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    EVALUATION OF A NOVEL DETECTION METHOD FOR RANAVIRUS INWATER SAMPLES FROM PINE MOUNTAIN WILDLIFE MANAGEMENT

    AREA, LETCHER COUNTY KENTUCKY

    By:

    Matthew R. Pettus

    Thesis Approved:

    Chair, Advisory Committee

    Member, Advisory Committee

    Member, Advisory Committee

    Dean, Graduate School

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    STATEMENT OF PERMISSION TO USE

    In presenting this thesis in partial fulfillment of the requirements for aMaster's degree at Eastern Kentucky University, I agree that the Library shall

    make it available to borrowers under rules of the Library. Brief quotations from this

    thesis are allowable without special permission, provided that accurateacknowledgment of the source is made.

    Permission for extensive quotation from or reproduction of this thesis may begranted by my major professor, or in his absence, by the Head of Interlibrary

    Services when, in the opinion of either, the proposed use of the material is forscholarly purposes. Any copying or use of the material in this thesis for financial gain

    shall not be allowed without my written permission.

    Signature _____________________________________

    Date _________________________________________

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    EVALUATION OF A NOVEL DETECTION METHOD FOR RANAVIRUS INWATER SAMPLES FROM PINE MOUNTAIN WILDLIFE MANAGEMENT

    AREA, LETCHER COUNTY KENTUCKY

    By:

    Matthew R. Pettus

    Bachelors of ScienceElmhurst CollegeElmhurst Illinois

    2006

    Submitted to the Faculty of the Graduate School ofEastern Kentucky University

    in partial fulfillment of the requirementsfor the degree of

    MASTER OF SCIENCEApril, 2010

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    ii

    DEDICATION

    This thesis is dedicated to my parents, Robert and Debbie Pettus. Without their

    help this thesis would never have been completed. To my father, you have

    always been there to support me. I thank you from the bottom of my heart. To

    my mother, without the lessons you taught me I would not be here. Little woman,

    you will always be loved and missed. You both have made me who I am, thank

    you.

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    iii

    ACKNOWLEGDEMENTS

    I would like to thank my advisor and graduate committee chair, Dr. Paul Cupp.

    Your knowledge and resources have helped make this project work. I would like

    to thank my co-committee chair Dr. Marcia Pierce for all the long hours and

    countless times you have stepped in to remedy my research woes. Also, for all

    your help in getting this thesis written and ready for review. Dr. Stephen Richter

    thank you for the use of your lab, as well as always making me feel welcome

    even though I wasnt part of your lab. Finally, Id like to say thank you to all of the

    graduate students. This would have been an impossible road without your

    camaraderie.

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    iv

    ABSTRACT

    Throughout the world amphibian populations have declined over the last

    ten years. Many factors have been implicated, yet emerging diseases are

    currently having the largest effects on amphibian populations. This research was

    intended to develop a protocol using water samples to detect Ranavirus, a

    recently emerging infectious agent, from environmental water samples at Pine

    Mountain Wildlife Management Area in Letcher County, Kentucky. Ranaviruses

    are dsDNA viruses that have been implicated in localized amphibian declines.

    Possible reservoirs for Ranaviruses include adult amphibians, reptiles, and

    fishes. Direct transmission has been well documented and indirect transmission

    is highly possible. Centrifugal filters were used to concentrate water samples

    from a volume of 15 ml down to 200 l. PCR was performed on the concentrated

    water samples and PCR products were separated using 1% agarose gel

    electrophoresis. Tissue samples from animals living in each pond were also

    taken for comparison to the water samples. Total samples obtained included 38

    water samples and 98 tissue samples. All of the samples tested negative for

    Ranavirus. To determine the lowest concentration of virus detectable by this

    novel system, double distilled water (ddH2O) and pond water was seeded with

    Ranavirus at a known concentration. This system could detect 13.3 PFU/l in

    ddH2O and 106.4 PFU/l in pond water. While there may have been several

    factors involved in this result, it is most likely that during the sampling period

    Ranaviruswas not present in the Pine Mountain Wildlife Management Area.

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    v

    TABLE OF CONTENTS

    CHAPTER Page

    INTRODUCTION.................................................................................................. 1

    Ranavirus Characteristics.................................................................... 3

    Viral Reservoirs ................................................................................... 6

    Possible Amphibian Reservoirs ................................................. 6

    Non-Amphibian Reservoirs........................................................ 7

    Ranavirus Transmission ..................................................................... 7

    Sampling............................................................................................. 9

    II.METHODS....................................................................................................... 11

    Field Sampling................................................................................... 11

    Laboratory Data Collection ................................................................ 12

    Lowest Detectable level of Virus.............................................. 12

    DNA Extraction from Water and Tissue Samples .................... 13

    Amplification of DNA................................................................ 14

    III. RESULTS...................................................................................................... 15

    Controls ............................................................................................. 15

    Lowest Detectable Level of Virus....................................................... 15

    Water Samples .................................................................................. 15

    Tissue Samples ................................................................................. 16

    IV. DISCUSSION................................................................................................ 17

    LITERATURE CITED ......................................................................................... 24

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    APPENDIX.. ................................................. 31

    VITA ................................................................................................................... 38

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    LIST OF TABLES

    TABLE

    1. Latitude and longitude of ponds with and

    without recorded die-offs and parkingplaces close to the ponds.............................................................................. 33

