A novel TaqMan probe-based pentaplex qPCR assay for the simultaneous detection of five pathogenic protozoans

The emergence of coinfection with Toxoplasma gondii, Neospora caninum, Eimeria stiedai, Giardia lamblia, and Trypanosoma evansi is an important problem that endangers human health, animal quality and public sanitary security. These pathogenic protozoans play important roles in establishment of similar clinical signs of diseases in humans, pigs, sheep, and rabbits, including fever, diarrhea, hepatitis, encephalitis, and reproductive disorders. Therefore, a rapid and specific diagnostic method to simultaneously detect these five pathogens is urgently required. Here, we developed a TaqMan-probe-based quantitative real-time polymerase chain reaction (qPCR) for the simultaneous detection of these five pathogens for the first time. Specific primers and probes were designed targeting the G3PDH gene of Toxoplasma gondii, the NC5 gene of Neospora caninum, the ADF gene of Eimeria stiedai, the GDH gene of Giardia lamblia, the COX1 gene of Trypanosoma evansi, and a TaqMan-probe-based pentaplex qPCR assay capable of simultaneously detecting these five pathogens was developed. The assay showed strong specificity, with no cross-reactivity detected against nucleic acids from other control pathogens. The assay demonstrated high sensitivity, with the lower limit of quantification (LLOQ) of 10 copies per reaction for the recombinant plasmid standards pTgG3PDH, pNcNC5, pEsADF, pGlGDH, pTeCOX1, and the limit of detection (LOD) as low as 1.1 copies. The standard curves exhibited excellent linearity (correlation coefficient values of 0.996, 0.996, 0.996, 0.992, and 0.996, respectively) and high amplification efficiencies (95.534%, 96.203%, 107.818%, 100.851%, and 104.487%, respectively). The assay also exhibited excellent repeatability and reproducibility, with inter- and intra-assay coefficient of variation (CV) ranging from 0.07% to 2.13%. The anti-interference test showed that high-concentration nucleic acids did not interfere with low-concentration nucleic acids, thus ensuring excellent detection results even in complex samples. Among 210 clinical samples, the assay detected Toxoplasma gondii in 2.38%, Neospora caninum in 2.38%, Eimeria stiedai in 10%, and Giardia lamblia in 36.19%. The coinfection rates were 8.1% for Eimeria stiedai & Giardia lamblia. This TaqMan-probe-based pentaplex qPCR assay offers a rapid, sensitive, and specific tool for the simultaneous detection of Toxoplasma gondii, Neospora caninum, Eimeria stiedai, Giardia lamblia, and Trypanosoma. It is of great significance to safeguard human health.