Matching Items (27)

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Protecting amphibians from a deadly Chytrid Fungus using a novel technology

Description

Infectious disease in wild animals has historically been a challenge that is difficult to overcome, primarily because isolating a disease outbreak to prevent further transmission in these types of populations

Infectious disease in wild animals has historically been a challenge that is difficult to overcome, primarily because isolating a disease outbreak to prevent further transmission in these types of populations is nearly impossible. Wild animals are free to roam, and humans often have limited means of tracking infection in populations. Vaccines and treatments can be formulated but are often somewhat impractical for wild populations because it is not feasible to vaccinate or treat every member in a susceptible community. One such pathogen, Batrochochytrium dendrobatidis (Bd) is infecting amphibian populations around the world to the point where many species are already extinct. Even though finding an effective preventative for the fungal pathogen may not mean that I am able to reach every member in a population, it may mean the difference between extinction and eventual release back into the wild for threatened populations.
In this study I hoped to create an attenuated version of Batrochochytrium dendrobatidis, by using a novel laser technology: SEPHODIS. This laser technology disrupts hydrogen bonds between proteins in the lumen of the cell while simultaneously preserving the membrane and associated proteins on the outside of the cell. This process ultimately affects the pathogenicity of the target but leaves identity markers intact so that the host immune system may recognize the pathogen and create antibodies against it. The laser was ultimately effective at killing Bd fungal cells, and I did observe a significant change in the appearance of the cells. However, samples obtained after exposure to the laser were contaminated and more research is needed to determine if SEPHODIS could be a feasible method for vaccine production.

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Created

Date Created
  • 2019-05

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Development of fungicide resistance in the amphibian chytrid fungus Batrachochytrium dendrobatidis

Description

Amphibians around the world are suffering the effects of the chytrid fungus, Batrachochytrium dendrobatidis (Bd). Whenever amphibians are housed in captivity, they must go through a decontamination protocol to ensure

Amphibians around the world are suffering the effects of the chytrid fungus, Batrachochytrium dendrobatidis (Bd). Whenever amphibians are housed in captivity, they must go through a decontamination protocol to ensure they are not infected with diseases such as Bd. Itraconazole is the most commonly used fungicide used in these protocols. This study set out to determine if Bd could develop resistance or tolerance to itraconazole. Two 24 well plates were prepared with different concentrations of itraconazole with Bd zoospores added. Plate 1 had concentrations similar to what animals are currently being treated with in decontamination protocols. Plate 2 had concentrations at and below the published minimum inhibitory concentration values (MIC). Plate 1 displayed the ability of itraconazole to kill Bd sporangia with higher concentrations and Plate 2 showed that even under published MIC values, Bd still struggled to complete its reproductive cycle. I find the evolution of a resistant/tolerant strain of Bd unlikely given the efficacy of this drug, the sensitivity of Bd to itraconazole, and the lack of evidence of the completion of Bd’s reproductive cycle under the conditions used in this study.

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Date Created
  • 2019-05

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Dragonfly naiads as potential reservoir hosts for the infectious amphibian chytrid fungus, Batrachochytrium dendrobatidis

Description

One way pathogen prevalence is maintained is by persistence within reservoir host species. Reservoir hosts are species that do not show any signs of disease when a pathogen infects them.

One way pathogen prevalence is maintained is by persistence within reservoir host species. Reservoir hosts are species that do not show any signs of disease when a pathogen infects them. As a result, the pathogen survives and is able to remain in the host population. Batrachochytrium dendrobatidis (Bd) is a chytrid fungus that has caused extensive amphibian declines. It has been suspected that reservoir hosts are a key to Bd remaining in certain amphibian populations. I studied dragonfly naiads (Anisoptera spp.), the aquatic life cycle stage immediately following hatching and preceding the emergence of wings, as potential reservoir hosts for Bd on the Mogollon Rim in Arizona. On the Mogollon Rim winter temperatures fall below the optimal thermal range for Bd. Boreal chorus frogs (Pseudacris maculata), the most common amphibian species on the Rim, maintain subzero body temperatures to survive the winter. Since the optimal thermal range for Bd is between 4°C and 25°C, it is unlikely that Bd can grow on the skin of these frogs during winter. As a result, it is unknown how Bd prevalence is maintained in the area. Recent studies showed that Bd can grow in non-amphibian hosts. I hypothesized that Bd could grow within the digestive tracts of dragonfly naiads, since they stay in the water and don’t maintain subzero body temperatures during the cold winters on the Rim. Non-native and native naiads were both included in this study; the non-native naiads were purchased from a company in California while the native naiads were captured from ponds on the Mogollon Rim. The digestive tracts of the naiads were then dissected, and the DNA was extracted using an animal tissue spin-column protocol. The extracted DNA was analyzed by qPCR. The qPCR analysis of the native and non-native dragonfly naiads revealed that the samples were either Bd-negative or very weakly Bd-positive, with most being the former. Based on these results, it does not appear that naiads are biologically significant reservoir hosts for Bd.

