Feline panleukopenia virus (FPV), a member of the species Protoparvovirus carnivoran1, is one of the most fatal pathogens of domestic and wild carnivores. The virus endemically infects domestic carnivores worldwide and its cross-species transmission threatens endangered wild carnivores, including Siberian tigers. In this study, a fatal FPV infection in endangered Siberian tigers was investigated to trace the origin of the virus and elucidate the reason behind FPV’s infection of the vaccinated tigers. Our genetic characterization and phylogenetic analysis revealed that the virus detected in the infected tigers, designated as the KTPV-2305 strain, was closely related to FPV strains circulating in Korean cats, suggesting that it might have been transmitted from stray cats wandering around the zoo. Compared with the prototype FPV reference strains, the KTPV-2305 strain carried three distinct amino acid (aa) mutations in the VP2 protein sequence (I101T, I232V, and L562V) in this study. These three mutations are commonly found in most global FPV strains, including Korean strains, indicating that these mutations are common evolutionary characteristics of currently circulating global FPVs. The reason why the vaccinated tigers were infected with FPV was most likely the insufficient protective immunity of the affected tigress or vaccine failure triggered by the interference of maternal-derived antibodies in the affected tiger cubs. These findings suggest that improved vaccination guidelines are urgently needed to save the lives of wild carnivores from this fatal virus.

Two species of porcine parainfluenza viruses (PPIV), PPIV1 and PPIV5, are globally distributed in pig herds and associated with porcine respiratory diseases, and a diagnostic tool for the simultaneous detection of the two viruses is required. In this study, a TaqMan probe-based duplex real-time reverse transcription polymerase chain reaction (dqRT-PCR) assay was first developed for the differential detection of PPIV1 and PPIV5 nucleocapsid protein (NP) genes in porcine clinical samples. The dqRT-PCR assay was highly sensitive, its limit of detection was approximately 10 RNA copies/reaction, it specifically amplified the targeted NP genes of PPIV1 and PPIV5 without cross-reacting with other porcine pathogens, and their clinical detection rates were 15.2% and 0.7%, respectively. The results from 441 clinical samples taken from 278 Korean domestic pig farms showed that the prevalence of PPIV1 and PPIV5 was 11.2% and 1.1%, respectively, and co-infection of both viruses was confirmed in a farm, suggesting that PPIV1 and PPIV5 are co-circulating in current Korean pig herds. Phylogenetic analysis based on the partial NP genes suggested that genetically diverse PPIV1 strains are circulating in Korean pig herds. The developed dqRT-PCR assay was found to be an accurate, reliable, and quantitative detection tool for PPIV1 and PPIV5 RNA in clinical pig samples and will be useful for etiological and epidemiological studies and the control of viral infections in the field.

For rapid and reliable detection of porcine epidemic diarrhea virus (PEDV) from pig clinical samples, a multiplex, real-time, reverse transcription loop-mediated isothermal amplification (mqRT-LAMP) was developed using two sets of primers and assimilating probes specific to the PEDV N gene and the Sus scrofa β-actin gene, which was used as an endogenous internal positive control (EIPC) to avoid false-negative results. The assay specifically amplified both target genes of PEDV and EIPC in a single reaction without any interference but did not amplify other porcine viral nucleic acids. The limit of detection was 10 copies/μL, 100-fold lower than that of a reverse transcription-polymerase chain reaction (RT-PCR) and equivalent to that of quantitative/real-time RT-PCR (qRT-PCR). This assay has high repeatability and reproducibility with coefficients of variation < 4.0%. The positive signal of the mqRT-LAMP assay was generated within 25 min, demonstrating advantages in rapid detection of PEDV over RT-PCR or qRT-PCR assay, which require at least 2 h turnaround times. In clinical evaluation, the detection rate of PEDV by mqRT-LAMP assay (77.3%) was higher than that of RT-PCR assay (69.7%), and comparable to qRT-PCR (76.8%) with almost 100% concordance (kappa value 0.98). The developed mqRT-LAMP assay can serve as an advanced alternative method for PEDV diagnosis because it has high sensitivity and specificity, rapidity, and reliability even in resource-limited laboratories.

Hye-Ryung Kim, Gyu-Tae Jeon, Jong-Min Kim, Ji-Su Baek, Yeun-Kyung Shin, Oh-Kyu Kwon, Hae-Eun Kang, Ho-Seong Cho, Doo-Sung Cheon, Choi-Kyu Park. Korean J. Vet. Serv. 2022;45:305-16. https://doi.org/10.7853/kjvs.2022.45.4.305

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections have been frequently reported in companion dogs and cats worldwide during the ongoing coronavirus disease. However, RT-qPCR methods developed for humans have been used for the diagnosis of SARS-CoV-2 infections in suspected companion dogs and cats owing to the lack of the companion animal-tailored methods. Therefore, we developed a multiplex RT-qPCR (mRT-qPCR) using newly designed primers and probes targeting RdRp and N genes of all currently circulating SARS-CoV-2 variants as well as the canine or feline 16S rRNA gene as an endogenous internal positive control (EIPC) for reliable diagnosis of SARS-CoV-2 infection from suspected dogs and cats. The developed mRT-qPCR assay specifically detected the target genes of SARS-CoV-2 but no other canine or feline pathogens. Furthermore, canine and feline EIPCs were stably amplified by mRT-qPCR in samples containing canine- or feline-origin cellular materials. This assay has high repeatability and reproducibility, with an optimal limit of detection (<10 RNA copies per reaction) and coefficients of variation (<1.0%). The detection rate of SARS-CoV-2 of the developed mRT-qPCR was 6.6% for canine and feline nasopharyngeal samples, which was consistent with that of a commercial mRT-qPCR kit for humans. Collectively, the newly developed mRT-qPCR with canine and feline EIPC can efficiently diagnose and evaluate the viral load in field specimens and will be a valuable tool for etiological diagnosis, epidemiological study, and controlling SARS-CoV-2 infections in canine and feline populations.

Ji-Su Baek, Jong-Min Kim, Hye-Ryung Kim, Yeun-Kyung Shin, Oh-Kyu Kwon, Hae-Eun Kang, Choi-Kyu Park. Korean J. Vet. Serv. 2023;46:123-35. https://doi.org/10.7853/kjvs.2023.46.2.123