Immunity and disease prevention technology

Immunity and disease prevention technology
Immunity, simply to mobilize the body’s own defense against pathogen invasion, propagation and spread, to maintain the internal environment of the spike set, to achieve the process of living organisms. Immune prevention is the use of artificial immunity method enhanced biological law of immunity in order to achieve the purpose of preventing disease, artificial immune is artificial made vaccine, Miao Pu, tumor vaccine, poison cable or cellular immune preparation and vaccination to fish, the fish itself defense ability of corresponding diseases. Made with pathogen pick preparation raw said Miao Pu, virus, made of rickettsial antigen preparations known as (some of the two referred to as vaccine) vaccine, made by tumor tissue known as tumor vaccine. Bacterial exotoxin after 0.3% – 4% formalin treatment, toxicity and disappear immunogenicity still retain is called toxoid. Cellular immune agents are dry, transfer factor, etc..
Prevention and control of fish diseases by artificial immune method. Than the use of drugs for prevention and treatment, has the following advantages: 1, fish with most drugs have different degrees of injury and poison, easy to cause the water environmental pollution and drug toxicity and immune prevention methods on the gold does not have this situation. 2, the fish farms often long-term use of antibiotics, the aquaculture water resistant strains increased significantly, the efficacy was significantly decreased, the drugs increase, immune prevention method does not produce resistance in the isolates. 3, a large area of water fish, the use of drugs cost is too high, and the immune prevention is simple, economic. 4, some diseases, such as virus diseases, tumor, robe worm disease, prevention and control of drug is difficult to bear fruit, but also need to study the immune prevention methods,

Cut off the source of infection disease

Cut off the source of infection disease
Control the spread of pathogens of fish diseases, reduce or inhibit the growth rate of the reproduction of the pathogen and drug prevention measures is very important, especially on fish, bait, tools disinfection is not neglect.
1, fish body disinfection
Disinfection of fish body mainly through the bath method, will fish body is arranged in the higher concentration solution in, after a short time of bath, killing fish pathogens. The bath container available barrel, plastic tub, cabin, water tanks, etc., if the number of fish, batch no bubble or close cage for soaking container. Soaking drug before it is best to check out the fish pathogen, and then select the drug, according to the fish body size and physical strength and Tianzhu, JuShui flexible grasp the concentration. In the process of immersion, the fish should be regularly checked for the tolerance of the fish, so that the time of immersion is easy to master. There are several drugs for the disinfection of fish body;
Salt: concentration 2% ~ 4%. Soak 5 to 10 points, the main prevention baizui disease, gill rot disease, killing some protozoa, three generations of insect, Dactylogyrus etc..
Copper sulfate: concentration of 8 mg / kg, no washing 20 points, mainly to prevent fish wave Bodo disease, Trichodina disease, kill parasites on the body surface of the protozoan pathogens.
Bleach: concentration of 10 ~ 20 mg / kg, soak 10 minutes or so, can prevent fine Han skin disease and gill disease.
Trichlorfon: concentration of 10 mg / kg, dipped 15 points, can kill some protozoa, three generations of insect, Dactylogyrusis etc..
2 food disinfection
Commonly used food and field disinfection method has suspension method and sprinkling method two kinds.
Suspension method: the drug is placed in a container with a micro hole, suspended in the food field, so that it can be dissolved in water, and can achieve the purpose of disinfection. Suspension for drug and food disinfection with field bleaching powder, sulfuric acid, pin dipterex. The container is hanging baskets, bags, plastic bags, a hollow foam block material. After suspected bagged liquid material, need to tip in bag nimble holes, hole size and number should be shellfish live Zhang Yue, the drug in more than 5 hours the dissolving as well, and to in suspension to surrounding reaches a certain concentration as the basis. Foam blocks cut inside after the drug is placed in the central chamber, and then have the rope hanging in the food field. Hang number tender to fish to into the feeding site for the degree, in the water and fish cage culture in the suspension feeding grounds of the disinfection effect is also very good.
Test method: medicine every 1 to 2 weeks, with chlorine preparation, such as bleaching powder 250 grams of water in the food field around it 1 times, better disinfection effect.
3 disinfection
Fish with a variety of tools, especially tools used in the pond onset, such as nets, cask, wooden ladle, fishing, waterproof clothing etc., tend to become a medium for the spread of fish diseases, small tools disinfection can be used 10 mg / kg CuSO4 or higher concentrations of potassium permanganate soak for more than 10 points, large tool can be in the sun drying in the reoccupy after. Disinfection should be complete, such as the attachment to the fish on the tool of the small melon worm, encountered a bad environment can form a cell capsule, and in the cell capsule continue to split, with the tools to bring people to the environment, thousands of larvae will be broken out, so that the small melon worm disease.
4 water disinfection
After a period of time, the organic matter and suspended substance increase, the water quality is gradually deteriorated, and the pathogen is gradually increasing. Therefore the fish disease epidemic season regular disinfection of aquaculture water, killing in water or fish pathogens, effective measures of prevention. Water disinfection is in the entire culture water body in the drug. Effective disinfection drugs commonly used is the lime, the water depth of 1 meters per acre with lime 25 kg. There are many excellent disinfectant, such as bleaching powder (1 mg / kg), bleaching powder concentrate (0.1 ~ 0.2 mg / kg) and trichloro isocyanuric acid (0.3 mg / kg) and sodium dichloroisocyanurate (0.3 mg / kg), chloramine T (2 mg / kg) and the sterilization effect is good; copper sulfate, ferrous sulfate mixture (5:2.0.7 milligrams (mg) / kg), trichlorfon (crystal content of 90%. 0.2 mg / kg), miechongling (0.5 mg / kg), good insecticidal effect.
5 food disinfection
Fish pathogens often with bait into the bait, so delivery must be clean and fresh, after disinfection. Plant food, such as water plants can be used 6 mg / kg bleach solution diffuse foam 20 to 30 points. The land plants collected under the sun can not be disinfected. Animal feed, such as snail, fish and shrimp and merchandise bait mix a small amount of CTC or Oxytetracycline Residue (according to the amount of feed 5 valves mixing ratio) can be fed. The fish manure must be rotten, and add 120 grams for every 500 kilograms of bleach disinfection treatment can be put on the big pool.

