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The present study examined the pharmacokinetics and bioavailability of oxytetracycline (OTC) in vannamei shrimp (Penaeus vannamei) after intra-sinus (10 mg/kg) and oral (10 and 50 mg/kg) administration and also investigated the net changes of OTC residues in the shrimp after the thermal, acid and alkaline processing methods. The hemolymph concentrations of OTC after intra-sinus dosing were best described by a twocompartment open model. The oral bioavailability was found to be 48.2 and 43.6% at doses of 10 and 50 mg OTC/kg, respectively. The peak hemolymph concentrations after 10 and 50 mg OTC/kg doses were 3.37 and 17.4 lg/ml; the times to peak hemolymph concentrations were 7 and 10 h. The elimination half-lives were found to be 15.0 and 11.5 h for the low and high dose, respectively. The residual OTC was rapidly eliminated from muscle with the elimination half-life value of 19.4 and 15.4 h, respectively, for the groups treated with doses of 10 and 50 mg/kg. The residual OTC levels in the muscle fell below the MRL (0.2 lg/g) at 72 and 96-h post-dosing at dose levels of 10 or 50 mg/kg, respectively. Residual OTC levels in muscle and shell were approximately 20-50% lower in the thermal treatment such as boiling, baking and frying. By the acid treatment, OTC residues were reduced to [80%, while those were reduced to around 30% by alkaline treatment.

White feces syndrome and acute hepatopancreatic necrosis disease (AHPND) are serious diseases that have recently been noted in Pacific white shrimp (Litopenaeus vannamei). Vibrio bacteria and 6 species of fungi (Aspergillus flavus, A. ochraceus, A. japonicus, Penicillium sp., Fusarium sp., and Cladosporium cladosporioides) were isolated from shrimp naturally infected with white feces syndrome. Antibiotics have been used to treatment the disease for many years, but these have been ineffective and have resulted in drug residue problems for the shrimp industry. In this study, an alternative method was tested for its efficacy in controlling these pathogens. The crude extract of galangal (Alpinia galanga Linn.), an herbal medicine, inhibited the growth of 8 vibrio species of the pathogen, V. parahaemolyticus (EMS/AHPND) in particular. The results also showed that 0.5 mg/ml of the galangal extract was a concentration that produced the strongest inhibition of the fungi A. ochraceus. Naturally infested shrimp L. vannamei were fed 2 and 4% (v/w) portions of the herb extract for 12 days and their progress was compared with that of a control group (no herb extract). At the end of the feeding trial, the numbers of total Vibrio spp. and the incidence of fungi infestation in the hepatopancreas and intestines of treated shrimp were significantly lower than that in the control group (P<0.05). Furthermore, the survival rates for the treatment groups, after injections with V. parahaemolyticus (EMS/AHPND), were significantly higher than that of the control group (P<0.05). Based on these results, we can report that the galangal extract has antimicrobial properties that are applicable as bio-medicinal agents against white feces syndrome and AHPND. Therefore, in the future this herb should be an alternative to chemotherapeutic agents that are being used in the shrimp industry.

White spot syndrome virus (WSSV) is highly pathogenic to penaeid shrimp and has caused significant economic losses in the shrimp farming industry in Thailand. Genotyping analysis was done in 124 WSSV isolates from cultured Pacific white shrimp