New coccidian Eimeria iyoensis n. sp. (Apicomplexa: Eucoccidiorida: Eimeriidae) in farmed ring-necked pheasants (Phasianus colchicus L.) in Ehime, Japan.

Eight Eimeria spp. (Apicomplexa: Eimeriidae) have been isolated from the ring-necked pheasant (Phasianus colchicus Linnaeus), native to the temperate zone of Asia and eastern regions of Europe. Enteric coccidiosis has become a major issue associated with the breeding of farmed pheasants for game bird release or meat production. In this study, 35 fecal samples were collected from two-to-three-month-old ring-necked pheasants from four pheasant-rearing farms in Ehime Prefecture, Japan. Microscopic examination using a saturated sugar solution technique detected numerous subspherical oocysts from the samples of one farm and ellipsoidal Eimeria phasiani Tyzzer, 1929 oocysts from the three other farms. The subspherical oocysts were artificially sporulated and measured 18.6 µm by 15.7 µm with a 1.18 shape index (n = 150). Each oocyst contained four 10.7 µm × 5.8 µm sporocysts (n = 30) and one coarse refractile polar granule; no micropyle or residua were detected. Each sporocysts contained two sporozoites with one large and one small refractile body and sparsely distributed residua. The complete, 1,443-bp cytochrome c oxidase subunit I gene (cox1) of this isolate exhibited low sequence identity with published Eimeria spp. sequences including E. phasiani that was previously recorded in the same area. Meanwhile, the oocyst morphology most closely resembled that of Eimeria tetartooimia Wacha, 1973, but with distinct refractile polar granules and sporocyst residua. The available GenBank cox1 sequence of E. tetartooimia exhibited a sequence identity of < 94.5% with the study isolate. Here, the coccidian isolate identified in this study represents a new Eimeria iyoensis n. sp. capable of infecting ring-necked pheasant.

Eimerian and capillariid infection in farmed ring-necked pheasants (Phasianus colchicus karpowi) in Ehime, Japan, with special reference to their phylogenetic relationships with congeners.

We performed a parasitological examination of the gastrointestinal tract of farmed ring-necked pheasants (Phasianus colchicus karpowi) on two farms in Ehime, Japan. Fecal examination through flotation and sedimentation methods (43, 103, and 50 samples in three consecutive years from 2020, respectively) detected coccidian oocysts (5-58%), or capillarid (40-56%) and heterakid eggs (45-72%). Following artificial sporology, most sporulated coccidian oocysts were ellipsoidal without micropyle nor residuum, but with 1-3 polar refractile granules, morphologically reminiscent of Eimeria phasiani (Apicomplexa: Eucoccidiorida: Eimeriidae). Intensive sequencing of mitochondrial cytochrome c oxidase subunit I gene (cox-1) using pan-eimerian primers and multiple oocyst samples from different pheasants indicated a single species. We characterized, for the first time, the cox-1 sequence of E. phasiani, known to be prevalent in wild and captive ring-necked pheasants worldwide. Worm recovery under a dissection microscope revealed two capillariid and one heterakid nematode species: Eucoleus perforans (Nematoda: Trichocephalida: Capillariidae) in the esophageal epithelium (prevalence, 8-73%), Capillaria phasianina (Capillariidae) in the cecal mucosa (10-87%), and Heterakis gallinarum (Nematoda: Ascaridida: Heterakidae) in the cecal lumen (69-88%). The small subunit ribosomal RNA gene (SSU rDNA) of E. perforans was perfectly identical to that in a previous isolate from farmed Japanese green pheasants (Phasianus colchicus versicolor) at a distant locality in Japan. The SSU rDNA of C. phasianina was characterized, for the first time, demonstrating a sister relationship with Capillaria anatis, parasites found in the ceca of domestic ducks, geese, and various wild anatid birds.