Strengthen the management of breeding and production

Strengthen the management of breeding and production
Fish live in water environment not only has the fish living necessary oxygen, food etc., also contain harmful to fish biological pathogens and non pathogens, when the relationship between fish and environmental and pathogen in equilibrium, fish in the water can live a normal life growth, and a Fangli lose balance, fish diseases may occur. For example, when the density of fish in the pond is too large, or a sudden change in weather may cause fish necessary material deficiency or insufficiency, or cause water in the dissolved oxygen is low caused by hypoxia. These can lead to changes in the body function, causing diseases and even death. If the change of water environment is conducive to a large number of pathogens, it will make the fish pathogenic. Environment can not only promote the occurrence of the disease, but also hinder the development of the disease. Therefore, occurrence of fish diseases is not isolated caused by a single factor, and always is the role of the interaction of inside and outside environment of the fish body, the interdependence between fish and environment, pathogen, restrict each other, organic combination of become a complex ecological system, that is, the water parasitic ecosystem. To maintain the balance of the ecological system of the breeding water body, to create a conducive environment for the growth of fish and aquatic animals, can achieve the purpose of preventing and reducing the incidence of fish. This is what is commonly known as ecological disease prevention.
To strengthen the management of breeding, and the content of the category of disease prevention and control. Continuous improvement feeding and management measures, improve the body resistance to disease in fish, ensure the balance relationship between the fish body, the environment and the pathogen; reasonable polyculture, and dense cultivation, quality feeding and reasonable fertilization, strengthen daily management of aquaculture.
Reasonable polyculture and dense cultivation is to improve the yield per unit area of one of the measures, for the prevention of fish disease also have certain positive significance, stocking improper proportion or density is too large, resulting in water feed the lack of water and oxygen in low for a long time, the fish growth slow, emaciated body, disease resistant force is reduced, susceptible to various diseases caused by a large number of deaths.
Adhere to the “quality” of feeding is to strengthen the breeding management, one of the most important management measures to prevent the occurrence of fish diseases. “Four” feeding is depending on the developmental stage of kinds of fish, fish, fish in the moat and season, the weather, the water temperature and water quality conditions and selection of wide source, low price, eating fish, good quality food, in proper time and a fish pond in proper position and feeding in sufficient quantities. Often referred to as the “four” (qualitative, quantitative, timing, positioning) feeding the specific methods of operation are as follows: qualitative; feeding bait to fresh and with a certain amount of nutrients, with pathogens or toxic substances, palatability is good, suitable for different species and size of fish feeding. When the condition is best, it is best to make the feed, to improve the nutritional value and reduce the loss of the feed ingredients in water. When necessary in the feeding of food before disinfection, especially in fish season to do more,
Quantitative: daily feeding to a certain amount, requirements make it appropriate and uniform, to prevent too much too little, suddenly more and less. In order to improve the use of fish to feed rate, promote growth, reduce disease, reduce the feed coefficient. The amount of feeding is the most important factor in the feeding technique. Feeding too little, the nutritional content of diets enough to sustain fish life activities, to grow with little; feeding too much, the fish to eat too full, will reduce the rate of digestion of food, improve the feed coefficient, and easy to cause diseases, reduce the survival rate and growth rate. Too much food will not only cause the waste of food, but also bad water quality.
