Prevention and treatment of debonding septicemia syndrome in European eel

Changle City is the key culture area of European eel and the largest European eel culture area in China. Judging from the breeding process over the past few years, each farm has varying degrees of European eel debonding sepsis syndrome, with a mortality rate of 5% to 20%. European eel debonding septicemia syndrome is a common and frequently-occurring disease in the process of European eel culture, and it is one of the most serious diseases in European eel culture in summer. If it is not handled properly, sensitive antibiotics can not be screened in time for effective treatment, which will bring serious economic losses to breeders. Therefore, how to correctly prevent and cure the debonding sepsis syndrome of European eel is an important factor to improve the survival rate and economic benefit of European eel culture. 1. It is reported that the pathogen is caused by non-01 Vibrio cholerae and Aeromonas, especially when the water quality is poor and the culture density is too high. 2. Epidemic characteristics since the discovery of debonding disease and septicaemia in 1995, the disease occurred alone before 1998, and it is easy to control by using some basic treatment schemes. However, in recent years, after the onset of debonding disease, it is often complicated with septicemia, which is one of the most serious diseases in summer. The disease is mostly prevalent in late spring and high temperature seasons in summer and autumn, and the epidemic peak is from June to August. The epidemic water temperature is generally 2432 ℃, and the incidence is relatively low in the low temperature period. It is easy to occur during the high temperature period and 3-5 days after medication, especially after the use of drugs that have a strong stimulating effect on European eel, such as formalin and high-dose chlorine-containing disinfectants. The disease is highly contagious and highly toxic. It takes only 3 to 5 days from the discovery of symptoms in individual eels to the severity of the disease, which generally causes infection in the whole field one after another. The course of the disease lasts for more than a month, and the mortality rate is high. If effective treatment is not carried out in time, the mortality rate can reach 5% and 20%. Third, symptoms and pathological changes 1. European eel does not have any warning before the onset of the disease, which usually occurs suddenly. The disease first showed the symptoms of debonding disease, the vitality of the diseased eel weakened, often swimming slowly and powerless at the edge of the pool or against the water, and some hung on the bait table. The water surface of the infected pond showed foam-like blisters, and with the increase of mucus in the water and the deterioration of water quality, the foam also increased. At the onset of the disease, there are mucus shedding spots on the body surface of the diseased eel, which are more obvious in the trunk and side of the body. In severe cases, there are ulcers in the debonding focus, and the periphery is red, usually accompanied by rotten gills. About 3-5 days after the development of debonding, it began to be accompanied by septicemia, Gill edema, hyperemia, Gill anemia or browning and adhesion. The pectoral and anal fins are severely congested and red, the anus is red and swollen, and the abdominal skin is bleeding seriously. Sometimes the jaw is congested to make the head look like a red head. Autopsy showed hemoperitoneum, hepatomegaly, lighter or yellowish color, gallbladder swelling, renal congestion, gastrointestinal emptiness, intestinal mucosal inflammation, hyperemia or hydronephrosis. 2. In the early stage of death, the diseased eel had obvious symptoms of debonding or septicemia, and the vitality of the eel weakened, and a large number of eels hung on the bait table or gathered around the sewage outlet, and did not eat. There are few symptoms of debonding in dead eels, but the symptoms of septicemia are obvious. In the later stage, the number of symptoms of debonding or septicemia decreased, red head or Gill, jaw congestion and edema, other parts of the body surface were basically intact, some abdominal cavity was filled with blood water, blood clots and liver faded, Gill filaments became white and swollen, similar to the phenomenon of discoloration and whitening after being immersed in water. The number of deaths has increased, and the death rate is relatively high. The whole onset cycle of one pool is 15-20 days. It is worth noting that the ulcer symptoms on the body surface of diseased eels are often related to myxosporidium (bipolar worms) parasitism. In eels with severe septicemia, the kidneys are usually parasitized by myxosporidium, with several to dozens of white spots (cysts) visible to the naked eye. Therefore, whether renal parasitic myxosporidium is the cause of eel disease is worth studying. 4. Comprehensive prevention 1. Disinfect eel seedling pond and build a new pond. Before use, soak with 1.0-1.5 mg / L oxalic acid to remove alkali, wash and change water many times, soak in water for more than 20 days, or directly soak in clean water for more than 40 days. The pH value was determined before use, and put into use after passing the test. 7 days before the seedling, soak and disinfect with 20 mg / L potassium permanganate for 3 days, drain and wash, put in new water and heating, and make the pH value of the water in the pool less than 8, and then set aside. The old pond should be fully exposed to the sun, sprinkle and disinfect the whole pond with 200 g / m3 quicklime or 20 g / m3 bleach for 10 days and wash it with clean water. 