Fish rickets, according to their pathogenic pathogens can be divided into bacterial gill disease, fungal gill disease (also known as mold mold), parasite rickets.
Bacterial gill rot disease is a common infectious fish disease. It often coincides with bacterial enteritis and red dermatosis. It seriously damages the grass carp species and adult fish. Once the outbreak occurs, the mortality of grass carp is as high as 60%, and it also seriously threatens herring. , salmon and squid. In recent years, with the rapid development of high-density and intensive farming methods, the famous varieties such as catfish, cockroach, clam, tilapia, catfish, and Californian clam are also seriously infected with bacterial gill disease, and the mortality rate is often as high as 40%. the above. Fish caries seriously affect the further development of aquaculture. Aquaculture workers have conducted a lot of research on this disease and have concluded a set of effective prevention and control technologies.
I. Pathogens
1. Bacterial gill disease: The pathogen of bacterial gill disease is Myxococcus. Slender, soft and easy to bend, the thickness is basically the same, about 0.3 microns, blunt at both ends, generally slightly curved, sometimes bent into a semi-circular, round, U-shaped, V-shaped and Y-shaped, etc.; but The short cells are usually straight. The cells are 2 to 4 microns long and some are as long as 37 microns. It is generally propagated by transverse division and split into two individuals of approximately the same length. The fungus does not have flagella and is usually gliding or shaking. Good growth occurs at pH 6.5-7.5, PH8 grows poorly, and pH 8.5 and above do not grow. Optimum temperature 25°C, good growth, but strong virulence; 18°C ​​slower growth, stronger virulence; 33°C good growth but poor virulence; 40°C slow growth, low virulence; 4°C no growth, 65 °C died in 5 minutes. The culture medium containing more than 0.7% of salt can inhibit the growth of this bacterium. This bacterium can grow in both aerobic and aerobic conditions, but it can also grow under anaerobic conditions, but its growth is slow and the number of propagation is small.
2. Fungal rickets (Mycosis ): The pathogen of Plasmodiosis is Plasmodium. Grass carp parasitic fungus mold, the mycelium is relatively straight and less bent, usually monopolar prolonged growth, very few branches, does not enter the blood vessels and cartilage, only in small pieces of tissue growth. The diameter of the mycelium is 20-25 microns, and the spore is 8 microns straight. Another kind of parasitic in herring, squid, squid, its hyphae often bent into a net shape, thin and thick, branching more, branches along the filaments of the blood vessels or penetrate the cartilage, vertical and horizontal The staggered filaments were filled with a small piece of cocoon and the mycelium had a diameter of 6.6 to 1.56 micrometers and an average spore diameter of 6.6 micrometers.
3. Parasitic rickets: rickets, the pathogens of the Chinese sturgeon. The female body is slender, cylindrical, milky, and has three parts: the head, the chest, and the abdomen. The head is slightly triangular, with five pairs of appendages, and the second pair of tentacles becomes slender hooks to attach to the host's silk. The chest is 6 knots, the first 4 knots are slightly longer than the longest, and the sixth is the smallest, known as the genitalia. When the female matures, a pair of elongated white oocysts are visible on the genitalia. Abdominal section 3, slender. Females have a total length of 2.2-3.0 mm. The male camp is free to live; its cockroach disease is caused by pathogens such as Chinese sturgeon. The female body is cylindrical in shape and milky white, but shorter and thicker than Chinese sturgeon. Separate body, chest, abdomen three. The head is slightly blunt, and the second pair of tentacles becomes short and wide. The chest is 5 knots, the first 4 knots are wide and short, and the fifth thoracic knot is very small. The other parts are similar to those of the Greater China Skull. The female has a total length of 1.9 to 2.7 mm.
