Browsing by Author "Pabilonia, Kristy, committee member"
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Item Open Access Bats as reservoir hosts: exploring novel viruses in New World bats(Colorado State University. Libraries, 2018) Malmlov, Ashley, author; Schountz, Tony, advisor; Bowen, Richard, committee member; Dinsmore, Page, committee member; Pabilonia, Kristy, committee memberTo view the abstract, please see the full text of the document.Item Open Access Environmental maintenance and transmission of Francisella tularensis in cottontail rabbits, prairie voles, and amoebae(Colorado State University. Libraries, 2016) Brown, Vienna Rae, author; Bowen, Richard, advisor; Bachand, Annette, committee member; Pabilonia, Kristy, committee member; Petersen, Jeannine, committee memberTularemia is a zoonotic disease that is endemic in much of the Northern Hemisphere, capable of causing severe disease in a wide range of hosts. This disease is caused by the gram-negative bacterium Francisella tularensis and most human cases are caused by either subsp. tularensis (type A) or holarctica (type B). Genetic clustering has led to further differentiation within type A and type B strains; type A strains are currently classified as A1a, A1b, and A2. Due to the high virulence and low infectious dose of this pathogen, naïve immune status of the public, and previous weaponization, F. tularensis has been classified as a Tier 1 Select Agent by the Centers for Disease Control and Prevention. Although the Francisella bacterium was discovered over a century ago, understanding of ecological factors that contribute to environmental maintenance and transmission remains enigmatic. Extensive research has been performed in a variety of laboratory animal models to evaluate factors related to disease progression and vaccine and therapeutic options; however, very little is known about reservoir and/or amplification hosts in a natural setting. Reported here are a series of experimental studies performed in cottontail rabbits and voles as well as in vitro infections of amoebae with multiple strains of F. tularensis. The objectives of the in vivo studies were to characterize clinical disease, tissue dissemination and organ burden, and morbidity and mortality in a species believed to play an important role in naturally acquired infections. Rabbits were inoculated using a strain and dose of organism as well as a route of infection in accordance with what would be expected in nature. The initial experimental infections of cottontail rabbits involved intradermal inoculation with one of several strains of F. tularensis which resulted in varied patterns of clinical disease, gross pathology, and histopathology. Each of the type A strains was highly virulent, with rabbits requiring euthanasia or succumbing to infection 3-13 days post-infection. Gross lesions observed in infected rabbits included numerous microabscesses in the livers and spleens, suggesting high bacterial organ burdens. In contrast, most rabbits infected with type B strains developed a mild fever and became lethargic, but the disease was infrequently lethal. Those rabbits infected with type B strains that survived longer than 14 days post-infection developed a robust humoral immune response, and F. tularensis was not isolated from liver, spleen, or lungs of those animals. These findings depict a clear difference in virulence and immune kinetics between type A and B strains of F. tularensis in cottontail rabbits. Based on findings from the original study with cottontail rabbits, I evaluated the protection afforded against infection with a type A strain of F. tularensis by prior inoculation with a type B strain. Previous infection with a type B strain of the organism was found to lengthen survival time and, in some cases, prevented death following inoculation with a type A2 strain of F. tularensis. In contrast, inoculation of a type A1b strain was uniformly lethal in cottontail rabbits irrespective of a prior type B inoculation. These findings provide important insight about the role cottontail rabbits may play in environmental maintenance and transmission of this organism. Prairie voles are believed to acquire a natural infection with F. tularensis from contact with infected waterways or cannibalism of another vole that died from a tularemia infection. To evaluate such infection experimentally, I inoculated prairie voles orally with 107 organisms of type B F. tularensis and serially euthanized them to characterize organ burdens and pathology. The inoculated voles failed to show any clinical signs of disease and upon necropsy did not present with any gross lesions. Furthermore, organisms were not recovered from the liver and spleen, and antibodies were not detected, despite evaluation >14 days post-infection. Eight voles were then challenged intranasally with 350-650 organisms of one of two strains of F. tularensis. Infection with one strain (OR96-0246) resulted in all the animals succumbing to death or euthanasia between 6 and 7 days post-infection, whereas voles infected with the other strain (KY99-3387) survived to the end of the study period (10 days post-infection), with the exception of one vole which succumbed to infection. These findings were surprising and require further investigation to understand how voles become infected in nature and what role they may play in F. tularensis persistence and transmission. Free-living amoebae are capable of harboring pathogens and have been implicated in various disease outbreaks. I evaluated 3 strains of Acanthamoebae and 1 strain of Hartmannella as hosts for three bacterial pathogens. All strains of amoebae were propagated in culture with virulent strains of F. tularensis, Burkholderia pseudomallei and methicillin-resistant Staphylococcus aureus, with the aim of elucidating both general principles and pathogen-specific mechanisms associated with bacteria-amoebae interactions. F. tularensis and B. pseudomallei were recoverable from the lysate for all four strains of amoebae at both 4 and 24 hours post-inoculation, whereas MRSA was recoverable from the lysate of all four strains at the 4 hour time point and from