Prevention of diseases in farmed fish
Prevention of fish diseases is one of the important measures for improving fish farming production. Because fish live in water, their activities are not easily perceived by people. Once they are sick, timely and correct diagnosis is more difficult and treatment is more troublesome. Internal medicines can only be actively eaten by fish. When the disease is severe, the fish has lost appetite. Even if there is a specific drug, it cannot achieve the therapeutic effect. In-vitro drug use generally uses the method of spraying and dipping in the whole pond. This is only suitable for small ponds, but it is difficult to use for large areas of lakes, rivers and reservoirs. Therefore, prevention work is particularly important in fish farming. The practice over the years has proved that only by implementing the correct approach of "comprehensive prevention and active treatment" in fish disease work, adopt a positive approach of "disease-free prevention, disease prevention and early treatment" to achieve reduction or avoid loss of fish due to illness. , ensure the production and quality of farmed fish per unit area. In the long-term production practice, the vast number of fishermen in China have summarized the unique "four determinants and four eliminations" of effective prevention measures, which greatly reduced the incidence of farmed fish. Prevention must pay full attention to all factors that can cause the occurrence and spread of fish diseases. In the prevention measures, we must pay attention to eradicate the cause, cut off the infection and invasion, but also to improve the fish's resistance to disease, and take comprehensive preventive measures to achieve the disease prevention effect during the prevention period. The other is a clear pond with water. The depth of the pond is about 1 meter, and 130 to 150 kg of lime are used per acre. Usually put the lime into the cask pulp and splash it in the whole pond, or put the lime into the basket, hang it on the side of the boat, sink into the water, wait for it to dissolve, then paddle the boat, slow it in the pool, shake the basket at the same time. The lime slurry is dispersed into the water and the mud is stirred in the pool the next day with an iron chain or nail to spread the lime slurry to the depth to enhance the elimination of the enemy. The advantage of this method is that it does not need to be filled with new water to prevent the danger of wild fish and diseases and insects from entering the pond with water. Therefore, the prevention effect of this dry pond clear pond method is better. However, the use of lime is large and the cost is high. 1, fish disinfection Drug prevention of fish diseases in the body is generally performed by oral administration. Since it is impossible to force the fish to take medicine, it is only possible to mix the medicine in the bait to make the bait. The commonly used drug baits made of sulfaguanidine (also known as sulfaguanidine) powder are mainly used to prevent bacterial enteritis. According to the different habits of grass carp and herring, the bait is generally made into two kinds of floating baits and heavy baits. Formulation of 10% formalin: A 36% to 40% formalin solution was prepared as a 100% concentration. That is 10 ml of formalin plus 90 ml of sterile water, which is a 10% solution of formalin. Extraction Kit Magnetics Bead Method
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First, improve the breeding environment
Good waters are not only conducive to the growth and development of fish, but also enhance their resistance to disease. Therefore, depending on the biological characteristics and habits of fish rearing, it is very important to carry out the necessary transformation of the fish pond. Specifically, it starts from the aspects of pond area, water depth, bottom sediment and its surrounding environment, water drainage and irrigation, etc. to improve the pond's ecological environment, maintain the pond's good water quality, and provide sufficient natural food, which is beneficial to fishes. The growth can also make the fish less sick or not sick.
Before the establishment of the farm, a detailed survey of the water supply environment should be conducted. Water sources are sufficient, clean, free from pathogens and toxic substances. The physical and chemical characteristics of water are suitable for the requirements of fish life, and are not affected by natural factors and man-made pollution. When it is found that the water source is not suitable, it should be used after finding another water source or removing toxic substances and pathogens from it.
When designing the intake and drainage systems, separate inlets and outlets should be provided for each pond. That is, each fish pond should be able to independently obtain the pumping water from the influent channel, and can independently discharge the pool water into the total drainage ditch, instead of discharging it to the adjacent fish pond, so that the spread of pathogens due to the water flow can be avoided. Possibility to another pond. The construction of reservoirs should be considered in the design of Jiantang. The water introduced from lakes or reservoirs should be purified first in the reservoir, and then introduced into the fish pond after precipitation or disinfection to prevent pathogens from entering the water source. Fish pond.
(I) Pond clearing
Ponds are places where fish live, and where fish pathogens are stored. The cleanliness of the pond environment directly affects the health of the fish, so it is absolutely necessary to thoroughly clear the pond. Commonly referred to as the clear pond, including two contents: First, clear the pond; Second, the drug clear pond. All are effective measures to improve environmental conditions, eliminate predators and eliminate pathogens.