II. Symptoms and Epidemic Situation of Fish Rickets
1. Bacterial gill rot disease: The diseased fish is slow in action, unresponsive, and swims alone or floating on the water surface. Breathing difficulties, loss of appetite, severe disease, fish do not eat, the fish body is thin, and the rim of the fins fades to be bordered. The diseased fish is dark in color, especially in the head, and fishermen call them heads. Severe disease in the epidermis of the epidermis, and the inner part of the epithelium is often eroded into a round or irregular round transparent window, commonly known as the open skylight, and the grass carp suffers from significant symptoms of this disease. Lifting the diseased fish gill cover can be seen in the increase of mucus on the diseased fish gill, some diseased fish stained with sludge, swollen gill filaments, some parts of gills, due to ischemia was pale red or gray white, and some parts were due to local congestion Purple. In severe cases, small pieces of necrosis come off, the ends of the silk defects, and the cartilaginous cartilage are exposed. There are often yellowish adherents around the diseased tissue.
Bacterial gill disease, the main damage to grass carp, often with enteritis disease, red skin disease. Water temperature began to prevail at temperatures above 20°C. 28 ~ 35 °C is the peak period of onset. Serious damages often cause a large number of grass carp deaths. In recent years, the occurrence of bacterial gill rot in high-density, intensive aquaculture ponds, cage fish farming, and industrialized fish cultures such as squid, cod, clam, tilapia, and Californian clams is also serious, often causing a lot of death.
2. Fungal mycosis: Mycoplasma mainly infects fingerlings, fingerlings and adult fishes such as herring, grass carp, carp, carp, carp, carp, etc. Pathogens produce large amounts of spores in the water through the mycelium. The spores come into contact with the fish, ie, they attach to the larvae and develop into hyphae. The mycelium continues to grow in the pod tissue and is repeatedly branched and branched or worn along the silk vessels. Into the cartilage, destroy the tissue, block the micro-vascular, flap loss of normal bright red and pink or pale. Sometimes it is a bit like congestion or bleeding. With the development of the disease, respiratory function is greatly hindered. The appearance of mold mildew is often an acute attack. From the time when the pathogen is found, if the environmental conditions are suitable, it can multiply in 1 to 2 days, and the fish will immediately die suddenly.
The status of pond water chemistry is an important factor in the prevalence of mold fungus, generally in the deterioration of water quality, especially the high organic matter content, extremely high eutrophication water temperature of 25 ~ 35 °C, the rapid growth of mushroom mold, often causing outbreaks of mold mold . Popular in the Yangtze River Basin
3. Chinese leeches: The pathogens of the Chinese sturgeon females are hooked on grass carp clams with large hooks. When parasites are numerous, the clams hang like many white clams, hence the name rickets. Destroys scorpion tissue, extracts fish nutrition, secretes an enzyme, stimulates squatting tissue, causes tissue to proliferate, causes swollen and whitish end of diseased fish reel, affects respiration, and makes the diseased fish impatience, squatting on the water, does not eat Body weight loss, growth obstruction and even death. The parasites of Chinese sturgeon open the door for bacteria to invade, often with bacterial disease. The most common and most widely distributed parasite is the Greater Chinese cricket, which can be found in Heilongjiang from the north and Guangdong from the south. It is widespread and occurs throughout the country. It is an epidemic season from April to November every year, and it can be seen from late May to the end of September. At the beginning of the month, it was the peak period of the epidemic. Ponds that used reservoirs, lakes, and rivers as their sources of water were more serious. The Chinese sturgeon only inhabits grass carp, herring and red-eye turtles. Major hazards Grass carp and grass carp older than 1 year old can cause death.
In the case of cockchafers, the pathogens of the Chinese sturgeon females are hooked on the gills and cocoons of cockroaches and catfish with big hooks. The damage to fish is similar to that of the Chinese sturgeon, which mainly affects large-age fish older than 1 year old, but larger The fish species can also be parasitic. After the eel and squid are sick, the fish body is wasted, and they swim or swim around the surface all day. The fish's caudal fins expose the water. In the Yangtze River basin, from April to November, it is the breeding season of Chinese quail, from mid-June to late July, as the main epidemic season, it is often accompanied by rickets, aggravating the condition, and harming eel and squid. The Chinese quail only parasitizes crickets and squid.
