Smärtlindring i samband med vaccination av fisk

Abstract: Vaccination of fish can be assumed to cause pain. This study was designed to see if we can minimize the suffering of fish following vaccination. Fishes are cold-blooded animals and thus more primitive than warm-blooded animals. Despite this, many organs, e.g. the nervous system, have the same basic structure as that of other vertebrates. The fibre system for conducting pain is more diffuse than in humans. No specific pain conducting tract seems necessary for pain transmission. All ethical rules and laws for animals include fish, but pain killing is still not common in fish production. Prostaglandins and bradykinin are substances which are released in the inflammatory process and cause pain. Vaccination causes peritonitis and adherence between organs and the abdominal wall (scarring). The peritonitis can be assumed to cause pain, which may be one reason why the fish stops feeding for several days following vaccination. Many analgesics inhibit the synthesis of prostaglandin, and thus inhibit both pain and inflammation. The local anasthetics used to immobilize fish are given in the water and taken up via the gills. This gives systemic effects. Atlantic salmon, Salmo salar, was used. 1980 parr were allocated in 14 tubs. Later another 400 parr in two tubs were used. The fish had free access to feed and had continuous daylight. The study was split into two parts. In the first part, two methods for measurement of feed intake was evaluated. In the second part different feeding models (starvation/feeding) and Aqui-S (isoeugenol, which probably diminishes the pain), was used to see if we could affect the time for recovery following vaccination. Before vaccination all groups besides the feed group were starved for two days. Following vaccination, the fish was fed again, except for the starvation group, that was not fed until day three after vaccination. The first feeding day the fish was fed for 10 hours. The pain level was measured as feed intake in percent of biomass, since feed intake is a very good indicator of the well-being of the fish. Before vaccination the fish was sedated with benzocain, the routine sedative at vaccination. The vaccine used was Norvax Compact 6 vet. for furunculosis, cold water vibriosis, vibriosis, winter wounds and IPN. The injection dose was 0,1 ml. This dose is used independent of the size of the fish. The group of fish that was fed all the way through the study recovered fastest; followed by the group that was starved for three days following vaccination. The Aqui-SÔgroup recovered much slower, and the feed intake was significantly lower than for the feed- and starving groups. The control group recovered more slowly than the starvation group but faster than the Aqui-S group. The Aqui-SÔgroup had most adherences, and the feed group had the least. The study clearly shows that starvation prior to vaccination of the fish is wrong. The pharmacological effects of Aqui-S need to be evaluated and more experiments need to be done before we can come to any conclusions about its effectiveness as an analgesic.