    2. The pond number, species collected, andthe collection number of the samples fromJuly 10, 2008 ................................................................................................ 34

    3. The pond number, species collected, andthe collection number of the samples fromJuly 25, 2008 ................................................................................................ 35

    4. The pond number, species collected, andthe collection number of the samples fromAugust 8, 2008 .............................................................................................. 36

    5. The pond number, species collected, andthe collection number of the samples fromAugust 26, 2008 ............................................................................................ 36

    6. The pond number, species collected, andthe collection number of the samples fromSeptember 11, 2008 ...................................................................................... 37

    7. The pond number, species collected, andthe collection number of the samples fromSeptember 28, 2008 ....................................................................................... 37

    8. The pond number, species collected, andthe collection number of the samples fromOctober 9, 2008.............................................................................................. 38

    9. The pond number, species collected, andthe collection number of the samples fromOctober 23, 2008.......................................................................................... 38

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    viii

    LIST OF FIGURES

    FIGURE

    1. Lowest detectable level of virus in water samples using

    20l, 10l, 5l, and 2.5l of Ranavirusstock virus ........................................ 16

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    1

    Chapter I

    Introduction

    Amphibians are the most threatened vertebrate class, more so than

    eitherbirds or mammals (Gascon et al. 2007). There are 1856 endangered or

    threatened species of amphibians; approximately 32% of amphibians are

    globally threatened, as compared to 12% of birds and 23% of mammals

    (Gascon et al. 2007). At least 2468 amphibian species (43.2%) are

    experiencing some form of population decrease, whereas

    28 species (0.5%)

    are increasing and only 1552 species (27.2%) are stable. Currently, 1661 or

    29.1% of amphibian species have an unknown trend (Gascon et al. 2007).

    In the last decade, global amphibian population declines have steadily

    gained more attention (Blaustein and Wake 1990). Many causes have been

    proposed for this decline including increases in UV radiation (Broomhall et al.

    2000), introduced species (Adams et al. 1999), and emerging infectious

    disease (Daszak et al. 2003; Collins and Storfer 2003; Wake and Vredenburg

    2008). While each of these is important, emerging infectious disease (EID)

    has been implicated in single and multiple population die offs and is of

    increasing importance each year (Jancovich et al. 2003; Daszak et al. 1999;

    Carey et al. 2003). Declines have been increasingly seen in pristine areas

    with little disturbance (Lips et al. 2003). EIDs have been found in both

    pristine and impacted areas, and as the presence of these diseases increase

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    we will see far-reaching consequences in our amphibian populations (Lips et

    al. 2003; Jancovich et al. 2003).

    Emergent infectious diseases are defined as diseases that are

    expanding their range, taking on new hosts, or are newly discovered (Daszak

    et al. 1999). There are two main emerging diseases implicated in the decline

    of amphibian populations: chytrid fungus and Iridovirusinfections.

    Chytridiomycosis is a fungal disease caused by Batrachochytrium

    dendrobatidis, which was first described in 1998 (Berger et al. 1998). This

    fungus attacks keratinized tissue including several skin layers in adult

    amphibians and the mouth parts of larval amphibians. Three hypotheses

    have been proposed to explain the death of amphibians infected with chytrid

    fungus: damage to the skin reduces the ability of amphibians to cutaneously

    breathe and/or osmoregulate; there is a release of fungal toxins that are

    absorbed; or a combination of these events occur (Berger et al. 1998, Pessier

    et al. 1999). Often highly virulent pathogens are dependent on the host

    density and as the pathogen suppresses the host population, transmission

    stops. This allows the host population to rebound (Anderson and May 1986;

    Dobson and May 1986). This does not appear to be the case with chytrid.

    The amphibian larval stages have been shown to live on after the death of the

    adults, implying that the larvae may be reservoir hosts (Daszak et al. 2000).

    This may allow chytrid to remain in reduced amphibian populations. In

    addition, chytrid can live as a saprophyte, or survive on decaying matter,

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    which may explain the lack of recolonization after amphibian die offs (Lips

    1998; Lips 1999).

    The second group of pathogens implicated in amphibian declines is the

    Iridoviruses. Unlike chytrid fungus, the Iridoviruses are not a single species.

    They are a group of viruses that infect fish, salamanders, frogs, and reptiles

    (Mao et al. 1999, Johnson et al. 2008, Gray et al. 2009, Ariel et al. 2009).

    Those affecting amphibians are in the genus Ranavirus. Several ranaviruses

    are common in amphibians and mortalities have been reported at all latitudes,

    and in most major families of anurans and urodeles (Carey et al. 2003;

    Daszak et al.2003).

    RanavirusCharacteristics

    Ranaviruses were first isolated by Granoff et al. (1965) from Lithobates

    pipiens. Ranaviruses are in the family Iridoviridae (Eaton et al. 2007).

    Iridoviridae contains 5 genera. The Iridoviruses and Chloridoviruses infect

    invertebrates. The Ranaviruses, Megalocystiviruses, and Lymphocystiviruses

    infect vertebrates (Chinchar et al. 2009).

    Ranaviruses have a diameter of 160-200 nm and have a linear

    double-stranded (ds) DNA genome (Fauquet et al. 2005, Williams et al.

