Oxytetracycline water bath treatment of juvenile blue abalone Haliotis fulgens (Philippi 1845) affected by the withering syndrom

Abstract

The fatal abalone disease named withering syndrome (WS), caused by a Rickettsiales-like prokaryote classified as Xenohaliotis californiensis, has been treated by injections and oral administration of oxytetracycline (OTC) with relatively successful results. These therapeutic treatments have practical limitations for their application in aquacultural and experimental facilities due to the inability to eat of severely ill organisms, and the need to incorporate the antibiotic in pelletized food, increasing production costs. During an experiment to determine the effect of photoperiod and temperature on the growth of juvenile blue abalone Haliotis fulgens, some animals showed overt symptoms of WS. Oxytetracycline baths at 400 mg L^–1 were used for one hour daily during seven days to treat diseased animals. The metabolic rate of one group of these organisms was also assessed. Recovery time (time for an organism to regain the upright position) and size were assessed on days 0, 14, and 29. By the third day of treatment, most treated animals regained a limited adhesion capacity, and began to ingest food and to produce feces. After one week, more than 50% of the treated abalone were capable of regaining the upright position within the first 10 min of being turned upside down. After 30 days all organisms showed strong adhesion to the substrate. Metabolic rate declined from 380 (initially) to 280 µL O₂ ind^–1 h^–1 after two weeks of treatment. This study opens the door for further research on the use of OTC baths for practical use in abalone culture and management.