Serological survey for Ehrlichia canis in urban dogs from the major population centres of northern Australia

Objective To detect evidence of Ehrlichia canis infection of dogs from the major population centres of northern Australia, if present. Design Serological investigation for E canis. Procedure The sera of 316 domestic dogs, collected from the northern Austra lian population centres of Townsville, Cairns, Darwin, Kununurra and Broome from May 1997 to August 1999, were investigated for evidence of infection with E canis. Samples were tested for antibodies to E canis using an indire ct fluorescent antibody (IFA) test. The buffy coats from blood of dogs whos e serum reacted in the FA test were subsequently tested with a nested PCR t o detect E canis DNA. When available, blood from these dogs was injected in to suckling mice, which were then examined for clinical disease and tested for the presence of E canis antibodies. Results Of the 316 samples tested seven reacted in the IFA test for E canis . None of the dogs from which these samples were obtained exhibited clinica l signs of acute or chronic ehrlichiosis. The six positive samples availabl e for testing were negative when tested with the nested POR. Suckling mice inoculated with blood from three of the dogs whose serum was positive by IF A test showed no signs of clinical disease nor did their give positive reac tions in the IFA test. Conclusions No evidence of E canis infection was confirmed in any of the do gs examined. Northern Australia would appear to remain free of this obligat e parasite.