    2005). Their nucleoprotein core is made up of a single coiled filament 10 nm

    wide. The capsid symmetry is skewed with a T=133 or 147. The unit

    genome size is ~105 kbp with a G+C content of ~54% (Fauquet et al. 2005).

    Ranaviruses have a distinctive icosahedral shape that is often visible in the

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    cytoplasm of infected cells in electron microscope images (Chinchar and

    Hyatt 2008). The genome encodes for 100 gene products with several genes

    thought to increase virulence and help in evasion of the host immune

    response (Chinchar 2002, Chinchar et al. 2009). The viral infection and

    immune response can be so overwhelming that cellular death can occur

    within hours of infection (Chinchar et al. 2003; Williams et al. 2005).

    Ranaviruses are known to infect anurans, urodeles, reptiles, and bony

    fish (Mao et al. 1997, Williams et al. 2005). Three species of Ranavirusare

    known to infect amphibians. These are Frog Virus 3 (FV3), Bohle iridovirus

    (BIV), and Ambystoma tigrinumvirus (ATV) (Chinchar et al. 2005). The major

    capsid protein (MCP) of these viruses make up approximately half the virus

    weight and is highly conserved (Hyatt et al. 2000).

    The major capsid protein (MCP) is an area that has been studied

    extensively (Mao et al. 1999). While Hyatt et al. (2000) found that the MCP is

    highly conserved there is still variation amongst isolated viruses. The genetic

    variation in the MCP of ATV shows geographic differences (Ridenhour and

    Storfer 2008), while FV3 seems to be more genetically conserved over its

    geographic range (Schock et al. 2008). Despite this variation, Mao e al.

    (1997) found that primers created for FV3 were able to adhere to nine wild

    strain iridoviruses and that those strains were more closely related to FV3

    than other iridoviruses. To this day the MCP remains one of the most

    commonly used genes in identifying ranaviruses.

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    Viral Reservoirs

    Possible Amphibian Reservoirs

    Amphibians are a likely reservoir for the ranaviruses. Due to the

    biphasic life cycle in amphibians it is possible that reservoirs are both aquatic

    and terrestrial. In aquatic environments it is probable that species with larva

    that mature in >1 season, have incomplete metamorphosis, and/or are highly

    aquatic adults are the most likely reservoirs (Gray et al. 2009). Gray et al.

    (2007) reported that 57% of overwintering tadpoles of Lithobates catesbeiana

    were infected with Ranavirus. Many individuals of overwintering tadpoles do

    not show physical signs of infection (Miller et al. 2009). This trend has also

    been shown in Desmognathus quadramaculatus(Gray et al. 2009). Because

    of this, both larval and adult amphibians may help Ranaviruspersist in the

    environment (Duffus et al. 2008)

    In situations where amphibian larvae do not over winter, adults may

    remain as a reservoir for Ranavirus. Sub-lethal infections in tadpoles have

    been shown to continue after metamorphosis (Ariel et al. 2009). Brunner et

    al. (2004) was able to show that ATV-infected Ambystoma tigrinumcould

    survive through metamorphosis and that 7% of returning salamanders the

    following year were infected with ATV. In the late 1990s, Jancovich et al.

    (1997) hypothesized that tadpoles and asymptomatic adults act as the

    reservoir for Ranavirus. As more research has come to light, it appears that

    pre- and post-metamorphic amphibians are likely to be the preeminent

    reservoirs for Ranavirus.

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    2006). Skin contact of one second between an infected animal and an

    uninfected animal has been shown to cause disease (Brunner et al. 2007).

    Many amphibians are cannibalistic (Alford 1999, Rosen 2007, Pizzatto and

    Shine 2008). Cannibalism may be the consumption of any life stage including

    eggs, which Ranavirusalso has been found to infect (Tweedell and Granoff

    1968, Alford 1999). Studies have shown that predation on infected

    individuals can led to infection (Harp and Petranka 2006, Brunner et al. 2007).

    Those species that have cannibalistic phenotypes may exhibit a lower

    occurrence of this phenotype due to poor survivorship (Pfennig et al. 1991).

    Indirect transmission is infection caused by virus circulating through

    the environment. This can be through the water or through soil. Salamander

    larvae exposed to ATV-infected individuals, but without direct contact, have

    become infected (Greer et al. 2008). Harp and Petranka (2006) were able to

    induce infection by exposing Lithobates sylvaticusto sediment from an active

    natural die-off. These studies suggest that Ranavirusthat is shed into the

    surrounding environment can infect new hosts. For indirect transmission to

    occur, Ranavirusmust be able to persist in the environment. However, this

    aspect of Ranavirusecology is not well understood. Jancovich et al. (1997)

    showed that ATV could persist for up to 2 weeks. However, this may be

    contingent on some level of moisture being present. Brunner et al. (2007)

    found that sediment that was inoculated with ATV and then dried for four days

    did not cause infection, while soil inoculated and kept moist caused 87%

    mortality in salamanders. The length of viability is unknown for ranaviruses,

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    during or after die-offs cannot aid us in understanding transmission or sub-

    lethal infections.

    Recently, a non-lethal method of sampling has been developed. St.

