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Endosymbiotic bacteria were identified in the parasitic ciliate Ichthyophthirius multifiliis, a common pathogen of freshwater fish. PCR amplification of DNA prepared from two isolates of I. multifiliis, using primers that bind conserved sequences in bacterial 16S rRNA genes, generated an approximately 1,460-bp DNA product, which was cloned and sequenced.(More)
Naive channel catfish Ictalurus punctatus were infected by 2 isolates of the parasitic ciliate Ichthyophthirius multifiliis that differed in virulence. The isolates, NY1 and G5, Serotypes A and D, respectively, express different surface immobilization-antigens. The virulence of the 2 isolates was compared using tail-fin infections to quantitate parasite(More)
Surface immobilisation antigens (i-antigens) were purified from two strains of Ichthyophthirius multifiliis (NY1 and G5) that represent different i-antigen serotypes, namely A and D, respectively. The efficacy of the purified antigens as subunit vaccines was then tested in challenge studies using parasites of the homologous or heterologous serotype. Three(More)
Applied and basic research on the ciliate Ichthyophthirius multifiliis, an obligate parasite of freshwater fishes, requires passage on fish hosts to maintain laboratory stocks. However, continual repeated passage results in senescence of parasite clones over time. Because growth and development are directly correlated to water temperature, our objective was(More)
B cell responses in channel catfish to infection with the parasitic ciliate Ichthyophthirius multifiliis were followed for 3 years. High titers of serum IgM antibodies recognizing I. multifiliis immobilization antigens were present 5weeks after immunizing infection, but by 1 year titers were at low or undetectable levels. Two to three years after infection(More)
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