Chagas disease.

To prepare samples for next generation sequencing, we had to quantify the amount of DNA extracted from R. pallescens, normalize the DNA concentrations, and optimize the PCR conditions for each portion of the next generation Taggimatrix technique.  The samples were put in three different groups consisting of high, medium, and low concentration DNA.  For optimization of the PCR, there were a series of tests with a known insect and vertebrate. Conditions such as number of cycles, temperature and time changed throughout each experiment. We then used the optimized PCR conditions on the DNA from the three groups (high, medium and low) to obtain amplification of vertebrate and trypanosome DNA. From the tests, we found that 30% of the new samples that were collected had the trypanosome parasite within the DNA of the insect while 68% showed vertebrate DNA within the blood meal.

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