Selection of fishery drugs

Farmers should select fishery drugs or feed drug additives according to the pathogens and instructions of fishery drugs, and the selected drug feed additives should comply with the provisions of the regulations on the Administration of Feed and Feed Additives (Annex 2). Drugs or additives prohibited by the state (Annex 3) shall not be selected, and feed with antibiotics shall not be stored for a long time.

Before the selection of fishery drugs, we should first diagnose the disease, and then accurately select the fishery drugs from the aspects of drugs, pathogens, environment, farmed animals themselves and human health.

The following procedures should be followed in the diagnosis of aquatic animal diseases:

(1) sampling

The main results are as follows: 1. Diseased aquatic animals choose individuals who are sick but have not yet died or have just died, and the symptoms are relatively typical, and not less than 3; samples should be preserved for diseases that can not be diagnosed immediately. All or part of the organs, tissues or pathogens of diseased animals can be fixed and preserved with fixatives and preservatives for further diagnosis.

2. The diseased aquaculture water samples were taken while the diseased aquatic animals were sampled, and analyzed immediately.

(2) observation and investigation

1. Species, sources, specifications, quality status and stocking density of culture.

2. The types, quality, dosage and methods of disinfectants in breeding facilities and utensils before stocking.

3. The type and source of feed, the method of feeding, the amount of feeding and the clearance of residual bait.

4. The feeding and management of aquatic animals.

5. Relevant environmental factors, such as water source, water quality, water temperature, sediment, application of pesticides in farmland around the culture surface, etc.

6. To observe the activities of similar and heterogeneous aquaculture animals in diseased and non-diseased aquaculture facilities, such as swimming, feeding, roosting and so on.

7. the incidence and the prevention and control measures that have been taken, including the time of onset, disease animals, disease syndrome and condition, death, measures taken, etc.

8. The area, structure, soil quality, water depth, water color, transparency, inlet and drainage system and the presence or absence of bubbles of the breeding facilities.

(3) pathogen identification

1. Visual inspection

(1) to observe the color changes of diseased aquaculture animals and diseased organs (including gills), inflammation, hyperemia, hemorrhage, anemia, swelling, ulcer and other pathological changes with naked eyes. whether there is foreign body attachment and the growth stage and development degree of the diseased individual.

(2) to observe with the naked eye whether there are fungi or parasites in diseased aquaculture animals, and if parasites are found, species identification should be carried out.

2. Microscopic examination

The main results are as follows: (1) scrape the mucus of external organs such as skin, fin and Gill with tweezers, or take part of the diseased tissue and make it into a water-immersed film, then examine it with a microscope to find the pathogen and pay attention to the pathological changes of the diseased tissue.

(2) to observe whether there is parasitism of fungi or parasites, and if parasitism is found, it can be identified from the morphology of pathogens.

3. Anatomical examination

(1) visually dissect the internal organs, first observe with the naked eye whether there are changes in the color and shape of the internal organs and tissues, and whether there are pathological changes such as inflammation, hyperemia, bleeding, swelling, ulcer, atrophy and degeneration, hypertrophy and hydrops in the body cavity, and whether there are parasites and their cysts.

(2) for microscopic examination of various organs and tissues, blood is taken from the heart for microscopic examination, and then mucus in the body cavity or other organ cavities is scraped for examination. A small piece of tissue such as liver and kidney can be examined by compression method, and pay attention to whether there are pathological changes and pathogens.

4. Pathological section examination takes a small piece of diseased tissue or organ, after fixation, dehydration, embedding and other procedures, the sample is cut into very thin slices, and then stained with corresponding staining methods to show the changes of different cells and cells. then light microscope examination (electron microscope is needed for further observation).

5. The detection technology of PCR instrument and PCR instrument has been recommended by the World Organization for Animal Health as one of the diagnostic methods of shrimp virus. Viral diseases such as white spot syndrome of shrimp and other diseases of aquatic animals that have established PCR diagnostic technology can be diagnosed by this method.

6. Nucleic acid probe detection of IHHNV, HPV and other viruses there are nucleic acid probe hybridization techniques for detection.

