Scholarship & Research
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/1
Browse
5 results
Search Results
Item Effect of landscape fragmentation on bat population dynamics and disease persistence in Uruguay(Montana State University - Bozeman, College of Agriculture, 2021) Botto Nunez, German; Chairperson, Graduate Committee: Raina K. Plowright; This is a manuscript style paper that includes co-authored chapters.The transmission of pathogens into novel host species, a process known as spillover, requires a series of conditions to align in space and time. A series of imperfect barriers prevent the jump of pathogens from one species to others. These may include the distribution and abundance of the primary host, the survival of the pathogen in the environment and the susceptibility of the recipient host to the pathogen. Only when permissive conditions align in time and space can the spillover occur. Spillovers may be relatively rare events and the understanding of the dynamics of the barriers is constrained by the ability of detecting and analyzing such events. Systems where spillover does not occur, despite apparent presence of all required conditions, provide an opportunity to understand barriers preventing inter-species transmission. Vampire bat-borne rabies in Uruguay provides such an opportunity. Despite large and stable livestock density, presence of vampire bats, and circulation of the virus in close proximity, the country did not experience livestock rabies outbreaks until 2007. Here we combined historical review, field sampling, and statistical and mathematical modeling to understand the factors driving the emergence of rabies in Uruguay in 2007 and the previous absence of the disease. Our results suggest that rabies outbreaks in the country are spatially and temporally associated with fragmentation of grasslands. We showed that proposed increased connectivity among colonies, in response to fragmentation, is sufficient to explain longer persistence of the virus in the bat colonies, allowing more opportunities for virus transmission to livestock. We showed that connectivity has a strong effect on rabies persistence and that reproductive seasonality and population turnover have only marginal effects compared to connectivity. As connectivity driven by shared feeding areas might not be detectable by genetic analyses of the bats, we proposed the use of a widespread virus persistently infecting bats as a marker to trace connectivity across colonies. Combined, the results presented here provide tools that can be applied to intervene and apply countermeasures to prevent spillover.Item Aerosol stability of severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2)(Montana State University - Bozeman, College of Agriculture, 2022) Bushmaker, Trenton John; Chairperson, Graduate Committee: Raina K. Plowright and Vincent J. Munster (co-chair); Neeltje van Doremalen and Dylan H. Morris were authors and Myndi G. Holbrook, Amandine Gamble, Brandi N. Williamson, Azaibi Tamin, Jennifer L. Harcourt, Natalie J. Thornburg, Susan I. Gerber, James O. Lloyd-Smith, Emmie de Wit and Vincent J. Munster were co-authors of the article, 'Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1' in the journal 'New England journal of medicine' which is contained within this thesis.; Claude Kwe Yinda and Dylan H. Morris were authors and Myndi G. Holbrook, Amandine Gamble, Danielle Adney, Cara Bushmaker, Neeltje van Doremalen, Raina K. Plowright, James O. Lloyd-Smith and Vincent J. Munster were co-authors of the article, 'Comparative aerosol stability of SARS-CoV-2 variants of concern' submitted to the journal 'Emerging infectious diseases - CDC' which is contained within this thesis.The routes of transmission of the zoonotic pathogen severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) have been extensively studied to understand the spread at individual and population levels. Aerosol particles produced by infected individuals and the deposition patterns inhaled are known to affect the virulence of bioaerosol pathogens. Droplet nuclei particles (< 5 microns) aerosols typically deposit within the alveolar spaces of the lungs, whereas droplet (>5 microns) aerosols typically deposit within the nasopharyngeal and tracheobronchial regions of the respiratory tract. A few studies have evaluated pulmonary disease following droplet nuclei size particles of SARS-CoV-2 aerosol inhalation in African green monkeys and golden hamsters, concluding that both models have mild respiratory disease representative of human disease. More importantly, human participants with SARS-CoV-2 infections have been studied to look at the generation of particles during breathing, talking, and singing; the study concluded droplet nuclei particles accounted for 85% of the copies of virus produced and play a significant role in transmission. However, the environmental persistence of the aerosolized droplet nuclei particles, and the likely role of environmental persistence in driving transmission, is unknown for SARS-CoV-2. In these studies, we show the changing aerosol stability of SARS-CoV-2 during the supplanting waves of Variants of Concern (VOC). With the determination of viable viral particles characterized over time, we can make inferences about the role VOC and aerosol transmission have in driving population-level pathogen transmission. A secondary objective of these studies was to characterize the role those evolving mutations have had on viral entry and aerosol durability. Our work suggests that aerosol stability may be important in driving some population-level phenomena (e.g., indoor transmission, including superspreader events) but given the short infected-to-naive transmission transit time, the variation in the duration of aerosol stability among VOCs may not explain the difference in transmission rates of VOCs. This data will be useful for assessing the future evolution of aerosol transmission of SARS-CoV-2.Item Influenza D viruses in polymicrobial infections(Montana State University - Bozeman, College of Agriculture, 2022) Robinson, Emily Faith; Chairperson, Graduate Committee: Agnieszka Rynda-AppleInfluenza D viruses (IDVs) comprise Deltainfluenzaviridae, the newest genus of the Orthomyxoviridae family. This group of viruses primarily infects the upper respiratory tract and causes only mild symptoms. Unlike most influenza viruses, IDVs infect a wide range of ungulates, including cattle, swine, and sheep. In cattle, IDVs are thought to act as an etiologic agent in bovine respiratory disease (BRD), a severe polymicrobial disease primarily impacting calves. In chapters 2-4 of this thesis, we report the first experimental infection of an IDV in sheep with and