Withering syndrome in the abalone Haliotis diversicolor supertexta

Abstract

Abalone aquaculture is a small but growing industry in Thailand and is based on both the exotic Haliotis diversicolor supertexta and the native H. asinina. Withering syndrome (WS) in abalone is caused by an infection with the Rickettsia-like organism (RLO) 'Candidatus Xenohaliotis californiensis' and has been spread to many countries globally. The present study reports the first observation of the WS-RLO agent in the small abalone, H. diversicolor supertexta in Thailand, Taiwan (ROC) and the People's Republic of China (PRC). Under light microscopy, the RLO was observed as intracytoplasmic inclusions within epithelial cells lining the post-esophagus and, to a minor extent, the intestine of H. diversicolor. Under transmission electron microscopy, inclusions were characterized as colonies of rod-shaped bacteria, 200 × 1800 nm in size, within a vesicle in the cytoplasm of the infected cell. The RLO from the small abalone bound with WS-RLO-specific in situ hybridization probes and was amplified by polymerase chain reaction (PCR), using primers designed from the 16S rDNA sequence of the original WS-RLO from California, USA. The PCR product of RLO samples from both the PRC and Thailand showed extremely high identity with the California WS-RLO (100 and 99%, respectively). These data combined with the history of abalone movements for aquaculture purposes indicate that RLOs observed in Thailand, Taiwan and the PRC are the WS-RLO that originated from California.KEY WORDS: Haliotis diversicolor · 'Candidatus Xenohaliotis californiensis' · 16S rDNA · Abalone · Withering syndrome · Thailand · Taiwan · People's Republic of China · California Resale or republication not permitted without written consent of the publisherDis Aquat Org 90: [69][70][71][72][73][74][75][76] 2010 rickettsial agent of withering syndrome (WS) are present in abalone under culture. Prior to the present study, the infection of Asian abalone species by Rickettsia-like organisms (RLOs) had not been observed or described; however, such knowledge is needed for the successful development and expansion of abalone aquaculture in Asia.WS is a catastrophic disease, caused by the intracellular RLO 'Candidatus Xenohaliotis californiensis . WS affects a variety of abalone species and was first observed in populations of wild black abalone Haliotis cracherodii in the mid-1980s (Haaker et al. 1992). Affected black abalone had an atrophied foot muscle and high mortality rates, especially in populations off southern California, USA (Haaker et al. 1992). The disease progressively spread throughout southern and central California (Haaker et al. 1992, Altstatt et al. 1996, Friedman & Finley 2003, Miner et al. 2006. By 1992, WS was associated with population declines on 6 of the 8 Channel Islands, with losses of up to 99% of H. cracherodii (VanBlaricom et al. 1993, Tissot 1995. These losses led, in part, to an initial closure of the California black abalone fishery in 1993, followed by total closure in 1997 (Haaker et al. 2001). Losses due to WS vary among host ...

Pathogenicity of two <i>Candidatus</i> Xenohaliotis californiensis genetic variants against three abalone species (the genus <i>Haliotis</i>)

“…The partial 16S rRNA gene we sequenced is presently used to diagnose WS in the OIE manual (OIE, 2015). Although our analyses did not include WS-RLO sequences from Japanese H. diversicolor supertexta, Wetchateng et al (2010) described the same 1-bp substitution from this species in Thailand waters, as mentioned before. This suggests that the 1-bp variant is characteristic of those WS-RLOs infecting Group B Haliotidae (H. diversicolor supertexta, H. diversicolor aquatilis, H. diversicolor diversicolor).…”

“…In contrast, WS-RLOinfected European abalone H. tuberculata showed no symptoms characteristic of WS (Balseiro et al, 2006). Additionally, WS-RLO-infected H. diversicolor supertexta showed no obvious sign of disease, and unusual losses did not occur among populations in Thailand (Wetchateng et al, 2010), and Crosson et al (2014) maintained that WS-RLO infection in H. diversicolor supertexta did not lead to mortality.…”

“…Infection is thought to be an emerging global disease (OIE, 2015) and is characterized by a severely shrunken body. Whereas PCRamplified 16S rRNA nucleotide sequences of WS-RLO from Japanese black abalone were 100% identical to those of North American black abalone (Kiryu et al, 2013), those from small tropical abalone in Thailand were not (Wetchateng et al, 2010).…”

Legislative and regulatory aspects of molluscan health management

“…• Californian abalone translocated to Chile, China, Taiwan, Iceland, Ireland, Israel, Japan, Spain and Thailand, and probably other countries, with Xenohaliotis californiensis being reported from Chile (Campalans and Lohrmann, 2009), Thailand, China and Taiwan (Wetchateng et al, 2010).…”

Physiological performance of juvenile Haliotis rufescens and Haliotis discus hannai abalone exposed to the withering syndrome agent

“…The disease was first observed in the 1980s in the Channel Islands southwest of California, where it caused a 99% decline in the population of the black abalone H. cracherodii. Since that time, this disease has been detected in pink (H. corrugata), flat (H. walallensis), white (H. sorenseni), red (H. rufescens), green (H. fulgens), and Taiwanese (H. diversicolor supertexta) abalones (Friedman et al, 2002;Wetchateng et al, 2010). The etiological agent of WS is the intracellular bacterium Candidatus Xenohaliotis californiensis, a Rickettsiales-like organism (WS-RLO).…”