RESUMO
Parvoviruses are a diverse group of viruses that are capable of infecting a wide range of animals. In this study, we report the discovery of a novel parvovirus, tilapia parvovirus HMU-HKU, in the fecal samples of crocodiles and intestines of tilapia in Hainan province, China. The novel parvovirus was firstly identified from crocodiles fed with tilapia using next-generation sequencing. Screening studies revealed that the prevalence of the novel parvovirus in crocodile feces samples fed on tilapia (75%-86%) was apparently higher than that in crocodiles fed with chicken (4%). Further studies revealed that the prevalence of the novel parvovirus in tilapia feces samples collected at four areas in Hainan province was between 40% and 90%. Four stains of the novel parvovirus were identified in this study based on sequence analyses of NS1 and all the four strains were found in tilapia in contrast only two of them were detected in crocodile feces. These findings proposed a possibility of cross-species transmission of the novel parvovirus from tilapia to crocodile. The nearly full-length genome sequence of the tilapia parvovirus HMU-HKU was determined and showed less than 28.3% and 25% amino acid identify with other members of Parvoviridae in NS1 and VP1 genes respectively. Phylogenetic analysis base on the NS1 and VP1 amino acid sequences showed that it was most closely related to members of the novel genus Chapparvovirus which did not belong to subfamily Parvovirinae nor Densovirinae. Tilapia parvovirus HMU-HKU formed an independent branch with Chapparvovirus and separated from it in the deep root of the phylogenetic tree. This indicated that the tilapia parvovirus HMU-HKU and Chapparvovirus viruses may had a common ancestor and they independently evolved in their natural hosts. The identification of tilapia parvovirus HMU-HKU provides further insight into the viral and genetic diversity of parvoviruses and its infections in tilapia populations need to be evaluated in terms of pathogenicity and production losses in tilapia farming.
RESUMO
Objective To analyze the molecular characteristics and genetic origin of a novel avian influenza A H7N4 virus casuing a case of human infection in China. Methods Specimens were collected from the patient and chickens and ducks kept by the patient and neighbours and then detected by real-time quantitative PCR. The original specimens and virus isolates were analyzed by next-generation sequencing technology to obtain viral whole-genome sequences. Pairwise sequence alignments and phylogenetic analysis were performed by BLASTs,ClustalX and MEGA 6. 1 softwares. Results In January 2018, a human case infected with avian influenza A H7N4 virus was confirmed. Seven H7N4 viruses were isolated from speci-mens collected from chicken and ducks kept in the patient`s backyard. H7N4 virus was a novel reassortant vi-rus with all eight gene fragments derived from wild waterfowl in Eurasia. HA protein contained a single basic amino acid residue R in cleavage site, suggesting that H7N4 virus was low pathogenic. The receptor-binding sites of HA had QSG at 226-228 residues, which indicated that the virus retained avian-type receptor speci-ficity (SAα2-3Gal). Different from H7N4 viruses in avian, the virus isolated from the patient had substitu-tion at position 627 ( E→K) in PB2 protein, which might increase its adaptation in human host. Conclusion This study reported a case of human infection with a novel reassortant avian influenza A H7N4 virus, which revealed that the traditional backyard breeding models might facilitate cross-species transmission of avian in-fluenza viruses in southern China.