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Franziska C Sandmeier - One of the best experts on this subject based on the ideXlab platform.
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Mycoplasma agassizii an opportunistic pathogen of tortoises shows very little genetic variation across the mojave and sonoran deserts
PLOS ONE, 2021Co-Authors: Agusto Luzuriaganeira, Franziska C Sandmeier, Richard C Tracy, Chava L. Weitzman, Richard L. Tillett, Shalyn N Bauschlicher, David AlvarezponceAbstract:Mycoplasma agassizii is a common cause of upper respiratory tract disease in Mojave desert tortoises (Gopherus agassizii). So far, only two strains of this bacterium have been sequenced, and very little is known about its patterns of genetic diversity. Understanding genetic variability of this pathogen is essential to implement conservation programs for their threatened, long-lived hosts. We used next generation sequencing to explore the genomic diversity of 86 cultured samples of M. agassizii collected from mostly healthy Mojave and Sonoran desert tortoises in 2011 and 2012. All samples with enough sequencing coverage exhibited a higher similarity to M. agassizii strain PS6T (collected in Las Vegas Valley, Nevada) than to strain 723 (collected in Sanibel Island, Florida). All eight genomes with a sequencing coverage over 2x were subjected to multiple analyses to detect single-nucleotide polymorphisms (SNPs). Strikingly, even though we detected 1373 SNPs between strains PS6T and 723, we did not detect any SNP between PS6T and our eight samples. Our whole genome analyses reveal that M. agassizii strain PS6T may be present across a wide geographic extent in healthy Mojave and Sonoran desert tortoises.
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High quality draft genome sequences of Mycoplasma agassizii strains PS6 T and 723 isolated from Gopherus tortoises with upper respiratory tract disease
Standards in genomic sciences, 2018Co-Authors: David Alvarez-ponce, Franziska C Sandmeier, Chava L. Weitzman, Richard L. Tillett, C. Richard TracyAbstract:Mycoplasma agassizii is one of the known causative agents of upper respiratory tract disease (URTD) in Mojave desert tortoises (Gopherus agassizii) and in gopher tortoises (Gopherus polyphemus). We sequenced the genomes of M. agassizii strains PS6T (ATCC 700616) and 723 (ATCC 700617) isolated from the upper respiratory tract of a Mojave desert tortoise and a gopher tortoise, respectively, both with signs of URTD. The PS6T genome assembly was organized in eight scaffolds, had a total length of 1,274,972 bp, a G + C content of 28.43%, and contained 979 protein-coding genes, 13 pseudogenes and 35 RNA genes. The 723 genome assembly was organized in 40 scaffolds, had a total length of 1,211,209 bp, a G + C content of 28.34%, and contained 955 protein-coding genes, seven pseudogenes, and 35 RNA genes. Both genomes exhibit a very similar organization and very similar numbers of genes in each functional category. Pairs of orthologous genes encode proteins that are 93.57% identical on average. Homology searches identified a putative cytadhesin. These genomes will enable studies that will help understand the molecular bases of pathogenicity of this and other Mycoplasma species.
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High quality draft genome sequences of Mycoplasma agassizii strains PS6T and 723 isolated from Gopherus tortoises with upper respiratory tract disease
BMC, 2018Co-Authors: David Alvarez-ponce, Franziska C Sandmeier, Chava L. Weitzman, Richard L. Tillett, Richard C TracyAbstract:Abstract Mycoplasma agassizii is one of the known causative agents of upper respiratory tract disease (URTD) in Mojave desert tortoises (Gopherus agassizii) and in gopher tortoises (Gopherus polyphemus). We sequenced the genomes of M. agassizii strains PS6T (ATCC 700616) and 723 (ATCC 700617) isolated from the upper respiratory tract of a Mojave desert tortoise and a gopher tortoise, respectively, both with signs of URTD. The PS6T genome assembly was organized in eight scaffolds, had a total length of 1,274,972 bp, a G + C content of 28.43%, and contained 979 protein-coding genes, 13 pseudogenes and 35 RNA genes. The 723 genome assembly was organized in 40 scaffolds, had a total length of 1,211,209 bp, a G + C content of 28.34%, and contained 955 protein-coding genes, seven pseudogenes, and 35 RNA genes. Both genomes exhibit a very similar organization and very similar numbers of genes in each functional category. Pairs of orthologous genes encode proteins that are 93.57% identical on average. Homology searches identified a putative cytadhesin. These genomes will enable studies that will help understand the molecular bases of pathogenicity of this and other Mycoplasma species
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chronic disease in the mojave desert tortoise host physiology and recrudescence obscure patterns of pathogen transmission
Ecology and Evolution, 2017Co-Authors: Franziska C Sandmeier, S. A. Dupre', Ron Marlow, Nichole Maloney, David Hyde, Hossein Ali Mohammadpour, Richard C Tracy, K. W. HunterAbstract:A seminatural, factorial-design experiment was used to quantify dynamics of the pathogen Mycoplasma agassizii and upper respiratory tract disease in the Mojave desert tortoise (Gopherus agassizii) over 2 years. Groups of initially healthy animals were separated into serologically positive (seropositive), seronegative, and artificially infected groups and paired into 23 pens. We found no evidence of long-term immune protection to M. agassizii or of immunological memory. Initially seronegative, healthy tortoises experienced an equal amount of disease when paired with other seronegative groups as when paired with seropositive and artificially infected groups—suggesting that recrudescence is as significant as transmission in introducing disease in individuals in this host–pathogen system. Artificially infected groups of tortoises showed reduced levels of morbidity when paired with initially seronegative animals—suggesting either a dilution effect or a strong effect of pathogen load in this system. Physiological dynamics within the host appear to be instrumental in producing morbidity, recrudescence, and infectiousness, and thus of population-level dynamics. We suggest new avenues for studying diseases in long-lived ectothermic vertebrates and a shift in modeling such diseases.
