Nucleotide sequences of the infectious DNA clones of two mink enteritis virus isolates exhibit the diversity of the terminal palindromic sequences and predicted secondary structures.

In this study, the infectious RF-DNA clones of two mink enteritis viruses, MEV-SD1 and MEV-SD7, were constructed, which generated progeny virions and seemed to contain an almost or completely full-length genome. The genomes of MEV-SD1 and MEV-SD7 were 5162 bp and 5113 bp in length, respectively. The genomic organizations of MEV-SD1 and MEV-SD7 were similar to that of the other carnivore parvoviruses. The 3'-UTR of the virion strand of MEV-SD1 and MEV-SD7 were 311 bp and 313 bp in length, respectively, containing a 208 bp palindromic sequence assuming Y-shaped configurations. Interestingly, the difference of the 3' palindromic sequences between MEV-SD1 and MEV-SD7 resulted in the orientation inversion of the hairpin ears. And the 5'-UTRs of MEV-SD1 and MEV-SD7 were 582 bp and 531 bp, respectively, containing a 198 bp palindromic sequence assuming U-shaped configurations, a triplet mismatch (5'-TAC-3') in the center of the duplex stem and a triplet mismatch (5'-AGA-3') forming a small asymmetric bubble. The findings demonstrated that the genomic termini of the carnivore parvoviruses showed the diversity in length, base composition, and predicted secondary structure.

Emergence of novel canine parvovirus type 2 and its pathogenesis in raccoon dogs.

Three parvoviruses were isolated from the raccoon dogs experiencing severe enteritis, named RDPV-DP1, RDPV-DP2 and RDPV-DP3, respectively. The VP2 genes of the 3 isolates showed 99.9% identity at the nucleotide level, and shared 99.1%-99.5% identity with the reference CPVs. The RDPVs resembled original CPV-2, but with four mutations. The RDPVs displayed S297A of VP2 protein as CPV-2a or CPV-2b prevalent throughout most of the world. Residue N375D was found in the 3 isolates, resembling CPV-2a/2b/2c. And the 3 isolates had a natural mutation of VP2 residue V562L, which is adjacent to residue 564 and 568 and might be involved in host range. Interestingly, VP2 S27T was firstly found in the isolates. Phylogenetic analysis of VP2 genes revealed that the RDPVs were clustered into one small evolutionary branch and shared the identical branch with 7 CPV-2 isolates from raccoon dogs and one CPV-2 isolate from fox, not with CPV vaccine viruses. Phylogenetic analysis of NS1 genes demonstrated that the RDPVs shared the identical branch with the reference CPV-2a/2b/2c. Experimental infection showed that RDPV infection caused a high morbidity in raccoon dogs. It implied that the RDPV was virulent to raccoon dogs and continued to evolve in China.

Serotype and virulence genes of Klebsiella pneumoniae isolated from mink and its pathogenesis in mice and mink.

In the study, 15 K. pneumoniae strains were isolated from the mink experiencing respiratory distress in mideastern Shandong province, China, and the prevalence of K. pneumoniae in the sampled mink was 11.9% (15/126). Fourteen (93.33%) of the 15 K. pneumoniae isolates were identified as serotype K2 and hypermucoviscosity phenotype. The 12 virulence-associated genes of the K. pneumoniae isolates were tested. The prevalence of the wabG gene for the isolates were 100% (15/15), the ureA gene 100% (15/15), the rmpA gene 93.33% (14/15), the aerobactin gene 93.33% (14/15), the uge gene 93.33% (14/15), the IucB gene 80% (12/15) and the ybtA gene 13.33% (2/15). But the other five genes, fim, iroNB, wcaG, alls and kfuBC, gave a negative PCR reaction in the 15 isolates, respectively. The animal experiments using K. pneumoniae-SD-12 and K. pneumoniae-SD-21 demonstrated that the serotype K2 was high virulence for mice and mink. These finding implied there exist potential threat that K. pneumoniae pathogens could transmit to human, especially the fur animal farm workers and residents lived near the fur animal farms. Therefore, the etiology and epidemiological surveillance of K. pneumoniae in mink should be strengthened for people's public health.

Intraspecies and interspecies transmission of mink H9N2 influenza virus.

H9N2 influenza A virus (IAV) causes low pathogenic respiratory disease and infects a wide range of hosts. In this study, six IAVs were isolated from mink and identified as H9N2 IAV. Sequence analysis revealed that the six isolates continued to evolve, and their PB2 genes shared high nucleotide sequence identity with H7N9 IAV. The six isolates contained an amino acid motif PSRSSR↓GL at the hemagglutinin cleavage site, which is a characteristic of low pathogenic influenza viruses. A serosurvey demonstrated that H9N2 IAV had spread widely in mink and was prevalent in foxes and raccoon dogs. Transmission experiments showed that close contact between H9N2-infected mink and naive mink, foxes and raccoon dogs resulted in spread of the virus to the contact animals. Furthermore, H9N2 challenge experiments in foxes and raccoon dogs showed that H9N2 IAV could infect these hosts. Virological and epidemiological surveillance of H9N2 IAV should be strengthened for the fur animal industry.

Molecular characterization of feline panleukopenia virus isolated from mink and its pathogenesis in mink.

Six feline panleukopenia viruses (FPV) were detected in the intestinal samples from the 176 mink collected in China during 2015 to 2016, named MEV-SD1, MEV-SD2, MEV-SD3, MEV-SD4, MEV-SD5 and MEV-SD6. The VP2 genes of the isolates shared 98.9%-100% identity with the reference sequences. The substitution of residue V300A in VP2 protein differentiates the isolates from the reference MEVs, and A300 is a characteristic of FPV. Furthermore, phylogenetic analysis of VP2 genes indicated that the six isolates were clustered into the same branch of all the reference FPVs. The NS1 genes of the isolates shared 98.2%-100% identity with the reference sequences. The NS1 genes of the six isolates and the three reference FPVs formed one unique evolutionary branch. To clarify the pathogenicity of the isolates, animal experiments were performed on healthy mink, using MEV-SD1. As a result, the morbidity of the inoculated animals was 100% and the mortality was as high as 38.9%. It was implied that the FPV infection caused a high morbidity and mortality in mink and the inoculation dose had an effect on pathogenicity of MEV-SD1 in mink.