1. Gantang Clear Pond
After fishing in winter every year, drain the pool water and remove a layer of sludge on the bottom of the pool. Then let the sun shine during the day and freeze for a week or so at night to accelerate the conversion of organic matter into nutrients in the soil and achieve the goal of eliminating pests and diseases. At the same time, it is easy to eliminate weeds at the foot of the beach and reduce spawning sites such as parasites and aquatic insects.
2, drug clear pond
Commonly used clear pond drugs are more, here only describes the use of lime, bleaching powder, tea cake usage and role.
(1) Lime clear pond
There are two ways. One is dry pond clear pond, first put the pool water to dry, or leave 6? 9 cm of water, use 50-60 kg of lime per acre, depending on the amount of sludge at the end of the pond and increase the amount of lime. In the clear pond, excavate a few small pits at the bottom of the pond to put the quicklime in order to melt it, and evenly sprinkle the entire pool without cooling. The next morning, it is best to stir the pond mud with a long-handled loach to give full play to the disinfection of lime. After clear ponds usually disappear after 7-8 days, the fish can be released. Lime clear ponds can kill wild fish, cockroaches, aquatic insects, vertebrate snails, shrimps, crabs, blue mud moss, germs, parasites and their eggs in a few hours. After clear ponds in Gantang, when re-injected, filtration measures should be taken to prevent wild fish and diseases and insects from entering the pond with water.
(2) Bleached clear pond
The active ingredients of bleaching powder are hypochlorous acid and calcium hydroxide, and hypochlorous acid releases the initial ecological oxygen immediately, which has strong bactericidal action. The general bleaching powder contains about 30% of available chlorine, and its amount can be used as 20 grams per cubic meter of water, that is, 1 meter of water per acre and 13.5 kilograms. After bleaching powder is dissolved in water, it is immediately sputtered with a wooden scoop and then swayed in the pool with a boat and a bamboo raft to uniformly distribute the drug in the water and enhance the effect. After 4 to 5 days, the drug power disappeared completely. Bleach has a strong bactericidal effect, and can kill wild fish, cockroaches, aquatic insects, etc., and the use of drugs is small, the drug quickly disappears, is conducive to the advantages of the turnover of the pond, but does not increase the effect of pond fertilizer.
When using bleaching ponds, the following points should be noted:
1, bleaching powder in the air is very volatile and deliquescence, should be placed in a dry place sealed to avoid failure. The remaining bleach should be tightly sealed and kept away from sunlight.
2. When dressing and spilling bleach, it is best to use pottery or woodware, not metalware, so as to avoid corrosion and reduce the efficacy.
3, bleaching powder before use, it is best to use chemical analysis of the iodometric method or use "hydraulic" bleach chlorine available chlorine measuring device to determine the available chlorine content, such as the content is not enough 30%, need to increase the amount of appropriate.
4. Operators should wear masks and rubber gloves to splash chemicals in the wind to prevent poisoning and prevent clothing from being contaminated and corroded.
(3) Tea Cake Clear Pond
The tea cake is a residue remaining after the fruit of the tea plants Camellia oleifera and Camellia oleifera is pressed. The shape of the tea cake is similar to that of the rape cake. Tea cake contains saponin, a toxin that is hemolytic. When the average water depth is 1 meter per mu, the amount is 40 to 50 kg. Put the tea cake into the cask and add water and mix well. Quanchiposa. After 6 to 7 days, the drug can disappear. Because tea cake contains saponin, it can solubilize red blood cells of fish, so it can kill wild fish, snails, river otters, frog eggs and some aquatic insects. However, the effect on bacteria and parasites is not great, so the disease prevention effect is poor, but there is an effect of increasing fish pond fertilizer.
(B) Pond Water Quality Management
Fish live in a water environment, and the state of pond water quality has a direct effect on fish, so the water quality management level has a great impact on fish diseases.
When the dissolved oxygen in the pond water is lacking, the diseased fish in the cervix are often exacerbated, and the disease with the first floating head is revealed, and even serious suffocation occurs. When fish live in oxygen-rich water bodies, it is beneficial to the recovery of the injured parts of the sacral part and the improvement of the fish's resistance. Pond water quality management mainly pays attention to the following points:
1. Ensure that the pool is rich in water-soluble oxygen: regularly add new water or start aeration equipment.
2. Prevent poisonous substances from entering water sources and contaminating pond water quality.
3. Regularly disinfect pool water with quicklime, bleaching powder and other drugs to kill pathogens in the water body and improve water quality.
4, appropriate amount of feeding. Prevent excessive water contamination caused by food. Remove excess grass and dead fish in time.