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Prevalence and Diversity of the Upper Respiratory Pathogen Mycoplasma agassizii in Mojave Desert Tortoises (Gopherus agassizii)
Herpetologica, 2017Co-Authors: Chava L. Weitzman, Franziska C Sandmeier, C. Richard TracyAbstract:Abstract: Upper respiratory tract disease (URTD), caused by Mycoplasma agassizii, has been deemed a threat to populations of Mojave Desert Tortoises, Gopherus agassizii. Previous work on URTD has focused on serology and visual health examinations to determine the extent of this disease in some natural tortoise populations. Here, we present the first range-wide study of the presence of the pathogen, M. agassizii, in Mojave Desert Tortoises. We detected M. agassizii in tortoise populations throughout the Mojave Desert, with notable differences in prevalence of M. agassizii among sampling sites within tortoise genotypes and sampling years. Analyses of three genetic markers in the M. agassizii genome indicated very low nucleotide diversity and no relevant spatial structuring of Mycoplasma haplotypes. We use published lines of evidence to discuss the roles of rare transmission events and long-term Mycoplasmal persistence in individual hosts on tortoise URTD dynamics.
Mary B. Brown - One of the best experts on this subject based on the ideXlab platform.
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Identifying genome-wide immune gene variation underlying infectious disease in wildlife populations – a next generation sequencing approach in the gopher tortoise
BMC, 2018Co-Authors: Jean P. Elbers, Mary B. Brown, Sabrina S. TaylorAbstract:Abstract Background Infectious disease is the single greatest threat to taxa such as amphibians (chytrid fungus), bats (white nose syndrome), Tasmanian devils (devil facial tumor disease), and black-footed ferrets (canine distemper virus, plague). Although understanding the genetic basis to disease susceptibility is important for the long-term persistence of these groups, most research has been limited to major-histocompatibility and Toll-like receptor genes. To better understand the genetic basis of infectious disease susceptibility in a species of conservation concern, we sequenced all known/predicted immune response genes (i.e., the immunomes) in 16 Florida gopher tortoises, Gopherus polyphemus. All tortoises produced antibodies against Mycoplasma agassizii (an etiologic agent of infectious upper respiratory tract disease; URTD) and, at the time of sampling, either had (n = 10) or lacked (n = 6) clinical signs. Results We found several variants associated with URTD clinical status in complement and lectin genes, which may play a role in Mycoplasma immunity. Thirty-five genes deviated from neutrality according to Tajima’s D. These genes were enriched in functions relating to macromolecule and protein modifications, which are vital to immune system functioning. Conclusions These results are suggestive of genetic differences that might contribute to disease severity, a finding that is consistent with other Mycoplasmal diseases. This has implications for management because tortoises across their range may possess genetic variation associated with a more severe response to URTD. More generally: 1) this approach demonstrates that a broader consideration of immune genes is better able to identify important variants, and; 2) this data pipeline can be adopted to identify alleles associated with disease susceptibility or resistance in other taxa, and therefore provide information on a population’s risk of succumbing to disease, inform translocations to increase genetic variation for disease resistance, and help to identify potential treatments
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Detection of Mycoplasma agassizii in the Texas tortoise (Gopherus berlandieri).
Journal of wildlife diseases, 2013Co-Authors: Amanda Guthrie, C. Leann White, Mary B. Brown, Thomas W. DemaarAbstract:Mycoplasma agassizii causes upper respiratory tract disease (URTD) in Texas tortoises (Gopherus berlandieri). To determine exposure to and shedding of M. agassizii, we collected blood samples and nasal swabs from 40 free-ranging Texas tortoises on public and private lands in Texas, USA, from May to October 2009. We used an enzyme-linked immunosorbent assay (ELISA) to detect M. agassizii–specific antibodies. Eleven (28%) tortoises were antibody positive, three (8%) were suspect, and the remaining 26 (65%) were negative. Nasal lavage samples were collected from 35 of the 40 tortoises for M. agassizii culture and PCR to detect shedding of M. agassizii. Current infection with M. agassizii was confirmed in one tortoise that had mild clinical signs of URTD and was positive by ELISA (antibody titer >512), PCR, and culture. The clinical isolate was confirmed as M. agassizii by restriction fragment length polymorphism and immunobinding.
