How to effectively prevent carp dropsy

What is carp dropsy?

Carp dropsy is also known as scale erection disease, pine scale disease, or pinecone disease. The pathogen is initially believed to be Pseudomonas punctata. It is a common disease of goldfish, carp, crucian carp, and various tropical fish, and frequently occurs in fish-farming areas such as North China, Central China, and East China. Grass carp, silver carp, bighead carp, and others raised in the south can sometimes also develop this disease. It mainly prevails in late winter and early spring, and generally occurs through skin infection when water quality deteriorates or fish are injured. When the disease is severe, it can cause a mortality rate as high as 85% among affected brood carp.

Symptoms of carp dropsy:

Sick fish swim alone, moving slowly and weakly. In the early stage of the disease, the fish body darkens, the body surface becomes rough, and the scales on the front part of the fish stand upright and spread outward like a pinecone; the scale sacs at the base of the scales become edematous, with translucent exudate accumulating inside, causing the scales to stand up.

In severe cases, the scales over the whole body stand upright, and the scale sacs contain blood-containing exudate. When the scales are pressed gently by hand, the exudate squirts out from under the scales, and the scales fall off as well.

Sick fish are often accompanied by slight congestion at the fin bases and skin, protruding eyeballs, abdominal swelling, ascites, and other symptoms; sick fish are anemic, the gills, liver, spleen, and kidneys all become pale, and the inner epidermis of the operculum is congested; in severely affected fish, the fin bases are congested and the fins show signs of rotting.

Affected fish swim sluggishly, have difficulty breathing, turn belly up, and die after 2 to 3 days.

Causes of carp dropsy:

Research has shown that the bacteria causing scale erection disease include Pseudomonas punctata, Pseudomonas species, Aeromonas hydrophila, and others. In seasons with low water temperatures, especially fish after overwintering, the body condition is poor and resistance is weak, making them susceptible to the disease. In addition, after injury, partial scale erection is likely to occur, and the frequency of water changes should not be too high.

Scale erection disease is commonly seen in carp, with more cases occurring each spring. The prevention and treatment of carp dropsy are introduced as follows:

Add fresh water: in the early stage of the disease, adding fresh water can stop the spread of the condition; garlic soak: add 0.5 kg of mashed garlic to 100 kg of water and soak the sick fish several times; baking soda soak: before stocking in spring, use a mixture of 3% baking soda solution and 2% salt water to bathe the fingerlings for 4 to 10 minutes; sprinkle lime water: during the disease season, splash quicklime water solution over the whole pond 1 to 2 times per month, keeping the pond water pH at around 8 as appropriate; apply Chinese herbal medicine: use an infusion of the Chinese herbal medicines Sophora flavescens or mugwort leaves to soak the sick fish for 20 minutes, once a day, for 4-5 consecutive times. Alternatively, per 667 sq m (one mu) of water surface, use 2500 g of Sophora flavescens or mugwort leaves, decoct 3 times into a concentrated juice and mix, then splash over the whole pond once daily for 3-5 consecutive days; oral oxytetracycline: add 2 to 4 g of oxytetracycline per kg of feed and feed continuously for 3 to 6 days; apply mixed medicinal solution: per cubic meter of water, use 5 g of copper sulfate, 2 g of ferrous sulfate, and 10 g of bleaching powder, and soak the sick fish for about 8 minutes. Alternatively, per cubic meter of water, use 1 g of copper sulfate, 0.5 g of ferrous sulfate, and 2 g of bleaching powder, splash over the whole pond once every other day for 2-3 consecutive times.