Description of Disease Spring Viraemia of Carp (SVC) is a contagious viral disease of fish which affects most species of carp, tench, pike, orfe and wels catfish. There is evidence to suggest that goldfish can also be affected by the disease. The disease is usually observed during the Spring and the outcome depends on the general condition of the fish, the water temperature, and any secondary bacterial infections. At low water temperatures (less than 10oC) the fish immune response is reduced and the disease is usually fatal. As temperatures rise the ability of the fish to survive increases and continuous rearing at 20 to 22oC should be protective. All ages are susceptible but the most severe losses occur in juvenile to yearling fish. Mortalities can range from 10 - 100%, and fish surviving an outbreak may still carry the virus, occasionally excreting it without necessarily showing any signs of infection. SVC is widespread in several countries in mainland Europe. There have been a number of cases in mainland Britain, but it has not occurred Northern Ireland to date. Clinical Signs The infection is characterised by dark body colouration, popeye, pale gills and a swollen abdomen. Sometimes pin-point haemorrhages can be observed in the skin, and there can be a thick mucoid cast trailing from an inflamed and protruding vent. Affected fish breath weakly and are lethargic although some may display sporadic hyperactivity. The fish can lose equilibrium and swimming can be uncoordinated. It is important to note that not all of the signs may be present, particularly during the earliest and very late stages of a disease outbreak