without a recent Mycoplasma ovipneumoniae (M. ovipneumoniae) bacterial infection. We found no evidence of overt illness in IDV-infected lambs. Our findings suggested that recent M. ovipneumoniae infection induced a mild proinflammatory innate immune response that contributed to an enhanced neutralizing antibody response compared to that of M. ovipneumoniae-naive IDV-infected lambs. These findings suggest that although these lambs did not present with clinical symptoms in response to IDV, carriage could contribute to the inflammatory response in sheep experiencing polymicrobial infections. Influenza infections can confer short-term protection against additional viral pathogens. This process, called heterologous viral interference, is mediated by type I interferon antiviral signaling. This phenomenon predominantly occurs when a host is infected with a mild virus followed by a more severe virus. In humans, heterologous viral interference can result in an attenuation or delay of symptoms associated with the more severe pathogen. Evidence suggests that IDVs infect humans, although there is no evidence that these infections are symptomatic. To gain insight into whether IDVs can reduce the symptoms of influenza A virus (IAV), we performed a series of experiments in mice. In Chapter 5 of this thesis we show that IDV infection can, but does not always, reduce disease associated with IAV. We subsequently sought to identify critical type I interferon signaling events underlaying this phenomenon, but our results remain inconclusive.Item Evaluation of conditions and mechanisms of alphaherpesvirus superinfection exclusion(Montana State University - Bozeman, College of Agriculture, 2022) Cwick, James Patrick; Chairperson, Graduate Committee: Matt Taylor; This is a manuscript style paper that includes co-authored chapters.Superinfection exclusion (SIE) is a natural phenomenon where one virus prevents subsequent entry of another virus. Studies have shown its impact on viral replication and reproduction of many different viruses, where exclusion targets specific parts of the virus' lifecycle. Alphaherpesviruses, specifically pseudorabies virus (PRV) and Herpes Simplex virus type 1 (HSV-1), have demonstrated at least two forms of SIE. However, the form of SIE that occurs early in viral replication remains of interest due to both its timing and unknown mechanisms of regulation. Research on this topic will stimulate development of vaccines in global health by providing targets for disruption of alphaherpesvirus infection and information on unknown aspects of alphaherpesvirus infection. We have developed two models for assessing early SIE for alphaherpesviruses: a fluorescent reporter model to quantify virions within the cell. Both models contributed to data that determined our early SIE is influenced by multiplicity of infection (MOI) for both the primary and secondary virions. Imaging flow cytometry was utilized in conjunction with fluorescent microscopy as a possible means to study early SIE in large population samples. Subsequent data from my experiments indicates that cellular factors like cellular receptors, clathrin, and actin arrangement had minimal influence on early SIE of alphaherpesviruses. However, the results from capsid trafficking model in combination with experiments involving heparin and bortezomib indicate that early SIE differs in PRV and HSV-1. Data indicates that PRV SIE inhibits the step of viral entry/fusion, while HSV-1 SIE disrupts in a post-entry manner. Data obtained from this dissertation indicates that early SIE influences alphaherpesviruses differently and presents possible means to study antiviral techniques and methods.Item Contact rates in ecology : using proximity loggers to explore disease transmission on Wyoming's elk feedgrounds(Montana State University - Bozeman, College of Letters & Science, 2011) Creech, Tyler Graydon; Chairperson, Graduate Committee: Scott Creel; Scott Creel and Paul C. Cross were co-authors of the article, 'Contacts between animals: emerging methods, questions, and challenges' in the journal 'Methods in Ecology and Evolution' which is contained within this thesis.; Paul C. Cross, Brandon M. Scurlock, Eric J. Maichak, Jared D. Rogerson, John C. Henningsen, and Scott Creel were co-authors of the article, 'Low density feeding reduces elk contact rates and brucella transmission on feedgrounds' in the journal 'Journal of Wildlife Management' which is contained within this thesis.Infectious diseases are an important consideration in the management of wildlife populations, and contact rate is a key parameter for understanding the epidemiology of such diseases. In the first section of this thesis, I review current issues and challenges that researchers face when designing animal contact studies and analyzing contact data. I examine how characteristics of methods for collecting contact data affect inferences that can be drawn about contact structures; describe applications of social network analysis of contact data to disease ecology and animal behavior, focusing on sampling issues and dynamic networks; suggest how new technologies can be used to answer important questions about variation in individual contact rates within populations; and propose a new statistical approach for analyzing contact data in a linear modeling framework. In the second section, I describe an experimental field study that used proximity loggers (a new technology for measuring contact rates) to understand transmission of Brucella abortus on elk feedgrounds in Wyoming. Brucellosis is a bacterial disease that causes abortions in elk and is transmitted by contact with infectious aborted fetuses. Supplemental feeding of elk on winter feedgrounds is believed to exacerbate B. abortus transmission by aggregating elk at high densities, increasing their chance of contacting infectious fetuses. I evaluated the effectiveness of a proposed low-density feeding strategy by comparing elk-fetus contact rates (as measured by proximity collars and video cameras) during high-density and low-density feeding treatments that provided the same total amount of food at different densities. Low-density feeding led to >50 percent reductions in the total number of contacts and the number of individuals contacting a fetus. Elk contacted fetuses and random control points equally, suggesting that elk were not attracted to fetuses but encountered them incidentally while feeding. The relationship between contact rate and disease prevalence is non-linear and simple disease models suggest that low-density feeding may result in dramatic reductions in brucellosis prevalence, though this depends on the amount of transmission that occurs on and off feedgrounds.