Cecal coccidiosis in turkeys: Comparative biology of Eimeria species in the lower intestinal tract of turkeys using genetically typed, single oocyst–derived lines
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Differentiating the Eimeria species causing cecal coccidiosis in turkeys is challenging. To obtain benchmark biological data for Eimeria gallopavonis Hawkins 1952 and Eimeria meleagridis Tyzzer 1929 and to support the stability of the species concept for each, genetically typed, single oocyst–derived lines of E. gallopavonis Weybridge strain and E. meleagridis USAR97-01 were used to redescribe the biological, pathological, and morphological features of these parasites. Oocysts of E. meleagridis and E. gallopavonis overlap in dimensions, but oocysts of the former have a single polar granule compared with multiple in the latter. Mature first-generation meronts of E. gallopavonis were observed histologically as early as 48 h post-inoculation alongside the villi in jejunum (before and after Meckel’s diverticulum), ileum, cecal neck and rectum, but not cecal pouches. Three asexual cycles were observed suggesting that early workers apparently overlooked one asexual cycle. Examination of endogenous development of a culture labeled “Eimeria adenoeides Weybridge strain” suggested that this strain (found in a number of publications as a large oocyst strain of “Eimeria adenoeides”) matched the species description of E. gallopavonis and so has been renamed herein. Macroscopic lesions induced by E. gallopavonis consisted of caseous material distally from posterior of the yolk stalk through the remaining intestinal tract, excluding the cecal pouches. For E. meleagridis, only the first asexual generation was observed outside of the cecal pouches within the jejunum around the yolk stalk. Second- and 3rd-generation asexual stages developed almost exclusively in the cecal pouches (but not cecal necks). Macroscopic lesions described for E. meleagridis were similar to those of E. adenoeides. Marked corrugation of the cecal serosal surface was observed. Cecal pouches contained creamy colored, caseous material varying from loose material to granular. Distinguishing features of the Eimeria species infecting the lower part of the small intestine are summarized in the present study, and new type specimens were designated for E. gallopavonis and E. meleagridis to provide a stable reference for future work with these parasites.
KeywordsEimeria gallopavonis Eimeria meleagridis Eimeria adenoeides Coccidiosis Turkey Eimeria Life cycle Endogenous development Nuclear 18S rDNA Mitochondrial cytochrome c oxidase subunit I Taxonomy
Julie Cobean and Julia Whale are thanked for their skilled technical assistance. Staff members of the CAF Animal Isolation Facility at the University of Guelph are thanked for their skilled care of experimental animals used in this study.
This work was supported by grants from the Natural Sciences and Engineering Research Council of Canada (NSERC, DG 400566); from the Ontario Ministry of Agriculture, Food, and Rural Affairs (OMAFRA, Tier II 200331); and from the Federal Economic Development Agency for Southern Ontario (FedDev) to J.R.B. Scholarship support was provided by the Ministry of Higher Education and Research (MOHE), Egypt, to S.E.S. administered through the Bureau of Cultural and Educational Affairs (BCEA) of Egypt in Canada; scholarship support was provided to M.E.O. by the Ontario Veterinary College (OVC PhD Scholarship).
Compliance with ethical standards
All experimental manipulations were reviewed and approved by the University of Guelph’s Animal Care Committee and complied with the Canadian Council on Animal Care’s Guide to the Care and Use of Experimental Animals (2nd edition).
Conflict of interest statement
The authors declare that they have no conflict of interest.
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