Investigation of round goby viral haemorrhagic septicaemia outbreak in New York

Eleven viral haemorrhagic septicaemia virus (VHSV) genotype IVb isolates were sequenced, and their genetic variation explored to determine the source of a VHS outbreak on the eastern shore of Cayuga Lake. An active fish kill of round gobies (Neogobius melanostomus, Pallas) was intensively sampled at King Ferry, NY and nearby Long Point State Park in May 2017. Gross lesions observed on 67 moribund round gobies and two rock bass (Ambloplites rupestris, Rafinesque) included moderately haemorrhagic internal organs and erythematous areas on the head, flank, and fins. RT‐qPCR tests for VHSV were positive for all 69 fish. Viral isolation on epithelioma papulosum cyprinid cells showed cytopathic effect characteristic of VHSV for six round goby samples from King Ferry. The complete nucleotide sequence of the VHSV IVb genomes of five Cayuga Lake round goby isolates were derived on an Illumina platform along with 2017 VHSV IVb isolates from round gobies collected from the following: Lake Erie near Dunkirk, NY; the St. Lawrence River near Clayton and Cape Vincent, NY; and Lake St. Lawrence near Massena, NY. The phylogenetic tree created from these aligned sequences and four other complete VHSV IVb genomes shows Cayuga Lake isolates are closely related to the Lake Erie isolates.     

Establishment and characterization of a fin tissue cell line derived from silver pomfret,Pampus argenteus

A cell line (PaF) derived from the fin tissue of silver pomfret (Pampus argenteus) was established and characterized in this study. The cell line has been subcultured for more than 50 times in Dulbecco's modified Eagle's medium (DMEM) containing 15% foetal bovine serum (FBS) since the initial primary culture. PaF cells grew well at temperatures from 24°C to 28°C in DMEM supplemented with 15% FBS. Partial amplification and sequence analysis of the cytochrome B gene indicated that PaF originated from silver pomfret. Cytogenetic analysis demonstrated that the modal chromosome number was 48. A significant cytopathic effect was observed in PaF cells during viral haemorrhagic septicaemia virus (VHSV) infection, and the VHSV replication was confirmed by qRT‐PCR and viral titre assays. In contrast, PaF cells were resistant to red‐spotted grouper nervous necrosis virus infection. Moreover, PaF cells could respond to VHSV and lipopolysaccharide treatments, as indicated by the expression of immune‐related genes, TLR5 and TLR9. In conclusion, the establishment of PaF cell line will provide an appropriate in vitro tool for the study of mechanisms of pathogen–silver pomfret interaction.     

河西走廊牛巴氏杆菌病的流行病学调查及病原分离鉴定

对河西走廊5个市的14个县区70个乡镇350个村7 000个场户进行了牛巴氏杆菌病的流行病学抽样调查和病原学分离鉴定.其结果：发病、死亡和致死率分别为1.72％、1.12％和65.52％.发病季节主要在2～4月和10～12月；肉牛的发病、死亡率分别为1.61％、1.05％,牦牛分别为2.46％、1.60％.180日龄以内的哺乳犊牛发病、死亡率最低,分别为1.19％、0.92％,0.5～1.0岁断奶犊牛最高,分别为2.24％、1.59％；哺乳犊牛致死率最高,为77.02％,0.5～1.0岁断奶犊牛次之,为70.65％,以后随着年龄的增大,逐渐下降.采集发病死亡牛病料56份,有52份检出了多杀性巴氏杆菌,同时对病原进行了分离鉴定.表明牛巴氏杆菌病在河西走廊流行广泛,发病、死亡率较高,危害严重.     

鹿溶血性大肠杆菌败血症病原特性的研究

作者对从长春、吉林两个地区搜集到的8株鹿溶血性大肠杆菌并对其杆菌的生化和血清学特性进行了系统地研究。结果表明,这些大肠杆菌生化特性活泼,均呈典型的β型溶血、毒力强、具有致病性。血清学分析表明,8株溶血性大肠杆菌可分为两种K抗原和3种O抗原,且多数为K_(80)。血清学的分析为用免疫学方法诊断和防治本病提供了理论依据。     

斑点叉尾鮰暴发性败血症病原的分离与鉴定

从3尾表现出血症状的患病斑点叉尾鮰（lctalurus Punctatus）体内各分离出一株病菌，测定结果显示致其急性死亡的致病菌为温和气单胞菌（Aeromonas sobria），慢性死亡的致病菌分别为嗜水气单胞菌（A．hydrophila）和温和气单胞菌（A．sobria）。药敏试验结果表明：3株菌对广谱抗生素如氨苄青霉素、青霉素、先锋霉素Ⅵ和红霉素等已产生耐药性，而对菌必治、头孢肤肟和复达欣等高度敏感；菌株Jh-1和菌株Yh-3对复方新诺明、四环素、氟哌酸和丁胺卡那霉素高度敏感，而菌株Jh-2却低度敏感；环丙沙星和诺氟沙星对3株致病菌均具较好的抑菌、杀菌作用。     

Factors controlling the early stages of viral haemorrhagic septicaemia epizootics: low exposure levels, virus amplification and fish-to-fish transmission

Viral haemorrhagic septicaemia virus, Genogroup IVa (VHSV), was highly infectious to Pacific herring, Clupea pallasii (Valenciennes), even at exposure doses occurring below the threshold of sensitivity for a standard viral plaque assay; however, further progression of the disease to a population‐level epizootic required viral amplification and effective fish‐to‐fish transmission. Among groups of herring injected with VHSV, the prevalence of infection was dose‐dependent, ranging from 100%, 75% and 38% after exposure to 19, 0.7 and 0.07 plaque‐forming units (PFU)/fish, respectively. Among Pacific herring exposed to waterborne VHSV (140 PFU mL^?1), the prevalence of infection, geometric mean viral tissue titre and cumulative mortality were greater among cohabitated herring than among cohorts that were held in individual aquaria, where fish‐to‐fish transmission was prevented. Fish‐to‐fish transmission among cohabitated herring probably occurred via exposure to shed virus which peaked at 680 PFU mL^?1; shed virus was not detected in the tank water from any isolated individuals. The results provide insights into mechanisms that initiate epizootic cascades in populations of wild herring and have implications for the design of VHSV surveys in wild fish populations.     

Development of an aquatic pathogen database (AquaPathogen X) and its utilization in tracking emerging fish virus pathogens in North America

The AquaPathogen X database is a template for recording information on individual isolates of aquatic pathogens and is freely available for download (http://wfrc.usgs.gov). This database can accommodate the nucleotide sequence data generated in molecular epidemiological studies along with the myriad of abiotic and biotic traits associated with isolates of various pathogens (e.g. viruses, parasites and bacteria) from multiple aquatic animal host species (e.g. fish, shellfish and shrimp). The cataloguing of isolates from different aquatic pathogens simultaneously is a unique feature to the AquaPathogen X database, which can be used in surveillance of emerging aquatic animal diseases and elucidation of key risk factors associated with pathogen incursions into new water systems. An application of the template database that stores the epidemiological profiles of fish virus isolates, called Fish ViroTrak, was also developed. Exported records for two aquatic rhabdovirus species emerging in North America were used in the implementation of two separate web-accessible databases: the Molecular Epidemiology of Aquatic Pathogens infectious haematopoietic necrosis virus (MEAP-IHNV) database (http://gis.nacse.org/ihnv/) released in 2006 and the MEAP- viral haemorrhagic septicaemia virus (http://gis.nacse.org/vhsv/) database released in 2010.