Monitoring of drugs in fish farming 2010

February 28, 2011 12:28

Analyses of farmed fish collected in 2010 consistently show an absence of drug residues in the samples, reports with reference to National Institute of Nutrition and Seafood Research.

Low concentrations of some delousing agents have been found in a few samples, but the values are well below the limits set for these substances. In addition, traces of the drug chloramphenicol was found in one sample. This drug is not approved for use in food-producing animals, including fish. Based on an overall assessment of the new results, the food safety is considered to be good.

No traces of delousing agents over the  limit

The regular monitoring programme has so far not detected residues of the delousing agents diflubenzuron and teflubenzuron above the detection limit of the methods, which is around one percent of the limit set for fish for human consumption. In addition to the regular monitoring programme, additional investigations were performed in 2010 of salmon collected from the fish farm immediately after the expiration of the withdrawal period following a treatment with the delousing agent diflubenzuron. Analyses of these samples found diflubenzuron in seven out of 34 examined samples. The highest value in these samples was 26 ng/g, which corresponds to 2.6% of the permitted limit of 1,000 ng/g.

Residues of another drug against salmon lice, emamectin benzoate, have been found in samples from the years 2008, 2009 and 2010, but never above the limit, which for this drug is 100 ng/g. In 2010, the drug was detected in six out of 180 pooled samples, and the highest concentration was 25 ng/g, which is the equivalent of 25% of the current limit. In 2010, the delousing agent cypermethrin was detected in one out of 20 examined samples, and the concentration was 10 ng/g. This represents 20% of the current limit.
Residues of chloramphenicol in a salmon sample

During the analyses of samples taken in 2010, residues of chloramphenicol were found in a pooled sample consisting of material from five fish. The concentration in this sample was just above the detection limit of 0.25 ng/g. This drug is an antibiotic agent that is not approved for use in food-producing animals, including fish. However, chloramphenicol is registered for use on humans. These monitoring results show that the system is capable of detecting banned drugs in very low concentrations.

Scope of testing and analysis

The majority of samples collected in 2010 have now been analysed and, as per 14 February 2011, a total of 6,079 samples have been investigated, consisting of material from 11,299 fish, mainly salmon. The fish were either analysed as pooled samples of five fish, where each pooled sample was tested for one parameter, or analysed as single samples. The following substances were examined, with the number of samples in brackets: azametifos (28), cypermethrin (20), deltamethrin (20), diklorvos (28), diflubenzuron (96), emamectin benzoate (180), ivermektin (6), teflubenzuron (60 ), praziquantel (68), fenbendazol (27), malachite green and crystal violet with metabolites (164), brilliant green (76), chloramphenicol (194), florfenikol (5), metronidazole (151), oxolinic acid (8), flumequine (8) , nitrofuranes with metabolites (98), oksytetracyclin (8), stilbenes (45) and steroids (49), quinolones inhibition zone test (1580), tetracyclines and amfenicoles inhibition zone test (1580) and sulfonamides inhibition zone test (1580).

The regular monitoring of medicines in fish farming

To ensure that farmed fish for human consumption does not contain residues of legally used drugs including delousing agents in harmful concentrations, or residues of illegal drugs, Norway has a control system that complies with international guidelines in this area (Directive 96/23). The Norwegian Food Safety Authority is responsible for the Norwegian system and NIFES is responsible for analyses of relevant samples. The system is monitored and regularly audited by EFTA's surveillance authority (ESA). The monitoring of drug use and residuesin aquaculture was introduced in Norway in the late 1990s and is based on the control and registration of drug use, the establishment of withdrawal periods to ensure that fish cannot be harvested until after a specified time following medications, and analytical controls for drug residues. The number of analyses per year is determined on the basis of production volume for fish, and most samples are of salmon. Collected samples should cover all species of fish from around the country. The  samples are collected randomly . The drugs to be included in the programme are specified in the current EU regulations.

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