Pharmacokinetics and efficacy of oxytetracycline in WS-RLP-infected abalone

Withering syndrome (WS) is a fatal disease affecting abalone throughout southern California. The desire to prevent the spread of WS to northern California abalone stocks necessitates further research on the development of WS, and a treatment for the disease.; Using nuclear magnetic resonance (1H NMR) based metabolomics, we have investigated the influence of bacterial infection, temperature, and food availability, both individually and in combination, on the metabolic status of the California red abalone (Haliotis rufescens ). Food limitation caused dramatic reductions in foot muscle metabolites, while at the same time, metabolite levels within the digestive gland were preserved or increased. Food limitation in conjunction with elevated seawater temperature led to greater metabolic perturbations than those observed under food limitation alone. WS-RLP infection and food reduction resulted in many of the same metabolic changes within the tissues studied although the effects of infection alone were more modest.; Histology along with 1H NMR metabolomics were then used to evaluate treatment of WS-RLP infected abalone with oxytetracycline (OTC) medicated feed at both 13.4+/-1.2°C and 17.3+/-1.3°C. Histological observations demonstrated the efficacious nature of OTC treatment in combating WS-RLP infection at both temperatures, while NUR metabolomics showed differences between treated and untreated animals only at 173+/-13°C. NMR spectra revealed that the most significant metabolic changes observed were related to the post-treatment times at which the animals were sampled, regardless of OTC treatment.; In addition, drug residue concentrations, WS-RLP burden, and WS-associated pathological changes were assessed for both OTC-treated and untreated abalone at 17.3°C. High OTC concentrations and long depuration times were observed within the digestive gland while drug depuration occurred rapidly from foot muscle. Digestive gland depuration conformed to a two-compartment model, with terminal phase elimination half lives of approximately 22 days. Cohabitation trials with WS-RLP infected abalone following a 10-day OTC-treatment showed reduced susceptibility to reinfection for up to 88 days after treatment. This study provides a further understanding of the tissue distribution and residue depletion, of OTC in abalone during treatment and has also documented the sequential metabolic changes that occur during the pre-clinical phases of the disease at both 13.4° and 17.3°C.