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Mycoplasma agassizii strain variation and distinct host antibody responses explain differences between enzyme linked immunosorbent assays and western blot assays
Clinical and Vaccine Immunology, 2010Co-Authors: Lori D. Wendland, Paul A. Klein, Elliott R Jacobson, Mary B. BrownAbstract:The precarious status of desert (Gopherus agassizii) and gopher (G. polyphemus) tortoises has resulted in conservation efforts that now include health assessment as an important component of management decisionmaking. Mycoplasmal upper respiratory tract disease (URTD) is one of very few diseases in chelonians for which comprehensive and rigorously validated diagnostic tests exist. In this study, serum samples obtained from eight Gopherus tortoises documented at necropsy to (i) be enzyme-linked immunosorbent assay (ELISA) seropositive using the PS6 antigen, (ii) be infected with Mycoplasma agassizii as indicated by direct isolation of the pathogen from the respiratory surfaces, and (iii) have histological lesions of Mycoplasmal URTD were used to evaluate four distinct clinical isolates of M. agassizii as antigens for ELISA and Western blot analyses. Each animal sample reacted in the Western blot with its homologous M. agassizii strain, but recognition of heterologous M. agassizii strains was variable. Further, individual animals varied significantly with respect to the specific proteins recognized by the humoral immune response. An additional 114 Gopherus serum samples were evaluated using ELISA antigens prepared from the four distinct M. agassizii strains; A405 values were significantly correlated (r 2 goodness of fit range, 0.708 to 0.771; P < 0.0001) for all antigens tested. The results confirm that strain variation is responsible for the observed differences between Western blot binding patterns. Thus, reliance on a single M. agassizii strain as an antigen in Western blot assays may provide false-negative results. This could have adverse consequences for the well-being of these environmentally sensitive hosts if false-negative animals were relocated to sites consisting of true-negative populations. Over the past two decades, disease has become an increasingly important issue for wildlife management. Disease surveillance is fundamental for disease prevention and control. Thus, the development of diagnostic assays will be critical to research and manage wildlife populations effectively. Diseases in freeranging animal populations are often managed by isolation or culling, predominantly because treatment of individuals is impractical and vaccination programs can be instituted only in limited situations, if at all. As available habitat shrinks, translocation or relocation may be used as management tools, especially for “at-risk” species, and the use of diagnostic tools to minimize the risk of pathogen transmission will increase. It is critical that tests be appropriately validated and have quality control mechanisms established, as there may be adverse consequences for animals with positive diagnostic test results for infectious agents, as well as for naive animals that might be exposed to pathogens by the relocation of diseased animals. Mycoplasmal upper respiratory tract disease (URTD) (11,
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Mycoplasma agassizii Strain Variation and Distinct Host Antibody Responses Explain Differences between Enzyme-Linked
2010Co-Authors: Immunosorbent Assays, Paul A. Klein, Elliott R Jacobson, Western Blot Assays, Lori D. Wendl, Mary B. BrownAbstract:tortoises has resulted in conservation efforts that now include health assessment as an important component of management decision-making. Mycoplasmal upper respiratory tract disease (URTD) is one of very few diseases in chelonians for which comprehensive and rigorously validated diagnostic tests exist. In this study, serum samples obtained from eight Gopherus tortoises documented at necropsy to (i) be enzyme-linked immunosorbent assay (ELISA) seropositive using the PS6 antigen, (ii) be infected with Mycoplasma agassizii as indicated by direct isolation of the pathogen from the respiratory surfaces, and (iii) have histological lesions of Mycoplasmal URTD were used to evaluate four distinct clinical isolates ofM. agassizii as antigens for ELISA and Western blot analyses. Each animal sample reacted in the Western blot with its homologous M. agassizii strain, but recognition of heter-ologous M. agassizii strains was variable. Further, individual animals varied significantly with respect to the specific proteins recognized by the humoral immune response. An additional 114 Gopherus serum samples were evaluated using ELISA antigens prepared from the four distinct M. agassizii strains; A405 values were signif-icantly correlated (r2 goodness of fit range, 0.708 to 0.771; P < 0.0001) for all antigens tested. The results confirm that strain variation is responsible for the observed differences between Western blot binding patterns. Thus, reliance on a single M. agassizii strain as an antigen in Western blot assays may provide false-negativ
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evanescent wave biosensor for field serodiagnosis of tortoise mycoplasmosis
Veterinary Immunology and Immunopathology, 2008Co-Authors: Daniel R. Brown, Lori D. Wendland, Mary B. Brown, Javier G Ortiz, Marianne F Kramer, Daniel V Lim, Paul A. KleinAbstract:Disease has become an increasingly important issue for wildlife management over the past two decades. Adequate surveillance is fundamental for disease prevention and control, thus there is an increasing need for diagnostic assays for wildlife management. The objective of this study was to evaluate the performance of a field-portable biosensor adapted for rapid detection of specific antibodies in tortoise plasma that reflect a history of exposure to Mycoplasma agassizii, which is an agent of tortoise upper respiratory tract disease. Banked plasma samples were tested in two blinded trials, and the parameters that define the reliability of a diagnostic test were estimated based on externally validated tortoise plasma controls. The mean sensitivity of the biosensor (ability to identify exposed tortoises in the group of all exposed individuals) was 78%; the mean specificity (unexposed individuals with negative test result, out of all unexposed individuals tested) was 73%; the mean positive predictive value (exposed individuals with positive test, out of all individuals with positive test) was 82%; the mean negative predictive value (unexposed individuals with negative test, out of all individuals with negative test) was 68%. In a 15-min field-portable format, the biosensor was able to discriminate between true seropositive (n = 34) and true seronegative (n = 23) tortoise plasma with overall accuracy of 84%. The goals established for the tortoise population can help managers decide whether potential diagnostic errors should impact management decision-making, and whether the benefits of the field-portable format of the biosensor assay outweigh any potential disadvantages.
