Withering Syndrome of abalone in California

Catastrophic declines in many abalone species in California, both wild and cultured, have been attributed to the bacterial disease, Withering Syndrome (WS). The etiological agent was recently described as a novel rickettsial bacterium, "Candidatus xenohaliotis californiensis" which infects gastroepithelial cells of abalone and results in morphologic changes in the digestive gland (degeneration and metaplasia) and foot muscle (atrophy). Digestive gland metaplasia appears pathognomonic for WS. Differences in susceptibility and tissue changes were noted between species with black abalone, Haliotis cracherodii, being more susceptible to WS than red abalone, H. rufescens. Climatic variation associated with ENSO events has been demonstrated to result in development of WS in red abalone, and exacerbate disease development in black abalone. Survivors appear relatively resistant to WS and are being considered as captive broodstock in species restoration programs. Molecular tools and therapeutants have been developed and will play a key role in the abalone culture industry and captive broodstock programs, particularly for the endangered white abalone, H. sorenseni, which is being cultured in a WS endemic region.