Coinfection with ThreeEhrlichiaSpecies in Dogs from Thailand and Venezuela with Emphasis on Consideration of 16S Ribosomal DNA Secondary Structure

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Abstract
As part of a larger study to investigate tick-borne infections in dogs from Thailand and Venezuela, documentation of coinfection with threeEhrlichiaspecies in two dogs, one from each country, became the focus of the present study. Although neither dog had clinical signs attributable to ehrlichiosis, both dogs were anemic and neutropenic and the Thai dog was thrombocytopenic. Genus- and species-specific PCR targeting the 16S rRNA genes indicated that both dogs were coinfected withEhrlichia canis,E. platys, andE. equi. To our knowledge, these results provide the first molecular documentation for the presence ofE. equiin dogs from these countries. Using universal bacterial PCR primers, one nearly full-length 16S rRNA gene could be amplified from each dog. The sequences were identical to each other and almost identical to that ofE. platys(AF156784), providing the firstE. platys16S ribosomal DNA (rDNA) sequences reported from these two geographically divergent countries. To determine whether these sequence differences allow differentiation between these two strains and other published 16S rDNAE. platyssequences, we performed a phylogenetic analysis of the rRNA, incorporating the consideration of secondary structure.