California Sea Grant College Program

Withering syndrome is a chronic, often fatal disease of multiple species of California abalone. It was first observed in the mid-1980s at the Channel Islands off Southern California and has since spread along the main coastline as far north as the San Francisco bay area. Recent research has demonstrated that the causative agent is a Rickettsiales-like prokaryote (WS-RLP, Friedman et al. 2000), and that WS expression is much more rapid and severe at elevated water temperatures (Moore et al. 2000). Aside from impacts on wild populations, WS has resulted in substantial losses in red abalone farms. As a result of these losses and our observation that the WS-RLP is sensitive to tetracyclines, we developed and oral administration of oxytetracycline in conjunction with researchers at The Abalone Farm, Inc.