only two of the strains at the 24 hour time point. Confocal microscopy allowed for the visualization of labeled bacteria of each strain and differentiation of amoebae morphology was possible. These findings provide intriguing evidence that amoebae are capable of phagocytosing pathogenic bacteria and that protozoa may play a role in environmental maintenance and persistence.Item Open Access Investigating the potential role of wildlife as reservoirs of Chikungunya virus: experimental infections and field studies(Colorado State University. Libraries, 2017) Blizzard, Emily Lauren, author; Bowen, Richard A., advisor; Pabilonia, Kristy, committee member; Schountz, Tony, committee member; Johnston, Matthew, committee memberChikungunya virus (CHIKV) is a mosquito-borne human pathogen endemic to Africa and Asia and the etiologic agent of chikungunya fever (CHIKF), a severe debilitating and often chronic arthralgic disease. The recent introduction of CHIKV into the Western Hemisphere has led to an increased initiative to investigate the role that mammals other than non-human primates might play during CHIKV sylvatic transmission cycles. The focus of the studies presented in this dissertation was to investigate the potential of several common rodent species to serve as reservoir and/or amplifying hosts for CHIKV during outbreaks in the Americas. Nine rodent species were subcutaneously inoculated with one of two strains of chikungunya virus during initial experimental infections. Of these, 7 out of 9 species became infected with CHIKV. Groundhogs (Marmota monax) were the mostly likely candidate to serve as a reservoir host in North America based on magnitude of viremia. All groundhogs included in this study developed significant viremias ranging from 4.0E2 to 1.6E6 and lasting 2-4 days post infection. The viral loads observed were sufficient to infect Ae. spp mosquitoes indicating that these animals are capable of serving as reservoir hosts. Additionally, groundhogs undergo periods of hibernation and further research is need to determine if these animals are capable of overwintering CHIKV in the U.S. Based on the findings from the CHIKV experimental infections, Cotton rats (Sigmodon hispidus), were evaluated as a laboratory animal model to study CHIKV pathogenesis. Thirteen of seventeen cotton rats developed a low-titer viremia, but no clinical or post-mortem pathological findings were observed. Mosquitoes fed on viremic cotton rats failed to become infected, suggesting that this species is not likely to play a role in CHIKV transmission cycles. Field studies investigating the likelihood of three mammals and eight reptilian and amphibian species were conducted in select regions of Cambodia and the Grand Cayman islands. Individuals from nine of eleven species examined had low levels of detectable CHIKV antibodies, suggesting that they may have been infected with CHIKV. The results of these studies provide some insight into the potential role of wildlife, mainly rodents, in CHIKV transmission cycles.Item Open Access Parasite communities of wild turkeys (Meleagris gallopavo) in Colorado(Colorado State University. Libraries, 2014) Shilling Littman, Paige Willever, author; Moore, Janice, advisor; Ghalambor, Cameron, committee member; Pabilonia, Kristy, committee memberWild turkeys (Meleagris gallopavo) are large galliform birds, are commonly hunted birds, and they are non-migratory. Wild turkeys were originally found over most of the United States. In the early 1900s they experienced widespread population declines which are thought to have been caused by overhunting and habitat loss. Due to many reintroduction efforts, the wild turkey is now found in its historical range and it has expanded its range even further. However, considering the popularity of wild turkeys as game birds, relatively few studies have addressed their parasites, and specifically the helminth parasites. Island Biogeography Theory has been applied to parasite and host relationships in which the host is considered an island. In particular, the Island Size hypothesis predicts that a larger island will allow for greater species diversity due to the increased area, and by extension, larger host species, in terms of body mass, will have more species of parasites. This study evaluates whether or not galliform birds support the Island Size Hypothesis in terms of their parasite communities. Birds in the order Galliformes have a wide range of sizes and are generally non-migratory; thus they will not pick up parasites from different locations. I reviewed twenty six studies of 19 species of galliform birds and recorded the number of helminth species reported in each host bird species. Based on these data, I show that there is a positive correlation (R2 = 0.212) between galliform host size and number of helminth parasite species. The model that best fits the data includes both the mean mass of the host species as well as the family of the host species. This is the first survey of helminth parasites in wild turkeys of Colorado. I collected 24 wild turkey intestines that were donated by hunters. These intestines were examined for helminth parasites, which were collected and identified. A total of 7 different species of helminth parasites were identified in these Colorado wild turkeys. Cestodes were the most commonly identified helminths, followed by acanthocephalans, trematodes, and nematodes. The Colorado data were then compared to a previous study of the helminths of wild turkeys in both Florida and New Zealand. A total of 14 helminth parasite species were reported from wild turkeys in Florida while 6 helminth species were reported in wild turkeys from New Zealand. These data suggest that there are differences in these parasite communities in terms of parasite species richness and prevalence of each helminth species. The fact that wild turkeys are not only a popular game bird, but also a common component of domestic poultry operations underscored the importance of understanding their parasites. This knowledge can help us to harvest wild turkeys safely when hunting as well as minimize the transfer of parasites between domestic and wild turkeys.