Coinfection with three Ehrlichia species in dogs from Thailand and Venezuela with emphasis on consideration of 16S ribosomal DNA secondary structure

As part of a larger study to investigate tick-borne infections in dogs fron t Thailand and Venezuela, documentation of coinfection with three Ehrlichia species in two dogs, one from each country, became the focus of the presen t study. Although neither dog had clinical signs attributable to ehrlichios is, both dogs were anemic and neutropenic and the Thai dog was thrombocytop enic. Genus- and species-specific PCR targeting the 16S rRNA genes indicate d that both dogs were coinfected with Ehrlichia canis, E. platys, and E. eq ui. To our knowledge, these results provide the first molecular documentati on for the presence of E. equi in dogs from these countries. Using universa l bacterial PCR primers, one nearly full-length 16S rRNA gene could be ampl ified from each dog. The sequences were identical to each other and almost identical to that of E. platys (AF156784), providing the first E. platys 16 S ribosomal DNA (rDNA) sequences reported from these two geographically div ergent countries. To determine whether these sequence differences allow dif ferentiation between these two strains and other published 16S rDNA E. plat ys sequences, we performed a phylogenetic analysis of the rRNA incorporatin g the consideration of secondary structure.