Abstract
Cross-species transmission of emerging viruses happens occasionally due to epidemiological, biological, and ecological factors, and it has caused more concern recently. Covert mortality nodavirus (CMNV) was revealed to be a unique shrimp virus that could cross species barrier to infect vertebrate fish. In the present study, CMNV reverse transcription-nested PCR (RT-nPCR)-positive samples were identified from farmed sea cucumber (Apostichopus japonicas) in the CMNV host range investigation. The amplicons of RT-nPCR from sea cucumber were sequenced, and its sequences showed 100% identity with the RNA-dependent RNA polymerase gene of the original CMNV isolate. Histopathological analysis revealed pathologic changes, including karyopyknosis and vacuolation of the epithelial cells, in the sea cucumber intestinal tissue. The extensive positive hybridization signals with CMNV probe were shown in the damaged epithelial cells in the in situ hybridization assay. Meanwhile, transmission electron microscopy analysis revealed CMNV-like virus particles in the intestine epithelium. All the results indicated that the sea cucumber, an Echinodermata, is a new host of CMNV. This study supplied further evidence of the wide host range of CMNV and also reminded us to pay close attention to its potential risk to threaten different aquaculture animal species.
Highlights
For most viruses, the virus–receptor interactions determine viral host range and constitute the interspecies barrier of viral infection, eventually leading to the strong host specificity of a virus [1,2]
Alphanodaviruses were mostly isolated from insects and their host range appears to be restricted to insects [11], except for Nodamura virus (NoV) and Flock House virus (FHV) [12,13]
We describe here the outcome of the detection of Covert mortality nodavirus (CMNV) in sea cucumber by reverse transcription-nested PCR (RT-nPCR), in situ hybridization (ISH), histopathology, and transmission electron microscopy (TEM)
Summary
The virus–receptor interactions determine viral host range and constitute the interspecies barrier of viral infection, eventually leading to the strong host specificity of a virus [1,2]. The cross-species transmission of emerging viruses happens occasionally due to a variety of epidemiological, biological, and ecological factors [3,4,5]. RNA viruses more cross species boundaries on account of the lack of exonuclease proofreading activity and easy variation [6], such as coronaviruses [7], the avian influenza virus [8], and the rabies virus [9]. Alphanodaviruses were mostly isolated from insects and their host range appears to be restricted to insects [11], except for Nodamura virus (NoV) and Flock House virus (FHV) [12,13]. NoV was originally isolated from mosquitoes (Culex tritaeniorhynchus) [14]; it could lethally infect mammals, including suckling mice and suckling hamsters [10,15]
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