Dalam parasit intrasel obligat seperti Eimeria tenella, protein membran dipercayai memainkan peranan yang penting dalam pengecaman dan pelekatan pada sel perumah supaya proses penyerangan parasit ke dalam sel perumah dapat disempurnakan. Untuk mengenalpasti protein pada membran E. tenella, penyaringan imuno telah dilakukan dengan menggunakan antiserum terhadap fraksi subsel yang telah diperkayakan dengan protein membran sporozoit. Usaha penyaringan imuno ini berjaya memencilkan 21 klon positif. Daripada jumlah ini, 13 klon menunjukkan pemadanan bermakna dengan jujukan dalam pangkalan data, iaitu 11 dengan protein mikronem EtMIC4, satu dengan EtMIC1 dan satu lagi dengan EtMIC2. Lapan klon selebihnya yang tidak menunjukkan sebarang pemadanan bermakna dengan jujukan dalam pangkalan data didapati membawa lima gen yang berlainan. Secara keseluruhannya, hasil kajian ini menunjukkan bahawa kaedah penyaringan imuno berupaya mengenalpasti gen baru yang kemungkinan besar mengekodkan protein membran dalam sporozoit E. tenella.
Eimeria tenggilingi is described from the pangolin or scaly anteater, Manis javanica, in Malaysia. The spheroid to subspheroid oocysts average 18.9 X 17.8 mum. The oocyst wall is composed of 3 layers, each approximately 0.6 mum thick. The 2 outer layers are striated and yellowish green. The inner layer is dark brown. One or 2 polar granules are present, but an oocyst residuum is absent. Ellipsoid sporocysts average 12.4 X 6.2 mum. A sporocyst residuum is present. This is the first Eimeria species reported from a host in the order Pholidota.
During 3 collecting expeditions between October 1996 and December 1996, fecal samples were obtained from 43 adult Gonocephalus grandis from Tanah Rata and the Cameron Highlands in Peninsular Malaysia. Two species of coccidia (Isospora gonocephali n. sp. [9/43, 23%] and Eimeria cameronensis n. sp. [3/43, 7%]) were discovered. Sporulated oocysts of I. gonocephali are subspherical to ovoidal, 22.3 x 18.7 (19-25 x 17-23) microm with a bilayered wall composed of a thin inner wall and a striated outer wall with a pitted surface; oocyst residuum absent; 1 polar granule present; sporocysts are almond-shaped, 13.5 x 9.2 (12-15 x 8.5-10) microm, Stieda body broad, domelike, substieda body fanlike, sporocyst residuum consisting of coarse, nonuniform granules in an amorphous cluster; sporozoites sausage-shaped with 1 large terminal, refractile body and lay randomly in the sporocyst. Sporulated oocysts of E. cameronensis are bilayered, smooth-walled, ellipsoidal, 26.5 x 12.4 (25-28 x 12-13) microm; with 1, small, polar granule composed of 2-3 splinter-like structures fused together; oocyst residuum absent; sporocysts ovoidal, almost rectangular-shaped 8.8 x 6.6 (8-9 x 5-7) microm, with no Stieda or substieda bodies, containing scattered residuum and 2 sausage-shaped sporozoites with 1 terminal, ovoidal refractile body. No individual lizard was host to both coccidian species.
Eimeria nebulosa n. sp. and Klossia pachyleparon n. sp. are described from the monitor lizard Varanus nebulosus in Malaysia. The flask shaped oocysts of E. nebulosa average 20.7 by 12.6 mum. The oocyst wall is composed of a single layer. There is a single polar granule but no residuum. Ellipsoidal sporocysts average 11.1 by 5.6 mum. A sporocyst residuum is present. Endogenous stages develop in the epithelial cells of the small intestine. The splerical oocysts of K. pachyleparon average 33.6 mum in diameter. The wall is about 2.5 mum thick and is composed of 3 layers. The spherical sporocysts average 10.8 mum in diameter. Sporocysts contain 4 sporozoites and residuum. Developmental stages were not observed.
Oocysts and endogenous stages of new species of Eimeria and Isospora from the house lizard, Gehyra mutilata, are described. The ellipsoid to subspherical 2-layered oocysts of E. cicaki averaged 24.0 X 21.0 mum. Polar granules are present. Micropyle and oocyst residuum are absent. Ellipsoid sporocysts average 12.2 X 9.0 mum. A sporocyst residuum is present, but the Stieda body is absent. Endogenous stages are in epithelial cells of the small intestine. The subspherical single-layered oocysts of I. thavari average 23.8 X 22.8 mum. The polar granule is present; micropyle and oocyst residuum are absent. Ellipsoid sporocysts average 12.8 X 9.4 mum. Stieda body and sporocyst residuum are present. There are endogenous stages in epithelial cells of the small intestine.
