Molecular comparisons of Babesia odocoilei using the internal transcribed spacers of ribosomal RNA

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Title: Molecular comparisons of Babesia odocoilei using the internal transcribed spacers of ribosomal RNA
Author: Schoelkopf, Lorien
Abstract: Babesia odocoilei is an intraerythrocytic apicomplexan parasite which infects cervidae , sometimes causing babesiosis . It is vectored by the tick Ixodes scapularis and is distributed throughout the southeastern United States . The geographic and host range continue to extend as new incidence of infection is detected . A genomic DNA region spanning the internal transcribed spacer 1 (ITS1 ) , 5 .8S rRNA gene , and ITS2 of ribosomal RNA (rRNA ) from 18 B . odocoilei isolates (speciation confirmed by small subunit rRNA analysis ) was amplified using the polymerase chain reaction , cloned and sequenced . The isolates originated from 6 different cervidae or bovidae hosts in various U .S . geographic areas . Included in the analysis was a previously described reindeer B . odocoilei -like isolate , RD61 , which showed only 99 .0 % identity in SSU rRNA analysis to B . odocoilei . Percent identity pairwise comparisons among the samples were calculated for both the full ITS1 -5 .8S -ITS2 and individual genomic regions . Identity values for all comparisons ranged from 90 % to 100 % , with the exception of RD61 , which showed no higher than 88 % identity for all gene regions . An analysis of fixed differences identified in the ITS1 and ITS2 gene regions of all clones revealed 21 fixed differences in ITS1 , and only 11 in ITS2 . Most isolates were found to have 2 overall patterns of fixed differences , although some had 1 or 3 . Phylogenetic analysis of all sequences for the entire ITS1 -5 .8S -ITS2 gene region placed most isolates into 2 distinct groups corresponding to those observed in the analysis of fixed differences . This suggested the presence of at least 2 rRNA transcription units in B . odocoilei . ITS analysis failed to demonstrate host or geographic differences that might serve to pinpoint the source of outbreaks of B . odocoilei in farmed and managed host animals . This failure might result from genetic recombination of ITS genomic regions during the tick vector stage . Lack of conspecificity between the RD61 isolate and B . odocoilei was supported by this study ; however , more data are needed to clarify the taxonomic status of this B . odocoilei -like isolate .
URI: http : / /hdl .handle .net /1969 .1 /2660
Date: 2005-11-01

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Molecular comparisons of Babesia odocoilei using the internal transcribed spacers of ribosomal RNA. Available electronically from http : / /hdl .handle .net /1969 .1 /2660 .

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