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Browsing by Author "Thomas, N. J."

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    Sarcocystis neurona infections in sea otter (Enhydra lutris): Evidence for natural infections with sarcocysts and transmission of infection to opossums (Didelphis virginiana)
    Dubey, Jitender P.; Rosypal, A. C.; Rosenthal, B. M.; Thomas, N. J.; Lindsay, David S.; Stanek, J. F.; Reed, S. M.; Saville, W. J. A. (American Society of Parasitology, 2001-12)
    Although Sarcocystis neurona has been identified in an array of terrestrial vertebrates, recent recognition of its capacity to infect marine mammals was unexpected. Here, sarcocysts from 2 naturally infected sea otters (Enhydra lutris) were characterized biologically, ultrastructurally, and genetically. DNA was extracted from frozen muscle of the first of these sea otters and was characterized as S. neurona by polymerase chain reation (PCR) amplification followed by restriction fragment length polymorphism analysis and sequencing. Sarcocysts from sea otter no. 1 were up to 350 mum long, and the villar protrusions on the sarcocyst wall were up to 1.3 mum long and up to 0.25 mum wide. The villar protrusions were tapered towards the villar tip. Ultrastructurally, sarcocysts were similar to S. neurona sarcocysts from the muscles of cats experimentally infected with S. neurona sporocysts, Skeletal muscles from a second sea otter failed to support PCR amplification of markers considered diagnostic for S. neurona but did induce the shedding of sporocysts when fed to a laboratory-raised opossum (Didelphis virginiana). Such sporocysts were subsequently fed to knockout mice for the interferon-gamma gene, resulting in infections with an agent identified as S. neurona on the basis of immunohistochemistry, serum antibodies, and diagnostic sequence detection. Thus, sea otters exposed to S. neurona may support the development of mature sarcocysts that are infectious to competent definitive hosts.
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    Sarcocysts of an unidentified species of Sarcocystis in the sea otter (Enhydra lutris)
    Dubey, Jitender P.; Lindsay, David S.; Rosenthal, B. M.; Thomas, N. J. (American Society of Parasitology, 2003-04)
    The number of Sarcocystis species that infect sea otters (Enhydra lutris) is unknown. Sea otter tissues were recently shown to harbor sarcocysts of S. neurona and of unidentified species of Sarcocystis. Whereas sarcocysts of S. neurona have walls 1-3 mum thick with type 9 villar protrusions, ultrastructure of a distinct thin-walled sarcocyst (0.5-0.7 mum thick) lacking villar protrusions, but instead exhibiting minute type I undulations on the sarcocyst wall, is described in this report. Parasites characterized from a sea otter infection were inferred to be related to, but distinct from, other species belonging to Sarcocystis, based on sequencing and phylogenetic analysis of a portion of the beta subunit of the plastid-encoded RNA polymerase gene.