RESEARCH Open Access Development of a generic Ehrlichia FRET-qPCR and investigation of ehrlichioses in domestic ruminants on five Caribbean islands

Background: The Ehrlichia are obligate intracellular Gram-negative tick-borne bacteria that are important human and animal pathogens. There is a need for assays to rapidly and reliably detect and differentiate the five generally recognized species into groups in a single reaction: E. canis, E. chaffeensis, E. ewingii, E. muris and E. ruminantium. Methods: We developed primers and probes against the 16S rRNA gene to enable us to reliably detect the five major Ehrlichia spp. in a single FRET-qPCR. We tested the Ehrlichia FRET-qPCR on reference strains and on DNA from the blood of domestic ruminants from five Caribbean islands. The Ehrlichia present were determined using melting point analysis and by sequencing the Ehrlichia FRET-qPCR products as well as those of a nested PCR against the citrate synthase gene (gltA). Results: Our Ehrlichia FRET-qPCR was negative for the closely related Anaplasma marginale and A. phagocytophilum but gave positive reactions with reference strains of the most generally recognized species and with other less characterized Ehrlichia of domestic ruminants, mainly E. ovina, the Panola Mountain Ehrlichia, and Ehrlichia sp. BOV2010. Melting point analysis revealed 4 distinct groups: E. ruminantium (Tm ~55.8 °C); E. chaffeensis and E. ewingii (Tm ~57.7 °C); E. canis, E. muris, E. ovina and Ehrlichia sp. BOV 2010 (Tm ~62.0 °C); and the Panola Mountain Ehrlichia (Tm ~65.5 °C). The detection limit of the FRET-qPCR was ~ 5 gene copies in a reaction and the sequence