K. W. Hunter - One of the best experts on this subject based on the ideXlab platform.
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chronic disease in the mojave desert tortoise host physiology and recrudescence obscure patterns of pathogen transmission
Ecology and Evolution, 2017Co-Authors: Franziska C Sandmeier, S. A. Dupre', Ron Marlow, Nichole Maloney, David Hyde, Hossein Ali Mohammadpour, Richard C Tracy, K. W. HunterAbstract:A seminatural, factorial-design experiment was used to quantify dynamics of the pathogen Mycoplasma agassizii and upper respiratory tract disease in the Mojave desert tortoise (Gopherus agassizii) over 2 years. Groups of initially healthy animals were separated into serologically positive (seropositive), seronegative, and artificially infected groups and paired into 23 pens. We found no evidence of long-term immune protection to M. agassizii or of immunological memory. Initially seronegative, healthy tortoises experienced an equal amount of disease when paired with other seronegative groups as when paired with seropositive and artificially infected groups—suggesting that recrudescence is as significant as transmission in introducing disease in individuals in this host–pathogen system. Artificially infected groups of tortoises showed reduced levels of morbidity when paired with initially seronegative animals—suggesting either a dilution effect or a strong effect of pathogen load in this system. Physiological dynamics within the host appear to be instrumental in producing morbidity, recrudescence, and infectiousness, and thus of population-level dynamics. We suggest new avenues for studying diseases in long-lived ectothermic vertebrates and a shift in modeling such diseases.
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Mycoplasmal upper respiratory tract disease across the range of the threatened mojave desert tortoise associations with thermal regime and natural antibodies
Ecohealth, 2013Co-Authors: Franziska C Sandmeier, S. A. Dupre', Bridgette E Hagerty, Hossein Ali Mohammadpour, Richard C Tracy, K. W. HunterAbstract:Most research of upper respiratory tract disease (Mycoplasmal URTD) in the threatened Mojave Desert tortoise (Gopherus agassizii) has worked under the hypothesis that the pathogen, Mycoplasma agassizii, has a relatively consistent and predictable effect on tortoise populations across their natural range. In contrast, we hypothesized that multiple factors influence the prevalence of disease and analyzed biological and environmental variables that vary significantly across the Mojave Desert. We used multiple regression models to analyze associations between Mycoplasmal URTD and the genetic structure of 24 tortoise populations, levels of natural antibody (NAb) to M. agassizii in tortoises (one component of the innate immune system), precipitation, and colder thermal regimes. We detected a significant, positive association between mean levels of NAb and seroprevalence to M. agassizii. We hypothesized that NAbs may provide tolerance to Mycoplasmal infections and that more tolerant populations may act as host reservoirs of disease. We also detected significant associations between colder winters and Mycoplasmal URTD, suggesting that colder winters may depress tortoise immune resistance against M. agassizii or enhance conditions for the growth of M. agassizii.
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quantitative pcr method for detection of Mycoplasma spp dna in nasal lavage samples from the desert tortoise gopherus agassizii
Journal of Microbiological Methods, 2011Co-Authors: S. A. Dupre', C R Tracy, K. W. HunterAbstract:Abstract Mycoplasma agassizii and M. testudineum have been associated with upper respiratory tract disease (URTD) in the threatened desert tortoise ( Gopherus agassizii ). Because microbiological culture methods have proven difficult to employ in wild desert tortoises, our goal was to develop a sensitive and specific qPCR method for detecting and quantifying Mycoplasma DNA in nasal lavage fluid collected in the field. Primers for 16S ribosomal RNA gene sequences specific for M. agassizii and M. testudineum were designed, together with primers that recognize conserved sequences of both microorganisms. Standard curves generated with DNA extracted from known numbers of Mycoplasma cells revealed a lower detection limit of approximately 5 fg. The qPCR method did not recognize normal flora DNA, and nasal lavage fluid contained no interfering substances. Nasal lavage samples collected from 20 captive desert tortoises housed at the Desert Tortoise Conservation Center (Clark County, Nevada, USA) revealed the presence of M. agassizii DNA in 100% of the tortoises. Concentrations ranged from a low of 6 pg ml − 1 to a high of 72,962 pg ml − 1 . Only one of the tortoises was positive for M. testudineum . Interestingly, not all of the qPCR positive tortoises showed evidence of seroconversion, suggesting that they were colonized but not infected. This new quantitative method will provide a critical tool for managing threatened populations of the desert tortoise.
