OXYTETRACYCLINE AS A TOOL TO MANAGE AND PREVENT LOSSES OF THE ENDANGERED WHITE ABALONE, HALIOTIS SORENSENI, CAUSED BY WITHERING SYNDROME

Abstract

Research and captive rearing programs targeted to restore the endangered white abalone, Haliotis sorensen, are being conducted in California and Washington state. Captive rearing, whereas successful, has demonstrated that this species is highly susceptible to withering syndrome (WS), a rickettsial disease of abalone; WS has not been demonstrated in remnant wild white abalone populations. Thus, WS may limit white abalone production and supplementation of captive abalone must include measures to preclude the introduction of WS into wild populations. Oxytetracycline (OTC) is approved for use in aquaculture and has been demonstrated to effectively reduce rickettsial loads, WS development, and associated losses. White abalone were medicated at 90.82 mg/kg of OTC daily for 20 days and the efficacy, elimination, and potential to protect against exposure to the WS rickettsia were examined. This study illustrated that OTC effectively eliminates rickettsial infections. High concentrations of OTC (1,089 ppm) were observed in the digestive gland after medication; depletion occurred over a prolonged period providing protection to rickettsial challenge in abalone with a mean of over 72 ppm in this tissue. These data highlight the need for further optimization of this drug for use in commercial and restoration aquaculture.