A new Eimeria coccidian species (Apicomplexa: Eimeriidae) from Père David’s deer ( Elaphurus davidianus Milne-Edwards, 1866) in Dafeng Milu National Nature Reserve in Jiangsu Province, eastern China

Background Eimeria coccidiosis is a significant intestinal parasitic disease, which can lead to weight loss, disease and even death of many animals . At present, there is no information about the prevalence of Eimeria among the world’s endangered species of Père David’s deer ( Elaphurus davidianus ). Therefore, the purpose of this study is to identify an unknown Eimeria genus in the Père David’s deer in Dafeng Milu National Nature Reserve, China. Results A new Eimeria species is described from Père David’s deer. Sporulated oocysts ( n = 54) are pyriform, with a rough, yellowish brown, 2-layered oocyst wall (2.5 μm thick). A numerous small granules are dispersed randomly on the wall. Oocysts measured 41.2 (39.2–42.8) μm × 29.5 (27.9–30.5) μm, oocyst length/width (L/W) ratio, 1.4. Oocyst residuum, a polar granule and a polar cap are absent. The micropyle (3.5 μm wide) is present. Sporocysts are spindle shaped, 18.2 (16.5–20.0) μm × 10.5 (9.8–11.9) μm, sporocyst L/W ratio, 1.7 (1.5–1.9). A thin convex Stieda body is present and the sporocyst residuum is composed of numerous small granules less than 2.0 μm in diameter dispersed randomly. Each sporocyst contained 2 comma-shaped sporozoites in head-to-tail arrangement. A nucleus is located immediately anterior to the posterior, strong refractive and subspherical refractile body (~ 8 μm). Molecular analysis was conducted at the 18S, ITS-1 and COI loci. Conclusion Based on the morphological and molecular data, this isolate is a new species of coccidian parasite, which is named Eimeria davidianusi after its host, the Père David’s deer ( Elaphurus davidianus ).