The daily feeding amount according to the specific circumstances, such as high and low temperature, sunny and rainy weather, water fat and fish feeding situation should be flexibility, generally within 3 hours after the appropriate.
Timing: normal weather, generally in 8 ~ 9 and 14 ~ 15 by feeding 1 times. In early spring and late autumn and early winter when the water temperature is low, usually at noon feeding 1 times. In summer, the water temperature is too high, the afternoon feeding time delayed properly. In a dense flow pool with feeding principle should be “eating”, each can put less points, but increased feeding frequency.
There must be a fixed location; feeding feed, fish bait to develop the habit of eating table fixed. Such not only can reduce feed waste and easy to observe the activity of the fish, easy to check the feeding, easy to remove uneaten food and food for disinfection to ensure farmed fish to eat health, is convenient for disinfection of fish drugs in fish disease incidence of the season, so as to improve the effect of prevention.
Feeding grass bait available bamboo into a triangular or square food box, easy to eat and clean up, Grass Carp megalobramaamblycephala left bait. The frame is fixed on the north shore of the pond, Xiangyang, and little to no shade, near the shore with stakes position.
Feeding merchandise bait, should be in the water below 30 ~ 40 cm with the reed mat or a bamboo mat barricaded area of 1 ~ 2 M L food and Taiwan, feeding on the eat desk and mesopelagic fish feeding. Demersal fish Nai material and Taiwan should be located in shore of 1.3 to 1.7 meters below the surface of the water, fertilization effect is mainly increase the nutrients in aquaculture water, make the plankton growth and reproduce rapidly, provide plenty of food for fish farming. Fertilizer fertilization of base fertilizer and top dressing in two ways. For thin water of the pond and the new pond, in order to change the nutritional status of sediment to become pond fish live comfortable environment, lasting supply of fish in the moat enough natural bait, it is necessary to apply sufficient base fertilizer. Fertilizer is to make water natural bait to maintain strong enough for breeding, feeding the fish. “In time, a small amount of fertilizer should be mastered, many” principle. Top dressing with the fermented manure or compost mixed pulp is better, without the fermentation of manure should be piled up by the side of the fish pond retting for several days and then evenly sprinkle people pool.
Because of the ecological environment is very complicated, we must strengthen the daily management, such as adhering to the daily morning, middle and late 1 times, especially in the morning. The pond should be paid attention to when the fish has no floating phenomenon, changes in water quality, fish activity, there are no problems etc.. Improve aquaculture water environment health, often weeds, often in addition to predators and pathogens of the intermediate host, timely remove residual bait and fish, regular cleaning and disinfection feeding grounds, inhibit the pathogen to multiply and spread, and standardize the operation, prevent injured fish, can Naga fish: a good living environment, enhance disease resistant ability of the fish body.
China also has many successful examples of ecological prevention and control. Such as rice grass carp culture, not only can make the rice yield and per mu paddy can gain 10 ~ 15 cm of the grass carp 300 ~ 500 tail. In the process of breeding paddy grass species, no epidemic. Also used for the Great Lakes area breeding characteristics raise double cropping grass carp to avoid the peak incidence of hemorrhage, in the pond in every year is divided into two batches of grass carp breeding species, the first species hemorrhage before the arrival of the peak of the epidemic, that every year in August, fish from the pond lake; the second batch of fish is put into the fish ponds in the aftermath of the epidemic peak of the hemorrhage. These are all make full use of in favor of fingerling cultivating ecological factors, and to avoid the epidemic peak pond environment on fish growth unfavorable ecological factors.

