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Eugene M. Burreson - One of the best experts on this subject based on the ideXlab platform.

  • a rapid phenotype change in the pathogen Perkinsus marinus was associated with a historically significant marine disease emergence in the eastern oyster
    Scientific Reports, 2021
    Co-Authors: Ryan B Carnegie, Susan E. Ford, Rita K Crockett, Peter R Kingsleysmith, Lydia M Bienlien, Lucia S L Safi, Laura Whitefleetsmith, Eugene M. Burreson
    Abstract:

    The protozoan parasite Perkinsus marinus, which causes dermo disease in Crassostrea virginica, is one of the most ecologically important and economically destructive marine pathogens. The rapid and persistent intensification of dermo in the USA in the 1980s has long been enigmatic. Attributed originally to the effects of multi-year drought, climatic factors fail to fully explain the geographic extent of dermo’s intensification or the persistence of its intensified activity. Here we show that emergence of a unique, hypervirulent P. marinus phenotype was associated with the increase in prevalence and intensity of this disease and associated mortality. Retrospective histopathology of 8355 archival oysters from 1960 to 2018 spanning Chesapeake Bay, South Carolina, and New Jersey revealed that a new parasite phenotype emerged between 1983 and 1990, concurrent with major historical dermo disease outbreaks. Phenotypic changes included a shortening of the parasite’s life cycle and a tropism shift from deeper connective tissues to digestive epithelia. The changes are likely adaptive with regard to the reduced oyster abundance and longevity faced by P. marinus after rapid establishment of exotic pathogen Haplosporidium nelsoni in 1959. Our findings, we hypothesize, illustrate a novel ecosystem response to a marine parasite invasion: an increase in virulence in a native parasite.

  • molecular epizootiology of Perkinsus marinus and p chesapeaki infections among wild oysters and clams in chesapeake bay usa
    Diseases of Aquatic Organisms, 2008
    Co-Authors: Kimberly S. Reece, Christopher F Dungan, Eugene M. Burreson
    Abstract:

    Perkinsus marinus and P. chesapeaki host ranges among wild Chesapeake Bay, USA, region bivalves were examined by surveying Crassostrea virginica oysters and members of several sympatric clam species from 11 locations. Perkinsus genus- and species-specific PCR assays were performed on DNA samples from 731 molluscs, and species-specific in situ hybridization assays were performed on a selected subset of histological samples whose PCR results indicated dual or atypical Perkinsus sp. infections. PCR assays detected P. marinus in 92% of oysters, but the P. chesapeaki PCR assay was positive for only 6% of oysters, and P. marinus was detected by PCR in only one clam. The very low prevalence of P. marinus infections in clams is noteworthy because all surveyed clams were sympatric with oyster populations showing high P. marinus infection prevalences. P. chesapeaki commonly infected Mya arenaria, Macoma balthica, and Tagelus plebeius clams, as well as the previously unreported P. chesapeaki host clams Mulinia lateralis, Rangia cuneata, and Cyrtopleura costata. Among 30 in vitro isolates propagated from surveyed hosts, 8 P. marinus isolates were exclusively from Crassostrea virginica oysters, and all 22 P. chesapeaki isolates were from clam hosts of 5 different species. Although both P. marinus and P. chesapeaki were previously both shown to be experimentally infective for oyster and clam hosts, this survey of wild bivalves in the Chesapeake Bay region reveals that P. marinus infections occur almost exclusively in oysters, and P. chesapeaki infections predominate among members of at least 6 clam species.

  • experimental cross infections by Perkinsus marinus and p chesapeaki in three sympatric species of chesapeake bay oysters and clams
    Diseases of Aquatic Organisms, 2007
    Co-Authors: Christopher F Dungan, Nancy A Stokes, Kimberly S. Reece, Rosalee M Hamilton, Eugene M. Burreson
    Abstract:

    In controlled laboratory transmission experiments, uniform doses of axenic in vitro isolate cultures of Perkinsus marinus from a Crassostrea virginica oyster, and of independent P. chesapeaki isolates from Chesapeake Bay Mya arenaria and Macoma balthica clams, were used to reciprocally challenge Perkinsus sp.-free C. virginica, M. arenaria, and M. balthica experimental hosts. Following mantle cavity inoculations, all 3 experimental hosts acquired high incidences (30 to 100%) of infections by each of the 3 Perkinsus sp. isolates, based on PCR assays of DNAs from exper- imental host tissues that were collected through 60 d post-inoculation. Lesions containing proliferat- ing pathogen cells were documented histologically in tissues of all experimental host species chal- lenged with all isolates of both Perkinsus species. Experimental Perkinsus sp. challenge isolates were re-isolated and propagated in vitro from infected tissues of host molluscs from most (5 of 9) experi- mental treatment groups. Koch's postulates were generally satisfied to confirm experimental infec- tions in all bivalve molluscs that were challenged with 3 isolates of 2 Perkinsus spp. These results suggest potential broad and overlapping host specificities for the 2 current Chesapeake Bay-endemic Perkinsus species: P. marinus and P. chesapeaki.

