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Withering syndrome in the abalone Haliotis diversicolor supertexta
Thanitsara Wetchateng1, Carolyn S Friedman, Nathan A Wight
1Department of Anatomy, Faculty of Science, Mahidol University, 272 Rama 6 Rd., Bangkok 10400, Thailand.
Diseases of Aquatic Organisms
|July 6, 2010
Summary
The Rickettsia-like organism (RLO) causing abalone withering syndrome (WS) was identified in Thailand, Taiwan, and China. This finding confirms the spread of the California-originating WS-RLO in farmed abalone populations.
Area of Science:
- * Aquaculture pathology
- * Marine microbiology
- * Infectious diseases in shellfish
Background:
- * Abalone aquaculture is expanding globally, utilizing both exotic and native species.
- * Withering syndrome (WS), caused by 'Candidatus Xenohaliotis californiensis' (a Rickettsia-like organism, RLO), is a significant disease affecting abalone populations worldwide.
- * The introduction and spread of WS-RLO pose a considerable threat to abalone farming industries.
Purpose of the Study:
- * To report the initial detection and characterization of the WS-RLO agent in small abalone (Haliotis diversicolor supertexta) in Thailand, Taiwan (ROC), and the People's Republic of China (PRC).
- * To confirm the identity of the detected RLO and trace its origin.
Main Methods:
- * Light microscopy and transmission electron microscopy (TEM) were used to visualize RLOs within host tissues.
- * In situ hybridization with WS-RLO-specific probes was performed.
- * Polymerase chain reaction (PCR) using primers targeting the 16S rDNA gene of the WS-RLO was employed for molecular identification and comparison.
Main Results:
- * RLOs were observed as intracytoplasmic inclusions in epithelial cells of the post-esophagus and intestine of infected H. diversicolor.
- * TEM revealed the inclusions as colonies of rod-shaped bacteria within cytoplasmic vesicles.
- * Molecular analysis confirmed the presence of WS-RLO, with PCR products showing high sequence identity (99-100%) to the original California WS-RLO.
Conclusions:
- * The RLO identified in Thailand, Taiwan, and the PRC is confirmed to be the WS-RLO originating from California.
- * The findings highlight the successful introduction and establishment of this pathogen in new geographical regions through abalone aquaculture movements.
- * This study underscores the importance of monitoring and managing disease spread in global aquaculture operations.
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