Fish disease prevention

Fish disease prevention
Fish disease prevention and control work must follow the principle of “no disease prevention, early treatment, prevention is more important on the treatment course, to avoid and reduce diseases caused by the loss. Because fish and other aquatic animals living in the water, their activities, people are not easy to detect, once sick, and timely and correct diagnosis and treatment have certain difficulties. Especially after the occurrence of many diseases, the disease of fish has no appetite, even with the use of specific drugs, can not enter the fish moving objects. Bird, animal disease by oral administration or injection of drugs and other methods of treatment, and the diseased fish, especially the fry and fingerling cannot adopt these methods. As a result, the use of oral medication for fish diseases, only in fish has not lost their appetite, it is more effective. In vitro drug use can only be applied to small areas of fish ponds, and for large areas of lakes, reservoirs or water fish is very difficult. Prevention and treatment, prevention and treatment, prevention first, in the prevention of the eradication of infectious diseases, as far as possible to cut off the route of transmission and invasion, but also to improve the disease resistance of fish, take comprehensive preventive measures to achieve the desired effect.
Disinfection of aquaculture water
Breeding water body is the place where fish live and grow, the quality of water environment, directly affect the health of the fish, so we must pay attention to the disinfection work of breeding environment. In recent years, due to the fish aquaculture neglect cleaning disinfection, the occurrence of freshwater fish bacterial septicemia to freshwater aquaculture in China brings loss is heavy, the lesson is profound. The pond cleaning disinfection mainly including dressing and drug cleaning pond.
Dressing fish pond fish culture water, especially fish ponds, after a period of time the fish, silt by HSI accumulation, if too much silt, not only affect the capacity of water and on water quality deterioration and pathogen growth, reproduction are the promotion of the role. Ignore the sludge removal work, provides a living environment for pathogens, causing diseases continue to occur, to bring greater losses. Dredging method and times often manpower digging pick and mechanical desilting and dredging in winter, to drain the water in the pool, and then clear the silt. After dredging for exposure to the fish pond, cold frozen for a period of time, and then filling it, in order to kill the remnants of the pathogen and fish predators.
Drug cleaning
Various types of aquaculture water, in addition to the cultured fishes for aquatic economic animals, exist including bacteria, algae, qingni moss, clam and snail aquatic insects, frogs, wild miscellaneous fish and aquatic plants, and other organisms. Fish pond water, give them provides a living water environment, some of them itself is a fish pathogen, some media of transmission of pathogens, some of them are fish predators and must therefore be manual removal and disinfected, to kill them. Medicine commonly used lime, bleaching powder and tea etc..
Is the best disinfection method of lime pondthe recognized. Lime is the lime, which is not the massive lime, commonly known as “pipe ash” (calcium chloride, CaO). Lime pondthe dry pondpond pond with water and two kinds of methods
Dry cleaning pond is in dressing the fish pond, the bottom of the pool, leaving only 6 ~ 10 cm deep water, in the bottom of the pool everywhere dug several pits, prepare investment and quicklime is now Tang hydration. How much is small, so that it can be poured over the whole pool. A small pit is dug, the lime into the water, ranging from the cooling to the surrounding it, across the pond everywhere (including embankment foot). Lime dosage is generally 75 kg per mu,
The amount of lime pond with water for 150 kg per mu in aquaculture water depth of 1 meters. Pond with water. First lime water, the water after the pool splash; better is the lime Sheng in the wicker basket, hanging on the boat, sinking into the water, a rowing boat in pool and amble, lime slurry scattered water soluble. Lime pond run out of time, good effect. Lime pond can not only kill the pathogens in the pool and other aquatic organisms and to clarify the pool water, precipitating the suspension of colloidal organic matter, such as cement, at the same time, the pool of mud and mineralization, the release of mud adsorbed nitrogen, phosphorus, potassium and other elements, increase water and fertilizer. In addition, lime in case of water into hydrogen chloride calcium, but also absorb carbon chloride precipitation of calcium carbonate, calcium carbonate to the silt into the porous structure, improve ventilation conditions of the bottom of the pool, accelerating the decomposition of organic matter of the role, calcium carbonate and stable water pH value of the role of thin Lin, is beneficial to the fish’s life, calcium is also essential for plant nutrition elements, so the application of lime, also played a role of fertilization.
Bleach cleaning, convenient operation, time-saving. Bleaching powder can kill wild and miscellaneous fish and other predators, bactericidal effect is very strong, but not of lime to improve water quality and make the water fertilizer effect, and bleaching powder easily deliquescence, easy to reduce the effect, the chlorine stable. Bleaching powder containing about 30% available chlorine, used to determine the content to accurately determine its use, by 30% of the available chlorine bleaching powder, mu 1 meters deep water use bleaching powder 13.5 kg, namely 1 meter no water amount 20 grams, that is, to make the water of 20 mg / L concentration. At present, there are sodium dichloroisocyanurate, trichloro isocyanide uric acid, monochloramine t chlorine containing drugs can also be used on the market, but it should be accurate calculation, so as to avoid ineffective or economic uneconomical,
Guangdong, Guangxi, Fujian and other areas in the habit of using tea fish pond. The tea cake is pomace remaining plants of Camellia fruit oil, saponin containing camp, haemolytic toxin. Tea can kill wild and miscellaneous fish, frog and tadpole Dou, snails, mussels, leech, shrimp, crab and some insects, but the fish pathogenic bacteria without killing effect, can help storm algae breeding, disease prevention effect than lime. Tea amount per mu water depth 1 m of water with 50 kg or so, use the method is, the first grinding tea, put in in a tank of water and warm water immersion, soaking for 1 day and night to use, with even the residue with water, edge spill edge water, times evenly sprinkle.