    Amour and Lesbarreres (2007) have been able to detect the Ranavirusin toe

    clippings. This has allowed investigators to determine the presence or

    absence of the Ranavirusin field samples and determine if lab raised animals

    are free of Ranavirus. Since the results are a positive or negative for the

    presence of Ranavirusand animals need to be caught, restrained, and toes

    removed, a faster method is possible.

    The purpose of my research is the detection of Ranavirusin Kentucky

    ponds using a water based non-lethal system. I plan to use this method as a

    quick and effective means to identify the presence of infection, and hopefully

    provide a tool for continued research into indirect transmission of ranaviruses.

    My novel detection method using water samples will be compared to tissue

    samples processed using the St. Amour and Lesbarreres (2007) protocols.

    Water samples will allow quick field sampling and reduce the overall cost of

    sampling, while maintaining the speed and reliability of PCR-based detection

    methods.

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    Chapter II

    Materials and Methods

    Sampling was done at Pine Mountain Wildlife Management Area

    (PMWMA). This management area is one of Kentuckys last contiguous and

    least disrupted forests. It is comprised of 4,849 acres located in the far

    southeast corner of Kentucky in Letcher and Harlan counties. In 2002, more

    than 50 ponds were built by Kentucky Department of Fish and Wildlife as

    wildlife watering holes. When these ponds were monitored in 2004 and 2007

    for amphibian populations it was found that there were active die-offs at

    several ponds.

    For this study, ponds were selected from the 20 best amphibian ponds

    at PMWMA (J. MacGregor, personal communication, August 30 2008). Of

    these 20 ponds, 11 had no previous die-offs and the remaining 9 had

    recorded die-offs suspected to be from Ranavirusbut that were never verified

    (J. MacGregor, personal communication, May 16 2008). Prior to entering the

    field, 5 ponds were randomly selected from each of these two groups. These

    ten ponds became the sampled ponds.

    Field Sampling

    At each pond, water and tissue samples were taken. Water samples

    were collected from July 10, 2008 to October 23, 2008 at two week intervals.

    Samples were taken at approximately 75 mm under the surface of the pond at

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    the edges where amphibian adults and larvae were often seen. Water

    samples consisted of 45 ml of pond water in a 50 ml plastic test tube. These

    water samples were immediately placed on ice for transport to the laboratory.

    Animals were obtained using a dip net. Tissue samples were taken from

    adults, larvae, and eggs. Tissue samples were obtained from adults by

    removing the third phalanx at the second joint with a pair of suture scissors.

    The toe was immediately placed in 1 ml tubes containing 100% ethanol and

    placed on ice. Tissue samples from larvae were obtained by tail clipping.

    Approximately 2 cm of the distal tail tip were cut using suture scissors. The

    samples were placed in 1ml tubes containing 100% ethanol and placed on

    ice. While the traditional means of sampling larvae is tissue homogenation,

    tail clippings have been used in many amphibian orders to test for Ranavirus

    (St. Amour and Lesberreres 2007). Eggs were sampled by excising 3 to 4

    eggs from the egg mass. Eggs were placed directly in 1 ml tubes containing

    100% ethanol and placed on ice for transport to the laboratory.

    Processing Samples in the Laboratory

    Minimum Ranavirus Detectable Concentrations

    A consistent control volume was needed for each following experiment.

    A volume of 20 l was chosen because it was a volume that consistently

    produced PCR products that were detected and was easily visible on gel

    electrophoresis. These controls were at a concentration of 106.4 plaque

    forming units (PFU)/l.

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    Double distilled water was used to produce viral dilutions, which were

    then used to determine the lowest concentration detectable by the water

    testing method. Stock Ranaviruswas obtained from ATCC (Manassas, VA)

    at a concentration of 8 x 107 PFU/ml. Double distilled water was seeded with

    20 l, 10 l, 5 l, 2.5 l, 1.25 l, 0.625 l, and 0.3125l to create a total

    volume was 15 ml. Concentrations of Ranaviruswere 106.4 PFU/l, 53.2

    PFU/l, 26.6 PFU/l, 13.3 PFU/l, 6.65 PFU/l, 3.325 PFU/l, and 1.662

    PFU/l respectively. The 15 ml sample was then pipetted into an Amicon 15

    filter unit (Millipore; Billerica, MA) with a pore size of 3 kDa. The Amicon Ultra

    15 centrifugal filter units containing the water samples were centrifuged until

    the volume was reduced to 200 l. Using the reduced volume of 200 l, a

    DNA extraction was performed using a MiniElute Virus Spin Kit(Qiagen;

    Valencia, CA).

    DNA Extraction from Water and Tissue Samples

    Pond water samples were vortexed to homogenize the contents. The

    maximum volume of water an Amicon 15 can process is 15 ml. Therefore,

    sub-samples of 15 ml were taken from each 45 ml sample. These were pre-

    filtered using a 0.45 micron syringe filter (Corning; Corning NY) to remove

    bacteria, detritus, and other debris. The filtrate was then placed in an Amicon

    15 filtration unit. Each Amicon 15 was centrifuged until the volume was

    reduced to 200 l. DNA extraction was done using the MiniElute Virus Spin

    Kit(Qiagen; Valencia, CA).

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    DNA extractions from tissue samples were done using a DNeasy

    Blood and Tissuekit (Qiagen; Valencia, CA).

    Amplification of DNA

    Forward and reverse primers for the MCP developed by Mao et al.

