Identification and cross-species transmission of a novel ichthyic parvovirus in marine species in Hainan Island, China

ABSTRACT

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.