DAO 62:133-145 (2004)  -  doi:10.3354/dao062133

Cryptosporidium scophthalmi n. sp. (Apicomplexa: Cryptosporidiidae) from cultured turbot Scophthalmus maximus. Light and electron microscope description and histopathological study

P. Alvarez-Pellitero1,*, M. I. Quiroga2, A. Sitjà-Bobadilla1, M. J. Redondo1,O. Palenzuela1, F. Padrós3, S. Vázquez2, J. M. Nieto2

1Instituto de Acuicultura Torre de la Sal, Consejo Superior de Investigaciones Científicas, Ribera de Cabanes, 12595 Castellón, Spain
2Departamento de Ciencias Clínicas Veterinarias, Facultad de Veterinaria, Universidad de Santiago, Campus Universitario, 27002 Lugo, Spain
3Servicio de Diagnóstico Patológico en Peces. Facultat de Veterinària, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain

ABSTRACT: Cryptosporidium scophthalmi n. sp. is described from the turbot Scophthalmus maximus L., sampled from different farms on the coast of NW Spain. The parasite was found mainly in the intestinal epithelium and very seldom in the stomach. Oocysts were almost spherical, with 4 naked sporozoites and a residuum, and measured 3.7–5.03 × 3.03–4.69 µm (mean 4.44 × 3.91) (shape index 1.05–1.34, mean 1.14). Sporulation was endogenous, as fully sporulated oocysts were found within the intestinal epithelium, lumen and faeces. Merogonial and gamogonial stages were in the typical extracytoplasmic position, whereas sporogonial stages were deep within the epithelium. Oocysts and other stages of C. scophthalmi comply with most of the diagnostic features of the genus Cryptosporidium, but differ from all hitherto described species. Ultrastructural features, including the characteristic feeding organelle, were mainly comparable with those of other Cryptosporidium species. Mitochondria were frequently observed in sporozoites. Infection prevalence was very variable, and juvenile fish were most frequently and intensively parasitised. External clinical signs were not detected, although some fish showed intestinal distension at necropsy. The marked histopathological damage occurring in severe infection includes distension of epithelial cells by large vacuoles, containing clusters of oocysts, and can lead to sloughing of epithelial cell remnants and oocysts or even detachment of intestinal mucosa. An inflammatory reaction involving leucocyte infiltration was sometimes observed.

KEY WORDS: Cryptosporidium scophthalmi n. sp. · Coccidia · Ultrastructure · Histopathology · Teleostei · Aquaculture

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