Molecular Characterization of Isosporoid Coccidia (Isospora and Atoxoplasma Spp.) in Passerine Birds

Abstract

Prevalence and disease caused by isosporoid coccidia in passerine birds are well recognized, but confusion about the life cycles of the parasites has led to taxonomic inconsistencies. In this study, we characterized segments of the chromosomal small and large-subunit ribosomal RNA (rRNA) genes of coccidial parasites from 23 species of passerine birds, as well as heat shock protein 70, apicoplast rRNA, and chromosomal 5.8s rRNA genes from a subgroup of these animals, and we correlated genetic data with morphologic findings for different parasite developmental stages, host phylogeny, and overall taxonomic relations within the phylum Apicomplexa. Our findings indicate that isosporoid coccidia of passerine birds are monophyletic but exhibit substantial diversity, with most avian species having one or several unique parasite lineages that underwent synchronous speciation with their hosts, interrupted by sporadic episodes of lateral transmission across species and families. Molecular analyses support a homoxenous life cycle, with sexual forms occurring chiefly in the intestines and asexual merozoites present systemically. Rarely, extraintestinal sexual stages can occur. The passerine coccidia are genetically most closely related to species of Eimeria rather than Isospora. We suggest that these parasites, whether identified from blood merozoite stages or fecal oocysts, be provisionally grouped as a homogeneous clade of individual species in a single taxon and formally named when reliable criteria allowing reclassification of related genera in the suborder Eimeriina are clarified.

Coccidia of New World passerine birds (Aves: Passeriformes): a review of Eimeria Schneider, 1875 and Isospora Schneider, 1881 (Apicomplexa: Eimeriidae)

“…Later, this species and more than 18 others, all with extra-intestinal life-cycles, were redescribed and allocated to Atoxoplasma Garnham, 1950by Levine (1982c. However, the validity of this genus was questioned by Boulard et al (1987) and, more recently, by Carreno & Barta (1999), Schrenzel et al (2005), Barta et al (2005) and Gill & Paperna (2008).…”

Introduced and Native Congeners Use Different Resource Allocation Strategies to Maintain Performance during Infection

“…The particular species of coccida used in this study, Isospora lacazei (family Eimeriidae; E. Greiner, personal communication), has a relatively broad geographical and host range within passerines (Levine 1982), though local adaption of haplotypes is likely common (Schrenzel et al 2005;Dolnik et al 2009). In infected chickens, oocysts are released in the feces 4-5 d postinfection, with peak shedding 6-9 d postinfection, followed by chronic shedding (Allen and Fetterer 2002).…”

Morphological and molecular characterization of Eimeria paludosa coccidian parasite (Apicomplexa:Eimeriidae) in a dusky moorhen (Gallinula tenebrosa, Gould, 1846) in Australia

“…The PCR for the 28S rRNA locus was carried out using a nested PCR with the external primers: 28SExF: 5′-TAC CCG CTG AAC TTA AGC-3′ and 28SExR: 5′-CMA CCA AGA TCT GCA CTA G-3′ as previously described (Schrenzel et al, 2005), which produced a PCR product size of~1495 bp. The internal primers (28InF: 5′-ACT ATG TTC CCT AGT AAC G-3′ and 28SInR 5′-AAC GCT TCG CCA CGA TCC-3′) were as previously reported (Yang et al, 2014) and produced an amplicon size of 1420 bp.…”