Description of a new species of Eimeria Schneider, 1875 (Apicomplexa: Eimeriidae) from the western Derby eland Taurotragus derbianusderbianus Gray (Artiodactyla: Bovidae) in Senegal
Examination of faecal samples from semi-captive western Derby elands Taurotragus derbianus derbianus Gray, in the Bandia and Fathala Reserves of Senegal, revealed the presence of oöcysts of the genus Eimeria Schneider, 1875 that we considered to represent a new species, Eimeria derbiani n. sp. The new species possesses nearly ellipsoidal oöcysts (length/width ratio 1.3) with a bi-layered wall and an average size of 27.6 × 21.5 μm. E. derbiani possesses a micropyle covered by a micropylar cap and ovoidal, single-layered sporocysts with an average size of 14.9 × 7.7 μm, each with a Stieda body. Sporozoites of E.derbiani possess a large refractile body and a nucleus. Sporulation lasted for 2 days at 23°C. The new species is differentiated from the two species parasitising Taurotragus oryx Pallas, E. canna Triffitt, 1924 and E. triffittae Yakimoff, 1934.
The western subspecies of the Derby eland Taurotragus derbianus Gray, T. derbianus derbianus, is on the Red list of threatened species with a status of critically endangered (IUCN 2011). The natural habitats of this subspecies of antelope are probably currently restricted to the Niokolo Koba National Park (NKNP). As a conservation measure, an ex situ breeding programme of semi-captive animals has been established at two managed wildlife nature reserves, Bandia and Fathala, in Senegal. Coprological examination, carried out during an expedition with the members of the conservation programme in 2011, revealed the presence of a new species of coccidia (Apicomplexa: Eimeriidae) in T. derbianus derbianus. This paper presents a description of the sporulated oöcyst of this new species.
Materials and methods
Eighty-two fresh excrement samples from the Western Derby eland (semi-captive herds in the Bandia and Fathala Reserves, originally captured in the wild, within the NKNP) were collected between 13 February and 22 March 2011 (dry season). Samples were collected immediately after defecation from herds consisting of all age classes (eight directly from the rectum of anesthetised animals). Samples were refrigerated, transported to the Laboratory of Parasitology of the State Veterinary Institute (Prague, Czech Republic) and examined within seven days. Unsporulated oöcysts were placed in Petri dishes with 2.5% (w/v) aqueous solution of potassium dichromate (K2Cr2O7) at ambient temperature of 23°C (± 2°C). Sporulation was observed daily for 20 days in native preparations (drops of homogenate transferred to a glass) and in parallel by flotation-centrifugation coprological method according to Breza (1957). Morphometric data were obtained for 30 sporulated oöcysts, according to Duszynski & Wilber (1997), using a Leica DMLB microscope equipped with a Leica DFC420 digital camera. All measurements are in micrometres and are given as a mean followed by the range in parentheses.
Eimeria derbiani n. sp.
Type-host: Western Derby eland Taurotragus derbianus derbianus Gray (Artiodactyla: Bovidae)
Type-locality: Bandia Reserve (14°33′31″N; 17°0′37″W), Senegal.
Type-material: Photosyntypes of oöcysts are deposited in the collection of the State Veterinary Institute Prague, Czech Republic (No. SVU013). Oöcysts kept in 2.5% (w/v) K2Cr2O7 solution are deposited in the Laboratory of Parasitology of the State Veterinary Institute Prague, Czech Republic.
Prevalence: 1 of 82 samples (1.2%).
Site: Unknown; oöcysts recovered from faeces.
Sporulation: 2 days at 23°C (± 2°C).
Etymology: The specific name is derived from the species name of the host.
Sporocysts ovoidal, 14.9 × 7.7 (13–16 × 7–8); shape index 1.9 (1.8–2.0). Sporocyst wall single-layered, thin and smooth. Stieda body present; substieda body absent; sporocyst residuum absent; large refractile body and nucleus present, located in central part of sporozoite.
Oöcysts were fully-sporulated within 2 days at 23°C.
No species of Eimeria Schneider, 1875 has ever been described from Taurotragus derbianus derbianus. However, two species of Eimeria have been described from another species of Taurotragus, the common eland T. oryx (Pallas); these are, E. canna Triffitt, 1924 and E. triffittae Yakimoff, 1934 (emend. Levine & Ivens, 1970). An unidentified Eimeria sp. has also been reported from this host (Pellérdy, 1974).
Eimeria derbiani n. sp. differs from E. canna in having somewhat wider oöcysts (24–30 × 19–24 vs 24–34 × 17–20 μm), indicating a different shape (no shape index was provided for E. canna). Furthermore, the oöcyst wall in the new species is bi-layered (vs tri-layered in E. canna); the polar granule and oöcyst and sporocyst residues are absent; and the sporocyst width is greater (7–8 vs 6–7 μm) (Triffitt, 1924; Levine & Ivens, 1970; Pellérdy, 1974).
The new species can be distinguished from E. triffittae in having bi-layered (vs single-layered) and larger oöcysts (24–30 × 19–24 vs 21–24 × 15–19; means 27.6 × 21.5 vs 21.1 × 17.8 μm), with a different shape index (1:1.3 vs 1:0.85). Sporocysts of E. derbiani are also larger (13–16 × 7–8 vs 9 × 5–6 μm) and possess a micropyle (absent in E. triffittae) (Yakimoff, 1934; Levine & Ivens, 1970; Pellérdy, 1974).
The above comparisons support the erection of the new species.
The period of two days for oöcyst sporulation appears somewhat brief as compared with data for other Eimeria spp. parasitising mammals (four days to three weeks; see for numerous examples, Levine, 1985). This might have been affected by the storage of the material during transportation in Senegal, which may have changed the conditions for sporulation. The acquisition of post-mortem material would enable the localisation of the developmental stages of this new coccidian species.
I am grateful to Ivan Pavlásek (State Veterinary Institute Prague) for his valuable comments, suggestions and help in preparing this project. Thanks are due to the leadership of the State Veterinary Institute Prague for providing laboratory equipment and to all colleagues from the Pathology and Parasitology Department for their support. I also thank Aneta Kostadinova for corrections to this manuscript, Miloslav Jirků (Institute of Parasitology, Academy of Sciences of the Czech Republic) for advice, the Institute of Tropics and Subtropics (Czech University of Life Sciences) and all members of the expedition. Finally, I thank Georges Rezk, Christian Dering, Vincent Dethier and the staff of Bandia and Fathala Reserve for their cooperation and permission to work in the field.