THE FIRST ISOLATION, IN-VITRO PROPAGATION, AND GENETIC-CHARACTERIZATION OF EHRLICHIA-CANIS IN ISRAEL

Ehrlichia canis, the etiologic agent of canine ehrlichiosis, was isola ted in Israel from a naturally infected dog with acute signs of the di sease, The organism designated E. canis 611, was passaged experimental ly to a beagle, from which it was propagated in primary canine monocyt es. The organism was then grown in vitro in a continuous canine cell l ine, DH82. Nine beagles subsequently injected with whole E. canis-infe cted blood all developed typical symptoms of ehrlichiosis. An indirect immunofluorescence antibody test to E. canis was developed and compar ed with a commercial kit, revealing a good correlation between the two assays. Transmission electron microscopy of DH82 cells infected with the Israeli strain of E, canis (611), revealed organisms similar to th ose described in the literature: two different forms of morulae appear ed, one tightly, the other loosely, packed. The 16S rRNA gene sequence obtained from the Israeli Ehrlichia isolate was compared with other i solates, E. canis Oklahoma and E. canis Florida. The Israeli strain 16 5 rRNA had three nucleotide differences from the Oklahoma isolate, and four nucleotide differences from the Florida isolate, in addition to one nucleotide gap in each. The Israeli isolate was found to be 0.54% different from the Oklahoma strain, and 0.61% different from the Flori da strain, These are the same magnitudes of differences displayed by t he other most closely related group in the phylogenetic tree, namely E hrlichia equi, Ehrlichia phagocytophilia and the human granulocytic eh rlichia.