The gills of the fish are black, red and rotten, which should be paid attention to. If you are not careful, you will infect other fish.

Gill rot is a common and frequently-occurring disease caused by Flavobacterium columnarum, which is harmful to goldfish and koi. It is reported abroad that dozens of species of fish, such as Salmonidae, Cyprinidae, Substomatidae, Formosidae, Cyprinidae, Cyprinidae and so on, can die of the disease. It can be harmed from fish species to adult fish, which is the most harmful to adult fish. The disease began to occur when the water temperature was more than 15 ℃, and in the range of 15-30 ℃, the higher the water temperature, the easier the outbreak and the shorter the lethal time, and there was a linear relationship between the logarithm of lethal time and water temperature. The disease can occur all the year round, and it is more common in late spring and early summer and early summer and early autumn (April to October), especially from July to September, which often results in the death of a large number of fish.

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Pathogeny

The pathogens of bacterial Gill rot of fish were reported in China, such as Myrococcus piscina, Fleibacter columnaris, Cytophaga colunaris and so on. At present, myxococcus, Flavobacterium columnar and Flavobacterium columnar are called Flavobacterium columnnre, and the optimum growth temperature of Flavobacterium is 28 ℃.

Flavobacterium columnar is abundant in bacteria-carrying fish, bacteria-contaminated water and pond mud. Diseased fish can continuously spread Flavobacterium columnar in water, but the survival time of Flavobacterium in water and pond mud is related to water temperature and water quality, but it has not been fully identified so far. It is reported that the higher the hardness of water, the longer the survival of Flavobacterium in water. Flavobacterium columnum infects fish through direct contact, especially when the gills are damaged (such as parasites, mechanical injuries or harmful substances, etc.).

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Main symptoms and pathological changes

The body color of diseased fish is black, especially in the head, commonly known as "aconite plague". Sick fish swim slowly, slow to respond to external spines, dyspnea, loss of appetite; when the condition is serious, they swim alone, do not eat, and lose response to external stimuli. The onset is slow, the course of disease is long, and the fish is emaciated. When you catch sick fish, you can see that the skin on the inner surface of the operculum is often congested and inflamed, and the Gill filaments of the diseased fish are pink or pale, followed by tissue destruction, increased mucus, with sludge, and in severe cases, the inner epidermis of the operculum is congested, and the epidermis in the middle is also corroded into a slightly round transparent area, commonly known as "skylight". With the further development of the disease, the small Gill pieces necrotic and fall off, the end of the Gill filament is defective, showing a "broom-like", with sundries and Gill cartilage exposed; around the diseased Gill filaments, there are often attached necrotic cells, mucus, pathogenic bacteria and various sundries in the water. When these attachments are mainly mucus, and pathogenic bacteria, they are yellowish, and the edge color of the fin is often light, showing a "rimmed shape". Due to the growth of Gill filament tissue, it is difficult for diseased fish to breathe after being destroyed. they often swim near the water surface in the shape of a floating head, and seriously ill fish still have a floating head after changing clean water. Diseased fish often die of respiratory obstruction and asphyxiation, with a high mortality rate.

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Main points of diagnosis

The main results are as follows: 1. The typical symptoms of the disease, such as blackening of fish body, swelling of Gill filament, increase of mucus, decay defect at the end of Gill filament, exposure of cartilage and so on, can be observed with naked eye.

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Prevention and cure measures

Precautionary measures

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Remove too much silt from the bottom of the pond to reduce the oxygen consumption of silt in the hot season.

Reasonable breeding to avoid the deterioration of water quality in fish ponds / tanks due to excessive culture density.

Feed the nutritionally balanced expanded bait to improve the feed utilization rate and reduce the water pollution caused by feeding.

Supplement appropriate amount of vitamins to improve the immunity and disease resistance of fish.

In the case of fish ponds, it is strictly forbidden to use unfermented organic fertilizer in spring, and it is best not to use organic fertilizer in high temperature season.

In the prone season, timely administration of drugs for prevention and treatment of Gill rot and drugs to improve immunity, in order to prevent the occurrence of bacterial Gill rot.

