What are the prevention and control methods for infectious fish hemorrhage disease?

(1) Pathogen Grass carp hemorrhage disease is a fish disease caused by a virus, specifically a reovirus.

(2) Symptoms In grass carp, various organs and tissues inside and outside the body show speckled or patchy congestion. Congestion appears in the mouth, operculum, fin base, muscles, intestines, liver, spleen, kidney and other organs, presenting a "red muscle type". In grass carp fingerlings of 10-15 cm or more, congestion mainly occurs in the intestines, fin base, operculum and mouth, presenting a "red fin and thin operculum type" or "intestinal type", but muscle congestion is milder or absent. Grass carp over one year old also show varying degrees of hemorrhage.

(3) Epidemiology The most suitable water temperature for the spread of hemorrhage disease is 25-30°C. April to June each year is the disease season for adult fish. July to October is the disease season for fingerlings.

(4) Prevention and control methods No ideal therapeutic drug has been found to date. At present, the main approach is immunization and prevention by injection with hemorrhage disease tissue pulp vaccine. In affected ponds, the disinfectant chlorine dioxide can be splashed for disinfection, followed by oral administration of rhubarb powder, using 0.5-1 kg mixed into feed per 100 kg of fish.