Examination of sick fish

The fish were examined for symptoms, symptoms, pathogen identification and histopathological examination.
1 external symptoms of examination
The external symptoms of the sick fish were examined mainly by the visual identification of symptoms and pathogens. In general, the symptoms of different pathogens are different from the symptoms caused by fish. The main pathogens are divided into two major categories of microbial and parasitic. The parasite that causes the disease often show excess mucus, bleeding, punctate or massive cyst and other symptoms, especially some large parasites, such as worms, crustaceans and size larger protozoa (such as sticky robe worm cyst, etc.), with the naked eye can see that. The disease caused by pathogenic microorganisms, more performance for the fish body hyperaemia, inflammation, abscess, decay, fin erosion, vertical scales and other symptoms.
According to the general order of the site is from the surface to the gills,
(1) surface from aquaculture fish out just dead or dying of disease fish and placed in white porcelain or fish plate, along the head, drive cadres to tail, namely according to the sequence of mouth, eyes, operculum, scales, fins and friends careful observation,
Some of the major pathogens, such as water mold, nematodes, anchor head), louse, glochidium and sticky Cryptosporidium cysts etc., easily detectable. But some small pathogens, the naked eye can not see, then should be judged according to the symptoms. Such as car rotifers, wave fish Bodo, Chilodonella, Ichthyophthirius, three generations of insects, such as caused by the symptoms, the general will lead to the excessive secretion of mucus of fish body surface, sometimes mixed with sludge, or is the head, mouth and node end rot, but Jing strip base department generally does not appear congestion phenomenon. The complex mouth of the fluke disease, the performance of the eyeball, the ax, there is a cataract. Grass carp hemorrhage, bleeding in the oral, head, eyes to sleep, fin base, jaw, operculum and abdominal occasional light red blood spots. Bacterial red skin disease, performance for shedding scales, skin congestion; furunculosis is in lesion inflammation and abscess; leukoderma is lesion inflammation, reduce mucus, rough to the touch; print disease is in massive erosion of decay for the disease. However, some symptoms, including symptoms of skin, gill disease, different disease symptoms are basically the same situation, such as red skin disease, gill rot disease, enteritis and other parts of the bacterial disease are symptoms of fin base congestion and moth fin, so fish disease diagnosis, unlike the diagnosis of human disease that interrogation, only through detailed investigation and comprehensive symptoms are analyzed, in order to make the accurate diagnosis and correct.
(2) the examination of the gill, with emphasis on the gill filaments. First observe the gill cover is opened inflation, then used a pair of scissors to the operculum to cut, the observation of the gill lamellae color is normal, mucus, gill filament end whether there enlargement decay. Bacterial Gill Rot Disease gill decay in the end, many mucous; Branchiomycosis gill lamellae of color than normal fish gill lamellae of the color white, tinged with blood red dots; if wave fish Bodo, cryptobia, Trichodina, Chilodonella, Dactylogyrus and insects, such as parasitic, gill plate more mucus; if Chinese Sao, narrowly abdominal), single insects and some Dactylogyrus and myxospore insect cell capsule and parasitic, gill enlargement, opercular swelling and other symptoms.
Internal symptom check
Check fish tissue disease mainly to gut check, the fish on the side of the abdominal wall cut off, the first observation of whether there is ascites and visible to the naked eye fish strange, nematodes, ligula intestinalis and other parasites; carefully observed the internal appearance is normal; then with a pair of scissors from by the throat of the foregut and by the anus intestine cut, remove the internal organs, placed in a white porcelain, one by one from liver, gall bladder, bladder and other organs. Finally, the intestinal once the gut and hindgut cut open, divided into before, during and after the three sections, gently put food and feces in the intestinal tract removed, carefully examined. Intestinal parasitic trematodes, cestodes, nematodes can be easily seen; bacterial enteritis will exhibit intestinal hyperemia and inflammation; hemorrhage of grass carp is intestinal or local is bright red bleeding, enteral without food, but the intestinal wall is still relatively strong, erosion; coccidiosis and sticky Cryptosporidium disease is in the intestinal wall with sheets or dilute the white dots scattered. Other internal organs, if not found in the appearance of symptoms, the general can no longer check.
Do check the detailed record, for fish disease diagnosis provide correct basis, and fish disease diagnosis and improve farming techniques accumulated data and experience.
3 pathogen identification
Pathogen identification is generally used in optical microscopy, and the anatomy of the disease fish to do a deeper pathogenic, pathological examination. With the exception of some of the more obvious and fish disease condition and relatively simple, by visual inspection can accurate diagnosis, the general must be microscopy can be diagnosed.
The examination of the lesions was carried out in the selected area, and the location and sequence of the examination were the same as the target.
Check method is from the lesion site from small amounts of tissue or mucous placed slide on, such as skin and gill tissues or mucus, plus a small amount of ordinary water, internal organs should add a small amount of normal saline (0.85% saline water), and then covered with coverslips, and slightly flattened, placed under the optical microscope observation. In order to accurately, at least 3 different points of each lesion were examined.
When in water bodies of the same breed, there are more than two kinds of fish, you need to to various pathogens and intensity of infection and the fish in the degree of damage were compared and analyzed, identified the major and minor pathogens, in order to facilitate the development of therapeutic measures.

