Development and validation of multiplex SYBR Green real-time PCR assays for detection and molecular surveillance of four tick-borne canine haemoparasites

Abstract

Two multiplex SYBR Green based real-time PCR assays were standardized and evaluated to detect DNA from four canine haemoparasites (Babesia gibsoni, Babesia vogeli, Ehrlichia canis and Hepatozoon canis), along with internal controls from dogs from selected districts of Punjab state, India. Amplicons of 126 bp, 337 bp, 234 bp and 106 bp corresponding to B. gibsoni (18S rRNA gene), B. vogeli (18S rRNA gene), E. canis (virB9 gene), and H. canis (18S rRNA gene) were obtained, without any non-specific amplification. Microscopic evaluation of 200 blood samples from dogs revealed the prevalence of B. gibsoni, E. canis and H. canis as 1.5%, 1.5% and 1.0%, respectively, while with the multiplex real-time PCR assays the values for B. gibsoni, B. vogeli, E. canis, and H. canis were 8.0%, 1.5%, 3.5% and 23.5%, respectively, with concurrent infections of B. gibsoni and H. canis (3.5%); E. canis and H. canis (2.0%) and B. gibsoni, B. vogeli, E. canis, and H. canis (0.5%). The diagnostic sensitivity of the multiplex real-time PCR assays with respect to microscopy in the detection of B. gibsoni, E. canis and H. canis was 100% while the specificity for B. gibsoni, B. vogeli, E. canis, and H. canis was 93%, 100%, 98% and 77%, respectively, revealing the respective strength of agreement as ″fair″, ″slight″, ″moderate″ and ″slight″ by kappa value statistics, and the data were statistically significant, for detection of B. gibsoni and E. canis infections, by Fisher's exact test. The analytical sensitivity of the multiplex PCR assays in detection of DNAs was 8.59 × 10⁵ and 9.9 × 10⁶ copies for B. vogeli and E. canis, respectively, and 1.15 × 10⁶ and 3.41 × 10⁵ copies for B. gibsoni and H. canis, respectively. Assessment of risk factors viz. age, sex, breed, season and locations showed no significant association with the prevalence of these haemoparasites except for B. vogeli, E. canis and H. canis where significant associations were found for location, age and breed, respectively by multiplex real-time PCR assays.

Keywords: Babesia gibsoni; Babesia vogeli; Ehrlichia canis; Hepatozoon canis; Multiplex real-time PCR assays; Risk factors; Sensitivity; Specificity.