  • real time pcr investigation of parasite ecology in situ determination of oyster parasite Perkinsus marinus transmission dynamics in lower chesapeake bay
    Parasitology, 2006
    Co-Authors: Corinne Audemard, Kimberly S. Reece, L Ragone M Calvo, Kennedy T Paynter, Eugene M. Burreson
    Abstract:

    SUMMARY Perkinsus marinus is a severe pathogen of the oyster Crassostrea virginica on the East Coast of the United States. Transmission dynamics of this parasite were investigated in situ for 2 consecutive years (May through October) at 2 lower Chesapeake Bay sites. Compared to previous studies where seasonal infection patterns in oysters were measured, this study also provided parasite water column abundance data measured using real-time PCR. As previously observed, salinity and temperature modulated parasite transmission dynamics. Using regression analysis, parasite prevalence, oyster mortalities and parasite water column abundance were significantly positively related to salinity. Perkinsus marinus weighted prevalence in wild oysters and parasite water column abundance both were significantly related to temperature, but the responses lagged 1 month behind temperature. Parasite water column abundance was the highest during August (up to 1200 cells/l) and was significantly related to P. marinus weighted prevalence in wild oysters, and to wild oyster mortality suggesting that parasites are released in the environment via both moribund and live hosts (i.e. through feces). Incidence was not significantly related to parasite water column abundance, which seems to indicate the absence of a linear relationship or that infection acquisition is controlled by a more complex set of parameters.

  • real time pcr investigation of parasite ecology in situ determination of oyster parasite Perkinsus marinus transmission dynamics in lower chesapeake bay
    Parasitology, 2006
    Co-Authors: Corinne Audemard, Kimberly S. Reece, L Ragone M Calvo, Kennedy T Paynter, Eugene M. Burreson
    Abstract:

    Perkinsus marinus is a severe pathogen of the oyster Crassostrea virginica on the East Coast of the United States. Transmission dynamics of this parasite were investigated in situ for 2 consecutive years (May through October) at 2 lower Chesapeake Bay sites. Compared to previous studies where seasonal infection patterns in oysters were measured, this study also provided parasite water column abundance data measured using real-time PCR. As previously observed, salinity and temperature modulated parasite transmission dynamics. Using regression analysis, parasite prevalence, oyster mortalities and parasite water column abundance were significantly positively related to salinity. Perkinsus marinus weighted prevalence in wild oysters and parasite water column abundance both were significantly related to temperature, but the responses lagged 1 month behind temperature. Parasite water column abundance was the highest during August (up to 1200 cells/l) and was significantly related to P. marinus weighted prevalence in wild oysters, and to wild oyster mortality suggesting that parasites are released in the environment via both moribund and live hosts (i.e. through feces). Incidence was not significantly related to parasite water column abundance, which seems to indicate the absence of a linear relationship or that infection acquisition is controlled by a more complex set of parameters.

Gerardo R Vasta - One of the best experts on this subject based on the ideXlab platform.

  • quantitative assessment of the proliferation of the protozoan parasite Perkinsus marinus using a bioluminescence assay for atp content
    International Journal for Parasitology-Drugs and Drug Resistance, 2013
    Co-Authors: Surekha Shridhar, Gerardo R Vasta, Kolaleh Hassan, David J Sullivan, Jose Fernandez A Robledo
    Abstract:

    Perkinsus marinus is a protozoan parasite that causes “Dermo” disease in the eastern oyster Crasssostrea virginica in coastal areas of the USA. Until now, intervention strategies against the parasite have found limited success, and Dermo still remains one of the main hurdles for the restoration of oyster populations. We adapted a commercial adenosine tri-phosphate (ATP) content-based assay to assess the in vitro proliferation of P. marinus in a 96-well plate format, and validated the method by measuring the effects of potential anti-proliferative compounds. The sensitivity (1.5–3.1 × 104 cells/well), linearity (R2 = 0.983), and signal stability (60 min) support the reliability of the assay for assessing cell proliferation. Validation of the assay by culturing P. marinus in the presence of increasing concentrations of triclosan showed a dose–response profile. The IC50 value obtained was higher than that reported earlier, possibly due to the use of different viability assay methods and a different P. marinus strain. The antibiotics G418 and tetracycline and the herbicide fluridone were active against P. marinus proliferation; the IC50 of chloramphenicol, ciprofloxacin, and atrazine was relatively high suggesting either off-target effects or inability to reach the targets. The validation of the ATP-based assay, together with significant advantages of the Perkinsus culture methodology (homogeneity, reproducibility, and high cell densities), underscores the value of this assay for developing high-throughput screens for the identification of novel leader compounds against Perkinsus species, and most importantly, for the closely-related apicomplexan parasites.

