الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
Multiple 18S r DNA sequences were obtained from two single oocyst derived lines of each of Eimeria meleagrimitis and Eimeria adenoeides. After analysingthe 15 new 18S rDNA sequences from 2 lines of E. meleagrimitis and 17 new sequences from 2 lines of E. adenoeides, there were clear indications that divergent, paralogous 18S rDNA copies exist within the nuclear genome of E. meleagrimitis. In contrast, mitochondrial cytochrome c oxidase subunit I (COI) partial sequences from all lines of a particular Eimeria species were identical and, in phylogenetic analyses, COI sequences clustered unambiguously in monophyletic and highly supported clades specific to individual Eimeria species. Phylogenetic analysisof the new 18S rDNA sequences from E. meleagrimitis showed that they formed two distinct clades: Type A with 4 new sequences; and Type B with 9 new sequences; Both Type A and Type B sequences were obtained from each of the single oocyst derived lines of E. meleagrimitis. Together these rDNA types formed a well supported E. meleagrimitis clade. Type A and B 18S rDNA sequences fromE. meleagrimitishad a mean sequence identity of only 97.4% whereas mean sequence identity within types was 99.1-99.3%. The observed intraspecific sequence divergence among E. meleagrimitis 18S rDNA sequence types was even higher (about 2.6%) than the interspecific sequence divergence present between some well recognized species such as E. tenella and E. necatrix (1.1%). Our observations suggest that, unlike COI sequences, 18S rDNA sequences are not reliable molecular markers to be used alone for species identification with coccidia, although 18S rDNA sequences have clear utility for phylogenetic reconstruction of apicomplexan parasites at the genus and higher taxonomic ranks.
Unlike with Eimeria species infecting chickens, specific identification and nomenclature of Eimeria species infecting turkeys is complicated and, in the absence of molecular data, imprecise. In an attempt to reconcile contradictory data reported on oocyst morphometrics and biological descriptions of various Eimeria species infecting turkey, we established single oocyst derived lines of five important Eimeria species infecting turkeys, Eimeria meleagrimitis (USMN08-01 strain), Eimeria adenoeides (Guelph strain), Eimeria gallopavonis (Weybridge strain), Eimeria meleagridis (USAR97-01 strain)and Eimeria dispersa (Briston strain). Short portions (514 bp) of mitochondrial cytochrome c oxidase subunit I gene (mt COI) from each were amplified and sequenced. Comparison of these sequences showed sufficient species specific sequence variation to recommend these short mt COI sequences as species specific markers. Uniformity of oocyst features (dimensions and oocyst structure) of each pure line was observed. Additional morphological features of the oocysts of these species are described useful for the microscopic differentiation of these Eimeria species. Combined molecular and morphometric data on these single species lines compared with the original species descriptions and more recent data have helped to clarify some confusing, and sometimes conflicting, features associated with these Eimeria spp. For example, these new data suggest that the KCH and KR strains of E. adenoeides reported previously represent two distinct species, E. adenoeides and E. meleagridis, respectively. Likewise, analysis of the Weybridge strainof E. adenoeides, which has long been used as reference strain in various studies conducted on the pathogenicity of E. adenoeides, indicates that this coccidium is actually a strain of E. gallopavonis. We highly recommend mtCOI sequence-based genotyping be incorporated into all studies using Eimeria spp. of turkeys to confirm species identifications and so that any resulting data can be associated correctly with a single named Eimeria species.
For the purpose of re-describing the Eimeria species that infect the turkey (Meleagrisgallopavo) and to establish benchmark biological information linked to genetic markers for each species, a strain of Eimeria meleagrimitis Tyzzer, 1929 was obtained from a litter sample from a turkey farm in Minnesota, USA in 2008. Multiple pure lines were derived by infecting turkey poults with a single oocyst; one of these lines was then used to re-describe biological and morphological features of E. meleagrimitis in the turkey. Oocyst morphometrics of this line matched those of this species as originally described by Tyzzer (1929). Three asexual generations of merogony (the first generation of meronts large in size and the second and third generations small) were detected in the intestines before the onset of gametogony; no developmental stages were detected in the cecal pouches. No mortality was induced by this line of E. meleagrimitiseven when turkey poults were infected with high doses of oocysts (up to 5×105 oocysts/bird) and despite the ability of E. meleagrimitis to induce severe mucosal damage in the upper and middle duodenum. Macroscopic lesions were characterized to provide a graded lesion scoring guide that should assist assessment of the severity of infections with this species in infected turkeys. The pathogenicity of the strain was investigated and a significant reduction in weight gain and feed conversion ratio was observed with doses of 104 oocysts/bird or more. The maximum yield of oocysts in the feces was obtained when birds were inoculated with 5×103 oocysts.
The Guelph strain of Eimeria adenoeides was obtained from a commercial turkey flock in Ontario, Canada; in approximately 1985. Single oocyst derived linesofE. adenoeides were propagated, and one of them used to re-describe biological and morphological features of E. adenoeides in the turkey. Oocysts of this strain are within the lower size ranges reported by Moore and Brown (1951) in the original species description but the average dimensions of the Guelph strain is 19±1.4 µm by 14±0.9 µm. It is likely that the original species description was based, at least in part, on a mixed culture of two or more Eimeria species. First generation meronts of E adenoeides Guelph strain were observed histologically as early as 32 hours post infection in the ileum and cecal neck. Early studies reported only two asexual generations suggested that first asexual cycle, appeared at 32 hours post infection (HPI) was overlooked. In the present study, three asexual generations were observed before the start of gametogony. The Guelph strain is also characterized by a prepatent period of 112 hours. The Guelph strain of E. adenoeides is a highly pathogenic coccidiumthat forms classic cecal lesions, including prominent caseous cecal cores, during moderate to severe infections. The maximum output of oocysts was obtained from birds inoculated with 1×103 oocysts and fecundity of 1.55×105 was obtained when birds were inoculated with 1× 102 oocysts; fecundity dropped dramatically as the inoculation dose increased.