Rapid isothermal molecular tests to discriminate between Leishmania braziliensis and Leishmania infantum infections in dogs.

Background: We standardized two recombinase polymerase amplification (RPA) assays coupled with lateral flow (LF) strips for the detection of Leishmania braziliensis and Leishmania infantum kinetoplast DNA (kDNA). Methods: The RPA-LF assays were tested at different temperatures and reaction times, using DNA from cultured L. braziliensis and L. infantum. The L. infantum RPA-LF was also tested using clinical samples (bone marrow and skin) from infected and uninfected dogs. Results: The detection limits (analytical sensitivity) of the assays were 0.04 pg/μl and 0.04 ng/μl for L. braziliensis and L. infantum kDNA, respectively. Using clinical samples, the L. infantum RPA-LF successfully detected the parasite kDNA in bone marrow (21/30; 70.0%) and skin samples (23/30, 76.6%) from naturally infected dogs. We found an almost perfect agreement (kappa = 0.807) between RPA-LF for L. infantum and our reference quantitative real-time polymerase chain reaction (qPCR), considering clinical samples with a quantification cycle (Cq) < 30, whereas the agreement with samples with a Cq > 30 (lower parasite loads) was moderate (kappa = 0.440). Conclusions: The RPA-LF assays developed here may be promising diagnostic tools for point-of-care diagnosis of L. infantum and L. braziliensis infection in dogs, particularly in remote rural areas lacking laboratory infrastructure. [ABSTRACT FROM AUTHOR]