    (1996) were used to detect the presence of Ranavirusthrough PCR. PCR

    conditions during amplification followed protocols described in Mao et al.

    (1996). Reactions were incubated for 5 minutes at 94C followed by 28

    cycles consisting of 94C for 1 minute, 45C for 2 minutes, 55C for 3 minutes,

    and a single cycle of 55C for 5 minutes. Gel electrophoresis was performed

    using 1% agarose gels (50 ml volume). Each gel was produced using 45ml

    distilled water, 5 ml of 10X TAE buffer, and 0.5g agarose. Samples were

    prepared for electrophoresis by adding a 10 l aliquot of each PCR product

    sample to 6.7 l distilled water and 3.3 l orange buffer (Invitrogen; Carlsbad,

    CA). Samples were vortexed and 10 l of each were pipetted in a single lane

    on the gel. 5 l of a 100 bp ladder was placed in the first and last wells of

    each gel. Gels were electrophoresed at 100 volts and stained with ethidium

    bromide (0.02%) before examination using a UV light box.

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    Chapter III

    Results

    Controls

    Initial testing determined Ranaviruscould be recovered from ddH2O

    samples at 53.2 PFU/l, 106.4PFU/l, 159.6PFU/l, and 266.0PFU/l. A

    consistent control volume was needed for each following experiment. These

    controls each contained 106.4 PFU/l.

    Lowest Concentration of RanavirusDetected

    The sample of 2.5l was the lowest volume visible on gel

    electrophoresis (Figure 1). The 2.5l of Ranavirusin 15ml distilled water was

    a concentration of 13.3 PFU/l.

    To determine the lowest detectable concentration in pond water, pond

    water samples were seeded to concentrations of 266 PFU/l, 106.4 PFU/l,

    53.2 PFU/l, 26.6 PFU/l, and 13.3 PFU/l. The lowest concentration that

    had PCR products detectable by electrophoresis was 106.4 PFU/l.

    Water Samples

    A total of 38 water samples were taken from 10 ponds at PMWMA.

    Ranaviruswas not detected in any environmental sample at PMWMA.

    Six randomly selected environment samples from PMWMA were seeded with

    virus stock solution at 106.4 PFU/l to determine if there were PCR inhibitors

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    present in the water samples. Of these samples, four were visible after gel

    electrophoresis. PCR and gel electrophoresis were attempted twice more on

    the samples that tested negative. These samples in subsequent tests

    continued to test negative.

    Figure 1. Lowest detectable level of virus in water samples using 20l, 10l,5l, 2.5l of Ranavirusstock virus (8 x 107 PFU/ml). L-DNA Ladder,E-Empty Lane

    Tissue Samples

    A total of 90 tissue samples were taken from the experimental

    ponds at PMWMA. No evidence of Ranavirusinfection were found in any

    tissue samples collected at PMWMA.

    L E E E E 2.5l 5l 10l20l L

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    Chapter IV

    Discussion

    I was able to create a novel protocol for the detection of Ranavirusin

    both seeded ddH20 and seeded pond water that is non-destructive. This

    method differs from other water sampling protocols for emerging infectious

    diseases (EID) in that it uses lower water sample volumes (see Krishtein et al.

    2007). The goal for this novel detection method was to be used to detect

    Ranavirusin small ephemeral ponds where the volume of water can be very

    low, amphibian larval densities can be high, and Ranavirusinfection is

    common. However, we were unable to detect Ranavirusin any

    environmental water samples, so more research needs to be conducted to

    further develop this method for use in the field.

    This is the first attempt to create a water based sampling method for

    the detection of Ranavirus. However, water sampling has been used to

    detect other EIDs. Kirshtein et al. (2007) proposed a sampling protocol for

    the detection of Batrachochytrium dendrobatidisin water and sediment.

    Using 0.2 m filters and sampling between 64 l and 50 ml, they were able to

    detect as little as 0.06 zoospores, or 10 copies of DNA. However, the lowest

    concentration detectable in 50 ml of water was 30 zoospores per liter. The

    protocol proposed for Ranavirusdetection in this paper uses lower volumes of

    water, samples were filtered after collection from the field, and isolates a

    smaller causative agent. The use of smaller water volumes may have caused

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    an increase in false negative results. Samples were collected in the field and

    put on ice until they could be returned to the lab for processing. This reduced

    the amount of equipment and time needed to sample. Ranaviruses are

    between 160-200 nm in size; because of their small size they are difficult to

    filter out of water. The Amicon 15 (Millipor; Billerica, MA) was selected

    because it had the ability to retain Ranavirusabove the filter and was easily

    used in the lab, however it is limited to a 15 ml sample size. In future studies

    using similar protocols for water sampling, it may be necessary to filter

    multiple sub-samples of 15 ml through a single filter to reduce the chance of

    false negative results. My goal was to keep the field sampling quick and the

    laboratory work simple and thereby keep the cost, both in time and money

    low, however using this system I was unable to detect Ranavirusin any

    environmental water samples.

    For water sampling to work an EID must be able to persist in the

    environment. While this is not well established for Ranavirus, Brunner et al.

    (2007) and Jancovich et al. (1997) showed Ranavirusinfections could be

    initiated through inoculated sediment. Harp and Petranka (2006) also

    showed that Ranaviruscould be transmitted through water between

    Lithobates sylvaticatadpoles without contact. The novel detection method

    presented here also anecdotally supports that Ranaviruscan be detected in

    water, though only in seeded samples.

