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Tetrahymena sp. infection in guppies, Poecilia reticulata Peters: parasite characterization and pathology of infected fish

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Tetrahymena sp. infection was diagnosed in guppies imported from Singapore. The parasite was isolated (Tet-NI) and optimally cultured in vitro in RM-9 medium. Cytological analyses [silver-staining and scanning electron microscopy (SEM)] revealed a pyriform-shaped, 64 × 41-μm holotrich ciliate without caudal cilium, containing a macro-nucleus (18.25 × 16.83 μm) and micro-nucleus (5.73 × 5.40 μm). Wet-mount examination and histological analyses of fish exposed to the parasite by co-habitation, immersion and infection by i.p. (intra-peritoneal) and i.m. (intra-muscular) injection revealed numerous ciliates on the skin, and in the gill and caudal fin blood vessels. Ciliates surrounded internal organs, the peri-orbital region of the eye, and were observed inside developing guppy embryos. Some muscle necrosis was associated with infection, but little or no inflammatory response. Immersion, co-habitation and i.m. injection caused relatively high infection rates and levels in the skin and tail, and lower infection in the gill blood vessels and internal organs; i.p. injection caused higher infection in the gill blood vessels and internal organs. Co-habited fish had relatively high infection levels in the hind-gut sub-mucosa. This is the first report of controlled systemic infection by Tetrahymena sp.

Keywords: Tetrahymena; fish; guppy; infection

Document Type: Research Article


Affiliations:  The French Associates Institute for Agriculture and Biotechnology of Drylands, The Jacob Blaustein Institutes for  Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, Israel

Publication date: October 1, 2009


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