Occurrence of iridoviruses and bacterial pathogens in bivalves, scavenging fish and trash fish in marine aquaculture facilities in Sabah, Malaysia

• Main Author: Suraini Lajimin
• Format: Thesis
• Language: English; English
• Published: 2015
• Subjects: SH171-179 Diseases and adverse factors
• Online Access: https://eprints.ums.edu.my/id/eprint/39469/1/24%20PAGES.pdf; https://eprints.ums.edu.my/id/eprint/39469/2/FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/39469/

Study was carried out to determine the occurrence of iridovirus and bacterial pathogen in bivalves, scavenging fish and trash fish collected from marine aquaculture facilities in Sabah. Bivalves and scavenging fish were collected from Kota Marudu, Kuala Penyu and Tuaran over a period of year from May 2012 to April 2013. Meanwhile, trash fish specimens were collected from fisheries landing stations Kudat, Semporna, Lahad Datu, Kuala Penyu and Kota Kinabalu. From the Polymerase Chain Reaction (PCR) analysis, specimens of bivalves and scavenging fish (n=2068) were detected positive for iridovirus (266), Photobacterium damselae (53), Vibrio harveyi (135), Vibrio alginolyticus (44) and Vibrio parahaemolyticus (147). Meanwhile, 35 of trash fish (n=221) specimens were also detected positive for iridovirus using PCR. The DNA of positive iridovirus samples was then characterized by DNA sequencing. From the DNA sequencing analysis, it was shown that the iridovirus found on bivalves, scavenging fish and trash fish are from the genus Megalocytivirus (Iridoviridae). Further strain divergence analysis suggested that the megaloctivirus from bivalves and scavenging fish are from the same strain that is the Infectious Spleen Kidney and Necrosis Virus (ISKNV) with the average percentage of nucleotide similarity of 98.77%. Similarly,the megalocytivirus from trash fish also showed the highest average percentage nucleotide similarity to ISKNV (99.40%), which suggested that the megalocytivirus in Sabah are from the strain of ISKNV. Finding of this study revealed that some of the bivalves and scavenging fish which are abundance in the aquaculture facilities particularly floating net cage, are carrier of iridovirus, Vibrio harveyi, Vibrio parahaemolyticus, Vibrio alginolyticus and Photobacterium damselae. These animals can become the hosts of viral and bacterial pathogens and possibly transmit them to cultured fish. Finding of this study also showed that the trash fish can become the carrier of iridovirus and may transmit it to cultured fish during feeding. Therefore, the study suggests that the aquaculture facilities should often be cleaned from biofouling organisms such as bivalves to prevent disease outbreak. Furthermore, the use of trash fish should be minimized for the similar reason.