  • The natural resistance-associated macrophage protein from the protozoan parasite Perkinsus marinus mediates iron uptake.
    Biochemistry, 2011
    Co-Authors: Zhuoer Lin, José-antonio Fernández-robledo, Mathieu F M Cellier, Gerardo R Vasta
    Abstract:

    Microbial pathogens succeed in acquiring essential metals such as iron and manganese despite their limited availability because of the host's immune response. The eukaryotic natural resistance-associated macrophage proteins mediate uptake of divalent metals and, during infection, may compete directly for metal acquisition with the pathogens' transporters. In this study, we characterize the Nramp gene family of Perkinsus marinus, an intracellular parasite of the eastern oyster, and through yeast complementation, we demonstrate for the first time for a protozoan parasite that Nramp imports environmental Fe. Three PmNramp isogenes differ in their exon-intron structures and encode transcripts that display a trans splicing leader at the 5' end. The protein sequences share conserved properties predicted for the Nramp/Solute carrier 11 (Slc11) family, such as 12-transmembrane segment (TMS) topology (N- and C-termini cytoplasmic) and preferential conservation of four TMS predicted to form a pseudosymmetric proton/metal symport pathway. Yeast fet3fet4 mutant complementation assays showed iron transport activity for PmNramp1 and a fusion chimera of the PmNramp3 hydrophobic core and PmNramp1 N- and C-termini. PmNramp1 site-directed mutagenesis demonstrated that Slc11 invariant and predicted pseudosymmetric motifs (TMS1 Asp-Pro-Gly and TMS6 Met-Pro-His) are key for transport function. PmNramp1 TMS1 mutants D76E, G78A, and D76E/G78A prevented membrane protein expression, while TMS6 M250A, H252Y, and M250A/H252Y specifically abrogated Fe uptake; the TMS6 H252Y mutation also correlates with divergence from Nramp specificity for divalent metals.

  • Perkinsus marinus superoxide dismutase 2 pmsod2 localizes to single membrane subcellular compartments
    Biochemical and Biophysical Research Communications, 2008
    Co-Authors: Jose A Fernandezrobledo, Eric J Schott, Gerardo R Vasta
    Abstract:

    Perkinsus marinus (Phylum Perkinsozoa), a protozoan parasite of oysters, is considered one of the earliest diverging groups of the lineage leading to dinoflagellates. Perkinsus trophozoites are phagocytosed by oyster hemocytes, where they are likely exposed to reactive oxygen species. As part of its reactive oxygen detoxifying pathway, P. marinus possesses two iron-cofactored SOD (PmSOD1 and PmSOD2). Immunoflourescence analysis of P. marinus trophozoites and gene complementation in yeast revealed that PmSOD1 is targeted to the mitochondria. Surprisingly, although PmSOD2 is characterized by a bipartite N-terminus extension typical of plastid targeting, in preliminary immunofluorescence studies it was visualized as punctuate regions in the cytoplasm that could not be assigned to any organelle. Here, we used immunogold electron microscopy to examine the subcellular localization PmSOD2 in P. marinus trophozoites. Gold grains were mostly associated with single-membrane vesicle-like structures, and eventually, localized to electron-dense, apparently amorphous material present in the lumen of a larger, unique compartment. The images suggested that PmSOD2 is targeted to small vesicles that fuse and/or discharge their content into a larger compartment, possibly the large vacuole typical of the mature trophozoites. In light of the in silico targeting prediction, the association of PmSOD2 with single-membrane compartments raises interesting questions regarding its organellar targeting, and the nature of a putative relic plastid in Perkinsus species.

  • transfection of the protozoan parasite Perkinsus marinus
    Molecular and Biochemical Parasitology, 2008
    Co-Authors: Jose A Fernandezrobledo, Zhuoer Lin, Gerardo R Vasta
    Abstract:

    Ongoing efforts for sequencing the genome of the protozoan parasite Perkinsus marinus, together with functional genomic initiatives, have continued to provide invaluable information about genes and metabolic pathways that not only will increase our understanding of its biology, but also have the potential to reveal useful targets for intervention. The lack of molecular tools for the functional characterization of genes of interest, however, has hindered progress in this regard. Here we report the development and validation of transfection methodology for this parasite. We first selected from our P. marinus EST collection a highly expressed gene, which we designated "MOE" (PmMOE), to which we fused at the C-terminus the enhanced green fluorescent protein (GFP) as a reporter gene (pPmMOE-GFP). The exogenous DNA was introduced into the trophozoite stage of the parasite by electroporation using the Nucleofector technology. The transfection efficiency was 37.8% with fluorescence detected as early as 14 h after electroporation, with the transfectants still remaining fluorescent after 8 months even in the absence of drug selection. The 5' flanking region was essential for transcription; constructs with 100 and 204 bp flanking the transcription start site also drove transcription effectively. Polymerase chain reaction (PCR) and Southern blot analyses was consistent with integration by non-homologous recombination. This transfection technique, the first one reported for a member of the Perkinsozoa, provides a new tool for studies of gene regulation and expression, protein targeting, and protein-protein interactions, and should significantly contribute to gain further insight into the biology of Perkinsus spp.

