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Outbreaks of mass mortalities occurred in Macrobrachium rosenbergii farms in Gaoyou county, Jiangsu Province of China. The bacterial isolates from M. rosenbergii exhibited the same phenotypic traits and biochemical characteristics, and were identified as non-O1/O139 Vibrio cholerae according to biochemical characteristics and molecular identification. In challenge test, M. rosenbergii infected with non-O1/O139 V. cholerae GXFL1-4 developed similar pathological signs to the naturally diseased prawns, and LD 50 of the strain to M. rosenbergii was 4.5 × 106 CFU/mL at 96 h post-infection. Histopathological analysis revealed that hepatopancreas and intestines of diseased M. rosenbergii exhibited obvious inflammatory responses to non-O1/O139 V. cholerae infection. Detection virulence factors of the strain GXFL1-4 showed that the bacteria produced caseinase, lipase, amylase, lecithinase and hemolysin, and carried toxR , hlyA , ompW , ompU , hap , rtxA and rtxC virulence related genes, supporting the strong virulence to M. rosenbergii. Additionally, the immune related gene expression in M. rosenbergii evaluated by qRT-PCR analysis showed that HSP70 , Crustin , Lysozyme , TRL1 , ALF1 , Lectin , Peroxinectin , proPO and SOD immune related genes were significantly up-regulated at 6 and 12 h after infection with GXFL1-4. The results of our study suggested that non-O1/O139 V. cholerae was an etiological element in the mass mortalities of M. rosenbergii and this study provided preliminary insights into the diversity in the immune response of M. rosenbergii to the bacterial invasion. • Mass mortalities of cultured M. rosenbergii from several farms in Gaoyou country of China was reported. • Pathogenesis and histopathological analysis related to M. rosenbergii with non-O1/O139 V. cholerae infection were studied. • Non-O1/O139 V. cholerae infection induced a wide defensive response of various immune related genes in M. rosenbergii. [ABSTRACT FROM AUTHOR]

Abstract Outbreaks of mass mortalities among cultured Macrobrachium nipponense occurred in a commercial hatchery during the autumn of 2017 in Jiangsu province, P. R. China, and non-O1 Vibrio cholerae was isolated and identified as causal agents of M. nipponense , with a LD 50 value 4.09 × 104 CFU/mL. Detection of virulence-associated genes by PCR indicated that XL1 was positive for Mp , HlyA , RtxA , OmpU , Ace , Zot and T6SS. Furthermore, the results of extracellular enzyme analysis revealed that the strain can produce lecithinase, amylase, gelatinase and hemolysin. Histopathological analysis revealed that the hepatic tubule lumen and the gap between the hepatic tubules became larger, and the brush border disappeared in the hepatopancreas. Quantitive real-time PCR (qRT-PCR) was undertaken to measure mRNA expression levels for thirteen immune related genes in M. nipponense after non-O1 V. cholerae infection. The transcriptional analysis of these immune related genes demonstrated that the expression levels of dorsal, relish, p38, crustin1, crustin2, crustin3, hemocyanin, i-lysozyme, anti-lipopolysaccharide factors 1, anti-lipopolysaccharide factors 2, prophenoloxidase were significantly up-regulated in hemolymph of M. nipponense post-infection. These results revealed varying expression profiles and clear transcriptional activation of these immune related genes in hemolymph, which will contribute to better understand the pathogenesis and host defensive system in non-O1 V. cholerae invasion. Highlights • Mass mortalities of cultured Macrobrachium nipponense from several farms in Yangzhou city of China is reported. • Non-O1 Vibrio cholerae XL1 carry Mp , HlyA , RtxA , OmpU , Ace , Zot and T6SS by PCR detection. • Non-O1 Vibrio cholerae triggers a wide defensive response of various immune related genes in Macrobrachium nipponense. [ABSTRACT FROM AUTHOR]

Outbreaks of mass mortalities among cultured Procambarus clarkia occurred in a commercial hatchery during the spring of 2019 in Jiangsu province of China. Here, we exploit the pathogenicity and immune response of Aeromonas hydrophila (GPC1-2), which was isolated from diseased P. clarkia. Crayfish challenged showed similar pathological signs to the naturally diseased P. clarkia , lethal dose 50% (LD 50) of the strain GPC1-2 to P. clarkia was 3.8 × 106 CFU/mL. Detection of virulence-associated genes by PCR indicated that the strain GPC1-2 carried hlyA , aerA , alt , ast , act , aha , ahp , ahpA , and ahpB. Histopathological analysis of hepatopancreas revealed that the hepatic tubule lumen and the gap between the hepatic tubules became larger, and the brush border disappeared in the P. clarkia infected by GPC1-2. Quantitive real-time PCR (qRT-PCR) was undertaken to measure mRNA expression levels for six immune-related genes in P. clarkia after A. hydrophila infection. The expression level of proPO , NOS , ALF1 , TLR2 , PX , and AST were detected in hemolymph, hepatopancreas, gill and intestine tissues, and clear transcriptional activation of these genes were observed in the infected individuals. These results revealed pathogenicity of A. hydrophila and its activation of host immune response, which will provide a scientific reference for the breeding and disease prevention in P. clarkia culture. • Mass mortality of cultured Procambarus clarkia from different farms in Gaoyou country of China was reported. • The strain Aeromonas hydrophila GPC1-2 had a strong virulence to P. clarkia , with a LD 50 value of 3.8 × 106 CFU/mL. • Aeromonas hydrophila triggers a wide defensive response of various immune related genes in Procambarus clarkia. [ABSTRACT FROM AUTHOR]