THE INTERACTION OF BETANODAVIRUS WITH THE CLAMS, TAPES PHILIPPINARUM

The integrated multi-trophic aquaculture aims to reduce the ecological problems generated by mariculture combining the breeding of different aquatic species such as fish, shellfish and seaweed. The coexistence of fish and invertebrate filter feeders, that concentrate also viruses, can influence the epidemiology of fish infectious diseases. The physical-chemical features of viruses can strongly affect their ability to survive and to be released from the contaminated shellfish, turn it into a dangerous reservoir of the pathogen or an useful "cleaner system" of the surrounding environment such as in the case of IPNV or ISAV respectively. Betanodavirus, the etiological agent of the Viral Encephalo-Retinophaty, are worldwide spread in farmed and wild finfish. Furthermore, our previous investigations detected betanodaviruses in Tapes philippinarum, Crassostrea gigas and Mytilus galloprovincialis originating from Mediterranean Sea and Atlantic Ocean. The presence of Betanodavirus in M. galloprovincialis was reported also in Korea. This study aimed to optimize culture and molecular assays to detect Betanodavirus in shellfish tissues and to determine the fate of Betanodavirus in T. philippinarum experimentally contaminated. Two bioaccumulation assays were arranged to verify the natural ability of the clams to collect virus from contaminated water. Viral presence in hepatopancreas was monitored during the bioaccumulation assays (24 hours) and after transferring the clams in clean water up to 72 hours. Betanodavirus was detected and quantify in hepatopancreas with a semiquantitative RT/nestedPCR and with virus culture and titration in SSN-1 cell line. The histological investigation, 24 hours after Betanodavirus-exposure, has not detected appreciable differences between the exposed and unexposed clams. Culture assay had a detection limit of 102.7TCID50/0,1mL. The Betanodavirus was consistently detected in the hepatopancreas by both molecular technique and virus culture until 72 hours post infection. Both molecular and titration assays showed no decrease in the viral RNA amount in hepatopancreas 24, 48 and 72 hours post-exposure, reaching the values of 103,77 and 104,6TCID50/0,1mL in the two bioaccumulation assays. The results demonstrated that Betanodavirus can accumulate and persist alive in clams up to 72 hours post-exposure. Further studies will be done to determine whether Betanodavirus is released into the environment, posing a disease risk for cohabited fish.