Prevention and Control of Eel Cold and Fever Diseases
Prevention and Control of Eel Cold Disease
Symptoms: In the early stages of the disease, sick eels eat less or not at all, often floating on the water surface or crawling on aquatic plants. As the condition worsens, their mouths open, breathing frequency increases, muscles become stiff and tense, leading to full-body spasms. The eels twist and struggle in an "S" shape or with their heads and tails connected, with the tail extremely raised. In severe cases, the eels rotate 360°, twist, and struggle, sinking helplessly to the bottom of the water. After 3-5 minutes, they suddenly rotate and twist back to the surface, repeating this cycle until death occurs. Most dead eels are twisted in a "zigzag" shape. Generally, sick eels die within 5-10 days. Upon visual inspection, it is found that the eels turn yellow from the snout to the eyes, with reduced melanin. From the eyes to the posterior edge of the gill cover, the color turns black with deepened melanin, forming a clear contrast between yellow and black. Their heads swell and become congested, with bleeding spots all over the body, especially prominent on the abdomen. The anus is red and swollen, even purplish. The tails rot or turn white. Upon dissection, no food is found in the intestines.
The epidemic season for this disease is from May to October, with July to September being the peak period. The water temperature during the outbreak is 20-32°C, with the fastest spread occurring at 25-30°C. The general incidence rate is 2%-20%, reaching 40%-50% in epidemic areas, with a mortality rate of 80%-100%. There have been recorded cases in provinces such as Hubei, Hunan, Anhui, and Jiangsu.
Prevention and Control Methods: Upon discovering the condition, only adding fresh water helps. Currently, there is no effective prevention or treatment method.
Prevention and Control of Eel Fever Disease
Cause unknown. Bacteria, parasites, and spores have not been detected in checks on the external body, internal intestines, organs, blood, and brain of the eels.
Symptoms: In the early stages of the disease, sick eels eat less or not at all, often floating on the water surface or crawling on aquatic plants. As the condition worsens, their mouths open, breathing frequency increases, muscles become stiff and tense, leading to full-body spasms. The eels twist and struggle in an "S" shape or with their heads and tails connected, with the tail extremely raised. In severe cases, the eels rotate 360°, twist, and struggle, sinking helplessly to the bottom of the water. After 3-5 minutes, they suddenly rotate and twist back to the surface, repeating this cycle until death occurs. Most dead eels are twisted in a "zigzag" shape. Generally, sick eels die within 5-10 days. Upon visual inspection, it is found that the eels turn yellow from the snout to the eyes, with reduced melanin. From the eyes to the posterior edge of the gill cover, the color turns black with deepened melanin, forming a clear contrast between yellow and black. Their heads swell and become congested, with bleeding spots all over the body, especially prominent on the abdomen. The anus is red and swollen, even purplish. The tails rot or turn white. Upon dissection, no food is found in the intestines.
The epidemic season for this disease is from May to October, with July to September being the peak period. The water temperature during the outbreak is 20-32°C, with the fastest spread occurring at 25-30°C. The general incidence rate is 2%-20%, reaching 40%-50% in epidemic areas, with a mortality rate of 80%-100%. There have been recorded cases in provinces such as Hubei, Hunan, Anhui, and Jiangsu.
Prevention and Control Methods: Upon discovering the condition, only adding fresh water helps. Currently, there is no effective prevention or treatment method.