To date, more than 50 Eimeria spp. have been isolated from marsupials of the family Macropodidae. Although 18 species of Eimeria have been previously detected from multiple animal species belonging to the genus Macropus of the family, limited genetic analyses of the parasites are available, and their pathogenicity remains unclear. Here, we report the isolation of Eimeria spp. from a zoo specimen of red-necked wallaby (Macropodidae; Macropus rufogriseus). Specifically, two distinct types of Eimeria oocysts were recovered, one from the feces before treatment with an anthelmintic and the second from the intestinal contents after death of the animal. The oocysts obtained from the two sources were morphologically identified as E. hestermani and E. prionotemni, respectively. We successfully determined partial gene sequences from the two isolates, including segments of the 18S rRNA genes, and for the first time have used phylogenetic analyses of these sequences to assign the species to distinct clades. In combination with further genetic data, these results are expected to help elucidate the pathogenicity and host ranges of Eimeria spp. within the respective family and genus.
A study of about 500 expressed sequence tags (ESTs), derived from a merozoite cDNA library, was initiated as an approach to generate a larger pool of gene information on Eimeria tenella. Of the ESTs, 47.7% had matches with entries in the databases, including ribosomal proteins, metabolic enzymes and proteins with other functions, of which 14.3% represented previously known E. tenella genes. Thus over 50% of the ESTs had no significant database matches. The E. tenella EST dataset contained a range of highly abundant genes comparable with that found in the EST dataset of T. gondii and may thus reflect the importance of such molecules in the biology of the apicomplexan organisms. However, comparison of the two datasets revealed very few homologies between sequences of apical organelle molecules, and provides evidence for sequence divergence between these closely-related parasites. The data presented underpin the potential value of the EST strategy for the discovery of novel genes and may allow for a more rapid increase in the knowledge and understanding of gene expression in the merozoite life cycle stage of Eimeria spp.
Eimeria is a genus of parasites in the same phylum (Apicomplexa) as human parasites such as Toxoplasma, Cryptosporidium and the malaria parasite Plasmodium. As an apicomplexan whose life-cycle involves a single host, Eimeria is a convenient model for understanding this group of organisms. Although the genomes of the Apicomplexa are diverse, that of Eimeria is unique in being composed of large alternating blocks of sequence with very different characteristics - an arrangement seen in no other organism. This arrangement has impeded efforts to fully sequence the genome of Eimeria, which remains the last of the major apicomplexans to be fully analyzed. In order to increase the value of the genome sequence data and aid in the effort to gain a better understanding of the Eimeria tenella genome, we constructed a whole genome map for the parasite.
Limitations with current chemotherapeutic and vaccinal control of coccidiosis caused by Eimeria species continue to prompt development of novel controls, including the identification of new drug targets. Glucose-6-phosphate isomerase (G6-PI) has been proposed as a valid drug target for many protozoa, although polymorphism revealed by electrophoretic enzyme mobility has raised doubts for Eimeria. In this study we identified and sequenced the Eimeria tenella G6-PI orthologue (EtG6-PI) from the reference Houghton strain and confirmed its position within the prevailing taxonomic hierarchy, branching with the Apicomplexa and Plantae, distinct from the Animalia including the host, Gallus gallus. Comparison of the deduced 1647 bp EtG6-PI coding sequence with the 9016 bp genomic locus revealed 15 exons, all of which obey the intron-AG-/exon/-GT-intron splicing rule. Comparison with the Weybridge and Wisconsin strains revealed the presence of 33 single nucleotide polymorphisms (SNPs) and 14 insertion/deletion sites. Three SNPs were exonic and all yielded non-synonymous substitutions. Preliminary structural predictions suggest little association between the coding SNPs and key G6-PI catalytic residues or residues thought to be involved in the coordination of the G6-PI's substrate phosphate group. Thus, the significant polymorphism from its host orthologue and minimal intra-specific polymorphism suggest G6-PI remains a valid anti-coccidial drug target.
The protozoan parasite Eimeria tenella has a complex life cycle that includes two major asexual developmental stages, the merozoite and the sporozoite. The expressed sequence tag (EST) approach has been previously used to study gene expression of merozoites. We report here the generation and analysis of 556 ESTs from sporozoites. Comparative analyses of the two datasets reveal a number of transcripts that are preferentially expressed in a specific stage, including previously uncharacterised sequences. The data presented indicate the invaluable potential of the comparative EST analysis for providing information on gene expression patterns in the different developmental stages of E. tenella.
Matched MeSH terms: Eimeria tenella/genetics*; Eimeria tenella/growth & development