(c) Drug prevention
In the epidemic season of fish disease, when fish transport, fish species are divided into ponds or transferred to large water surface for stocking, fish diseases can be promptly prevented, and baits, fish body disinfection, and Quanchiposa drugs can prevent fish diseases. The occurrence and spread of fish will reduce the chance of outbreaks of fish diseases and reduce the losses caused by fish diseases. The main methods are disinfection of fish, splashing of drugs in whole ponds and feeding of baits.
Years of practice have proved that even healthy fish always carry some pathogens. Therefore, ponds that have been sterilized in the clear ponds will be brought into the pathogen if they are stocked without disinfection. There are three main methods for disinfection of fish.
(1) The bathing method places the fish in a relatively high drug concentration and bathes it for a suitable period of time. The general requirement is that in a relatively short period of time, the killing of the pathogen on the fish body will prevail. The length of time depends on the size of the fish, the strength of the body, the drug concentration, and the temperature of the water. In general, the longer the time, the more thorough the killing of pathogens, but a long time, the lack of dissolved oxygen in the water, can cause fish floating head or death. Bathing can be carried out in wooden barrels, boathouses, canvas buckets or tanks, and can also be done with a tie box at the bottom of the pond. There are many types of drugs used for bathing and disinfection of fish. Commonly used are 3% 4% saline, 10ppm bleach, 8ppm copper sulfate, 20ppm potassium permanganate and so on.
(2) Hanging disinfection method This method is applicable to fish that eat floating baits, such as grass carp. When you start feeding in the spring, choose a suitable location and use a bamboo pole as a triangle box as a food field. Thirty-six bamboo sticks were hung in the center and corner of each side of the triangle box, and the mouth of the bamboo stick was exposed on the surface. Put a stone in the bamboo basket as a sinker. Load 100 to 150 grams of bleach each day in each bamboo basket. Before bleaching powder the next day, wash the bleach residue from the previous day in place. After each time the bamboo poles are hung, duckweed or grass is fed into the triangle to attract fish. The bleaching powder breaks down into hypochlorous acid when it meets water, spreads from the bamboo raft to the surrounding of the food field, and has strong sterilizing ability. Grass carp enters the food field to graze, passes through the hypochlorous acid-containing water, and the pathogenic bacteria in the fish can be killed. The bleaching powder has a corrosive effect and should not be used in sacks or sacks for bleaching powders.
(3) Hanging bag method In order to prevent parasitic rickets, skin diseases, such as trichoderma, oblique tuberculosis, and Chinese rubabaria, etc., a 5:2 sack of copper sulphate and ferrous sulfate mixture is regularly hung on the food field. The number of bags and the number of medicines in each bag depend on the size of the fish pond and the water depth of the food field. Generally 3, each loaded with 100 grams of copper sulfate and 40 grams of ferrous sulfate. After the first bag, you should observe for about 1 hour at the pool to see if the fish come to eat. If you do not eat, indicating that the concentration of the drug is too high, you should reduce the number of bags hanging on the side of the pool, until the medicine in the bag has not yet dissolved and the fish is appropriate to eat.
2, Quanchiposa drugs
This is the most commonly used and one method of treating fish diseases with drugs. The use of certain pathogens has a killing effect, and the drug concentration of the fish itself is sprinkled in the fish pond to kill the pathogens hidden in the body surface and the stern of the fish as well as in the water body, so that the disease condition is improved or healed. To use the sprinkler method, first accurately measure the area and depth of the fish pond. According to the volume of the fish pond water, calculate the dose of the drug used, and weigh the drug in the wooden barrel to open it with water, dilute it, and evenly spill it into the fish pond.
Before the epidemic season of fish diseases, regular use of drugs to sprinkle the entire pool, there is the effect of preventing fish diseases. Commonly used as Quanchiposa drugs are the following:
(1) Bleaching powder: In the epidemic season of bacterial fish disease, use it once every half a month, and splash the whole water with bleached powdered water so that the bleaching concentration of the pool water is 1 ppm. That is, the depth of the pool is 1 meter, and 667 grams of bleached powdered water per acre is poured along the edge of the pool and the food field.
(2) Copper sulphate and ferrous sulphite mixture: Prevent parasitism fish diseases, such as tick whipworm disease, pigeon phosporosis, caterpillar disease, trichoderma, every month or every two months, with sulfuric acid The copper and ferrous sulphate mixture (5:2) was splashed in the whole pond to make the pool water 0.7ppm.
(3) Quicklime: To improve water quality and kill pathogenic bacteria in water. 1 meter deep water per mu, cast 15? 20 kg of quick lime, have the effect of disease prevention and treatment.
