4-Hexylresorcinol as inhibitor of shrimp melanosis: efficacy and residues studies; evaluation of possible toxic effect in a human intestinal in vitro model (Caco-2); preliminary safety assessment.

Studies were performed on the efficacy, residues and in vitro enterocyte toxicity of 4-hexylresorcinol (4-HR), which could be utilized as an inhibitor of shrimp melanosis (black spot). Mediterranean sea shrimp (Parapaeneus longirostris) were treated with solutions of 4-HR in sea-water, at three different concentrations, 25, 50 or 100 mg/kg of shrimp, to test its antioxidative property. As a comparison a group of shrimp was treated with sodium metabisulphite (1 g/kg), while another group was left untreated. 4-HR showed a marked ability to inhibit or slow down melanosis (black spot) in shrimp; the most effective concentration was 100 mg/kg within an optimum period of 7 days but with effects up to the tenth day. During the first 5 days, 4-HR residues in the edible part of the shrimp showed a fast decrease in all three groups, going from initial average values of 20 mg/kg at 0 time, to 0.9 in the group treated at 25 mg/kg; from 42 to 1.8 mg/kg in the group at 50 mg/kg and from 85 to 1.9 mg/kg in the group at 100 mg/kg. In vitro studies on enterocyte-like Caco-2 cells did not indicate any cytotoxic effect up to a concentration of 50 micrograms/ml. Moreover, no inhibition of protein synthesis was observed, which lends further support to the absence of significant damage to the intestinal mucosa induced by 4-HR. The available database on 4-HR pharmacology and toxicology is inadequate to determine even a provisional ADI. There is negative evidence of carcinogenesis and no significant untoward effects were observed in humans when it was used as an anthelmintic. However, it is not possible to determine a NOEL for non-genotoxic effects. 4-HR could become an interesting alternative to the use of sulphites to prevent black spot. However, a more complete database is needed to achieve a regulatory evaluation.

Residues of clenbuterol in tissues of the rainbow trout (Oncorhynchus mykiss).

There have been many studies on the efficacy of beta 2-adrenergic drugs as feed additives but no data are available at present on the use of clenbuterol in fish production. To evaluate the residues of clenbuterol in tissues of fish, 50 trout (Oncorhynchus mykiss) were fed for 21 days on a fish feed containing 5 ppm of the drug. The livers, muscles and skins of sample groups of fish were analysed by HPLC with visible spectrophotometric detection on days 15 and 21 of treatment and at intervals during a 30-day withdrawal time. Clenbuterol reached its highest levels in the liver (mean 440 ppb; SD = +/- 159; n = 5) on day 15 of treatment, with a slow depletion curve; 24 +/- 3 ppb was still present at the end of the withdrawal period. At this time, residues were still present in the edible tissues, i.e. muscle (5 +/- 1 ppb) and skin (7 +/- 3 ppb). Side-effects were noted during the first week of treatment.

Experimental studies on the maintenance of Toscana and Arbia viruses (Bunyaviridae: Phlebovirus).

Transovarial transmission (TOT) of Toscana (TOS) and Arbia (ARB) viruses in a laboratory colony of Phlebotomus perniciosus is reported. Toscana and ARB viruses were maintained in P. perniciosus females, initially infected by intrathoracic inoculation, for 2 and 3 consecutive generations respectively. TOT was demonstrated in F1 (75%) and F2 (67%) generation adults for TOS and F1 (47%), F2 (37%), and F3 (34%) generation adults for ARB virus. The progressive decline of virus infection rates in each generation suggests that these agents cannot be maintained indefinitely by TOT. No infection was observed in F1 progeny after female parents were fed through membranes with either virus. Transovarially infected females were able to transmit TOS virus by bite to a susceptible vertebrate. Venereal infection of P. perniciosus females mated to males transovarially infected with TOS virus was seen.