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Date Created
  • 2018-05

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Occurrence of a Pathogenic Fungus in Captive Arizona Amphibians

Description

Amphibians have been experiencing a worldwide decline that is in part caused by an infectious disease, chytridiomycosis, specific to frogs and salamanders. Globally many species have declined or gone extinct

Amphibians have been experiencing a worldwide decline that is in part caused by an infectious disease, chytridiomycosis, specific to frogs and salamanders. Globally many species have declined or gone extinct because of the pathogenic fungus Batrachochytrium dendrobatidis, also known as the amphibian chytrid or Bd. By the time Bd was discovered it was too late to stop the spread and it has now been found on almost every continent. The trade of captive amphibians, used as pets, bait, and educational animals provides an opportunity to spread Bd. Because some amphibians can carry Bd without experiencing symptoms, it is possible for even healthy looking amphibians to spread the amphibian chytrid if they are moved from one location to another. Recently, a new species Batrachochytrium salamandrivorans (Bsal) was found on salamanders. Bsal was identified before it reached the United States, prompting concern regarding its spread and a call for regulation regarding the trade of captive amphibians. There are some regulations in place controlling the trade of amphibians, but they are insufficient to stop the spread of amphibian chytrid in captive populations. A 2016 law prohibits the importation of 201 salamander species. However, there is no central organization to sample or certify if amphibians are free from Bd or Bsal. Although some stores say they test for these pathogens the tests are unregulated and not reported to any central body. If the captive amphibian trade is to go disease free, there would need to be a significant push to coordinate testing efforts. To estimate Bd's prevalence in Arizona captive amphibian populations, I contacted pet stores, bait stores, and sanctuary or educational organizations to ask if I could sample their amphibian collections. My research built on the 2008 work of Angela Picco, who sampled for the amphibian chytrid in Arizona bait shops. I found that amphibian owners were often hesitant and unwilling to participate in this research opportunity. There are multiple reasons for this hesitancy including a fear of increased regulation, the potential for reporting to a government agency (USDA), or the eventual cessation of amphibian trade. The lack of willing participants suggests there may be difficulties in coordinating future sampling efforts for Bd and Bsal.

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Date Created
  • 2018-05

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A Comparative Study of the Institutional Priorities of the Arizona-Sonora Desert Museum and the Phoenix Zoo

Description

Today, some modern zoos, aquariums, and similar animal-exhibiting institutions continue to shift their priorities toward a focus on the conservation of wildlife. Conservation challenges span a broad subject area. The

Today, some modern zoos, aquariums, and similar animal-exhibiting institutions continue to shift their priorities toward a focus on the conservation of wildlife. Conservation challenges span a broad subject area. The focus that any institution chooses can vary greatly in terms of magnitude and measures of significance. Many modern zoos often choose to make global conservation a central institutional priority: conservation of biodiversity, habitat protection, species extinction, and more. Some institutions, however, set conservation priorities on a smaller scale, focusing on contributions that have a more indirect effect on wild species and habitats, such as the welfare of populations in captivity, raising public awareness of conservation missions, and conservation education. By comparing the institutional priorities of two organizations within the Association of Zoos and Aquariums (AZA), the Arizona-Sonora Desert Museum and the Phoenix Zoo, I explore how each institution manages its living collections and works toward its respective conservation mission. I interviewed members of each institution and analyzed the similarities and differences between the organizations based on their management of living collections, and how different mission statements might shape their work. This included investigating the focus each institution has on animal welfare, in situ and ex situ conservation, and maintaining public interest. This also required defining what conservation and welfare mean to each institution and how that affects the management of their living collections. From a literature review and interviews with representatives from each institution, I was able to determine that despite any differences in style or in the language of respective mission statements, each institution prioritizes connecting the public and conservation of biodiversity. While they employ different approaches - one institution takes a regional interest in the Sonoran Desert ecosystem and landscape; the other takes a more global approach to its experiences, exhibits, and collections - the core values and ultimately the vision remain the same. Conservation may serve as the primary motivator for both the Museum and the Zoo, but my thesis is that this rationale could not be realized by itself for these institutions. Rather, conservation as a core value relies upon the support of other critical institutional priorities working together. In this way animal welfare, public engagement, and conservation relate to one another as institutional values and create the impact that the zoo and museum have on their local communities, as well as on conservation as a whole.

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Date Created
  • 2021-05

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The Impacts of Conservation Practices on Indigenous Populations

Description

Conservation is a complicated entity consisting of a multitude of professional fields including social issues, cultural issues, and physical science. This thesis evaluates the positive and negative aspects of two

Conservation is a complicated entity consisting of a multitude of professional fields including social issues, cultural issues, and physical science. This thesis evaluates the positive and negative aspects of two broad types of conservation: top down fortress conservation and bottom up community-based conservation. Fortress conservation has many negative aspects, such as displacing human communities and preventing utilization of resources. However, it also has positive aspects, such as preventing the destruction of delicate ecosystems and slowing down extinctions. Community-based conservation is more inclusive and focuses on including the indigenous populations located within the proposed conservation site in the decision-making process. Its negatives include having an anthropocentric goal instead of valuing nature's intrinsic values. Understanding the differences inherent in these two methods is necessary in order to implement a conservation network with the highest chance for success.

