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Title: ANALYSIS OF SEQUENCE DIVERSITY OF RIBOSOMAL DNA (RDNA) GENES IN FOUR SPECIES OF EIMERIA

Author
item Miska, Kate
item Allen, Patricia

Submitted to: American Association of Veterinary Parasitologists Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/2/2005
Publication Date: 5/2/2005
Citation: Miska, K.B., Allen, P.C. 2005. Analysis of sequence diversity of ribosomal dna (rdna) genes in four species of eimeria. American Association of Veterinary Parasitologists Proceedings. p. 43.

Interpretive Summary:

Technical Abstract: Of the seven species that cause coccidiosis in chickens only Eimeria maxima field isolates exhibits significant antigenic diversity. This situation is problematic for vaccine design since multiple E. maxima strains must be used if sufficient cross-protection is to be elicited. Currently there is very little that is known about the genetic diversity of poultry Eimeria. In an effort to expand this knowledge we have characterized the diversity of the ITS-1, 5.8S, and ITS-2 regions in four species of Eimeria. Material from single isolates of Eimeria tenella and Eimeria papillata were included, while three and six isolates of Eimeria acervulina and Eimeria maxima were included, respectively. From these 11 isolates the sequences of 130 clones were analyzed. The data supports the presence of a single rDNA lineage in the genomes of E. acervulina, E. papillata, and E. tenella, which displays modest amounts of intra-species diversity. On the other hand, multiple rDNA lineages were found in all six E. maxima isolates. The phylogenetic analysis of E. maxima ITS-1 separates these sequences into three clades, however the analysis of ITS-2 sequences results in formation of two clades. Clearly the structure of E. maxima rDNA differs from that of the other three species. The E. maxima data can be explained by the presence of at least two rDNA loci that are on separate chromosomes, or that are spaced sufficiently far apart on the same chromosome that recombination between them does not take place. The amount of genetic diversity found in E. maxima rDNA is up to 20-30 times greater than that of E. tenella and is also much greater than the diversity observed in species of tissue-cyst forming coccidia such as Toxoplasma gondii.