7 days before planting, soak in 20 mg / L potassium permanganate for 3 days, drain and rinse. The pond was flooded the day before the seedling was released, and the water level was 30cm to 35cm. 2. The stocking density should be reasonable according to the different stages of European eel. The general stocking density should be controlled as follows: the stocking density of white fry stage should be controlled at 500 / square meter, the stocking density of black eel should be controlled at 300 fish / square meter, and the stocking density of young eel and adult eel should be controlled at less than 30 fish / square meter. 5. drug treatment should be diagnosed as soon as possible according to the symptoms of eels and corresponding measures should be taken. In the early stage of the disease, the use of antibiotics can not significantly inhibit the development of death, but sometimes accelerate the death of diseased eels. Therefore, in the early stage of the disease, conventional disinfectants such as bromochlorohydantoin, chlorine dioxide, Blue Angel + Vibrio Jing can be selected to control the development of the disease. At this time to disinfect the water body must also use less irritating drugs, and so on after a large number of deaths, and then select sensitive drugs for treatment. In the high temperature period, we should pay attention to the changes of water temperature and water quality. In general, ventilation should be strengthened, dissolved oxygen in water should be increased, and if necessary, the water level should be raised to prevent the increase of eel death caused by the sharp change of water temperature during medication. In order to feed the eel in the pond as soon as possible to restore its physical strength, bait can be given. At the same time, the eel can be bathed with Haizhongbao, Duowei and glucose to eliminate the bacteria in the eel and promote the eel to eat. After the occurrence of the disease, it is necessary to send for bacterial drug sensitivity test in order to prescribe the right medicine in time. In recent years, the use of the following drugs for treatment have achieved good results. ① eel was sprinkled with electrolytic Vita 4g / m3 for 3 hours, then bathed with Eel Leling 8g / m3 for 24 hours, and then changed water and tonic for 2 or 3 times. ② eel Leling VPY 5g / m3 Canon University of high stability CBM 3g / m3 Jiajiaodu 20g / m3 medicine bath for 48 hours. ③ salt 3 ‰ ~ 5 ‰ plus fungus poison powder 10 mg / L plus eel Leling VMET 5 mg / L plus agricultural university high stable Cpene 3 g / m3, sewerage and water supplement were used daily for 2 to 3 days. ④ sodium chloride (salt) 4 ‰ + sodium bicarbonate 4 ‰ + chlorine disinfectant. If you choose one of the above treatments, after the disease is under control, you should still use euiodoxin 2mg / L + antivirus pioneer 0.3mg / L medicine bath for 2 times. The longer recovery period should not be impatient, disinfect the water with euiodoxin 1.5 mg / L for 2 times, use chlorine-containing disinfectants alternately, and take eel Leling, vitamin C and electrolytic vitamins for eel for about 10 days. 6. Analysis and discussion when using drugs to deal with European eel debonding sepsis syndrome, do not use drugs urgently and indiscriminately, do not use illegal drugs, resulting in drug residues and affect the quality of adult eels. Due to the need for long-term medication, it is easy to cause water quality deterioration, so at the end of each medication cycle, it is best to greatly change the water and keep the water environment clean. In the high temperature period, we should pay attention to the changes of water temperature and water quality. In general, ventilation should be strengthened, dissolved oxygen in water should be increased, and if necessary, the water level should be raised to prevent the increase of eel death caused by the sharp change of water temperature during medication. In the early stage of the disease, try not to use antibiotics, you can choose bromochlorohydantoin, chlorine dioxide, blue angel + virus net and other conventional disinfectants to control the development of the disease, and so on after a large number of deaths, and then treated with drugs. After the peak of death, eels in the pond must be fed as soon as possible to regain their strength. Can be fed with bait to eliminate bacteria in the eel. At this time to disinfect the water body to use less irritating drugs, at the same time, Haizhongbao, multi-dimensional, glucose and other eels can be bathed to promote eel eating. In the treatment of bacteria, we should pay attention to check whether there are Gill mold and parasitic diseases, if so, should be treated first, especially Gill mold must be killed first. Otherwise, the use of antibiotics will cause Gill mildew outbreaks, resulting in a large number of deaths. If the number of parasites is small, the treatment can be postponed. Eel summer syndrome is a barrier, and it will be plain sailing after that.