Third, the prevention of fish caries
(I) Bacterial gill disease
1. prevention:
(1) Tissue vaccine injection: In 1969, the Pearl River Fisheries Research Institute used the inactivated liver and spleen vaccine of diseased fish to conduct fish inoculation immunoassay. The survival rate of grass carp was 88%. The survival rate after injection of tissue vaccine under conditions of pond conditions and feeding and management can be increased by 20 to 30%. In 1975, the Pearl River Fisheries Research Institute continued to expand the trial with lyophilized vaccines, and the immune survival rate was as high as 80%. Tissue vaccine immunization with fish has become one of the main measures for the control of bacterial gill disease in grass carp in Guangdong fish-producing areas.
(2) Thoroughly clearing the pond: 100-150 kilograms of lump of quick lime for the mu, splashing the whole pond of the slurry, neutralizing the acidity of the bottom mud and killing pathogens.
(3) During the rearing period, fish ponds should be used to splash lime every 20 days to make the pool water 20PPM. The fish ponds splash lime once a week to make the pool water 20ppm.
(4) During the rearing period, the Quanchipang Baoshui II series of aquatic products was splashed on a monthly basis to make the pool water 0.15 ppm.
(5) Frequently inject new water to control the pool fatness and keep the pool water more than 35 cm.
(6) In the main grass carp ponds, during the main growing season of grass carp, the aerators are activated at noon on a sunny day for 2 hours. Fish cages and industrialized fish farming should maintain sufficient water-soluble oxygen in the ponds to prevent floating of fish heads.
2. treatment:
(1) Quanchiposa Bao Shengtang, a series of aquatic products, bactericidal agent II, to make the pool water 0.3ppm. If the disease is serious in the pond, repeat the medication every other day; or whole pool of Bao Shengtang series of aquatic product bacteria nitrogen clear, so that the pool of water was 0.1 ~ 0.15ppm, diluted with water, Quanchiposa after dilution. Spilling drugs is best done when the dissolved oxygen in the pool is high.
(2) After three days of spilling the above-mentioned drugs, the whole pool is splashed with the massive lime solution, so that the pH value of the pool water reaches about 8.5.
(3) Oral administration of Baoshengtang series of aquatic products chlorothalonil medicine baits. Add baits in 1% quantities, feed twice a day, and feed for three days.
(B) Blight mildew
(1) Keep the quality of fish ponds fresh and clean to prevent deterioration of water quality.
(2) In the season of fish growth, Shi Baoshengtang series of aquatic drugs rejuvenate Fei Shuibao, once every two weeks, one meter deep water pond per acre, use 1 to 1.5 kg, water and dissolve, and it will be sunny in the morning from 11 to 12 When Quanchipia spattered, after applying the complex fertilizer Fei Shuibao, do not stir the water and keep the water calm.
(1) Quanchiposa Bao Shengtang series of aquatic product bacteria nitrogen clear, 0.1 to 0.15 grams of drug per cubic meter of water, dissolved in water Quanchiposa. The condition is serious in the pond. Repeat the medication every other day.
(2) In the pond where the mildew develops, one-half of the pool water is immediately drawn out, and new water is quickly added to the original water level to reduce the pool water fertility.
(c) Chinese rickets
During the period of fish rearing, from April onwards, once a month, the Quanchiposa of Baoshengtang Aquatic Products Co., Ltd. will be splashed once a month. Each cubic meter of water will have a volume of 0.009-0.018 litres. Diluted by 1000 times, Quanchiposa or spray.
(1) Quanchiposa Baoshengtang series aquatic products fish insect enemy, so that the pool of water was 0.125 ~ 0.075ppm, a serious condition of the pond, repeated three days after the drug once; or Quanchiposa fish hate II, per cubic meter water body Product 0.018 ~ 0.03 ml.
(2) After splashing the fish and insects and hating II or the fish, the next day, Quanchipa will be splashed with a germ-poisoning agent II to make the pool water 0.3 ppm.
Reminder: The use of the Baoshengtang series of aquatic products, fish and shellfish II, should be noted that the above two drugs must not be mixed with alkaline drugs; mixed with shrimp, crab, and whitefish are prohibited in the pond; Use concentration, should be spilled evenly; Avoid liquid contact with the skin, especially the eyes, if found poisoning, should be sent to the hospital for emergency treatment of new pesticides.
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