Porcine respiratory disease complex (PRDC), a common piglet disease, causes substantive economic losses in pig farming. To investigate the viral diversity associated with PRDC, the viral communities in serum and nasal swabs from 26 PRDC-affected piglets were investigated using metagenomics. By deep sequencing and de novo assembly, 17 viruses were identified in two pooled libraries (16 viruses from serum, nine from nasal swabs). Porcine circovirus (PCV)-2, porcine reproductive and respiratory syndrome virus (PRRSV) and pseudorabies virus, all commonly associated with PRDC, were identified in the two pooled samples by metagenomics, but most viruses comprised small linear and circular DNAs (e.g. parvoviruses, bocaviruses and circoviruses). PCR was used to compare the detection rates of each virus in the serum samples from 36 PRDC-affected piglets versus 38 location-matched clinically healthy controls. The average virus category per sample was 6.81 for the PRDC-affected piglets and 4.09 for the controls. Single or co-infections with PCV-2 or PRRSV had very high detection rates in the PRDC-affected piglets. Interestingly, porcine parvovirus (PPV)-2, PPV-3, PPV-6 and torque teno sus virus 1a were significantly associated with PRDC. These results illustrate the complexity of viral communities in the PRDC-affected piglets and highlight the candidate viruses associated with it.

Feline calicivirus (FCV) is an important pathogen of cats that has two genogroups (GI and GII). To investigate the prevalence and molecular characteristics of FCVs in southwestern China, 162 nasal swab samples were collected from cats in animal shelters and pet hospitals. In total, 38 of the clinical samples (23.46%) were identified as FCV positive using nested RT-PCR. Phylogenetic analyses using 10 capsid protein VP1 sequences revealed that 8 GI and 2 GII strains formed two independent clusters. Additionally, three separated FCVs that were not clustered phylogenetically (two GI and one GII strains) were successfully isolated from clinical samples and their full-length genomes were obtained. Phylogenetic and recombinant analyses of a GI FCV revealed genomic breakpoints in ORF1 and ORF2 regions with evidence for recombinant events between GI sub-genogroups, which is reported in China for the first time. Furthermore, sera obtained from mice immunized independently with the three FCV isolates and a commercial vaccine were used to evaluate the cross-reactivity of neutralizing antibodies. The three separate FCVs were neutralized by each other at a 1:19 to 1:775 titer range, whereas the triple-inactivated vaccine was at a titer of 1:16, which suggested that different genogroup/sub-genogroup FCV strains exhibit significantly different titers of neutralizing antibodies, including the commercial FCV vaccine. Thus, our study revealed the genetic diversity and complex cross-reactivity levels of FCVs in southwestern China, which provides new insights for application in vaccination strategies.

Feline coronavirus (FCoV) is the causative agent of feline infectious peritonitis and diarrhoea in kittens worldwide. In this study, a total of 173 feline diarrhoeal faecal and ascetic samples were collected from 15 catteries and six veterinary hospitals in southwest China from 2017 to 2020. FCoV was detected in 80.35 % (139/173) of the samples using the RT-nPCR method; these included infections with 122 type I FCoV and 57 type II FCoV. Interestingly, 51 cases had co-infection with types I and II, the first such report in mainland China. To further analyse the genetic diversity of FCoV, we amplified 23 full-length spike (S) genes, including 18 type I and five type II FCoV. The type I FCoV and type II FCoV strains shared 85.5–98.7% and 97.4–98.9% nucleotide (nt) sequence identities between one another, respectively. The N-terminal domain (NTD) of 23 FCoV strains showed a high degree of variation (73.6–80.3 %). There was six type I FCoV strains with two amino acid insertions (159HL160) in the NTD. In addition, 18 strains of type I FCoV belonged to the Ie cluster, and five strains of type II FCoV were in the IIb cluster based on phylogenetic analysis. Notably, it was first time that two type I FCoV strains had recombination in the NTD, and the recombination regions was located 140–857 nt of the S gene. This study constitutes a systematic investigation of the current infection status and molecular characteristics of FCoV in southwest China.

Liu X, et al. J Vet Sci. 2021 Aug;22(5):e69. https://doi.org/10.4142/jvs.2021.22.e69

Porcine epidemic diarrhea virus (PEDV) causes porcine epidemic diarrhea (PED). The emergence of the novel G2b strains of PEDV has increased the need for new vaccines. We generated a recombinant adenovirus expressing the spike (S) protein of G2b PEDV based on human adenovirus serotype 5 (Ad5), named rAd5-PEDV-S. Immunization with rAd5-PEDV-S elicited a significant PEDV-specific humoral immune response in sows, including IgA and IgG in colostrum and serum and circulating neutralizing antibodies. The efficacy of rAd5-PEDV-S was superior to that of the commercial inactivated vaccine, and the intramuscular (IM) route was more effective than the intranasal route. Interestingly, there was no significant difference in immunization effect between the twice and once-immunized IM groups (administered 5 weeks before farrowing). Five-day-old piglets born to sows immunized with the rAd5-PEDV-S through the IM route had less diarrhea and weight loss when challenged with PEDV. Fecal PEDV RNA expression in the PEDV-challenged rAd5-PEDV-S IM group piglets was considerably lower than that in the other groups; all five piglets from the rAd5-PEDV-S IM group survived the infection period. Histopathological examination of small intestinal sections revealed evident shedding of ileum intestinal mucosal epithelial cells in the phosphate-buffered saline (PBS) group. These findings suggest that vaccinating pregnant sows with rAd5-PEDV-S induces immune responses in the pregnant sows and passively protects piglets. Our findings highlight the potential of rAd5-PEDV-S as a candidate vaccine for PED. IMPORTANCE: Porcine epidemic diarrhea (PED) is a highly infectious and economically significant gastrointestinal disorder that affects pigs of all ages. Preventing and controlling PED is achieved by immunizing sows with vaccines, enabling passive piglet immunization via colostrum. The prevalence of G2b porcine epidemic diarrhea virus (PEDV) continues in China despite the use of commercial vaccines, raising questions regarding current vaccine efficacy and the need for novel vaccine development. Adenovirus serotype 5 (Ad5) has several advantages, including high transduction efficiency, a wide range of host cells, and the ability to infect cells at various stages. In this study, we expressed the immunogenic proteins of spike (S) using an Ad5 vector and generated a PED vaccine candidate by inducing significant humoral immunity. The rAd5-PEDV-S prevented PED-induced weight loss, diarrhea, and intestinal damage in piglets. This novel vaccine candidate strain possesses the potential for use in the pig breeding industry.