Comparison of Leishmania OligoC-TesT PCR with conventional and real-time PCR for the detection of canine Leishmania infection

There is a need for standardization and simplification of the existing methods for molecular detection of Leishmania infantum in the canine reservoir host. The commercially available OligoC-TesT kit incorporates standardized PCR reagents with rapid oligochromatographic dipstick detection of PCR products, and is highly sensitive in humans, but not yet independently validated in dogs. Here we compare the sensitivity of the OligoC-TesT with that of nested kinetoplast DNA (kDNA) PCR, nested internal transcribed spacer-1 (ITS-1) PCR, and a PCR/hybridization protocol, in longitudinal naturally infected canine bone marrow samples for which parasite burdens were measured by real-time quantitative PCR (qPCR). Sensitivity of the OligoC-TesT in infected dogs was 70% (95% C.I. 63-78%), similar to that of kDNA PCR (72%; 95% C.I. 65-80%; P=0.69), but significantly greater than PCR/hybridization (61%; 95% C.I. 53-69%; P=0.007) and ITS-1 nested PCR (54%; 95% C.I. 45-62%; P<0.001); real-time qPCR had the highest sensitivity (91%; 95% C.I. 85-95%; P<0.001). OligoC-TesT sensitivity was greater in polysymptomatic and oligosymptomatic dogs compared to asymptomatic dogs (93%, 74%, and 61%, respectively; P=0.005), a trend also observed in the other qualitative PCR methods tested (P</=0.05). Test positivity increased with increasing parasite burden measured by real-time qPCR: OligoC-TesT and kDNA PCR detected 100% and 99% of positive samples when parasite burden exceeded 74 and 49 parasites/ml, respectively. The OligoC-TesT has high sensitivity for detection of canine Leishmania infections; ease of operation and interpretation are further advantages for veterinary diagnostic laboratories, and for large-scale survey work in developing countries