FIRST MOLECULAR DETECTION OF INFECTIOUS SPLEEN AND KIDNEY NECROSIS VIRUS (ISKNV) STRAIN OF MEGALOCYTIVIRUS IN ASIAN SEABASS (Lates calcarifer) AND WATER SYSTEMS FROM NORTHERN PENINSULAR MALAYSIA

Abstract

Lates calcarifer is a commercial species in both aquaculture and capture fisheries in Southeast Asian countries and accounts for 50% to 90% of Malaysia’s total annual production. However, the most challenging issue facing L. calcarifer farmers is Megalocytivirus infection, which causes high mortality. Thus, this study aimed to detect the presence of Megalocytivirus and its genotype in fish and water samples from a L. calcarifer farm via PCR analysis. A total of 45 samples of L. calcarifer juveniles, eggs, and water samples from different sites (egg pond, juvenile pond, water outlet, untreated reservoir, and treated reservoir) were collected at two sampling times from the L. calcarifer hatchery, Hang Lekir, Perak. The PCR assay demonstrated that all the samples from both sampling times were positive for Megalocytivirus DNA. External clinical signs in the fish samples included tail erosion, scale loss, haemorrhages (mouth), and body erosion during the first sampling; however, no clinical signs were observed during the second sampling. Sequence analysis of the positive samples showed 97% to 98% nucleotide similarity to the Infectious Spleen and Kidney Necrosis Virus (ISKNV) strain, and samples from similar sampling times showed high nucleotide similarity (> 98%) to each other. Furthermore, the positive samples from this study were grouped within the ISKNV strain.