What disease is the rotten fin of grass carp in fish pond?

Erythroderma of grass carp: the base or the whole fin is congested, and the end of the fin rots like a broom.

This disease is a common infectious disease of cultured fish caused by Pseudomonas fluorescens, and it is called "the third disease" together with gill rot and enteritis.

Pathogenic Pseudomonas fluorescens is an aerobic Gram-negative Brevibacterium with a round end and a size of (0.7 ~ 0.75) μ m× (0.4 ~ 0.45) μ m, one or two of which are connected. Have athletic ability, and bear 1 ~ 3 flagella. No spores, β hemolysis. The colony on agar medium is slightly convex and round, with a diameter of 1 ~ 1.5 mm, a smooth and moist surface, neat edges and grayish white and translucent.

Epidemiology: The disease mainly harms grass carp. Most of them occur in big fish aged 2 ~ 3 years, and fish species can also occur in the same year, often occurring at the same time as enteritis and gill rot, forming complications.

Symptoms: The scales on the body surface of the diseased fish are partially or mostly loose or shed (Figure 3- 1), and the skin at the shed area is eroded, and skin bleeding and inflammation can be seen at the same time, especially on both sides and abdomen of the fish. The base of the fin or the whole fin is congested, and the end of the fin decays like a broom, forming a rotten fin (Figure 3-2). The parasitism of water mold mostly occurs in the place where scales fall off and fins rot, which aggravates the disease. Ill for a few days and will die.

At the early stage of the disease, muscle fibers were broken, muscle fibers were necrotic and dissolved, interstitial edema widened, inflammatory cells infiltrated, and capillaries were congested. When the lesion is serious, pathological changes such as congestion, bleeding, degeneration and necrosis of liver, kidney, digestive tract and other tissues and organs often occur.

Diagnosis can be made according to external symptoms and pathological changes. The pathogenic bacteria of the disease can not invade the skin of healthy fish, but often invade through the wound after the skin is broken, so the sick fish has a history of trauma, which is of great significance for diagnosis.

The prevention and control of the disease should try to avoid fish from being hurt in the process of fishing, transportation and stocking. Prevention: bleaching powder, the dosage is per cubic meter of water1~1.5g; Or trichloroisocyanuric acid powder, the main dosage is 0.3-0.5g； per cubic meter of water; Or 80% chlorine dioxide, with a dosage of 0.1~ 0.3g per cubic meter of water; Or povidone iodine solution (containing available iodine 1%), and the dosage at one time is per cubic meter of water 1 ~ 2g. Spill the whole pool every 15 days 1 time in epidemic season. Treatment: In addition to spraying disinfectant in the whole pond, norfloxacin was taken orally at the same time, with the dosage of 10 ~ 30 mg per kilogram of fish weight for 5 ~ 7 days. Or tetracycline, the dosage is 40-80mg per kilogram of fish weight; Or flumequine, with a dosage of 30mg per kilogram of fish. Feed the mixture 2 ~ 3 times a day for 5 ~ 7 days.

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