Eimeria legionensis and Eimeria kofoidi (Apicomplexa: Eimeriidae) infection and associated lesions in naturally infected red-legged partridges (alectoris rufa)

With the aim to identify the Eimeria species responsible for coccidiosis in 50 deceased red-legged partridges (Alectoris rufa), individual faecal samples were collected, dissolved in 2.5% K2Cr2O7 solution and maintained at room temperature to allow sporulation of the oocysts. Morphology and dimensions of sporulated oocysts were microscopically evaluated. To assess Eimeria intestinal localisation, faecal samples and scrapings taken from the different intestinal segments of each deceased animal were examined by fresh smears and flotation test, while the intestines were examined for gross lesions, then fixed in 10% formalin and processed for histopathological analysis. From scrapings and morphological analysis, Eimeria kofoidi and Eimeria legionensis were identified in the small intestine and in the caecum and colon, respectively. Histopathological analysis confirmed the presence of two distinct Eimeria species. In particular, E. kofoidi macrogamonts were found in epithelial cells of jejunum and ileum, between the basal lamina and the nucleus of the infected intestinal cells. This latter was flattened and displaced above. E. legionensis macrogamonts were instead found localised between the nucleus and the luminal surface of the infected caeca and colonic cells and these macrogamonts were larger than those of E. kofoidi. Chronic enteritis and severe displacement of the deep crypts of the small intestine, large areas of caeca and colonic epithelial necrosis associated to thickened wall and mononuclear cells infiltration diffused in a transmural manner, were the main histopathological lesions.