Iridovirus disease in two ornamental tropical freshwater fishes: African lampeye and dwarf gourami

Abstract

Many species of ornamental freshwater fishes are imported into Japan from all over the world. We found African lampeye Aplocheilichthys normani and dwarf gourami Colisa lalia suffering from an iridovirus infection just after being imported by tropical fish wholesalers from Singapore. African lampeye were cultured on the Indonesian Island of Sumatra and dwarf gourami were cultured in Malaysia before export. Diseased fishes displayed distinct histopathological signs of iridovirus infection: systemic appearance of inclusion body-bearing cells, and necrosis of splenocytes and hematopoietic cells. Electron microscopy revealed viral particles (African lampeye:180 to 200 nm in edge to edge diameter; dwarf gourami: 140 to 150 nm in diameter) in an inclusion body within the cytoplasm of inclusion body-bearing cells as well as in the cytoplasm of necrotized cells. Experimental infection with an iridovirus isolate from African lampeye (ALIV) revealed pathogenicity of ALIV to African lampeye and pearl gourami Trichogaster leeri. Polymerase chain reaction (PCR) products from ALIV and an iridovirus isolate from dwarf gourami (DGIV) using iridovirus-specific primers were indistinguishable. The nucleotide sequence of PCR products derived from ALIV (696 base pairs) and DGIV (701 base pairs) had 95.3% identity. These results indicate that ALIV and DGIV have a single origin. KEY WORDS: Tropical iridovirus · African lampeye · Dwarf gourami · Inclusion body-bearing cells · Polymerase chain reaction assay · DNA sequence Resale or republication not permitted without written consent of the publisherDis Aquat Org 48: [163][164][165][166][167][168][169][170][171][172][173] 2002 brown-spotted groupers Epinephelus tauvina (Chua et al. 1994) and E. malabaricus (Danayadol et al. 1996), farmed in Singapore and Thailand, respectively; sea bass, Lateolabrax sp., captured in the South China Sea ; mandarin fish Siniperca chuatsi, reared in offshore pens in the South China Sea in China (He et al. 2000); red sea bream Chrisophylus major (= Pagrus major, Inouye et al. 1992), yellowtail Seriola quinqueradiata, and striped jack Caranx delicatissimus, etc., farmed in Japan (Miyazaki unpubl.); and striped beakperch Oplegnathus fasciatus, cultured in Korea (Jung & Oh 2000).Here we present the results of histopathological and electron microscopic (EM) examinations of the diseased African lampeye and dwarf gourami. We report the results of artificial infections with an isolate from African lampeye to African lampeye and pearl gourami. We also describe a polymerase chain reaction (PCR) assay and DNA sequence analysis of the PCR products for identification of iridovirus isolates from African lampeye (ALIV) and dwarf gourami (DGIV). MATERIALS AND METHODSHistopathological and EM examinations, virus culture in natural outbreaks. Diseased African lampeye and dwarf gourami were found just after being imported to Japan from Singapore by tropical fish wholesalers. The African lampeye had been cultured in freshwater ponds on Sumatra Island, Indonesia, a...

Histological, ultrastructural, and in situ hybridization study on enlarged cells in grouper Epinephelus hybrids infected by grouper iridovirus in Taiwan (TGIV)

“…However, in contrast to tropical iridovirus-infected cells, in TGIV-infected cells there is no apparent slit or membranous structure separating the viromatrix from the cytoplasm as sometimes seen in tropical virus infections (Sudthongkong et al 2002b). The nuclei of TGIV-infected cells disintegrated before the viromatrix was fully established in the cytoplasm; however, the nuclei was displaced to one side in tropical iridovirus-infected cells, even when the inclusion bodies occupied most of the cytoplasm , Sudthongkong et al 2002a. The most striking difference is that the eosinophilic enlarged cells in tropical iridovirus infections are ballooning, degenerated cells with few remaining virions in their inclusion bodies, while in TGIV-infected cells all the eosinophilic enlarged cells observed were phagocytes containing cell debris.…”

Histopathological and ultrastructural features of enlarged cells of humpback grouper Cromileptes altivelis challenged with Megalocytivirus (family Iridoviridae) after vaccination

“…data). In ornamental freshwater fishes, megalocytivirus has also been isolated from diseased African lampeye Aplocheilichthys normani, which were cultured on Sumatra Island and exported to Japan (Sudthongkong et al 2002a), and diseased dwarf gourami Colisa lalia, which were exported to Australia from southeast Asia (Go & Whittington 2006). Moreover, megalocytivirus diseases have also been found in both marine and freshwater fishes in other Asian countries (Inouye et al 1992, Chua et al 1994, Matsuoka et al 1996, Danayadol et al 1997, Kasornchandra & Khongpradit 1997, Chou et al 1998, Jung & Oh 2000, Chao et al 2002, Sano et al 2002, Sudthongkong et al 2002b, Weng et al 2002, Chen et al 2003, GibsonKueh et al 2003, Shi et al 2004.…”

Outbreaks and risks of infectious spleen and kidney necrosis virus disease in freshwater ornamental fishes

“…In Australia iridovirus-like virions from dwarf gourami Colisa lalia imported from Singapore (Anderson et al 1993) were reported in 1988, and in 2006 Murray cod iridovirus (MCIV) from intensively farmed Murray cod Maccullochella peelii peelii was observed there ; Armstrong & Ferguson (1989) reported an iridovirus in chromide cichlid Etroplus maculatus in Canada, also imported from Singapore; and Sudthongkong et al (2002) reported outbreaks of African lampeye Aplocheilichthys normani iridovirus (ALIV) and dwarf gourami C. lalia iridovirus (DGIV) in Japan.…”

“…Iridoviruses have been associated with severe mortality and economic loss in freshwater ornamental fish, including angelfish Pterophyllum scalare, gourami Trichogaster spp., swordtail Xiphophorus hellerii, dwarf gourami Colisa lalia, chromide cichlid Etroplus maculatus, guppy Poecilia reticulata, doctor fish Labroides dimidatus, mollies Poecilia latipinna and African lampeye Aplocheilichthys normani (Armstrong & Ferguson 1989, Anderson et al 1993, Hedrick & McDowell 1995, Rodger et al 1997, Paperna et al 2001, Sudthongkong et al 2002, as well as in a wide variety of marine fish species (Inouye et al 1992, Bloch & Larsen 1993, Chua et al 1994, Matsuoka et al 1996, Jung & Oh 2000. Such iridoviruses are becoming ubiquitous due to transfer of ornamental fish by international trade.…”