Optimization of oxytetracycline treatment in two abalone species,Haliotis sorenseni and H. rufescens

摘要

Withering syndrome (WS), a rickettsial disease, causes losses of wild and farmed abalone. The endangered white abalone, Haliotis sorenseni, is highly susceptible to WS and information on management of this disease is essential for successful restoration. White abalone were fed a medicated diet containing oxytetracy-cline (OTC) for 20 d; digestive gland (DG) and foot muscle (FM) were assayed for OTC and rickettsia at days 3, 18, 24, 40, 67, 80, 110, 129, 165 and 185 post-medication. Abalone were rechallenged with rickettsia at 24, 40, 67, 146 and 171 d. DG contained higher levels and retained OTC longer than FM. Mean DG drug levels peaked at 996 ppm at 25 d post-medication and leveled off at 30 ppm after 68 d. FM peaked at 18 ppm and declined to below 2 ppm, the FDA tolerance level, between 25 and 41 d. Protection from rickettsial infections occurred in abalone with over 50 ppm in the DG. We investigated the pharmacokinetics of one oral OTC dose in red abalone and that of 1, 2 or 3 intramuscular (IM) injections with Liquamycin-LA 200 in white abalone. One oral dose cleared 90-100% (p < 0.05) of infections. A mean of 239 ppm OTC was detected in the DG 5 d after medication followed by depletion to 2.34 ppm after 130 d. In a second trial, 688 ppm accumulated in the DG at 1 d and declined to 326 ppm by day 5. Interestingly, total body OTC was only 89 ppm at day 1 (688 ppm in DG), IM injections resulted in DG accumulations of 7.15, 20.3 and 27.4 ppm after 1, 2 and 3 doses, respectively.