  • the protistan parasite Perkinsus marinus is resistant to selected reactive oxygen species
    Experimental Parasitology, 2003
    Co-Authors: Eric J Schott, Wolf T Pecher, Florence Okafor, Gerardo R Vasta
    Abstract:

    The parasite Perkinsus marinus has devastated natural and farmed oyster populations along the Atlantic and Gulf coasts of North America. When viable P. marinus trophozoites are engulfed by oyster hemocytes, the typical accumulation of reactive oxygen species (ROS) normally associated with phagocyte activity is not observed. One hypothesis to explain this is that the parasite rapidly removes ROS. A manifestation of efficient ROS removal should be a high level of resistance to exogenous ROS. We investigated the in vitro susceptibility of P. marinus to ROS as compared to the estuarine bacterium Vibrio splendidus. We find that P. marinus is markedly less susceptible than V. splendidus to superoxide and hydrogen peroxide (H(2)O(2)), but equally sensitive to hypochlorite. Viable P. marinus trophozoites degrade H(2)O(2) in vitro, but lack detectable catalase activity. However, extracts contain an ascorbate dependent peroxidase activity that may contribute to H(2)O(2) removal in vitro and in vivo.

Kimberly S. Reece - One of the best experts on this subject based on the ideXlab platform.

  • molecular epizootiology of Perkinsus marinus and p chesapeaki infections among wild oysters and clams in chesapeake bay usa
    Diseases of Aquatic Organisms, 2008
    Co-Authors: Kimberly S. Reece, Christopher F Dungan, Eugene M. Burreson
    Abstract:

    Perkinsus marinus and P. chesapeaki host ranges among wild Chesapeake Bay, USA, region bivalves were examined by surveying Crassostrea virginica oysters and members of several sympatric clam species from 11 locations. Perkinsus genus- and species-specific PCR assays were performed on DNA samples from 731 molluscs, and species-specific in situ hybridization assays were performed on a selected subset of histological samples whose PCR results indicated dual or atypical Perkinsus sp. infections. PCR assays detected P. marinus in 92% of oysters, but the P. chesapeaki PCR assay was positive for only 6% of oysters, and P. marinus was detected by PCR in only one clam. The very low prevalence of P. marinus infections in clams is noteworthy because all surveyed clams were sympatric with oyster populations showing high P. marinus infection prevalences. P. chesapeaki commonly infected Mya arenaria, Macoma balthica, and Tagelus plebeius clams, as well as the previously unreported P. chesapeaki host clams Mulinia lateralis, Rangia cuneata, and Cyrtopleura costata. Among 30 in vitro isolates propagated from surveyed hosts, 8 P. marinus isolates were exclusively from Crassostrea virginica oysters, and all 22 P. chesapeaki isolates were from clam hosts of 5 different species. Although both P. marinus and P. chesapeaki were previously both shown to be experimentally infective for oyster and clam hosts, this survey of wild bivalves in the Chesapeake Bay region reveals that P. marinus infections occur almost exclusively in oysters, and P. chesapeaki infections predominate among members of at least 6 clam species.

  • experimental cross infections by Perkinsus marinus and p chesapeaki in three sympatric species of chesapeake bay oysters and clams
    Diseases of Aquatic Organisms, 2007
    Co-Authors: Christopher F Dungan, Nancy A Stokes, Kimberly S. Reece, Rosalee M Hamilton, Eugene M. Burreson
    Abstract:

    In controlled laboratory transmission experiments, uniform doses of axenic in vitro isolate cultures of Perkinsus marinus from a Crassostrea virginica oyster, and of independent P. chesapeaki isolates from Chesapeake Bay Mya arenaria and Macoma balthica clams, were used to reciprocally challenge Perkinsus sp.-free C. virginica, M. arenaria, and M. balthica experimental hosts. Following mantle cavity inoculations, all 3 experimental hosts acquired high incidences (30 to 100%) of infections by each of the 3 Perkinsus sp. isolates, based on PCR assays of DNAs from exper- imental host tissues that were collected through 60 d post-inoculation. Lesions containing proliferat- ing pathogen cells were documented histologically in tissues of all experimental host species chal- lenged with all isolates of both Perkinsus species. Experimental Perkinsus sp. challenge isolates were re-isolated and propagated in vitro from infected tissues of host molluscs from most (5 of 9) experi- mental treatment groups. Koch's postulates were generally satisfied to confirm experimental infec- tions in all bivalve molluscs that were challenged with 3 isolates of 2 Perkinsus spp. These results suggest potential broad and overlapping host specificities for the 2 current Chesapeake Bay-endemic Perkinsus species: P. marinus and P. chesapeaki.