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Flow cytometric method for quantifying viable Mycoplasma agassizii, an agent of upper respiratory tract disease in the desert tortoise (Gopherus agassizii)
Letters in Applied Microbiology, 2010Co-Authors: Hossein Ali Mohammadpour, S. A. Dupre', Chad R. Tracy, Doug Redelman, K. W. HunterAbstract:AIMS: Mycoplasma agassizii can cause upper respiratory tract disease in the threatened desert tortoise of the Southwestern United States. Two technical challenges have impeded critical microbiological studies of this microorganism: (i) its small size limits the use of light microscopy for cell counting and (ii) its extremely slow growth in broth and agar cultures impedes colony counting. Our aim was to develop a rapid and sensitive flow cytometric method using a vital fluorescent dye to enumerate viable M. agassizii cells. METHODS AND RESULTS: Here, we demonstrate that the nonfluorescent molecule 5-carboxyfluorescein (5-CF) diacetate acetoxymethyl ester penetrates M. agassizii cell membranes and it is converted in the cytoplasm to the fluorescent molecule 5-CF by the action of intracellular esterases. Labelled Mycoplasma cells can be easily detected by flow cytometry, and cultures with as few as 100 viable Mycoplasma cells ml(-1) can be labelled and counted in less than 1 h. Experiments using temperature-induced cell death demonstrated that only viable M. agassizii cells are labelled with this procedure. CONCLUSIONS: A rapid and sensitive flow cytometric technique has been developed for enumerating viable M. agassizii cells. SIGNIFICANCE AND IMPACT OF THE STUDY: This technique should facilitate basic immunological, biochemical and pharmacological studies of this important pathogen which may lead to new diagnostic and therapeutic methods.
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upper respiratory tract disease urtd as a threat to desert tortoise populations a reevaluation
Biological Conservation, 2009Co-Authors: Franziska C Sandmeier, S. A. Dupre', Richard C Tracy, K. W. HunterAbstract:The relationships between Mycoplasma agassizii, a causative agent of upper respiratory disease (URTD), and desert tortoise (Gopherus agassizii), generally illustrate the complexities of disease dynamics in wild vertebrate populations. In this review, we summarize current understanding of URTD in Mojave desert tortoise populations, we illustrate how inadequate knowledge of tortoise immune systems may obfuscate assessment of disease, and we suggest approaches to future management of URTD in desert tortoise populations. We challenge the view that M. agassizii causes consistent levels of morbidity and/or mortality across the Mojave desert. Instead, URTD may be described more accurately as a context-dependent disease. In addition, new evidence for relatively high levels of natural antibodies to M. agassizii in desert tortoises suggests possible problems in conventional diagnostic tests of disease in tortoises as well as a possible tortoise immune mechanism to protect against M. agassizii. Partly because of the problems in diagnostic testing, we recommend abandoning policies to euthanize tortoises that test positive for an immune response to M. agassizii. Based on this review, we question management strategies aimed solely at reducing Mycoplasma spp. in desert tortoise populations, and advocate a more careful consideration of extrinsic factors as a cause of symptomatic disease.
Paul A. Klein - One of the best experts on this subject based on the ideXlab platform.
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Mycoplasmosis and upper respiratory tract disease of tortoises: A review and update
Veterinary journal (London England : 1997), 2014Co-Authors: Mary B Brown, Paul A. Klein, Daniel R. Brown, Lori D. Wendland, Mary M. Christopher, Kristin H BerryAbstract:Abstract Tortoise mycoplasmosis is one of the most extensively characterized infectious diseases of chelonians. A 1989 outbreak of upper respiratory tract disease (URTD) in free-ranging Agassiz's desert tortoises ( Gopherus agassizii ) brought together an investigative team of researchers, diagnosticians, pathologists, immunologists and clinicians from multiple institutions and agencies. Electron microscopic studies of affected tortoises revealed a microorganism in close association with the nasal mucosa that subsequently was identified as a new species, Mycoplasma agassizii . Over the next 24 years, a second causative agent, Mycoplasma testudineum , was discovered, the geographic distribution and host range of tortoise mycoplasmosis were expanded, diagnostic tests were developed and refined for antibody and pathogen detection, transmission studies confirmed the pathogenicity of the original M. agassizii isolate, clinical (and subclinical) disease and laboratory abnormalities were characterized, many extrinsic and predisposing factors were found to play a role in morbidity and mortality associated with Mycoplasmal infection, and social behavior was implicated in disease transmission. The translation of scientific research into management decisions has sometimes led to undesirable outcomes, such as euthanasia of clinically healthy tortoises. In this article, we review and assess current research on tortoise mycoplasmosis, arguably the most important chronic infectious disease of wild and captive North American and European tortoises, and update the implications for management and conservation of tortoises in the wild.
