Symptoms and Control Measures of Scale Protrusion Disease in Fish

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

Main Symptoms of Scale Protrusion Disease

Sick fish swim alone away from the group, 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 body stand erect and open outward like a pinecone. The scale sacs at the base of the scales become edematous, and translucent exudate accumulates inside, causing the scales to stand up.

In severe cases, the scales over the whole body stand erect, and the scale sacs contain blood-tinged exudate. When the scales are gently pressed by hand, the exudate spurts out from beneath the scales, and the scales fall off as well.

Sick fish are often accompanied by slight congestion at the fin bases and skin, exophthalmos, abdominal distension, ascites, and other symptoms. Sick fish are anemic, and the color of the gills, liver, spleen, and kidney all becomes pale, with congestion of the inner epidermis of the operculum. In severely affected fish, the fin bases become congested and the fins show signs of decay.

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

Causes of Scale Protrusion Disease

Research shows that the bacteria causing scale protrusion disease include: Pseudomonas punctata, Pseudomonas species, Aeromonas hydrophila, and others. In seasons with low water temperature, especially in 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.

A preliminary diagnosis can be made based on symptoms and prevalence. At the same time, the exudate in the scale sacs must be examined under a microscope, and a diagnosis can be made when large numbers of short bacilli are seen. It must be noted that when large numbers of Ichthyobodo parasitize the scale sacs of common carp, they can also cause scale protrusion symptoms, and examination of the exudate in the scale sacs under a microscope can distinguish between them.

Scale protrusion disease mainly harms common carp. It often occurs in farming areas in Northeast China, North China, East China, and other areas, and there are two epidemic seasons: one is the spawning period of common carp, and the other is the overwintering period of common carp. Generally, the spawning period of common carp is the main epidemic season. The mortality rate of brood fish due to this disease can reach as high as 85%. The prevalence of this disease is related to fish injury, turbid pond water, and reduced disease resistance of the fish.

Treatment Methods for Scale Protrusion Disease

1. Soak the fish in nitrofurazone or furazolidone at a concentration of 20MG/KG. When the water temperature is below 20°C, soak for 20-30 minutes. At 21-32°C, soak for 10-15 minutes, used for prevention and early treatment.

2. Spread nitrofurazone or furazolidone throughout the pond at a concentration of 0.2-0.3MG/KG; in severe cases, the concentration can be increased to 0.5-1.2MG/KG, used for prevention and early treatment.

3. Soak the fish in erythromycin at a concentration of 2-2.5MG/KG. When the water temperature is below 34°C, soak for 30-50 minutes, once a day, for 3~5 consecutive days, until the condition improves.

4. Inject streptomycin or kanamycin at 120,000-150,000 international units per kilogram of fish body weight, usually only once; in severe cases, a second injection can be given on the fifth day.

5. Administer norfloxacin orally, using 0.8-1.0G of powder per 10KG of fish body weight per day, once a day, for six consecutive days.

6. Soak in rivanol at a concentration of 20MG/KG. When the water temperature is 5-20°C, soak for 15-30 minutes. At 21-32°C, soak for 10-15 minutes. It has a remarkable effect when used for early treatment.

7. Spreading rivanol throughout the pond at a concentration of 0.8-1.5MG/KG has a particularly good effect.

While using the above treatment methods, carrying out a saltwater bath at the same time has a remarkable effect.

External Medicines for Scale Protrusion Disease

Choose any 1 of the following medicines and splash once every other day, for a total of 1-3 splashes:

1. Spread trichloroisocyanuric acid containing 85% available chlorine throughout the pond, using 0.3-0.5 grams of medicine per cubic meter of water.

2. Spread chlorine dioxide throughout the pond, using 1 gram of medicine per cubic meter of water; it must first be activated with citric acid or acetic acid before splashing.

3. Spread ground gallnut throughout the pond after soaking it in boiling water, using 2-4 grams of medicine per cubic meter of water.

4. Spread bleaching powder concentrate containing 60% available chlorine throughout the pond, using 0.5-0.6 grams of medicine per cubic meter of water.

5. Spread sodium dichloroisocyanurate containing 60% available chlorine throughout the pond, using 0.5-0.6 grams per cubic meter of water.

6. Soak the fish in 3% salt water for 10-15 minutes.

7. In 1 cubic meter of water, add 5 grams of copper sulfate, 2 grams of ferrous sulfate, and 10 grams of bleaching powder, and soak the sick fish for about 10 minutes.