Emergence of a novel GIII Getah virus variant in pigs in Guangdong, China, 2023.

From May to July of 2023, one pig farm in Heyuan city, Guangdong Province of China, suffered severe piglet death and sow reproductive disorders. The common pig viruses and bacteria tested negative. To uncover the possible cause of the disease, a metagenomic analysis was performed in the pooled small intestine samples from three 8-day-old diseased piglets. The results showed that Getah virus (GETV), an RNA virus, might be the potential pathogen that affects pig health. Subsequently, GETV nucleotide was detected in all of the 15 samples collected from three diseased piglets using quantitative reverse transcription PCR, suggesting GETV as the main pathogen of the disease. A GETV strain, designated as GDHYLC23, was successfully isolated using the swine testicle cell line. Sequence analysis showed that the epidemic strain had a unique 32-nucleotide repeat insertion in the 3' noncoding region. Phylogenetic analysis showed that GDHYLC23 belonged to the pandemic group III. The identification of GETV with new variations implies the continuous evolution of the virus, which poses potential threats to the swine industry.IMPORTANCEPig farms are faced with emerging and re-emerging viruses that may cause substantial economic loss. The identification of potentially pathogenic viruses helps to prevent and control the spread of diseases. In this study, by using metagenomic analysis, we found that a neglected virus, GETV with a unique insertion in the genome, was the main pathogen in one pig farm that suffered severe piglet death and sow reproductive disorders. Although the potential impact of such an insertion on viral pathogenicity is unknown, the surveillance of the continuing evolution of GETV in pig farms cannot be ignored.

Development of a multiplex qRT-PCR assay for the detection of porcine epidemic diarrhea virus, porcine transmissible gastroenteritis virus and porcine Deltacoronavirus.

Currently, porcine coronaviruses are prevalent in pigs, and due to the outbreak of COVID-19, porcine coronaviruses have become a research hotspot. porcine epidemic diarrhea virus (PEDV), Transmissible Gastroenteritis Virus (TGEV), and Porcine Deltacoronavirus (PDCoV) mentioned in this study mainly cause diarrhea in pigs. These viruses cause significant economic losses and pose a potential public health threat. In this study, specific primers and probes were designed according to the M gene of PEDV, the S gene of TGEV, and the M gene of PDCoV, respectively, and TaqMan probe-based multiplex real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was developed for the simultaneous detection of PEDV, TGEV, and PDCoV. This method has high sensitivity and specificity, and the detection limit of each virus can reach 2.95 × 100 copies/µl. An assay of 160 clinical samples from pigs with diarrhea showed that the positive rates of PEDV, TGEV, and PDCoV were 38.13, 1.88, and 5.00%; the coinfection rates of PEDV+TGEV, PEDV+PDCoV, TGEV+PDCoV, PEDV+TGEV+PDCoV were 1.25, 1.25, 0, 0.63%, respectively. The positive coincidence rates of the multiplex qRT-PCR and single-reaction qRT-PCR were 100%. This method is of great significance for clinical monitoring of the porcine enteric diarrhea virus and helps reduce the loss of the breeding industry and control the spread of the disease.

Evaluation of immunogenicity and protective efficacy of recombinant outer membrane proteins of Haemophilus parasuis serovar 5 in a murine model.

Glässer's disease is an economically important infectious disease of pigs caused by Haemophilus parasuis. Few vaccines are currently available that could provide effective cross-protection against various serovars of H. parasuis. In this study, five OMPs (OppA, TolC, HxuC, LppC, and HAPS_0926) identified by bioinformatic approaches, were cloned and expressed as recombinant proteins. Antigenicity of the purified proteins was verified through Western blotting, and primary screening for protective potential was evaluated in vivo. Recombinant TolC (rTolC), rLppC, and rHAPS_0926 proteins showing marked protection of mice against H. parasuis infection, and were further evaluated individually or in combination. Mice treated with these three OMPs produced humoral and host cell-mediated responses, with a significant rise in antigen-specific IgG titer and lymphoproliferative response in contrast with the mock-immunized group. Significant increases were noted in CD4+, CD8+ T cells, and three cytokines (IL-2, IL-4, and IFN-γ) in vaccinated animals. The antisera against candidate antigens could efficiently impede bacterial survival in whole blood bactericidal assay against H. parasuis infection. The multi-protein vaccine induced more pronounced immune responses and offered better protection than individual vaccines. Our findings indicate that these three OMPs are promising antigens for the development of multi-component subunit vaccines against Glässer's disease.