(4) Trichlorfon: Cylindrotheca spp., parasitoids, cockroaches, Chinese sturgeons, and anchor stings that cause parasitic rickets or skin diseases. They are splashed with crystal trichlorfon in a pool of 0.2 to 0.5 ppm for these parasites. Insects have a killing effect.
The Quanchiposa method can simultaneously act on pathogens in fish and water, and the effect is relatively good. As long as the calculation of water volume and dosage is accurate, the operation method is relatively simple and easy to grasp. However, with large water bodies, the use of this method, the amount of drugs used and the labor force are relatively large, and it is difficult to determine irregularities. At the same time, due to the many opportunities for exposure to drugs, the safety of people and animals should be given special attention.
First, the formulation of a floating bait: the ratio of 2.5 to 5 grams of sulfa powder mix rice bran or bran 500 grams. Reconcile with hot water, knead into a soft and hard moderate block, pressed into a bar or cut into small ingots, dry and spare. When eucalyptus powder is used as a binder, sweet potato flour or flour can be used instead. The bait required to be able to float on the surface of the still water for 4 hours or so can be floated for 2 to 3 hours in the water with fish swimming, which is beneficial to the feeding of fish. In recent years, some units used young grasses to cut into small pieces of palatable species, mixed with batter with sulfamethoxime, and dried and fed afterwards to achieve the same effect.
The second is the preparation of heavy baits: the same amount as the above plus 500 grams of cake flour or bean flour and 100 grams of eucalyptus powder. Reconcile with hot water, knead into a soft and hard moderate block, pressed into a bar or cut into small ingots, dry and spare.
Both prepared baits should be stored in a dry place to prevent mold deterioration.
The delivery time of the bait is suitable for feeding baits starting from the first half or one month before the epidemic. In order to have a bait for each fish, every time a bait is fed to a grass carp, it is not necessary to cast any other bait; the herring pond is fed with a bait before the bait is reduced by 40% than usual. About 50%, when the food is ready to be eaten soon, it will not only ensure that the herring eats enough, but also guarantee that the bait is eaten.
Preparation of baits using commercial grain baits: For the prevention and treatment of fish disease in fish feeding commercial grain pellets, select specific drugs according to the weight of the fish and determine the dosage for the disease prevention and species, and then use water to dissolve and stir and spray on the bait. Make it evenly absorbed and dry it before use. The practice of prevention and treatment shows that using baits for feeding fish has good preventive and therapeutic effects.
Second, immune prevention
The implication of immunization, simply put, is to produce resistance to pathogens without being infected. Immunity and species can be roughly divided into two types: innate immunity and acquired immunity. Innate immunity is divided into immunity, immunity and individual immunity. Immunity varies from species to species. Because of animal body temperature, food, living habits, morphological characteristics, tissue reactions, the amount of natural antibodies contained in the blood and the different types. Immunity is also different in the same animals because of different ethnic groups. This is also due to differences in heredity and living habits. In addition, differences in animals' sex, age, endocrine, body structure, nutritional status, and environmental factors also make the same type of individuals different and immune. For example, when grasses and bluefishes suffer from bacterial enteritis, the white cod in the same pool is not affected, or some of the grasses and herrings in the disease are not affected. Acquired immunity can be divided into two types of automatic immunity and passive immunity. Acquired autoimmunity is the production of antibodies in the body of a diseased fish under natural conditions, and immunity to the disease or immunity generated by artificially injecting bacterins, vaccines, or toxoids to produce antibodies. Acquired passive immunity is the maternal immune material transmitted to the offspring, or artificial injection of the same species or heterogeneous animal immune serum, so as to activate the body's resistance to disease.
(I) Inactivated vaccine for grass carp hemorrhage
1. Vaccine preparation: The fish liver, spleen, kidney and muscle tissues with obvious hemorrhagic symptoms were weighed, cut and crushed, and homogenized at a concentration of 1 gram tissue plus 0.65% physiological saline diluted 1:10 or 1:100. mashed. The centrifuge was centrifuged at 3000 rpm for 30 minutes and the supernatant was taken. 800 units of penicillin and 800 units of streptomycin were added per milliliter of virus suspension. If the streptomycin and streptomycin each bottle 1 million units, can be dissolved in 100 ml of sterile water, each milliliter contains 10,000 units of streptomycin. To make a 500 ml vaccine, it is not necessary to add 40 ml of the above-mentioned aqueous solution of streptomycin to meet its content requirement. Finally 10% formalin was added to a final concentration of 0.1% (ie 100 ml of virus suspension plus 10% formalin 0.1 ml). Shake well and inactivate in a 32-degree constant temperature water bath for 72 hours. In the process of inactivation, shaking twice a day or more. After inactivation, samples were taken for safety and efficacy tests. After the vaccine is made, it is stored in a 4 to 8°C freezer for use.
