No 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 (NGS). 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. The nearly full-length genome sequence of the tilapia parvovirus HMU-HKU-1 was determined and showed less than 45.50 and 40.38% amino acid identity with other members of Parvoviridae in NS1 and VP1 genes, respectively. Phylogenetic analysis based on the complete helicase domain amino acid sequences showed that the tilapia parvovirus HMU-HKU-1 formed a relatively independent branch in the newly proposed genus Chaphamaparvovirus in the subfamily Hamaparvovirinae according to the ICTV’s most recent taxonomic criteria for Parvoviridae classification. Tilapia parvovirus HMU-HKU-1 likely represented a new species within the new genus Chaphamaparvovirus. 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.

Lactoferricin (Lfcin) B, derived from lactoferrin in whey, has attracted considerable attention because of its multiple biological functions. Zoonotic enterohemorrhagic Escherichia coli (EHEC) O157:H7 has adverse effects on intestinal epithelial barrier function, leading to serious intestinal disease. In this study, the EHEC O157:H7-induced intestinal dysfunction model was developed to investigate the effects of Lfcin B on EHEC O157:H7-induced epithelial barrier disruption and microbiota dysbiosis. Results showed that the inflammatory infiltration indexes in the jejunum of Lfcin B-treated animals were significantly decreased. Lfcin B administration also significantly improved ZO-1 and occludin expression following O157:H7induced injury. Finally, microbiota analysis of the cecal samples revealed that Lfcin B inhibited the O157:H7-induced abnormal increase in Bacteroides. Therefore, Lfcin B efficiently attenuated O157:H7-induced epithelial barrier damage and dysregulation of inflammation status, while maintaining microbiota homeostasis in the intestine, indicating that it may be an excellent food source for prevention and therapy of EHEC O157:H7-related intestinal dysfunction.

Hundreds of farmed Siamese crocodiles (Crocodylus siamensis) died during July 2016 at a farm in Wenchang, Hainan, China. In two necropsied crocodiles, we observed symptoms of dermatorrhagia, hepatomegaly and hepatic congestion. Pulmonitis was diagnosed by pulmonary congestion and pulmonary fibrinous exudate. Septicaemia was diagnosed by isolation of three Aeromonas species from blood and visceral tissues; A. dhakensis, A. hydrophila and A. jandaei were identified by biochemical and molecular tests. We used a zebrafish model to determine the half‐maximal lethal dose (LD50), and A. dhakensis was found to be the most virulent species, with an LD50 of 8·91 × 105 CFU per ml. The results of a drug sensitivity test indicated that these species were sensitive to 11 antibiotics. This is the first report of A. dhakensis, A. hydrophila and A. jandaei being isolated from a mixed infection in Siamese crocodiles. Significance and Impact of the Study In this study, we isolated three species of Aeromonas (A. dhakensis, A. hydrophila and A. jandae) from farmed Siamese crocodiles with fatal fibrinous pneumonia and septicaemia. This is the first description of a mixed infection with three Aeromonas species among captive crocodilians.