Global transcriptome landscape of the rabbit protozoan parasite Eimeria stiedae

Background Coccidiosis caused by Eimeria stiedae is a widespread and economically significant disease of rabbits. The lack of studies on the life-cycle development and host interactions of E. stiedae at the molecular level has hampered our understanding of its pathogenesis. Methods In this study, we present a comprehensive transcriptome landscape of E. stiedae to illustrate its dynamic development from unsporulated oocysts to sporulated oocysts, merozoites, and gametocytes, and to identify genes related to parasite-host interactions during parasitism using combined PacBio single-molecule real-time and Illumina RNA sequencing followed by bioinformatics analysis and qRT-PCR validation. Results In total, 12,582 non-redundant full-length transcripts were generated with an average length of 1808 bp from the life-cycle stages of E. stiedae. Pairwise comparisons between stages revealed 8775 differentially expressed genes (DEGs) showing highly significant description changes, which compiled a snapshot of the mechanisms underlining asexual and sexual biology of E. stiedae including oocyst sporulation between unsporulated and sporulated oocysts; merozoite replication between sporulated oocysts and merozoites; and gametophyte development and gamete generation between merozoites and gametocytes. Further, 248 DEGs were grouped into nine series clusters and five groups by expression patterns, and showed that parasite–host interaction-related genes predominated in merozoites and gametocytes and were mostly involved in steroid biosynthesis and lipid metabolism and carboxylic acid. Additionally, co-expression analyses identified genes associated with development and host invasion in unsporulated and sporulated oocysts and immune interactions during gametocyte parasitism. Conclusions This is the first study, to our knowledge, to use the global transcriptome profiles to decipher molecular changes across the E. stiedae life cycle, and these results not only provide important information for the molecular characterization of E. stiedae, but also offer valuable resources to study other apicomplexan parasites with veterinary and public significance. Graphic Abstract

Clinico-pathologic observations of spontaneous hepatic coccidiosis in broiler rabbits maintained in Bannerghatta biological park in Karnataka state of India

The present study reports the clinico-pathologic changes observed in spontaneous hepatic coccidiosis caused by Eimeria stiedae in rabbits at Bannerghatta Biological Park (BBP) in Karnataka state of India. The clinical signs observed in the affected rabbits included sudden death, stunted growth, anorexia, weight loss, diarrhoea and abdominal pain. Increased liver enzymes and bilirubin was noticed upon biochemical examination. At necropsy, lesions included grossly enlarged liver (hepatomegaly) with presence of discrete yellowish-white nodules ranging from 1mm to 5mm size throughout the parenchyma containing a thick creamy white fluid. Faecal sample examination demonstrated the presence of Eimeria oocyts. The impression smears from the liver and intestinal mucosa also showed Eimeria oocysts, degenerative changes, necrotic cells and mononuclear cell aggregation to form oocyst granuloma. Histological observation revealed distension of bile duct, hyperplasia of epithelium along with numerous coccidian oocysts at the centre. Granulomatous tissues were observed to have encircled the bile duct with infiltration of inflammatory cells. Microscopic examination of exudates from liver also revealed numerous oocysts of E. stiedae. Multiple areas of coagulative necrosis of hepatic cells surrounded with inflammatory cells were also found.