A colorimetric assay for Neospora caninum utilizing the loop-mediated isothermal amplification technique

Abstract

Neospora caninum (N. caninum) is a protozoan parasite that poses a serious risk to livestock by infecting various domestic and wild animals. Loop-Mediated Isothermal Amplification (LAMP) offers a cost-effective, highly sensitive, and specific method for detecting protozoan parasites. This study aims to develop a precise, rapid, and visually assessable colorimetric LAMP method, improving on traditional techniques. We employed a rigorous screening process to identify the optimal primer set for this experiment. Subsequently, we fine-tuned the LAMP reaction at 65 °C for 40 min with 270 μmol/L neutral red. We then confirmed the specificity of primers for N. caninum through experimental validation. The LAMP method demonstrated a lower detection limit compared to traditional Polymerase Chain Reaction (PCR) techniques. While LAMP offers clear advantages, the prevalence of DNA detected in 89 sheep serum and 59 bovine serum samples using the nested PCR method was 3.37 % (3/89) and 1.69 % (1/59), respectively. In contrast, when the LAMP method was employed, the prevalence of detected DNA rose to 5.61 % (5/89) for sheep and 3.38 % (2 /59) for bovine. A comparison of two molecular assays using the intragroup correlation coefficient (ICC) resulted in a value of 0.999 (95 % CI: 0.993–0.996, p < 0.001), indicating the LAMP method is in the “better” range according to James Lee's categorization. The LAMP technique, optimized with specific primers of N. caninum and neutral red dye, not only exhibited higher sensitivity but also provided convenience over conventional PCR methods, highlighting its potential for on-site applications and cost-effective field detection.