  • real time pcr investigation of parasite ecology in situ determination of oyster parasite Perkinsus marinus transmission dynamics in lower chesapeake bay
    Parasitology, 2006
    Co-Authors: Corinne Audemard, Kimberly S. Reece, L Ragone M Calvo, Kennedy T Paynter, Eugene M. Burreson
    Abstract:

    SUMMARY Perkinsus marinus is a severe pathogen of the oyster Crassostrea virginica on the East Coast of the United States. Transmission dynamics of this parasite were investigated in situ for 2 consecutive years (May through October) at 2 lower Chesapeake Bay sites. Compared to previous studies where seasonal infection patterns in oysters were measured, this study also provided parasite water column abundance data measured using real-time PCR. As previously observed, salinity and temperature modulated parasite transmission dynamics. Using regression analysis, parasite prevalence, oyster mortalities and parasite water column abundance were significantly positively related to salinity. Perkinsus marinus weighted prevalence in wild oysters and parasite water column abundance both were significantly related to temperature, but the responses lagged 1 month behind temperature. Parasite water column abundance was the highest during August (up to 1200 cells/l) and was significantly related to P. marinus weighted prevalence in wild oysters, and to wild oyster mortality suggesting that parasites are released in the environment via both moribund and live hosts (i.e. through feces). Incidence was not significantly related to parasite water column abundance, which seems to indicate the absence of a linear relationship or that infection acquisition is controlled by a more complex set of parameters.

  • real time pcr investigation of parasite ecology in situ determination of oyster parasite Perkinsus marinus transmission dynamics in lower chesapeake bay
    Parasitology, 2006
    Co-Authors: Corinne Audemard, Kimberly S. Reece, L Ragone M Calvo, Kennedy T Paynter, Eugene M. Burreson
    Abstract:

    Perkinsus marinus is a severe pathogen of the oyster Crassostrea virginica on the East Coast of the United States. Transmission dynamics of this parasite were investigated in situ for 2 consecutive years (May through October) at 2 lower Chesapeake Bay sites. Compared to previous studies where seasonal infection patterns in oysters were measured, this study also provided parasite water column abundance data measured using real-time PCR. As previously observed, salinity and temperature modulated parasite transmission dynamics. Using regression analysis, parasite prevalence, oyster mortalities and parasite water column abundance were significantly positively related to salinity. Perkinsus marinus weighted prevalence in wild oysters and parasite water column abundance both were significantly related to temperature, but the responses lagged 1 month behind temperature. Parasite water column abundance was the highest during August (up to 1200 cells/l) and was significantly related to P. marinus weighted prevalence in wild oysters, and to wild oyster mortality suggesting that parasites are released in the environment via both moribund and live hosts (i.e. through feces). Incidence was not significantly related to parasite water column abundance, which seems to indicate the absence of a linear relationship or that infection acquisition is controlled by a more complex set of parameters.

  • ADVANCED Perkinsus marinus INFECTIONS IN CRASSOSTREA ARIAKENSIS MAINTAINED UNDER LABORATORY CONDITIONS
    Journal of Shellfish Research, 2006
    Co-Authors: Jessica Moss, Eugene M. Burreson, Kimberly S. Reece
    Abstract:

    Abstract The Suminoe oyster, Crassostrea ariakensis, has been under investigation since the early 1990s for potential use in restoring the commercial harvest or for aquaculture of oysters in the Chesapeake Bay, USA. Initial studies focusing on C. ariakensis documented a significant level of tolerance to the protozoan parasite Perkinsus marinus, a pathogen found in almost all reaches of the Bay and widely acknowledged as one of the main reasons for the decline in the eastern oyster, Crassostrea virginica, harvest since the late 1980s. Crassostrea ariakensis was demonstrated to acquire P. marinus, however infection intensities, as measured using Ray's thioglycollate medium assay indices, generally were found to be light. As part of a series of experiments to study potential impacts on the Chesapeake Bay region of pathogens found in C. ariakensis in Asia, a challenge experiment was conducted to study the pathogenicity of Perkinsus olseni to C. ariakensis. During this study, we observed the acquisition of mod...

Jerome F La Peyre - One of the best experts on this subject based on the ideXlab platform.