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Mycoplasma agassizii strain variation and distinct host antibody responses explain differences between enzyme linked immunosorbent assays and western blot assays
Clinical and Vaccine Immunology, 2010Co-Authors: Lori D. Wendland, Paul A. Klein, Elliott R Jacobson, Mary B. BrownAbstract:The precarious status of desert (Gopherus agassizii) and gopher (G. polyphemus) tortoises has resulted in conservation efforts that now include health assessment as an important component of management decisionmaking. Mycoplasmal upper respiratory tract disease (URTD) is one of very few diseases in chelonians for which comprehensive and rigorously validated diagnostic tests exist. In this study, serum samples obtained from eight Gopherus tortoises documented at necropsy to (i) be enzyme-linked immunosorbent assay (ELISA) seropositive using the PS6 antigen, (ii) be infected with Mycoplasma agassizii as indicated by direct isolation of the pathogen from the respiratory surfaces, and (iii) have histological lesions of Mycoplasmal URTD were used to evaluate four distinct clinical isolates of M. agassizii as antigens for ELISA and Western blot analyses. Each animal sample reacted in the Western blot with its homologous M. agassizii strain, but recognition of heterologous M. agassizii strains was variable. Further, individual animals varied significantly with respect to the specific proteins recognized by the humoral immune response. An additional 114 Gopherus serum samples were evaluated using ELISA antigens prepared from the four distinct M. agassizii strains; A405 values were significantly correlated (r 2 goodness of fit range, 0.708 to 0.771; P < 0.0001) for all antigens tested. The results confirm that strain variation is responsible for the observed differences between Western blot binding patterns. Thus, reliance on a single M. agassizii strain as an antigen in Western blot assays may provide false-negative results. This could have adverse consequences for the well-being of these environmentally sensitive hosts if false-negative animals were relocated to sites consisting of true-negative populations. Over the past two decades, disease has become an increasingly important issue for wildlife management. Disease surveillance is fundamental for disease prevention and control. Thus, the development of diagnostic assays will be critical to research and manage wildlife populations effectively. Diseases in freeranging animal populations are often managed by isolation or culling, predominantly because treatment of individuals is impractical and vaccination programs can be instituted only in limited situations, if at all. As available habitat shrinks, translocation or relocation may be used as management tools, especially for “at-risk” species, and the use of diagnostic tools to minimize the risk of pathogen transmission will increase. It is critical that tests be appropriately validated and have quality control mechanisms established, as there may be adverse consequences for animals with positive diagnostic test results for infectious agents, as well as for naive animals that might be exposed to pathogens by the relocation of diseased animals. Mycoplasmal upper respiratory tract disease (URTD) (11,
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Social behavior drives the dynamics of respiratory disease in threatened tortoises.
Ecology, 2010Co-Authors: Lori D. Wendland, Paul A. Klein, John B Wooding, C. Leann White, Dina L. Demcovitz, Ramon C. Littell, Joan Diemer Berish, Arpat Ozgul, Madan K. Oli, Mary C. ChristmanAbstract:Since the early 1990s, morbidity and mortality in tortoise populations have been associated with a transmissible, Mycoplasmal upper respiratory tract disease (URTD). Although the etiology, transmission, and diagnosis of URTD have been extensively studied, little is known about the dynamics of disease transmission in free-ranging tortoise populations. To understand the transmission dynamics of Mycoplasma agassizii, the primary etiological agent of URTD in wild tortoise populations, we studied 11 populations of free-ranging gopher tortoises (Gopherus polyphemus; n = 1667 individuals) over five years and determined their exposure to the pathogen by serology, by clinical signs, and by detection of the pathogen in nasal lavages. Adults tortoises (n = 759) were 11 times more likely to be seropositive than immature animals (n = 242) (odds ratio = 10.6, 95% CI = 5.7-20, P < 0.0001). Nasal discharge was observed in only 1.4% (4/296) of immature tortoises as compared with 8.6% (120/1399) of adult tortoises. Nasal lavages from all juvenile tortoises (n = 283) were negative by PCR for Mycoplasmal pathogens associated with URTD. We tested for spatial segregation among tortoise burrows by size class and found no consistent evidence of clustering of either juveniles or adults. We suggest that the social behavior of tortoises plays a critical role in the spread of URTD in wild populations, with immature tortoises having minimal interactions with adult tortoises, thereby limiting their exposure to the pathogen. These findings may have broader implications for modeling horizontally transmitted diseases in other species with limited parental care and emphasize the importance of incorporating animal behavior parameters into disease transmission studies to better characterize the host-pathogen dynamics.
