Pathogenicity Of Non-O1/O139 Vibrio Cholerae And And Its Induced Immune Response In Macrobrachium Rosenbergii

Macrobrachium rosenbergii is one of the largest freshwater prawn in the world.It has the advantages of fast growth,large individual,wide eating habit,easy domestication,strong adaptability and short production cycle.The shrimps that were propagated in the same year can reach the market specifications after 3-5 months of breeding.They have extremely high economic value and become an important economic crustacean in inland aquaculture.They are cultured in more than 10 provinces,municipalities and autonomous regions in China.China has become a global giant of Macrobrachium rosenbergii.With the rapid development of the Macrobrachium rosenbergii industry,a large number of deaths in aquaculture production occur frequently,causing huge economic losses to the majority of farmers.At present,the disease problem has become the main bottleneck restricting the further development of the Macrobrachium rosenbergii industry in the world.Outbreaks of mass mortalities among cultured of Macrobrachium rosenbergii characterized by red body occurred in several farms of Jiangsu Province of China from 2017 to 2018.The bacterial isolates from diseased M rosenbergii were identified as non-01/0139 Vibrio cholerae according to biochemical characteristics and molecular identification.In challenge test,M.rosenbergii infected with non-01/0139 V.cholerae GXFL1-4 developed similar pathological signs to the naturally diseased prawns,and LD50 of GXFL1-4 to M rosenbergii was 4.5×106 CFU/mL at 96 h post-infection.Besides,histopathological features of M rosenbergii infected by GXFL1-4 were carried out by Hematoxylin and Eosin(H&E).Furthermore,the isolate GXFL1-4 produced caseinase,lipase,amylase,lecithinase and hemolysin,supporting the strong virulence to M rosenbergii,and the isolate GXFL1-4 was found to be carrying toxR,hlyA,ompW,ompU,hap,rtxA and rtxC virulence related genes,as revealed by PCR.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 after infection with GXFL1-4.The results of our study suggested that non-01/0139 V.cholerae was an etiological element in the mass mortalities of M rosenbergii and this study provide preliminary insights into the differences in the immune response of M.rosenbergii to the bacterial invasion.