Worldwide Dispersion of Coccidia from Migratory Birds: First Report of Eimeria bazi Chauhan et Bhatia, 1970 (Eimeriidae) Outside Asia from Buff-Necked Ibises Theristicus caudatus (Boddaert, 1783) (Threskiornithidae) in South America

Abstract

Background: Eimeria spp. are coccidian protozoan parasites of domestic and wild animals. Pelecaniform birds are hosts of some Eimeria spp., however, from the family Threskiornithidae only one eimerian species is recorded, Eimeria bazi Chauhan et Bhatia, 1970 which was described from red-naped ibises Pseudibis papillosa (Temminck, 1824) in India. In this study, in turn, this species is morphologically and molecularly identified from buff-necked ibises Theristicus caudatus (Boddaert, 1783) in Brazil.

Purpose: This study aimed to report E. bazi from buff-necked ibises T. caudatus in southeastern Brazil, revealing the worldwide distribution of this coccidian species, in addition to providing preliminary genotypic identification via sequencing of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene.

Methods: A total of 73 fecal samples were collected from a flock of buff-necked ibises, which remained on the campus of the Federal Rural University of Rio de Janeiro (Universidade Federal Rural do Rio de Janeiro-UFRRJ) from March 2019 to August 2020. Fecal samples were processed by the Sheather's method to recover oocysts. The morphological and morphometrical studies of the oocysts were performed using an optical microscope and graphic editing software. Molecular analysis was performed by sequencing of the COI gene, and the phylogenetic analysis was based in the neighbor-joining and maximum likelihood estimates.

Results: Forty-five fecal samples were positive for oocysts identified as E. bazi. This oocysts are ovoidal, 26.2 × 18.9 μm, with smooth to slightly rough wall, c.1.7 μm thick. Micropyle robust and protruding, sometimes with a polar body attached. Oocyst residuum absent, but one or two small polar granules are present. Sporocysts ovoidal to lemon-shaped, 14.2 × 8.7 μm. The Stieda body is knob-like to rounded and sub-Stieda body is absent or vestigial. Sporocyst residuum is composed of granules often membrane-bound. Sporozoites are vermiform, with refractile bodies. This morphology was consistent with the original description of E. bazi from P. papillosa in India. Molecular analysis at the COI gene exhibited low similarity with coccidians sequenced for the same genic region deposited in GenBank, sitting E. bazi separately on the cladogram.

Conclusions: The morphological and molecular studies support the identification of E. bazi from T. caudatus in South America, thus revealing the wide distribution of this eimerian species in the world provided by migratory birds and/or with intercontinental distribution.

Keywords: Coccidia; Federal Rural University of Rio de Janeiro; Ibises; Migratory birds; Molecular biology; Morphology; Oocysts; Phylogeny; Taxonomy.