Experimental inoculation of beagle dogs with Ehrlichia species detected from Ixodes ovatus

Three beagle dogs were inoculated with mice spleen/liver homogenate infected with Ehrlichia species detected from Ixodes ovatus (EIO) and one dog was used as a control. All three infected dogs did not show clinical signs of disease except for mild pyrexia throughout the 41-day study period. Splenomegaly was observed from Day 7 post-inoculation (p.i.) in two of the dogs. Hematological and biochemical abnormalities included mild thrombocytopenia, hypoproteinaemia, hypoalbuminaemia and increased C-reactive protein values. One of the dogs' splenic aspirate sample was PCR-positive for Ehrlichia Day 7 p.i. and another dogs' blood and bone marrow aspirate sample was PCR-positive Day 41 p.i. Sequence analysis of the PCR products showed 100% homology with the 16SrRNA partial gene sequence of Ehrlichia sp. HF565. Antibody titers to EIO were observed in all three experimentally infected dogs starting from the first week p.i. and cross-reactivity with Ehrlichia canis was detectable in one of the dogs starting Day 7 p.i. These data suggest that infection of dogs with EIO is possible, though is probably of low pathogenic importance. Cross-reactivity of EIO infected dog serum with E. canis raises the likelihood of false E. canis seropositive dogs.