Development of a TaqMan-based multiplex real-time PCR for simultaneous detection of four feline diarrhea-associated viruses

TaqMan-based real-time polymerase chain reaction for the detection of feline chaphamaparvovirus

Feline chaphamaparvovirus (FeChPV) is a new viral strain detected in Chinese Mainland in recent years. The symptoms mainly include diarrhea and bloody stool in young cats, which can lead to death in severe cases. In this study, a TaqMan-based real-time quantitative PCR (qPCR) with specific primers and TaqMan probes based on the VP1 gene sequence of FeChPV was performed to detect the virus. The established qPCR indicated that there is no cross-reaction of FeChPV with other common feline viruses. The minimum detection limit of the established qPCR method is 3.75 × 10 copies/µL, while conventional PCR is 3.75 × 103 copies/µL. The result that the proposed qPCR protocol was shown to be 100 times more sensitive than conventional PCR. The correlation coefficients exceeded 0.995, and the amplification efficiency was 98%. The difference within and between groups is less than 5%, indicating that the established method has good repeatability. The results of clinical sample detection shown that 16 positive samples were detected from 45 stool samples by the established qPCR method. The conventional PCR method only detected 3 positive samples. In conclusion, the established qPCR method is fast and effective in identifying FeChPV, with higher specificity and sensitivity. It could be used as a diagnostic tool to quantitatively detect the virus content, which is conducive to disease monitoring and epidemiological investigation.

Multiplex One-Step RT-qPCR Assays for Simultaneous Detection of SARS-CoV-2 and Other Enteric Viruses of Dogs and Cats

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was transmitted from humans to dogs and cats (reverse zoonosis) during the COVID-19 pandemic. SARS-CoV-2 has been detected in fecal samples of infected dogs and cats, indicating potential fecal-oral transmission, environmental contamination, and zoonotic transmission (i.e., spillback). Additionally, gastrointestinal viral infections are prevalent in dogs and cats. In this study, we developed and validated a panel of multiplex one-step reverse transcription-quantitative polymerase chain reaction (RT-qPCR) assays for the simultaneous detection of SARS-CoV-2 and common canine enteric viruses: Canine Enteric Assay_1 (CEA_1) for the detection of canine adenovirus-1, canine enteric coronavirus, canine distemper virus, and canine parvovirus, and CEA_2 for the detection of rotavirus A (RVA), and SARS-CoV-2); or common feline enteric viruses (Feline Enteric Assay_1 (FEA_1) for the detection of feline enteric coronavirus, feline panleukopenia virus, RVA, and SARS-CoV-2). All assays demonstrated high analytical sensitivity, detecting as few as 5-35 genome copies/µL in multiplex format. The repeatability and reproducibility of the multiplex assays were excellent, with coefficient of variation <4%. Among the 58 clinical samples tested, 34.5% were positive for at least one of these viruses, and SARS-CoV-2 was detected in two samples collected from one dog and one cat, respectively. In conclusion, these newly developed one-step multiplex RT-qPCR assays allow for rapid diagnosis of enteric viral infections, including SARS-CoV-2, in dogs and cats.

A quadruplex real-time PCR assay combined with a conventional PCR for the differential detection of Marek's disease virus vaccines and field strains

To evaluate the effect of the vaccine and differentiate vaccine from virulent MDV, a new quadruplex real-time PCR assay based on TaqMan probes was developed to differentiate and accurately quantify HVT, CVI988 and virulent MDV-1. The results showed that the limit of detection (LOD) of the new assay was 10 copies with correlation coefficients >0.994 of CVI988, HVT and virulent MDV DNA molecules without cross-reactivity with other avian disease viruses. The intra-assay and inter-assay coefficients of variation (CVs) of Ct values for the new assay were less than 3%. Analysis of replication kinetics of CVI988 and virulent MDV of collected feathers between 7 and 60 days post-infection (dpi) showed MD5 had no significant effect on the genomic load of CVI988 (p > 0.05), while vaccination with CVI988 could significantly reduce the viral load of MD5 (p < 0.05). Combined with meq gene PCR, this method can effectively identify virulent MDV infections in immunized chickens. These results demonstrated that this assay could distinguish between the vaccine and virulent MDV strains and had the advantages of being reliable, sensitive and specific to confirm the immunization status and monitor the circulation of virulent MDV strains.