Control Methods for Bump Disease in Eel Farming

Pathogen: Eimeria anguillae is the pathogen of eel bump disease, belonging to the order Microsporida. The spores are small and simple in structure. Eimeria anguillae parasitizes the muscles on the sides of the body, and the spores spread inside and outside the muscle tissue, while dissolving the surrounding tissue and causing the body surface to sink inward, presenting an uneven, bumpy appearance, hence the name bump disease. There is no particular restriction on the epidemic period of this disease; infection can occur in water at 15°C~30°C. The higher the temperature, the faster the spores develop, but below 25°C the course of the disease is very slow. Both young eels and adult eels can be infected. In heated eel ponds, even white fry eels can contract the disease. This disease is especially harmful to young eels; even if they do not die, they cannot be raised into adult eels of commercial value, and it spreads very easily. Spores in the water or mixed into feed and fed to the eels can both cause infection.

In the early stage, diseased eels do not show reduced appetite, and as the disease develops they still retain a certain ability to seek food. Only after a fairly long period will the special external lesions be discovered. Although they still grow slowly, they have already lost commercial value, and once infected with other bacteria, the whole body's muscles are invaded, and they weaken and die. Japanese eels, European eels, and American eels can all be infected by this disease.

Prevention and control: During purchasing, carefully observe the fish body and avoid buying diseased eels. During rearing, avoid excessive density and maintain good water quality. If diseased eels are found during harvesting and sorting, they should be picked out and destroyed immediately to prevent infection. Before stocking, it is advisable to turn over and dry the soil, and thoroughly clear the pond with a large dose of quicklime.