Bioavailability and pharmacokinetics of a praziquantel bolus in kingfish Seriola lalandi.

Oral praziquantel (PZQ) preparations have recently been investigated for the treatment of monogeneans that infect the skin and gills of kingfish Seriola lalandi cultured in sea-cages. To evaluate an oral PZQ dosing strategy, the pharmacokinetics of a dissolved and in feed oral PZQ preparation (40 mg kg(-1) body weight) were compared with an intravenous bolus in kingfish plasma and skin using HPLC. Compared with intravenous administration, PZQ bioavailability (area under curve, AUC0-24h) was slightly improved when the drug was administered with food in both kingfish plasma (56.8% in feed vs. 50.8% in solution) and skin (55.5% in feed vs. 50.3% in solution). After oral dosing, maximum drug concentrations in skin were approximately one-third of those achieved in plasma and higher when the drug was administered in solution (5.26 microg ml(-1)) than in feed (3.96 microg ml(-1)); additionally, the time to achieve maximum PZQ concentration was similar in plasma and skin, although markedly reduced when the drug was administered in solution (1 h) than in feed (6 h). However, clearance of the drug was delayed in skin; administered as an oral formulation, PZQ concentrations in the systemic circulation fell below the limit of quantification after 24 h, but remained quantifiable (0.3 microg g(-1)) in skin at this time. These initial studies indicate that a daily treatment interval will lead to the exposure of parasites to highly variable anthelmintic concentrations, which may be sub-optimal for the treatment of monogeneans in this finfish species.

Effects of temperature on fecundity in vitro, egg hatching and reproductive development of Benedenia seriolae and Zeuxapta seriolae (Monogenea) parasitic on yellowtail kingfish Seriola lalandi.

Globally, aquaculture industries involved with commercial culture of kingfish (Seriola spp.) experience outbreaks of monogenean parasites, which can cause heavy stock losses. In Australia and New Zealand, aquaculturists of kingfish Seriola lalandi incur financial losses caused by two monogenean species: Benedenia seriolae and Zeuxapta seriolae which parasitise the skin and gills, respectively. This study provides information on some basic temperature-dependent life-cycle parameters of these problematic monogeneans on S. lalandi. Hatching times and age at maturity were inversely related to water temperature within the range experienced by wild kingfish in New Zealand (13-21 degrees C). Mature B. seriolae in vitro laid on average 37 eggs/day that hatched over approximately 4 days; peak hatching occurred 9, 11 and 22 days post-deposition at temperatures of 21, 17.5 and 13+/-1.0 degrees C, respectively. Z. seriolae in vitro laid on average 246 eggs/day that hatched over 2 days; peak hatching occurred 7, 9 and 15 days post-deposition at these respective temperatures. B. seriolae matured within 20, 25 and 48 days p.i. at 21, 18 and 13 degrees C. Z. seriolae matured within 25, 37 and >52 days p.i. at the same temperatures. This research describes stages in the reproductive development of B. seriolae and Z. seriolae and discusses the inclusion of basic parasitic life-cycle parameters into management strategies designed to maximise treatment efficacy and limit monogenean epizootics in sea-cage kingfish culture.