    Ranaviruswas detected in concentrations as low as 13.3 PFU per l in

    ddH2O and 106.4PFU per l in pond water, or13.3 x 103 PFU ml-1 and 10.6 x

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    10 4 PFU ml-1respectively. The concentration of Ranavirusthat is biologically

    significant is not known. However, Rojas et al. (2005) used a laboratory study

    to suggest that an environmentally relevant concentration of Ranavirusvirions

    in water inhabited with infected salamanders may be between 103 to 104 PFU

    ml-1. The concentrations detected by my novel detection method in pond

    water falls just above the projected biologically significant concentrations of

    Ranavirus. It may be possible to reduce the lowest detectable volume by

    adjusting PCR parameters, and reducing the chance of inhibitors in the pond

    water. Inhibitors in the water are a possible problem with this system.

    When six randomly selected samples of pond water were seeded with

    20 l ofRanavirusat 8 x 107 PFU/ml, then filtered and processed normally,

    only four tested positive for Ranavirus. This could lead to a high level of false

    negatives. If Ranaviruswas present in these samples it is possible that the

    primers do not adhere well to the wild strain of Ranaviruspresent at PMWMA.

    However, this is a highly conserved region. Mao et al. 1997 tested nine

    Iridovirus wild strains and was able to detect each of them using these

    primers. In subsequent tests, positive results were not consistent and the

    lowest detectable level of Ranavirusfluctuated. This may indicate that there

    are PCR inhibitors in the water samples. However, more field research is

    necessary to determine if these projected concentrations are indeed

    biologically significant and whether or not inhibitors in the water are affecting

    the lowest concentration detectable in pond water samples.

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    The prevalence of Ranavirusin known infected areas has been

    studied. In China, Ranaviruswas found to infect 5.7% of adults and 42.5% of

    larva of Rana dybowskii(Xu et al. 2010). Gray et al. (2007) found that

    between 15% and 40% of Rana clamitanstadpoles were infected with

    Ranavirusdepending on time of the year and whether there was cattle access

    to the wetland. These high percentages of infected animals were not found in

    sampling sites at PMWMA. There may be several explanations for these

    results. First, it is possible that sublethally infected animals tested negative

    due to reduced levels of Ranaviruswithin their tissues. Brunner et al. (2007)

    found that Ambystoma tigrinumlarvae that survived with sub-lethal infections

    of ATV did not always test positive. Seven of ten sublethally infected animals

    tested positive only once out of three tests. However, only a small portion of

    individuals were sub-lethally infected. While this could have reduced the total

    number of animals that tested positive it is not likely to cause all animals

    sampled to test negative. Ninety-eight animals were sampled in this study

    with most being tadpoles. With others reporting high percentages of tadpoles

    being infected (Gray et al. 2007, Xu et al. 2010) it is not probable that sub-

    lethal infections were a factor in PMWMA negative persistence of Ranavirus.

    A second possibility is that through multiple exposures to Ranavirus,

    the population at PMWMA is gaining immunity to Ranavirus. Gantress (2006)

    found that Ranaviruswas cleared from Xenopus laevismore quickly after a

    second exposure, and Majji et al. (2006) found that exposure to one

    Ranavirusgave partial immunity to other Ranaviruses. Die-offs have

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    occurred over the last six years at PMWMA (J. MacGregor, personal

    communication, August 30 2008) and may be reducing a portion of the

    susceptible adults and increasing the number of metamorphs that have

    cleared a Ranavirusinfection. It is also possible that breeding has shifted to

    reduce the presence of genes that lead to high-susceptibility to Ranavirus.

    Teacher et al. (2009) found that Ranavirushad imposed selection for

    particular haplotypes and that some amphibians were adapting to the

    presence of Ranavirus. While more research would be necessary to

    determine if this was occurring at PMWMA, it is possible that susceptible

    individuals are dying and being replaced by animals that are less susceptible.

    It is also possible that Ranaviruswas not detected at PMWMA

    because it was not present at the time of sampling. Gray et al. (2007) found

    that there was a higher percentage of infected tadpoles in the fall and winter.

    Sampling in this study was conducted from July to October. This time frame

    was chosen based on observations made at PMWMA (J. MacGregor,

    personal communication, May 16 2008). Die-offs were observed historically

    in May at PMWMA. Since sampling was done after May there is a possibility

    that the concentration of Ranavirusin the water was lower than it would have

    been if sampling was done earlier in the year. At PMWMA die-offs in wood

    frogs and green frogs were most common. Due to my later sampling it is

    possible that wood frog die-offs had already occurred and the level of

    Ranaviruspresent was reduced. In this study a large amount of green frogs

    were captured and tested without any evidence of Ranavirusbeing present.

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    In future work at PMWMA it will be necessary to sample as early as possible

    to determine if wood frog die-offs occur and whether or not there is an

    increase in Ranavirusin water samples during this time. However, it is

    possible that winter and fall infections and die-offs occur also at this location.

