Bacterial diseases of sweet fish and their control

Vibrio disease

The main results are as follows: 1. According to the type of Vibrio infection, Vibrio can be divided into three types: yellow liver type, intestinal tip type and ulcer type. the diseased fish are characterized by swimming weakness, blackening, exophthalmos, epidermis bleeding, and in severe cases, deep into the muscle layer, the inner surface of the operculum, the base of the fin and the snout end blood stasis, anal redness and swelling, light Gill color, enlarged liver of diseased fish, some local discoloration and hyperemia. The liver of the diseased fish is full of blood bubbles, the gallbladder is enlarged, and the sac is filled with orange or brown-green bile. The kidneys are inelastic, some diseased fish kidneys are enlarged or some white lumps appear, and sometimes transparent ascites accumulates. Fragrant fish with vibrio disease generally have mixed infection with other pathogens, but small fish with acute disease may die without symptoms.

2. Epidemic and harmful vibrio disease generally occur from January to September, and the harm of vibrio disease varies according to drug resistance. Sulfadimethoxine and dumb quinolinic acid were used in Shizuoka Prefecture of Japan to test the drug resistance of Vibrio serotype an and c in Shizuoka prefecture, Japan. the results showed that the susceptibility of Vibrio to drugs was different in different years, and the drug resistance of serum type a was stronger than that of type c. The results showed that the vibrio disease of land-sealed type was more difficult to control than that of migratory type. The incidence of Vibrio in different serotypes was also different. The incidence of migratory fish was higher from January to April, but it was less after May, while the incidence of land-sealed fish was rarely from January to April, but the incidence was high after May. Vibrio disease is the most harmful fish disease in fragrant fish culture, and the mortality rate can be higher than 50%, especially in young fish. In recent years, due to the promotion and application of fragrant fish vaccine, the loss has been reduced.

3. Prevention and treatment (1) prepare Vibrio fragrans vaccine, dilute it 10 times, soak the fish fry for 2 minutes, and the immune validity period is 60-100 days. (2) do not feed oxidized and deteriorated feed, but should be fed with high-quality full-price compound feed, and pay attention to the feeding times and feeding methods, pay attention to keep the water quality clean and prevent the reproduction of bacteria. (3) the following drugs are mixed periodically and alternately in the feed: a, 20 grams of sulfamethoxine and other sulfonamides per 100 kg of fragrant fish for 3 days, stop for one day, and then for 3 days; b, 4-6 grams of tetracycline per 100 kg of fragrant fish for 10 consecutive days.

2. Pseudomonas disease

The main results are as follows: 1. There is a spot-like white mucus on the side epidermis of the diseased fish, and gradually expands. In severe cases, the body appearance is covered with a white film, the blood stasis at the tip of the Gill filament, the congestion at the base of the pectoral fin, the symptoms of internal organs are not significant, and the liver becomes light brown. There are varying degrees of kidney swelling and ascites, and a few diseased fish eyeballs are cloudy, white, or even fall off. Diseased fish swim slowly, lose appetite, lose weight, have difficulty breathing, and sometimes swim wildly.

2, epidemic and harm easy infection in March and April, the incidence of fish is generally 10-20 grams, the daily mortality rate is 1% 2%, lasting for half a month, often accompanied by bacterial bleeding, septicaemia symptoms. The water temperature of Japanese scented fish is mostly below 20 ℃, while that of Taiwan is about 22 ℃. The disease can be stopped by raising the water temperature to more than 26 ℃.

3, prevention and treatment (1) prevent fish body injury, the invasion of pathogens is related to skin damage, so do not hurt fish body in transportation, separate culture and other operations. In addition, parasites should be killed in time to prevent bacterial infection caused by parasite destruction of tissue, reduce stocking density and improve water quality environment. (2) adding any of the following groups of drugs into the feed, the curative effect is better: a, 10 grams of compound sulfamethoxazole per 100kg of fragrant fish, halving the dosage from the second to the sixth day for 6 days; b, oxytetracycline 3-5g per 100kg of fragrant fish for 5-7 days; c) rhubarb, Phellodendron Phellodendri, Scutellaria baicalensis Georgi at 5:3:2, 1kg Sanhuang powder per 100kg fragrant fish for 3-5 days.

III. Aeromonas aeruginosa

The main results are as follows: 1. The symptoms of Aeromonas aeruginosa are different due to different species, biotypes and places of attack on fragrant fish, which are usually related to hemorrhagic septicemia of fish, which is urgent for some reason. the clinical and pathological manifestations are similar to the infection of Vibrio and Pseudomonas, that is, systemic septicemia, dark body color, large irregular bleeding in the epidermis and fin base, anorexia. The cluster dies at the outlet, and in serious cases, it causes ulcers and rotten tails of diseased fish. It is necessary to isolate bacteria to determine the cause. Intestinal type Aeromonas punctata is a conditional pathogen, which is easy to cause disease in adverse environments such as deterioration of water quality, low air pressure, overeating and so on, such as slow action, loss of appetite, blackening of the head, abdominal enlargement and erythema, and protruding anal redness. gently pressing the abdomen with hands has blood-yellow mucus outflow, hydrops in the abdominal cavity, congestion and protrusion of the intestinal wall, generally no food in the intestine, and contains a lot of yellowish mucus or pus. Congestion is also found in other parts of the liver, showing red spot-like blood stasis.