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Mycoplasma agassizii Strain Variation and Distinct Host Antibody Responses Explain Differences between Enzyme-Linked
2010Co-Authors: Immunosorbent Assays, Paul A. Klein, Elliott R Jacobson, Western Blot Assays, Lori D. Wendl, Mary B. BrownAbstract:tortoises has resulted in conservation efforts that now include health assessment as an important component of management decision-making. Mycoplasmal upper respiratory tract disease (URTD) is one of very few diseases in chelonians for which comprehensive and rigorously validated diagnostic tests exist. In this study, serum samples obtained from eight Gopherus tortoises documented at necropsy to (i) be enzyme-linked immunosorbent assay (ELISA) seropositive using the PS6 antigen, (ii) be infected with Mycoplasma agassizii as indicated by direct isolation of the pathogen from the respiratory surfaces, and (iii) have histological lesions of Mycoplasmal URTD were used to evaluate four distinct clinical isolates ofM. agassizii as antigens for ELISA and Western blot analyses. Each animal sample reacted in the Western blot with its homologous M. agassizii strain, but recognition of heter-ologous M. agassizii strains was variable. Further, individual animals varied significantly with respect to the specific proteins recognized by the humoral immune response. An additional 114 Gopherus serum samples were evaluated using ELISA antigens prepared from the four distinct M. agassizii strains; A405 values were signif-icantly correlated (r2 goodness of fit range, 0.708 to 0.771; P < 0.0001) for all antigens tested. The results confirm that strain variation is responsible for the observed differences between Western blot binding patterns. Thus, reliance on a single M. agassizii strain as an antigen in Western blot assays may provide false-negativ
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evanescent wave biosensor for field serodiagnosis of tortoise mycoplasmosis
Veterinary Immunology and Immunopathology, 2008Co-Authors: Daniel R. Brown, Lori D. Wendland, Mary B. Brown, Javier G Ortiz, Marianne F Kramer, Daniel V Lim, Paul A. KleinAbstract:Disease has become an increasingly important issue for wildlife management over the past two decades. Adequate surveillance is fundamental for disease prevention and control, thus there is an increasing need for diagnostic assays for wildlife management. The objective of this study was to evaluate the performance of a field-portable biosensor adapted for rapid detection of specific antibodies in tortoise plasma that reflect a history of exposure to Mycoplasma agassizii, which is an agent of tortoise upper respiratory tract disease. Banked plasma samples were tested in two blinded trials, and the parameters that define the reliability of a diagnostic test were estimated based on externally validated tortoise plasma controls. The mean sensitivity of the biosensor (ability to identify exposed tortoises in the group of all exposed individuals) was 78%; the mean specificity (unexposed individuals with negative test result, out of all unexposed individuals tested) was 73%; the mean positive predictive value (exposed individuals with positive test, out of all individuals with positive test) was 82%; the mean negative predictive value (unexposed individuals with negative test, out of all individuals with negative test) was 68%. In a 15-min field-portable format, the biosensor was able to discriminate between true seropositive (n = 34) and true seronegative (n = 23) tortoise plasma with overall accuracy of 84%. The goals established for the tortoise population can help managers decide whether potential diagnostic errors should impact management decision-making, and whether the benefits of the field-portable format of the biosensor assay outweigh any potential disadvantages.
Richard C Tracy - One of the best experts on this subject based on the ideXlab platform.
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Mycoplasma agassizii an opportunistic pathogen of tortoises shows very little genetic variation across the mojave and sonoran deserts
PLOS ONE, 2021Co-Authors: Agusto Luzuriaganeira, Franziska C Sandmeier, Richard C Tracy, Chava L. Weitzman, Richard L. Tillett, Shalyn N Bauschlicher, David AlvarezponceAbstract:Mycoplasma agassizii is a common cause of upper respiratory tract disease in Mojave desert tortoises (Gopherus agassizii). So far, only two strains of this bacterium have been sequenced, and very little is known about its patterns of genetic diversity. Understanding genetic variability of this pathogen is essential to implement conservation programs for their threatened, long-lived hosts. We used next generation sequencing to explore the genomic diversity of 86 cultured samples of M. agassizii collected from mostly healthy Mojave and Sonoran desert tortoises in 2011 and 2012. All samples with enough sequencing coverage exhibited a higher similarity to M. agassizii strain PS6T (collected in Las Vegas Valley, Nevada) than to strain 723 (collected in Sanibel Island, Florida). All eight genomes with a sequencing coverage over 2x were subjected to multiple analyses to detect single-nucleotide polymorphisms (SNPs). Strikingly, even though we detected 1373 SNPs between strains PS6T and 723, we did not detect any SNP between PS6T and our eight samples. Our whole genome analyses reveal that M. agassizii strain PS6T may be present across a wide geographic extent in healthy Mojave and Sonoran desert tortoises.