7. Immunological techniques such as serum neutralization test, immunofluorescence and enzyme-linked immunosorbent assay can be selected.

8. Drug sensitivity test for diseases that may be caused by bacteria, the corresponding drug sensitivity test can be carried out after pathogen isolation, culture, identification, artificial infection and other tests.

(4) Diseases caused by multiple pathogens

According to the number of pathogens and the degree of harmfulness to determine the main pathogens, and then symptomatic treatment.

(5) principles of drug selection

1. Effectiveness

First of all, it depends on the therapeutic effect of a certain drug on a certain disease. Generally, the reduction of mortality after administration is the main basis for determining the curative effect. In addition, the feeding rate and weight gain rate must be compared with the control group, and the cure effect must be proved by histopathology.

2. Security

When choosing drugs, we should pay attention to both its curative effect and its adverse reactions. Although some drugs are very effective, they have to be banned because of their toxic side effects on farmed animals or potential harm to human beings.

3. Convenience

Medicine and veterinary drugs are mostly used directly by individuals, while fishery drugs are used indirectly in groups, feeding baits or putting drugs into aquaculture water for medicine bath except injection and smearing in a few cases. Therefore, easy to operate and easy to master usage and dosage is one of the requirements for the selection of fishery drugs.

4. Economy

Consider from two aspects: the economic analysis of ① clinical drug use should analyze whether the disease of farmed animals can be cured; after cure, the growth speed of farmed animals, product quality, @ # @ 136 medicine price, etc., to determine the economy of drug use. If you don't need medicine, you'd better not use medicine. ② chooses cheap and easily available drugs, aquaculture has the characteristics of wide range, dispersion and large area, and the overall drug dosage is relatively large, especially in the drug bath method, so cheap and easily available drugs should be selected under the principle of ensuring the efficacy and safety.

(6) Choice of ways of administration

1. Oral method

The oral method has the advantages of low dosage, convenient operation, no environmental pollution and so on. This method is often used to increase nutrition, recovery after illness and infection of pathogenic organisms in the body, especially bacterial enteritis and parasitic enteropathy. However, the therapeutic effect is affected by the condition and feeding ability of farmed animals, and it is not effective for individuals who are seriously ill and lose their feeding ability, and it is also difficult for filter feeding and active biological food.

2. Medicine bath method

According to the size of the water body of the medicine bath, it can be divided into sprinkling method and immersion method. According to the concentration and time of soaking, it can be divided into instant soaking method, short-time soaking method, long-time soaking method and running water soaking method. Spraying method is a method often used in disease prevention and treatment. The soaking method has the advantages of low dosage, simple operation, and can be controlled artificially. It has a good control effect on the pathogens on the body surface and Gill, and has no effect on other organisms in the culture water. In artificial reproduction production, parent fish, shrimp, shellfish and their fertilized eggs purchased from other places or caught in natural water bodies can also be disinfected by immersion method.

3. Injection method

There are two kinds of injection methods commonly used in the prevention and treatment of fish disease and spawning, that is, intramuscular injection and intraperitoneal injection. This method has incomparable advantages such as accurate dosage, fast absorption, high curative effect (drug injection) and good effect of prevention (vaccine and vaccine injection), but it is troublesome to operate and easy to damage fish. The suitable targets are those small and precious species, or parents used to reproduce. Antibiotics are used to treat bacterial diseases, vaccines and vaccines are used to prevent viral diseases or bacterial infections.

4. Smear method

The utility model has the advantages of less medication, safety and less side effects, but the scope of application is small. It is mainly used for the treatment of a small number of farmed animals such as fish, frog and soft-shelled turtle, as well as body surface diseases such as body injury or parent fish after operation and long-distance transportation. Suitable for skin ulcers and other local infections or injuries.

5. Suspension method

Used in the prevention or mild occasions before the epidemic season, it has the advantages of low dosage, low cost, simplicity and less toxic and side effects, but it does not kill pathogens thoroughly, only when fish and shrimp swim to the hanging bag food ground for food and activities. it's possible to play a role. At present, the commonly used suspension drugs are chlorine disinfectant, copper sulfate, trichlorfon and so on.