Fish tank / fish pond sprinkled with Bacillus subtilis and photosynthetic bacteria to promote the decomposition and utilization of organic matter in water and reduce the formation of harmful water quality.

Replace part of the old water in the fish tank / fish pond in time to ensure that the water quality is fat, alive, tender and cool.

Ensure sufficient dissolved oxygen in the water body and maintain the stability of the water environment in the fish tank / fish pond so as to reduce the decrease of fish immunity caused by stress.

The health status and water quality of the fish are tested regularly, and timely measures are taken to find problems.

Kill the parasites on the gills in time. Although there are not many parasites on the gills, parasites do not directly cause fish death, but the parasites damage the Gill tissue of fish, which opens the door for the invasion of Flavobacterium columnarius.

Treatment

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In the early stage of the disease, it can be cured by spraying disinfectant in vitro; when the disease is serious, the combination of disinfectant and internal drug feeding can achieve a good therapeutic effect.

(1) choose one of the following drugs for external use and spray them for 1 to 3 times

Bleach (containing 30% available chlorine), 1: 1.2 grams per cubic meter of water, first dissolve the bleach in water, filter out the residue, and then evenly spread the wine in the whole pool.

Bleaching powder (containing 60% available chlorine), 0.5-0.6 grams per cubic meter of water.

Sodium dichloroisocyanurate (containing 60% available chlorine), 0.5-0.6 g per cubic meter of water.

Trichloroisocyanuric acid (containing 85% available chlorine), 0.4-0.5 g per cubic meter of water.

Dissolve penicillin or gentamicin in the pool (tank). The dosage is 800000-1.2 million international units of penicillin or 160000 international units of gentamicin, dissolved in 50 kilograms of water and sprinkled throughout the pool.

0.4 grams of povidone iodine per cubic meter of water, sprinkle and disinfect the whole pool at dusk.

Rhubarb, 2.5-3.7 grams per cubic meter of water, first soak the rhubarb with 20 times the weight of 0.3% ammonia water to improve the effect, and then sprinkle it evenly over the whole pool with water belt residue, or use 1.5-3 grams of gallnut decoction per cubic meter of water and sprinkle it throughout the pool.

(2) taking medicine internally

After adding 2g sulfamethoxazole 2g / kg feed and stirring evenly, the granules with good stability in water were made and fed for 3 to 5 days, once a day in the morning and once in the afternoon.

Add 2g of sulfa-6-methoxine 2g / kg feed, mix well and make granule medicine with good stability in water for 4 days, doubling the dosage on the first day. Feed once a day.

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Matters needing attention in diagnosis and treatment

1. There are three main causes of Gill rot in differential diagnosis.

One is bacterial Gill rot caused by bacteria.

The other is Gill mildew caused by fungus Gill mold.

Third, all kinds of Gill diseases caused by parasites, including myxosporidium, ring worms and Chinese oysters. Attention should be paid to differential diagnosis.

(1) the location of the focus for medical treatment

Bacterial rotten Gill filament rot, serious Gill cartilage exposed, and often with mud, Gill cover inside surface hyperemia, the central epidermis is often corroded into a round transparent hole, commonly known as "skylight".

Gill mildew caused by fungi in which the gills of diseased fish are pale and sometimes have a little congestion or bleeding. The disease often occurs as a sudden and sharp death, such as microscopic examination of Gill mycelium.

The pathogens of Gill diseases caused by parasites include protozoa, myxosporidia, ring worms and Chinese oysters, among which:

1. Protozoa, its mass reproduction and harassment make the Gill of the fish produce a large amount of mucus, which seriously affects the respiration of the fish, so the floating head takes a long time, when the body color is black, it swims alone from the group and floats on the water surface.

2. Gill disease caused by myxosporidium generally has many white dotted or massive cysts in the epidermis of the Gill, which can be easily seen by the naked eye.

3. The Gill disease caused by ring worms is significantly swollen, the lid is slightly opened, the mucus increases, and the Gill filaments are dark gray.

The above prevention and control measures are applicable to fish tanks and fish ponds. I hope the above contents can help you. If there are any deficiencies, I also hope that your seniors can give advice.