2. Epidemic and harm of the disease is easy to occur when the climate is changeable in spring and summer, and it often coexists with Vibrio and Pseudomonas, causing great harm.

3. Prevention and control to keep the water quality fresh, especially in the changeable climate season, the quantitative, fixed-point, regular and qualitative feed should be fed with "Siding". When mild enteritis symptoms are found, 0.3 g / kg feed mixed with allicin or refer to the dosage described in the prevention and treatment of vibrio disease.

Streptococcosis (penicillin sensitive)

1. The symptoms of diseased fish swim slowly, disperse in slow flow, float on the water or head up, tail down in a suspended shape, diseased fish or intermittent wild swimming when they die of disease, or abdominal upward, black body color, thin body, light Gill color, anemic state Eyeball stasis protruding, white turbidity, even eyeball falling off, ventral punctate bleeding, anal redness and swelling, pathological changes of internal organs and ascites are similar to the aforementioned phenomena of vibriosis and pseudomonas infection, which cannot be determined by appearance alone.

2. Epidemic and harm once streptococcosis is infected, the strain has been isolated from wild fish. It is more popular in Kagoshima and Miyazaki in Japan, but the epidemic situation in China is not clear. The suitable water temperature for the disease is 25-28 ℃, so it is popular in the summer high temperature season.

3. Prevention and treatment (1) avoid overdense culture, strengthen feeding management, feed high-quality feed, timely add vitamins, pay attention to pond cleaning and disinfection, once the disease occurs, fasting for 2-3 days can delay the disease. (2) for every 100 kg of fragrant fish, 5 grams of antibiotics (doxycycline, spiramycin, erythromycin or oxytetracycline) plus compound vitamin b1 grams were added to the feed for 5-10 days. (3) 5-20 grams of sulfadimethoxine per 100 kg of fragrant fish, doubled on the first day and effective for 4-6 days.

5. Columnar disease

1. The symptoms of diseased fish are slow in action and loss of appetite, which are common in the skin and gills of the head and back, but can also occur in other parts of the fish body. Initially a raised white plaque surrounded by a red congested area, it soon developed into a matrix formed by hemorrhagic ulcers, overlying bacterial cells and necrotic tissue. Gill damage is often greater, Gill filament swelling, mucus increase, end decay lack, whitening, the inner epidermis of the operculum is often congested, which quickly causes the diseased fish to die.

2. Epidemic and harm are more popular in spring, summer and autumn, especially in summer, which is often complicated with enteritis, especially when the water quality becomes turbid due to rainstorm in summer. A large number of deaths can be caused when the disease occurs, and the harmfulness of the disease tends to increase in Japan, which may be related to water pollution and the increase of drug resistance of virulent strains.

3. Prevention and treatment (1) improve the environment, increase oxygen supply, control the entry of organic matter into the water, and reduce the water temperature. If the turbid water source is purified, it is quite effective in supportive therapy. (2) 2-5ppm Chinese nutgall decoction, or erythromycin 0.3ppm or clo20.11ppm sprinkled in the whole pool has preventive and therapeutic effect. (3) when the condition is more serious, in addition to the whole pool medicine bath, it should be taken orally, that is, adding drugs into the feed, the specific dose is: a, every 100 kg of fragrant fish should be given 5 grams of erythromycin on the first day and 2.5 grams per day from the second to the sixth day. B, 1 kg of rhubarb powder for every 100 kg of fragrant fish for 3-5 days.

6. Cold water disease

The main results are as follows: 1. symptoms of naked eye damage are usually seen in fins, skin and muscles, rotten gills are first anemic and swollen in varying degrees, and then fester, while mouth decay is caused by blood stasis on the lips and then ulceration; the base of the fin and tail becomes red at first, and the bacteria can be isolated from the viscera in the late stage. Due to the low water temperature, there is generally no inflammatory cell infiltration, and when the festering of the fin or tail is accompanied by poor water quality, the epidermis and dermis often have a high degree of edema, and a large number of colonies have been formed on the damaged surface.

2. Epidemic and harm in the breeding facilities with low water temperature, high stocking density and rich organic matter residue, the disease has replaced vibrio disease as the first harm in spiced fish culture in Japan. It has also been reported in Taiwan that once the young fish are infected, a large number of deaths can occur, and the mortality rate is more than 50%. There is no report of cold water disease in China. In the epidemic season, the water temperature is generally below 16 ℃, which may be related to the premature release of fragrant fish and the low water temperature.

3. As the prevention and treatment of cold water disease is easy to occur in low water temperature and rich organic matter in the water, choosing breeding sites with sufficient water source, good water quality and suitable water temperature and improving environmental conditions is the fundamental way to prevent the disease. It has been reported that the effect of disinfecting the body surface with formalin is good, and if the affected fish can ingest food, sulfonamides can also be mixed into the bait.