Efficacy of a modified polymerase chain reaction assay for detection of Ehrlichia canis infection

Detection of Ehrlichia canis in acutely infected and convalescent dogs is i mportant for effective treatment and control. However, accurate detection h as been difficult to achieve, in part because dogs that have been treated t herapeutically often remain seropositive for extended periods. A new method , polymerase chain reaction (PCR) assay using biotinylated E. canis-specifi c primers (PCR-BP), was developed for detection of E. canis. Four dogs expe rimentally infected with E. canis by intravenous inoculation of whole blood from carrier dogs and 2 naturally infected convalescent carriers were used to compare the specificity and sensitivity of the new method with that of microscopy/blood smear evaluation, serologic test, and conventional PCR ass ay using E. canis-specific primers. In experimentally infected animals, inf ection was detected as early as 7 days postexposure using PCR-BP. Although the 2 naturally infected dogs were positive by serologic test and PCR-BP, b oth were negative by conventional PCR. Results suggest that the new method is a sensitive assay for detection of E. canis infection. In addition, resu lts were obtained more rapidly than with other PCR-based assays.