Diagnosis of fish diseases

Correct diagnosis of diseases of fish and aquatic animals is an important part of preventing and curing diseases. Only through field investigation, detailed examination of diseased fish, in order to achieve accurate diagnosis, suit the remedy to the case, in order to achieve the purpose of effective treatment, in order to provide the basis for taking further measures of preventing disease and breeding.
Field investigation
The purpose of the survey is to understand the pathological phenomenon, feeding management and water quality changes in the fish, and provide the first hand data for the comprehensive analysis and accurate diagnosis of the disease.
Pathological phenomena and medical history of fish culture
The genesis of fishes and aquatic economic animal diseases, acute and chronic, acute disease, body color and the constitution of the fish body with normal little difference, but careful observation, lesions vary slightly. In the short term, there will be a peak of death. Chronic diseases, the body color of the fish body black hair, emaciated body, travel alone, slow activity, mortality increased slowly, in a relatively long time peak mortality occurred, some do not appear the death peak, just a long time continuous fish. When the fish in the water set door prefectural uneasy, a shoe to jump, while dramatically mad swim should pay attention to two, either the body surface of fish parasites invasion, or that is in the water containing toxic substances, such as pesticides or toxic industrial wastewater. The former showed a slow increase in the number of deaths, but the death rate was not high, then a large number of deaths, and including wild fish, including the death of a variety of fish.
In aquiculture water the same. Every year the emergence of a fish, such as sticky Cryptosporidium disease, bacterial septicemia and, should history investigation, for fish disease diagnosis to provide information, in order to take effective measures.
Feeding and management situation investigation
Fish and aquatic economic animals, often associated with poor feeding and management. Application without the rotten manure or dosage is too large, commercial feeds are of poor quality or fed too much, will cause the deterioration of water quality, oxygen in the water, to the growth of pathogens and predators, reproduction provide a favorable environment. On the contrary, the water quality is thin, lack of food, and can cause anemia, a disease. Trawl and other improper operation, it is very easy to cause the white fish injury, disease and saprolegniasis. Therefore, the specific circumstances of the various aspects of fertilization, feeding, and dragnet operation and stocking varieties and specifications, density and onset of the calendar year should detailed investigation.
Investigation on water quality of aquaculture water
Water pH value and dissolved oxygen changes but also caused one of the reasons of fish diseases, especially suspected by the water quality changes cause the death of fish, but also to the laboratory for chemical composition of water analysis. In the greenhouse environment, we should take into consideration the need to improve the control system such as light, circulating water, and so on.