    The lack of Ranavirusat PMWMA may have been due to the

    misdiagnosis of the causative agent behind the die-offs that have occurred

    there. The diagnosis of the causative agent was based on a few physical

    symptoms and the fact that Ranavirushad been found in elsewhere in

    Kentucky. While only one pond in Kentucky has had confirmed amphibian

    Ranavirusdie-offs, Ranavirushas been confirmed in Terrapene carolinain

    Ohio County, Kentucky via oral swabs (J. MacGregor, personal

    communication, May 12 2009).

    A recently emerging disease exhibits similar symptoms to Ranavirus.

    Perkinsus-like disease, or Dermomycoidessp. causes lethargy, bloat, and

    hemorrhaging of the skin (Cook 2009). While these previous symptoms are

    similar to both fungal and viral EIDs, Perkinsus-like disease also causes

    erratic swimming, and Davis et al. (2007) found that they were able to hand

    catch infected animals. These symptoms have not been reported in the die-

    offs at PMWMA; however, it will be necessary to continue to sample at

    PMWMA during an active outbreak to determine definitively the causative

    agent of the die-offs.

    Another possibility is that after several drought years Ranavirusno

    longer persisted in PMWMA. Die-offs may be affected by rainfall (J.

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    MacGregor, personal communication, August 23 2007). Kentucky had lower

    than average rainfall in Letcher County in both 2006 and 2007 (Robert Watts,

    unpublished data). When sampling was done in 2008, Letcher County had

    average rainfall for the year (National Weather Service Forecast Office).

    Brunner el at. (2007) found that sediment that had dried for four days could

    not cause infection. During sampling in 2008, 7 of 10 ponds dried for some

    period of time over the sampling period, despite an average amount of

    rainfall. It is a possibility that due to the occurrence of drought over a two

    year span that Ranavirusdid not persist at PMWMA.

    While many questions about the findings of this study persist, I am

    confident that I have laid the ground work for water sampling to detect

    Ranavirus. In the future it will be necessary to further refine this sampling

    method by optimizing the PCR reaction and eliminating the possibility of

    inhibitors in the water samples. Consistent long term sampling of PMWMA

    will help to determine a base line of Ranavirusactivity in the area and

    increase the sample size of both water and tissue collected. A positive

    Ranavirusdie-off needs to be sampled to determine if Ranaviruscan be

    detected in actual environmental samples and what concentrations of

    Ranavirusare actually biologically relevant. Despite the future work needed, I

    believe that this study has begun to establish the ground work necessary to

    found a quick, inexpensive, and non-destructive testing method using water

    samples that will elucidate the ecology of Ranaviruses.

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    APPENDIX

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    Table 1. Latitude and longitude of ponds with and without previous die-offs

    and parking places close to the ponds.

    Pond #

    Latitude andLongitude for

    Parking

    Latitude andLongitude of Pond

    LocationsPrevious Die-Offs

    Documented

    52 N 57 04' 14.8'' N 57 04' 11.1'' N

    W 82 49' 10.0'' W 82 49' 08.0''

    26 N 37 02' 36.3'' N 37 02' 41.6'' N

    W 82 52' 48.0'' W 82 52' 45.8''

    23 N 37 02' 23.1'' N 37 02' 19.5'' N

    W 82 53' 04.5'' W 82 53' 04.5''

    18 N 37 01' 47.8'' N 37 01' 44.8'' N

    W 82 54' 00.4'' W 82 53' 57.6''

    13 N 37 01' 32.5'' N 37 01' 31.9'' N

    W 82 54' 49.9'' W 82 53' 49.7''

    47 N 37 03' 47.2'' N 37 03' 43.1'' Y

    W 82 50' 21.7'' W 82 50' 20.4''

    44 N 37 03' 42.6'' N 37 03' 39.6'' Y

    W 82 50' 38.3'' W 82 50' 37.6''

    40 N 37 03' 11.3'' N 37 03' 10.9'' Y

    W 82 51' 43.3'' W 82 51' 45.0''

    36 N 37 03' 04.6'' N 37 03' 02.8'' Y

    W 82 51' 57.6'' W 82 51' 01.0''

    27 N 37 02' 42.6'' N 37 02' 38.3'' Y

    W 82 52' 34.3 W 82 52' 34.3

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    Table 2. The pond number, species collected, and the collection number of

    the samples from July 10, 2008.

    Pond Number Species Sampled Collection Number

    26 N. viridescens Tail (adult) 26-1R. clamitans tail clip (Tadpole) 26-2

    R. clamitans tail clip (Tadpole) 26-3

    N. viridescens Tail (adult) 26-4

    N. viridescens Tail (adult) 26-5

    N. viridescens Tail (adult) 26-6

    13 Rana clamitans toe (Adult) 13-1

    R. clamitans tail clip (Tadpole) 13-2

    R. clamitans tail clip (Tadpole) 13-3

    Rana clamitans toe (Adult) 13-4

    36 R. clamitans tail clip (Tadpole) 36-1

    N. viridescens Tail (adult) 36-2

    R. clamitans tail clip (Tadpole) 36-3R. clamitans tail clip (Tadpole) 36-4

    40 Rana clamitans toe (Sm Adult) 40-1

    R. clamitans tail clip (Tadpole) 40-2

    R. clamitans tail clip (Tadpole) 40-3

    R. clamitans tail clip (Tadpole) 40-4

    44 Rana clamitans toe (Adult) 44-2

    Rana clamitans (Adult) 44-2

    47 Dry

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    Table 3. The pond number, species collected, and the collection number of

    the samples from July 25, 2008.

