Molecular detection and characterization of Anaplasma platysand Ehrlichia canisin dogs from the Caribbean

Anaplasma platysis a tick-transmitted rickettsial pathogen, which is known to be the etiologic agent for cyclic thrombocytopenia in its primary canine host. Infections with this pathogen are also reported in cats, cattle and people. Similarly, Ehrlichia canisis another tick-borne rickettsial pathogen responsible for canine monocytic ehrlichiosis and is also reported to cause infections in people. We describe infections in dogs with these two pathogens on the Caribbean island of Grenada, West Indies by detection using molecular methods. We utilized a 16S rRNA gene-based PCR assay to detect both Ehrlichiaand Anaplasmaspecies by screening 155 canine blood samples from asymptomatic dogs. We found 18.7 % of the dogs to be positive for A. platysand 16.8 % for E. canis. Samples that tested positive for A. platyswere further assessed by sequence analysis targeting 16S rRNA, 23S rRNA, citrate synthase (gltA)and heat shock protein (groEL)genes. Phylogenetic analysis revealed high correlation of A. platys16S rRNA and gltAgene sequences with the geographic origins, while 23S rRNA and groELgene sequences clustered independent of the geographic origins. This study represents an important step in defining the widespread distribution of active rickettsial infections in Caribbean dogs with no apparent clinical signs, thus posing a high risk for canine health and to a lesser extent to humans, as most dogs in the Caribbean are free-roaming.