Fish body to disease susceptibility and resistance to disease

After the pathogen enters the water body, the lack of fish and aquatic animals, the disease still does not occur, so the susceptible and resistant to the fish and aquatic animals are essential conditions for the occurrence of diseases. Such as the occurrence of hemorrhagic disease of grass carp silver carp, catfish, not a body without injury is not unboiled water mildew and susceptibility to disease in animal breeding is with the non-specific immunity and specific immunity of the strength of the two changes.
According to fish immune response to antigen targeted, divided into non specific immunity and specific immunity,
Non specific immunity, at least including physiological factors, physical defense structure of the two part.
Non – specific immunity from physiological factors, with age, body temperature, nutrition and breathing and so on. Such as cryptobiosis and Trichodina disease is fry, fingerling stage common parasite epidemics, and with the growth of the age of the fish body, even with the presence of pathogens. It is not easy to cause disease occurrence; Jiujiang Bothriocephalus acheilognathi usually not parasitic in 1 above the age of grass carp intestine, in low temperature cold northern area or in fall and winter, most microbial carbon diseases, such as hemorrhagic disease of grass carp, Bacterial Gill Rot Disease of sex, enteritis will not occur. Under the condition of hypoxia, fish are prone to disease.
The main factors that affect the immune function of non specific immunity in fish are the scale, skin and other surface barrier, and the second line of defense. Scales, skin and mucus is an important barrier for parasite invasion of the fish body resistance. Therefore, the protection of fish body surface is not damaged and without predators attack injured, pathogen could not invade, leaf spot, tail handle disease, disease and water mildew of print would not have happened. The concentration of chemical substances in the breeding water is too high, which can cause the fish to secrete a large amount of mucus, and once the excess secretion of mucus, it can not protect the role of the fish, and can not resist the invasion of pathogenic bacteria. After entering the body of the pathogen, the pathogen of the pathogen is often swallowed up by the phagocytic cells, and attracts the white blood cell to the injured site to swallow the pathogenic microorganism, which shows the inflammatory reaction. When the phagocytic cells and the phagocytic ability of white blood cells can not stop the rapid growth and reproduction of pathogenic microorganisms, the local lesions will be expanded, more than the fish body’s tolerance and lead to fish death. Therefore, health cultivation is an important measure to prevent the disease.
Specific immunity is the body of the body in the process of life to accept the foreign body to stimulate the immune system, also known as acquired immunity. According to the different ways of the different, can be divided into automatic and passive immunization. In addition to a very small number of viral and bacterial diseases can be obtained after a specific immunity, can be lifelong immunity, the vast majority of the disease’s specific immunity has a certain time limit. Such as patient Lernaea disease of silver carp and bighead carp can produce specific immunity, but not lifelong immunity of grass carp hemorrhage immune killing injections of vaccine, immunity can keep 14 months and thereafter gradually decreased. Therefore, according to the master of fish disease causes, control and improve aquaculture water environmental conditions, enhancement of fishes and aquatic economic animals body resistance is the key to the prevention and treatment of diseases of the livestock.

Analysis of fish disease pathogen

Disease of freshwater fishes in China has more than 100, and the shrimp disease, disease frog, turtle disease and aquaculture fish disease, kinds is more, the pathogens are viruses, bacteria, fungi, algae, protozoa and trematodes, nematodes, Acanthocephala, tapeworm, leeches, the Glochidia larvae, crustaceans and other. Some of these pathogens often make the fish sick, causing many diseases, common diseases,
In aquaculture water, if there is no pathogen, or at least pathogens control in the degree of damage to the extent of the following, fish and aquatic animal diseases will not occur, the pathogen is parasitic organisms, they can not survive or thrive in the environment of the outside world, and must be in the main body of the breeding. Source of infection of pathogenic diseases come from the fish, especially parasitic pathogens and not a moment in the pathogenesis of carry pathogens, pathogenic spread faster and more subtle. Some parasitic diseases infectious bird. Animals and humans, such as export trematodes, ligulosis source of infection is of European birds, herons and other birds, fish Clonorchis vampire disease to infect a source are cats, dogs and other mammals, the human body is also infected with the disease, the original Hugh reports, some fish parasites, the developmental stage of the larval stage is spent in birds, animals or humans, so bird, animal or human has become some fish parasitic disease to infect a source,
Fish pathogens discharged into the water, with water irrigation and drainage into other aquaculture water, the waters of the original pathogen becomes foci.
Contagious pathogens and the strength of the pathogen in the host settle, reproduction and discharged from the host number has a close relationship, is conducive to the parasite growth and reproduction of the environment, the infectious force will be very strong; on the contrary, the drugs to kill and ecological methods inhibition of pathogen activity make it infectious reduction or elimination of pathogens, is not conducive to the parasite growth and reproduction, fish has a chance of less.
The virulence of the pathogen is the ability of the pathogen to cause disease, and it is determined by the number of pathogens. The number of species in the living environment, the virulence of pathogenic bacteria and the strong and weak points. Larger number of pathogens in fish, fish disease symptoms of more serious, such as more than 10 Chinese) parasitic in 2nd instar gill of grass carp, grass carp and no significant response to the disease; and when hundreds of parasites in strontium grass carp, it will cause the gill filaments to inflammation of the end, pale and swollen, bending deformation, anemia, sick fish irritability, but also in wound bacterial infection, concurrent disease caused by bacteria, serious will cause mass mortality of grass carp.
The pathogen is the result of a prerequisite for the occurrence of fish diseases. Cut off pathogens in aquaculture water route of infection, or according to the characteristics of pathogen infectivity and pathogenicity, targeted for ecological control, drug prevention and immune prevention, reduce fish, its control below the extent of damage, in order to reduce economic losses.