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High quality draft genome sequences of Mycoplasma agassizii strains PS6T and 723 isolated from Gopherus tortoises with upper respiratory tract disease
BMC, 2018Co-Authors: David Alvarez-ponce, Franziska C Sandmeier, Chava L. Weitzman, Richard L. Tillett, Richard C TracyAbstract:Abstract Mycoplasma agassizii is one of the known causative agents of upper respiratory tract disease (URTD) in Mojave desert tortoises (Gopherus agassizii) and in gopher tortoises (Gopherus polyphemus). We sequenced the genomes of M. agassizii strains PS6T (ATCC 700616) and 723 (ATCC 700617) isolated from the upper respiratory tract of a Mojave desert tortoise and a gopher tortoise, respectively, both with signs of URTD. The PS6T genome assembly was organized in eight scaffolds, had a total length of 1,274,972 bp, a G + C content of 28.43%, and contained 979 protein-coding genes, 13 pseudogenes and 35 RNA genes. The 723 genome assembly was organized in 40 scaffolds, had a total length of 1,211,209 bp, a G + C content of 28.34%, and contained 955 protein-coding genes, seven pseudogenes, and 35 RNA genes. Both genomes exhibit a very similar organization and very similar numbers of genes in each functional category. Pairs of orthologous genes encode proteins that are 93.57% identical on average. Homology searches identified a putative cytadhesin. These genomes will enable studies that will help understand the molecular bases of pathogenicity of this and other Mycoplasma species
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chronic disease in the mojave desert tortoise host physiology and recrudescence obscure patterns of pathogen transmission
Ecology and Evolution, 2017Co-Authors: Franziska C Sandmeier, S. A. Dupre', Ron Marlow, Nichole Maloney, David Hyde, Hossein Ali Mohammadpour, Richard C Tracy, K. W. HunterAbstract:A seminatural, factorial-design experiment was used to quantify dynamics of the pathogen Mycoplasma agassizii and upper respiratory tract disease in the Mojave desert tortoise (Gopherus agassizii) over 2 years. Groups of initially healthy animals were separated into serologically positive (seropositive), seronegative, and artificially infected groups and paired into 23 pens. We found no evidence of long-term immune protection to M. agassizii or of immunological memory. Initially seronegative, healthy tortoises experienced an equal amount of disease when paired with other seronegative groups as when paired with seropositive and artificially infected groups—suggesting that recrudescence is as significant as transmission in introducing disease in individuals in this host–pathogen system. Artificially infected groups of tortoises showed reduced levels of morbidity when paired with initially seronegative animals—suggesting either a dilution effect or a strong effect of pathogen load in this system. Physiological dynamics within the host appear to be instrumental in producing morbidity, recrudescence, and infectiousness, and thus of population-level dynamics. We suggest new avenues for studying diseases in long-lived ectothermic vertebrates and a shift in modeling such diseases.
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comparison of current methods for the detection of chronic Mycoplasmal urtd in wild populations of the mojave desert tortoise gopherus agassizii
Journal of Wildlife Diseases, 2017Co-Authors: Franziska C Sandmeier, Richard C Tracy, Chava L. Weitzman, Nichole K Maloney, Nathan C Nieto, Mike B Teglas, Kenneth W Hunter, Sally A Dupre, C. M. GiengerAbstract:Abstract Pathogens that cause subclinical diseases or exhibit low infection intensities are difficult to quantify in wild populations. Mojave desert tortoises (Gopherus agassizii) have been the focus of much research aimed at measuring the presence of upper respiratory disease (URTD) and URTD-associated pathogens, and techniques used to quantify disease in Gopherus species have also been used for disease surveillance in other species of turtles and tortoises of conservation concern. Published surveys of G. agassizii populations have found a relatively low prevalence of URTD, with most URTD-positive animals exhibiting moderate, intermittent signs of morbidity. Therefore, multiple tests have been developed to quantify URTD including genetic detection of the pathogens Mycoplasma agassizii and Mycoplasma testudineum, detection of M. agassizii-specific antibodies, and standardized quantification of clinical signs of URTD and body condition. These diagnostic tests have only been compared in diseased or moribund...
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Mycoplasmal upper respiratory tract disease across the range of the threatened mojave desert tortoise associations with thermal regime and natural antibodies
Ecohealth, 2013Co-Authors: Franziska C Sandmeier, S. A. Dupre', Bridgette E Hagerty, Hossein Ali Mohammadpour, Richard C Tracy, K. W. HunterAbstract:Most research of upper respiratory tract disease (Mycoplasmal URTD) in the threatened Mojave Desert tortoise (Gopherus agassizii) has worked under the hypothesis that the pathogen, Mycoplasma agassizii, has a relatively consistent and predictable effect on tortoise populations across their natural range. In contrast, we hypothesized that multiple factors influence the prevalence of disease and analyzed biological and environmental variables that vary significantly across the Mojave Desert. We used multiple regression models to analyze associations between Mycoplasmal URTD and the genetic structure of 24 tortoise populations, levels of natural antibody (NAb) to M. agassizii in tortoises (one component of the innate immune system), precipitation, and colder thermal regimes. We detected a significant, positive association between mean levels of NAb and seroprevalence to M. agassizii. We hypothesized that NAbs may provide tolerance to Mycoplasmal infections and that more tolerant populations may act as host reservoirs of disease. We also detected significant associations between colder winters and Mycoplasmal URTD, suggesting that colder winters may depress tortoise immune resistance against M. agassizii or enhance conditions for the growth of M. agassizii.