  • the combined influence of sub optimal temperature and salinity on the in vitro viability of Perkinsus marinus a protistan parasite of the eastern oyster crassostrea virginica
    Journal of Invertebrate Pathology, 2010
    Co-Authors: Megan K La Peyre, Sandra M Casas, Whitney Gayle, Jerome F La Peyre
    Abstract:

    Perkinsus marinus is a major cause of mortality in eastern oysters along the Gulf of Mexico and Atlantic coasts. It is also well documented that temperature and salinity are the primary environmental factors affecting P. marinus viability and proliferation. However, little is known about the effects of combined sub-optimal temperatures and salinities on P. marinus viability. This in vitro study examined those effects by acclimating P. marinus at three salinities (7, 15, 25 ppt) to 10 °C to represent the lowest temperatures generally reached in the Gulf of Mexico, and to 2 °C to represent the lowest temperatures reached along the mid-Atlantic coasts and by measuring changes in cell viability and density on days 1, 30, 60 and 90 following acclimation. Cell viability and density were also measured in 7 ppt cultures acclimated to each temperature and then transferred to 3.5 ppt. The largest decreases in cell viability occurred only with combined low temperature and salinity, indicating that there is clearly a synergistic effect. The largest decreases in cell viability occurred only with both low temperature and salinity after 30 days (3.5 ppt, 2 °C: 0% viability), 60 days (3.5 ppt, 10 °C: 0% viability) and 90 days (7 ppt, 2 °C: 0.6 ± 0.7%; 7 ppt, 10 °C: 0.2 ± 0.2%).

  • Serine protease inhibitor cvSI-1 potential role in the eastern oyster host defense against the protozoan parasite Perkinsus marinus
    Developmental and Comparative Immunology, 2009
    Co-Authors: Jerome F La Peyre, Naoki Itoh, Yanli Li, Richard K. Cooper
    Abstract:

    The serine protease inhibitor cvSI-1, purified from plasma of eastern oysters, inhibited the proliferation of the protozoan parasite Perkinsus marinus in vitro. In situ hybridization located cvSI-1 gene expression in basophil cells of the digestive tubules and cvSI-1 expression measured by real-time quantitative reverse transcriptase polymerase chain reaction was several hundred folds greater in digestive glands than in other organs examined or circulating hemocytes. cvSI-1 gene expression was also significantly greater in winter than in summer. Finally, cvSI-1 gene expression and plasma protease inhibitory activity in oysters selected for increased resistance to P. marinus were significantly greater than in unselected oysters. These findings support the hypothesis that cvSI-1 plays a role in eastern oyster host defense against P. marinus possibly through inhibition of parasite proliferation.

  • defining optimal freshwater flow for oyster production effects of freshet rate and magnitude of change and duration on eastern oysters and Perkinsus marinus infection
    Estuaries and Coasts, 2009
    Co-Authors: Megan K La Peyre, Bryan Gossman, Jerome F La Peyre
    Abstract:

    In coastal Louisiana, the development of large-scale freshwater diversion projects has led to controversy over their effects on oyster resources. Using controlled laboratory experiments in combination with a field study, we examined the effects of pulsed freshwater events (freshet) of different magnitude, duration, and rate of change on oyster resources. Laboratory and field evidence indicate that low salinity events (<5 psu) decreased Perkinsus marinus infection intensities. Furthermore, when salinity was low (<5 psu), parasite infection intensities continued to decrease even as temperatures exceeded 20°C. At the same time, oyster growth was positively correlated with salinity. To maximize oyster production, data indicate that both low and high salinity events will be necessary.

  • production of serine proteases by the oyster pathogen Perkinsus marinus apicomplexa in vitro
    Journal of Eukaryotic Microbiology, 1995
    Co-Authors: Jerome F La Peyre, Doris Y Schafhauser, Esam H Rizkalla, Mohamed Faisal
    Abstract:

    . Analysis of the cell-free supernatants of Perkinsus marinus cultures by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and silver staining revealed the presence of as many as 17 bands ranging in molecular weight from 239 to 32 kDa. These bands were not present in un-inoculated medium. Moreover, P. marinus produces extracellular proteins that possess proteolytic activities; the cell-free supernatants of P. marinus cultures could digest a variety of proteins including gelatin, casein, fibronectin and laminin. Oyster plasma was also digested by cell-free culture supernatants. The proteolytic activity in cell-free culture supernatants was detected 24 h post-inoculation, while no proteolytic activity could be detected in cell lysates. The proteolytic activities were characterized using substrate-impregnated sodium dodecylsulfate-polyacrylamide gels and had approximate molecular weights ranging from 55 to 35 kDa. The proteolytic activity of cell-free culture supernatants was inhibited by the serine protease inhibitors phenylmethylsulphonyl fluoride, 3,4-dichloroisocoumarin and soybean trypsin inhibitor. In contrast, inhibitors (i.e. trans-epoxysuccinyll-leucylamido(4-guanidino)-butane, 1, 10-phenanthroline, captopril, ethylenediaminetetracetic acid, pepstatin A or diazoacetyl-DL-norleucine methyl ester) from the other three classes of proteases had no effect. It was concluded that the P. marinus proteases in cell-free culture supernatants are serine proteases.