The causes of fish diseases

Fish and aquatic animals, like all living things, need to have a living environment that is suitable for them. Fish live in the water environment, you have to have a good water environment and continuously enhance the ability to adapt to the environment, with high yield for the purpose, many of the environmental conditions of the water body is under the control of artificial. If the breeding environment has changed, is not conducive to the survival of the living, living, or the body of the body should not be adapted to the living environment, fish and aquatic animals will lose the ability to resist the invasion of pathogens, it will cause the disease.
The occurrence of fish diseases or not, is mainly determined by environmental factors, disease resistance and susceptibility to pathogens and fish etc..
Environmental factor
The environmental factors of fish diseases including natural conditions, human factors and biological factors.
1 natural conditions
(1) water aquaculture, fish are poikilotherm, changes in water temperature with the temperature elevating life change. The sharp fluctuation of water temperature, fish body is not easy to adapt to the pathological changes and even death. Such as fish pond, water temperature and water temperature of raw water of life is not more than 2 DEG C, species of not more than 4 DEG C. The temperature difference is too large, it will lead to a large number of dead fish fry, put the fish, that is, the main reason for low survival. All kinds of pathogens in the appropriate temperature of water will also be a large number of breeding, leading to fish sick.
(2) the water quality of aquaculture water, fish can not do without water, better water quality environment is more conducive to the growth of fish. The changes of water quality according to the determination of pH value, dissolved oxygen, organic oxygen consumption, fatness and transparency to determine, although fish for aquaculture water pH value have great adaptation range, but at pH value 7 to 8.5 appropriate, if below pH 5 and pH value is higher than the 9.5, the lighter the fish growth bad, the person that weigh fish deaths caused by. As addicted to dinoflagellates “caused by acid egg powder is acidic water, disease” results. Have a direct impact on the level of dissolved oxygen content in the aquaculture of fish growth and survival, per liter of water dissolved oxygen content of less than 1 mg, the fish will “floating head”, if you do not take timely measures of Zo oxygen, will make the fish suffocate to death. When the weather is hot and the air pressure is low, the phenomenon of hypoxia is the most common. There are many harmful substances in the waste water of the environment, which can cause the fish to be deformed, or cause the bubble disease,
(3) in the bottom of the water body, the bottom sediment is the soil and the silt layer which is in contact with the water. In particular, the sludge contains a large amount of nutrients, such as organic matter and nitrogen, phosphorus, potassium, etc., through the decomposition of fine seedlings and ion exchange, and constantly dissolved and released to the water, to provide the food for the growth of nutrients. The mud has fertilizer, fertilizer preservation and regulate water quality, keep the amount of silt layer is necessary. However silt accumulation, organic oxygen consumption is too large, in the summer and autumn easily lead to fish in the hypoxic, but also make the water turns sour, thus inhibit fish growth, even endanger the fish life. Nutrient substance in the sludge is a good medium for pathogenic bacteria, and some inorganic substances can enhance the virulence of the disease. The more silt accumulation, the more likely the disease occurs. Practice has proved, in aquaculture sediment dredging, drying pond disinfection, fish incidence can be decreased. Nowadays, there are many short acting sex, in the long term is not clear silt, bring endless trouble to the sustainable development of aquaculture, occurrence of fish diseases will be very hard to detect, serious will likely crops. You often freshwater fish bacterial septicemia and the long term is not clear there is a direct relationship between silt.
Human factor
(1) the stocking density and improper polyculture imbalance
Polyculture of varieties and proportion and stocking density and fish disease have great relationship, such as per unit area in the stocking density is too large or, fish from the lower proportion of improper collocation, resulting in lack of Nai, malnutrition, weaken the resistance of fish, but also a waste of available water.
(2) aquaculture mismanagement should strictly adhere to the “four fire”, “four” technical specification for aquaculture. Artificial feeding should be according to the amount of the fish body daily need, not Zhang full, feeding are not, more can not vote feed do not clean or metamorphic bait, corruption of plants, dead stinky the snail, with parasite eggs and pathogenic vaccine bait. Otherwise, the growth rate will reduce the fish, the fish body resistance weakened, leading to disease epidemic.
(3 mechanical damage, net fishing and transportation of fingerlings can easily scratch the fish body, making it susceptible to fine seedlings, water mold etc. the causative pathogens. Such as the water is the parasitic in the injured area of the.
3, biological factors
To make fish pathogenic organisms, known as fish pathogens, by virus, small seedlings, seedlings and algae invasion caused the fish, commonly known for infectious diseases of fish; fish diseases caused by protozoa and trematodes, cestodes and nematodes, crustaceans and other parasites, known as parasitic fish disease. In addition, there are many cultured fish predators, such as a mouse, birds, snakes, frogs, ferocious fish, aquatic insects, Hydra, qingni moss, Hydrodictyon reticulatum.
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