Isospora streperae n. sp. (Apicomplexa: Eimeriidae) from a grey currawong (Strepera versicolour plumbea) (Passeriformes: Artamidae) in Western Australia.

A new species, Isospora streperae n. sp., (Apicomplexa: Eimeriidae) is described from a single grey currawong bird (Strepera versicolour) (subspecies S. v. plumbea) in Western Australia. Sporulated oocysts (n = 32) are spherical to subspherical, with smooth colourless bilayered oocyst wall, 1.0 µm thick (outer layer 0⋅8 µm, inner 0.2 µm thick). Oocyst with a polar granule, an oocyst residuum and two spheroidal to subspheroidal sporocysts. Oocyst length, 23.8 (20.4-25.0) µm; oocyst width, 22.5 (20.0-24.6) µm; a shape index of 1.06, with Stieda, substieda bodies. Micropyle is absent. Sporocysts with compressed sporocyst residuum and four sporozoites. Sporocyst length, 14.4 (12.5-15.2) µm; sporocyst width, 11.2 (10.6-14.0) µm, sporocyst L/W ratio, 1.29. Necropsy of the bird identified haemorrhaging along the ileum and jejunum, which is where Isospora oocysts were also mostly detected. Molecular analysis was conducted at three loci; the 18S, 28S ribosomal RNA and the mitochondrial cytochrome oxidase (COI) gene. At the 18S locus, I. streperae n. sp. exhibited 99.5% and 99.4% similarity respectively to an Isospora sp. (MS-2003) from a Southern cape sparrow (Passer melanurus melanurus) and Isospora dovati from a domestic pigeon (Columba livia domestica). At the 28S locus, I. streperae n. sp. exhibited 96.9% similarity to an Isospora sp. (MS-2003) from a grosbeak starling (Scissirostrum dubium) and 95.8% similarity with the Isospora sp. (MS-2003) from a Southern cape sparrow. At the COI locus, I. streperae n. sp. exhibited 95.0% similarity to Isospora sp. from a yellow-necked mouse (Apodemus flavicollis) from the Czech Republic. Based on morphological and molecular data, this isolate is a new species of Isospora, which is named Isospora streperae n. sp. after its host, the grey currawong (Strepera versicolour plumbea). Crown