  • In vitro interaction of Perkinsus marinus merozoites with eastern and pacific oyster hemocytes
    Developmental and comparative immunology, 1995
    Co-Authors: Jerome F La Peyre, Fu-lin E. Chu, Wolfgang K. Vogelbein
    Abstract:

    This study compared hemocyte responses of eastern and Pacific oysters to Perkinsus marinus, in vitro. Except for the percentage of hemocytes associated with P. marinus there was little or no significant difference between eastern and Pacific oysters with regard to their hemocytic response to P. marinus. In phagocytosis assays, merozoites were bound to all hemocyte types but in unequal proportions, unlike zymosan which was found predominantly associated with granulocytes. The number of merozoites enlarging in Ray's fluid thioglycollate medium after incubation with hemocytes in plasma for one day was significantly lower than after incubation in plasma alone in both oyster species. Electron microscopy or merozoites indicated that the parasites were rapidly phagocytosed and that some of the merozoites showed signs of degeneration in less than 12 h. The results suggest that limited intracellular killing of P. marinus had occurred, but was probably not mediated by oxygen metabolites, since no increase in chemiluminescence was observed when hemocytes of either eastern or Pacific oysters were exposed to merozoites.

Susan E. Ford - One of the best experts on this subject based on the ideXlab platform.

  • a rapid phenotype change in the pathogen Perkinsus marinus was associated with a historically significant marine disease emergence in the eastern oyster
    Scientific Reports, 2021
    Co-Authors: Ryan B Carnegie, Susan E. Ford, Rita K Crockett, Peter R Kingsleysmith, Lydia M Bienlien, Lucia S L Safi, Laura Whitefleetsmith, Eugene M. Burreson
    Abstract:

    The protozoan parasite Perkinsus marinus, which causes dermo disease in Crassostrea virginica, is one of the most ecologically important and economically destructive marine pathogens. The rapid and persistent intensification of dermo in the USA in the 1980s has long been enigmatic. Attributed originally to the effects of multi-year drought, climatic factors fail to fully explain the geographic extent of dermo’s intensification or the persistence of its intensified activity. Here we show that emergence of a unique, hypervirulent P. marinus phenotype was associated with the increase in prevalence and intensity of this disease and associated mortality. Retrospective histopathology of 8355 archival oysters from 1960 to 2018 spanning Chesapeake Bay, South Carolina, and New Jersey revealed that a new parasite phenotype emerged between 1983 and 1990, concurrent with major historical dermo disease outbreaks. Phenotypic changes included a shortening of the parasite’s life cycle and a tropism shift from deeper connective tissues to digestive epithelia. The changes are likely adaptive with regard to the reduced oyster abundance and longevity faced by P. marinus after rapid establishment of exotic pathogen Haplosporidium nelsoni in 1959. Our findings, we hypothesize, illustrate a novel ecosystem response to a marine parasite invasion: an increase in virulence in a native parasite.

  • modeling the transmission of Perkinsus marinus in the eastern oyster crassostrea virginica
    Fisheries Research, 2017
    Co-Authors: Gorka Bidegain, Susan E. Ford, David Bushek, Eric N Powell, John M Klinck, Eileen E Hofmann, Tal Benhorin, Daphne M Munroe, Ximing Guo
    Abstract:

    Abstract Dermo disease caused by the protistan Perkinsus marinus in Eastern oysters Crassotrea virginica is an important source of mortality impacting oyster population dynamics resulting in substantial losses in fisheries and aquaculture. The rapid transmission and spread of the disease minimized the importance of transmission models and past models (proliferation-based models) assumed simple density-dependent transmission or rapid infection post-settlement. This approach is a good approximation only for low population densities. A transmission model was developed for P. marinus in Eastern oysters that accounts for the seasonal change in disease dynamics and density-dependent foraging (of suspended particles) interference among hosts. The model, verified and evaluated against field observations, incorporates parasite release to the water column from live and dead individuals, parasite consumption by living oysters, the diffusion of parasites in the water, body burden-based dose-dependent transmission, recruitment, and disease-caused mortality. The model returns a basic reproduction number R 0 for Dermo much greater than unity ( R 0  = 90) in accordance with the current persistence and pandemic nature of this disease in oysters. No population density is obtained that is low enough to suppress R 0 below 1 (i.e. disease extinction). R 0 is also estimated for high oyster densities (>300 individuals m −2 ) and particularly for relatively large oysters (∼90 mm), today rare but once common before generalized overfishing occurred on healthy oyster reefs. In this scenario, R 0 drops below 1, indicating that high oyster density can limit disease invasion through foraging interference and depletion of parasites in the water column. High intensity recruitment events allow the oyster population to attain such densities and limit the development of epizootics. These results provide insight into the transition from past populations, where Dermo is inferred to have been limited in its impact, to the current persistent and pandemic nature of this disease. Further coupling of this model into metapopulation and hydrodynamic models could be a promising tool to support management decision-making for bivalve populations impacted by Dermo disease.