2. Vaccine efficacy test: After the vaccine is made, it must be tested for efficacy before it is applied to production, otherwise unsafe accidents can occur easily. The test procedure is: The prepared vaccine is drawn and the healthy grass carp is injected intraperitoneally. Put the needle in the depression on the inner side of the base of the pectoral fin and inject the body cavity. The needle and the abdominal wall form an angle of about 45 degrees. Each fish was injected at 0.3 to 0.5 ml. The injected fish was placed in water tanks at a temperature of 25 to 28°C and observed continuously for 15 days. If no death due to the symptoms of bleeding is found, it is initially determined that the vaccine is safe. And a virus suspension made of 1:10 fresh or glycerol-preserved virus tissue was injected into the injected fish and the unvaccinated fish respectively, and the injection dose was 0.3 to 0.5 ml per tail. Continuous observation for 15 days. If the control group had all the symptoms of hemorrhagic disease and had the same symptoms as the naturally occurring fish, the mortality of the diseased fish was more than 70%, while the immunized group did not have hemorrhagic disease, which could prove that the vaccine was effective.
3. Immunization route: The route of fish immunity includes four methods: injection, oral administration, spraying, and vaccine immersion after the vaccine is directly added to water. Among them, the method of injection production has high reliability and good effect. However, its operation is more troublesome and it takes more manpower and time. And if not handled properly, it may cause the death of fingerlings.
Inactivated vaccine for grass carp bleeding, using one or two injection methods. The vaccine dose depends on the size of the fish. Each injection range is 0.3 to 0.5 ml. The syringe should have a volume of 5 ml. The size of the needle depends on the size of the fish and the particle size and viscosity of the suspension of the vaccine. Normally, about 3.3 centimeters of fingerlings use the 4th needle; 6.6 to 10 centimeters use the 5th needle; 20 to 23 centimeters can use the 6 to 7 needles.
(b) Grass carp indigenous vaccine (grass carp, enteritis, gill rot)
1. Preparation: Remove the liver, spleen, kidney and other tissues of the diseased grass carp, and weigh them in the ratio of 1:5 or 1:10 plus normal saline. That is, 1 gram of liver, spleen and other tissues plus 5 ml or 10 ml of normal saline (0.85% saline). Grind with a mortar and then filter with two layers of gauze. The filtrate is tissue pulp. The tissue slurry was placed in a water bath and kept at a constant temperature of 60 to 65°C for 1 hour in a concentration of 1% formalin. When used, it must be diluted again. Sealed with paraffin and placed in the refrigerator, usually save 2 to 3 months.
2. Immunization method: The method of injecting vaccine is used. Grass carp is generally required to weigh about 0.25 kg per body and have a body length of about 3 inches or more. The fish body is too small to operate.
(1) Injection dose: It depends on the size of the fish. There are some differences in the doses used everywhere. Usually a grass carp weighing 0.25 kg, 0.2 ml of grass carp injected with 0.1 ml of 0.5 kg body weight, or 0.2 kg of grass carp 0.5 kg or less, and 0.5 ml of a 0.5 kg body weight injection.
(2) Injection site: base of pectoral fin, back muscle, base of dorsal fin, among which the former two are more. The injection depth is 0.2 to 0.5 centimeters, so it is better not to hurt the internal organs.
For ease of handling, dip insects were used to dip the fish before injection. There are two aspects of its role, one is that after dipping, the fish anesthesia, reduce the beating, to avoid fish damage. The second is to kill fish parasites. The concentration of trichlorfon crystals dipping is one-500 to one-hundred and one-hundred and one-hundred and one-hundred and one-hundred and one hundred and one hundred, placed in a cask dipped for 3-5 minutes, or dip for 5 minutes with a concentration of 1.5 parts per thousand. Dipping should be carried out in batches, and pay attention to the water temperature and grass carp activity and be flexible.
3. Immune effects: The raw materials used to prepare the vaccine for the soil preparation are the internal organs of the diseased grass carp, mainly the antigens contained in the liver, spleen, and kidney. The types of the vaccine are various, not only bacteria but also viruses. According to current data, there are more obvious effects on the prevention of grass carp virus or bacterial diseases. The immunization period is not less than 10 months and the survival rate can reach more than 90%. The method of producing the indigenous vaccine is simple and the vast majority of fishermen and farmers can master it.