    Pond Number Species Sampled Collection Number

    52 Ambystoma sp. (larva) 52b-1Ambystoma sp. (larva) 52b-2

    Rana clamitans tail clip (Tadpole) 52b-3

    Rana clamitans tail clip (Tadpole) 52b-4

    26 Notophthalmus viridescens Tail 26b-1

    Rana clamitans toe (Sm. Meta) 26b-2

    Rana clamitans toe (Sm. Meta) 26b-3

    Rana eggs 26b-4

    23 Dry

    18 Dry

    13 Notophthalmus viridescens Tail 13b-1

    Rana clamitans toe (Adult) 13b-2

    Hyla sp. (Tadpole) 13b-327 Notophthalmus viridescens Tail 27b-1

    Rana clamitans toe (Adult) 27b-2

    36 Notophthalmus viridescens Tail 36b-1

    Rana clamitans toe (Adult)*** 36b-2Rana clamitans tail clip(Tadpole)*** 36b-3

    Rana clamitans tail clip (Meta)*** 36b-4Rana clamitans tail clip(Tadpole)*** 36b-5

    40 Notophthalmus viridescens Tail 40b-1

    Rana clamitans tail clip (Tadpole) 40b-2

    Rana clamitans toe (Sm. Meta) 40b-3

    Rana clamitans tail clip (Tadpole) 40b-444 Rana clamitans toe (Adult) 36-1

    Notophthalmus viridescens Tail 36-2

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    Table 4. The pond number, species collected, and the collection number of

    the samples from August 8, 2008.

    Pond Number Species Sampled Collection Number

    52 Ambystoma sp. 52C-1Notophthalmus viridescens 52C-2

    Rana clamitans 52C-3

    26Emerging Tads- Ranaclamitans 26C-1

    Notophthalmus viridescens 26C-2

    Rana clamitans 26C-3

    23 Rana clamitans 23C-1

    13 Rana clamitans tadpoles 13C-1

    Notophthalmus viridescens 13C-2

    27 Rana clamitans 27C-1

    Rana sylvatica 27C-2

    36 Notophthalmus viridescens 36C-1

    40 Rana clamitans tadpole 40C-1

    Notophthalmus viridescens 40C-2

    Rana clamitans tadpole 40C-3

    Rana clamitans adult 40C-4

    44 Notophthalmus viridescens 44C-1

    47 Dry

    Table 5. The pond number, species collected, and the collection number of

    the samples from August 26, 2008.

    Pond Number Species SampledCollectionNumber

    52 Bufo sp. Tadpoles 52D-1

    23 Dry

    13 Notophthalmus viridescens 13D-1

    Rana clamitans Tadpoles 13D-2

    Rana clamitans Tadpoles 13D-3

    36 Rana clamitans 36D-1

    47 Dry

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    Table 6. The pond number, species collected, and the collection number of

    the samples from September 11, 2008.

    Pond Number Species SampledCollectionNumber

    13 Rana clamitans Tadpole 13E -1

    Rana clamitans Tadpole 13E -2

    27 Rana clamitans Adult 27E -1

    36 Rana clamitans Tadpole 36E -1

    Rana clamitans Tadpole 36E -2

    47 Dry

    Table 7. The pond number, species collected, and the collection number of

    the samples from September 28, 2008.

    Pond Number Species SampledCollectionNumber

    52 Ambystoma sp. Larva 52F-1

    Ambystoma sp. Larva 52F-2

    26 Rana clamitans Tadpoles 26F-1

    Rana clamitans Tadpoles 26F-2

    Rana clamitans Tadpoles 26F-3

    18 Dry

    13 Rana clamitans Tadpoles 13F -1

    Rana clamitans Tadpoles 13F -2Rana clamitans Tadpoles 13F -3

    Rana clamitans Tadpoles 13F -4

    27 Rana clamitans Adult 27F -1

    44 Rana clamitans Adult 44F-1

    47 Dry

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    Table 8. The pond number, species collected, and the collection number of

    the samples from October 9, 2008.

    Pond Number Species SampledCollectionNumber

    52 Ambystoma sp. 52F2-1

    Ambystoma sp. 52F2-2

    26 Dry

    23 Dry

    18 Dry

    13 Rana clamitans Tadpoles 13F2 -1

    Rana clamitans Tadpoles 13F2 -2

    Rana clamitans Tadpoles 13F2 -3

    27 Rana clamitans Adult 27F2 -1

    47 Dry

    Table 9. The pond number, species collected, and the collection number of

    the samples from October 23, 2008.

    Pond Number Species SampledCollectionNumber

    13 Rana clamitans Tadpole 13G-1

    47 Dry

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    Vita

    Mathew Robert Pettus was born on January 7, 1979 to Robert and

    Debbie Pettus in St. Louis, Missouri. At age 3, he and his family moved to the

    northwest suburbs of Chicago. He went to elementary school at Central

    School, junior high school at Westfield Junior High School, and high school at

    Lake Park High School. In 1997, Matthew graduated high school and began

    a long college career. In 2006, Matthew graduated from Elmhurst College

    with a B.S. in biology. Matthew began work on a masters degree at Eastern

    Kentucky University later that year. In 2010, Matthew received his M.S.

    degree in biology from Eastern Kentucky University.