  • microarray analysis of gene expression in eastern oyster crassostrea virginica reveals a novel combination of antimicrobial and oxidative stress host responses after dermo Perkinsus marinus challenge
    Fish & Shellfish Immunology, 2010
    Co-Authors: Shaolin Wang, Susan E. Ford, David Bushek, Eric Peatman, Hong Liu, Huseyin Kucuktas, Jonas P Quilang, Richard K Wallace, Yongping Wang
    Abstract:

    Dermo disease, caused by Perkinsus marinus, is one of the most severe diseases of eastern oysters, Crassostrea virginica. It causes serious mortalities in both wild and aquacultured oysters. Using existing expressed sequence tag (EST) resources, we developed a 12K in situ oligonucleotide microarray and used it for the analysis of gene expression profiles of oysters during the interactions between P. marinus and its oyster host. Significant gene expression regulation was found at day 30 post-challenge in the eastern oyster. Putative identities of the differentially expressed genes revealed a set of genes involved in several processes including putative antimicrobial defenses, pathogen recognition and uptake, anti-oxidation and apoptosis. Consistent with results obtained from previous, smaller-scale experiments, expression profiles revealed a large set of genes likely involved in an active mitigating response to oxidative stress and apoptosis induced by P. marinus. Additionally, a unique galectin from C. virginica, CvGal, which serves as a preferential receptor for P. marinus trophozoites, was found to be significantly down-regulated in gill tissue of oysters with both light and heavy infection, suggesting an attempt to control parasite uptake and proliferation in the later stages of infection. Potential histone-derived antimicrobial responses to P. marinus were also revealed in the gene expression profiles.

  • discovery of genes expressed in response to Perkinsus marinus challenge in eastern crassostrea virginica and pacific c gigas oysters
    Gene, 2004
    Co-Authors: Arnaud Tanguy, Ximing Guo, Susan E. Ford
    Abstract:

    The protozoan pathogen Perkinsus marinus is the causative agent of Dermo, a lethal disease of the eastern oyster Crassostrea virginica, but not the Pacific oyster Crassostrea gigas. To understand the response of these two oysters to parasite exposure, a suppression subtractive hybridization (SSH) method was employed to characterize genes up-regulated during parasite challenge in both hemocytes and gills. The number of differentially expressed gene sequences obtained was 107 for C. virginica and 69 for C. gigas, including 46 and 37 sequences, respectively, that matched known genes in GenBank. Most of the sequences have not been characterized in other molluscs. Nineteen genes involved in immune system and cell communication, protein regulation and transcription, cell cycle, respiratory chain and cytoskeleton were selected for expression analysis by semi-quantitative PCR. Although varying in magnitude and timing post exposure, all genes screened showed over-expression in challenged oysters in both species, validating the SSH method. Results of this study highlighted some differences in gene expression between the two oysters in response to P. marinus infection, providing candidate genes and pathways for further analysis.

  • comparison of in vitro cultured and wild type Perkinsus marinus i pathogen virulence
    Diseases of Aquatic Organisms, 2002
    Co-Authors: Susan E. Ford, Marnita M Chintala, David Bushek
    Abstract:

    Perkinsus marinus is a highly contagious pathogen of the eastern oyster Crassostrea vir- ginica. Until recently, transmission studies have employed wild-type parasites isolated directly from infected oysters. Newly developed methods to propagate P. marinus in vitro have led to using cul- tured parasites for infection studies, but results suggest that cultured parasites are less virulent than wild-type parasites. In this paper, we report results of experiments designed to quantify differences between wild-type and cultured P. marinus virulence and to test the following hypotheses: (1) in vitro-cultured parasites are less virulent than wild-type parasites; (2) virulence decreases gradually during in vitro culture; (3) virulence of in vitro cultures can be restored by in vivo passage; (4) viru- lence changes with culture phase. Our results demonstrate that parasites freshly isolated from infected hosts are much more virulent than those propagated in culture, indicating a potential defi- ciency in the culture medium used. Virulence was lost immediately in culture and, for that reason, the practice of repassing cultured cells through the host to restore virulence does not work for P. marinus. Virulence was also associated with culture phase: log-phase parasites were significantly more viru- lent than those obtained from lag- or stationary-phase cultures.