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Date Created
  • 2014-05

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Analysis of Global Variance of the Thermal Maxima of an Amphibian Pathogen

Description

Batrachochytrium dendrobatidis (Bd), the amphibian chytrid fungus causing chytridiomycosis, is the cause of massive amphibian die-offs. As with any host-pathogen relationship, it is paramount to understand the growth and reproduction

Batrachochytrium dendrobatidis (Bd), the amphibian chytrid fungus causing chytridiomycosis, is the cause of massive amphibian die-offs. As with any host-pathogen relationship, it is paramount to understand the growth and reproduction of the pathogen that causes an infectious disease outbreak. The life-cycle of the pathogen, Bd, is strongly influenced by temperature; however, previous research has focused on Bd isolated from limited geographic ranges, and may not be representative of Bd on a global scale. My research examines the relationship between Bd and temperature on the global level to determine the actual thermal maximum of Bd. Six isolates of Bd, from three continents, were incubated at a temperature within the thermal range (21°C) and a temperature higher than the optimal thermal range (27°C). Temperature affected the growth and zoosporangium size of all six isolates of Bd. All six isolates had proliferative growth at 21°C, but at 27°C the amount and quality of growth varied per isolate. My results demonstrate that each Bd isolate has a different response to temperature, and the thermal maximum for growth varies with each isolate. Further understanding of the difference in isolate response to temperature can lead to a better understanding of Bd pathogen dynamics, as well as allow us the ability to identify susceptible hosts and environments before an outbreak.

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Date Created
  • 2016-12

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Testing a novel method of viral inactivation of a lethal amphibian pathogen

Description

The amphibian pathogen Ambystoma Tigrinum Virus (ATV) has been an important topic of study within the amphibian community since its discovery. ATV threatens many salamander populations across the US, including

The amphibian pathogen Ambystoma Tigrinum Virus (ATV) has been an important topic of study within the amphibian community since its discovery. ATV threatens many salamander populations across the US, including those in east-central and southeast Arizona. These populations remain at risk since there are no treatments available. In this thesis, a novel method of inactivation is tested to produce a vaccine with the aim of safely eliciting an immune response within the salamander host. This novel form of inactivation has been tested on several human pathogens but has yet to be used on amphibian pathogens. It has the potential to revolutionize our traditional approach to inactivating viruses. After laser treatment, viral plaque assays suggested that inactivated ATV ceased to grow completely, pointing to the possibility of creating a vaccine. Animal challenge trials were conducted with 60 juvenile Ambystoma tigrinum, but surprisingly there was no protective effect from viral inactivation. Further study is needed to clarify why in vitro and in vivo tests of viral inactivation produced contradictory results.

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Date Created
  • 2019-05

Considering the Social Context of Exhibit Design History

Description

As zoos’ goals, designers’ values, and guests’ expectations change, so do the structures seen at the zoo. Exhibit history is not clear cut, and – despite what some may claim

As zoos’ goals, designers’ values, and guests’ expectations change, so do the structures seen at the zoo. Exhibit history is not clear cut, and – despite what some may claim – is not inherently linear. Exhibit strategies develop as a result of tensions, both social and operational, imposed from both inside and outside of zoos. This literature review examines the history of zoo architecture by defining six design periods and considering the lenses of race, class, and nature.

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Date Created
  • 2021-05

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A Fungal Pathogen of Amphibians, Batrachochytrium dendrobatidis, Attenuates in Pathogenicity with In Vitro Passages

Description

Laboratory investigations into the amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), have accelerated recently, given the pathogen’s role in causing the global decline and extinction of amphibians. Studies in which host

Laboratory investigations into the amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), have accelerated recently, given the pathogen’s role in causing the global decline and extinction of amphibians. Studies in which host animals were exposed to Bd have largely assumed that lab-maintained pathogen cultures retained the infective and pathogenic properties of wild isolates. Attenuated pathogenicity is common in artificially maintained cultures of other pathogenic fungi, but to date, it is unknown whether, and to what degree, Bd might change in culture. We compared zoospore production over time in two samples of a single Bd isolate having different passage histories: one maintained in artificial media for more than six years (JEL427-P39), and one recently thawed from cryopreserved stock (JEL427-P9). In a common garden experiment, we then exposed two different amphibian species, Eleutherodactylus coqui and Atelopus zeteki, to both cultures to test whether Bd attenuates in pathogenicity with in vitro passages. The culture with the shorter passage history, JEL427-P9, had significantly greater zoospore densities over time compared to JEL427-P39. This difference in zoospore production was associated with a difference in pathogenicity for a susceptible amphibian species, indicating that fecundity may be an important virulence factor for Bd. In the 130-day experiment, Atelopus zeteki frogs exposed to the JEL427-P9 culture experienced higher average infection intensity and 100% mortality, compared with 60% mortality for frogs exposed to JEL427-P39. This effect was not observed with Eleutherodactylus coqui, which was able to clear infection. We hypothesize that the differences in phenotypic performance observed with Atelopus zeteki are rooted in changes of the Bd genome. Future investigations enabled by this study will focus on the underlying mechanisms of Bd pathogenicity.

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Date Created
  • 2013-10-10