Document Type



Virginia Institute of Marine Science

Publication Date



Journal Of Shellfish Research





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Withering syndrome (WS) has been associated with catastrophic declines in black abalone populations in southern and central California. In an effort to identify the etiological agent of WS and to characterize the progression of this disease, we initiated a transmission study in which abalone from Ano Nuevo Island, a location free of WS, shared aquaria with animals from Vandenberg Airforce Base, a location where WS is epizootic. The mean incubation period of WS (time to develop overt signs of the disease) was 245 days with a mean time to death after development of clinical signs of 42 days. Median time to death was 41 wk in the experimentally exposed Ano Nuevo Island abalone and 16 wk in the positive control Vandenberg abalone. Cumulative mortality was significantly different between the negative control (unexposed) Ano Nuevo Island abalone (25% mortality) and both the exposed Ano Nuevo Island abalone (85% mortality; P = 0.0001) and the positive control Vandenberg abalone (100% mortality; P = 0.0001). In addition, significant differences in prevalences of a recently described Rickettsiales-like procaryote (RLP), "Candidatus Xenohaliotis californiensis," were observed between negative control animals (no RLPs) and those with WS (both the experimentally exposed Ano Nuevo Island and Vandenberg abalone were infected with RLPs; P < 0.001). All abalone infected with the RLP had signs of WS, including decreased condition indices, foot muscle atrophy, and digestive gland degeneration (P < 0.05). No correlation between intensity of RLP infection and degree of WS was observed (P > 0.05), suggesting a complex relationship between the RLP and clinical disease in black abalone. Despite this, these data in conjunction with a lack of observation of any other significant pathogens in the abalone provides evidence that the RLP infecting abalone ("Candidatus Xenohaliotis californiensis") is the etiological agent of WS.


Withering Syndrome; Black Abalone; Haliotis; Rickettsiales; "Candidatus Xenohaliotis Californiensis"

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This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.