CATDOLL : CATDOLL: How should the injection method in fish vaccination be performed?

How should the injection method in fish vaccination be performed?

Fish vaccination is the best choice for preventing diseases that are difficult to control and often cause huge losses. Vaccines for preventing bacterial diseases on the domestic and foreign markets include formalin-inactivated bacteria and oil-adjuvanted products; in addition, oral vaccines that can be mixed with bait and fed have also appeared on the foreign market. There are monovalent vaccines that only fight against one type of bacteria, and there are also multivalent vaccines that can fight against more than one type of bacteria.

So here's the specific method.

Injection vaccination: When the fish are large enough (average weight of 50 g/tail or more), intraperitoneal injection can be used for vaccination. If the immersion method is used at this time, the number of fish isolated by tarpaulin is small due to the large size of the fish. When anesthetizing, the larger the fish, the greater the risk of self-injury due to stress reaction, so extra caution is required. Subsequently, a small group of fish is scooped out with a net and placed in a container with a higher concentration of anesthetic dilution until the fish are still. When operating on the vaccination table, the fish's head is facing outward and the fish's belly is facing up, and the vaccine (usually 0.1-0.2 ml) is injected into the fish's abdomen. The needle penetrates the abdominal cavity about 0.5 cm. A fully automatic syringe can be used. After the injection, the fish is placed in a temporary holding tank and will recover from the anesthesia after a few minutes.

Immersion vaccination: For this method of vaccination, a large group of fish is separated from the rest of the cage by a tarpaulin and a small amount of diluted anaesthetic is added to tranquilize the fish. Air or oxygen is pumped in continuously during this period to prevent hypoxia. The appropriate dose of vaccine is calculated based on the estimated weight of the fish to be vaccinated (usually 1 litre of vaccine is required for every 100 kg of fish). The vaccine is diluted in seawater or freshwater in a suitable container (a common dilution ratio is 1:10, i.e. 1 litre of vaccine to 9 litres of water). Oxygen may be slowly introduced into the vaccine diluent to reduce stress on the fish. The sedated fish are removed from the tarpaulin, approximately 0.5 kg at a time, to avoid overcrowding or crushing. The water is drained and the fish are placed in the vaccine diluent for a period of time, usually at least 30 seconds. The routine procedure is to place the fish removed from the tarpaulin in a perforated plastic bowl in the vaccine diluent and, at the end of the soaking period, the fish are removed from the vaccine solution and placed in a holding facility.

Finally, let me talk about some precautions

In order to keep the stomach and intestine almost empty during inoculation, the fish should be fasted before inoculation. The smaller the fish and the higher the water temperature, the shorter the fasting time required. Fasted fish have poor tolerance to stimulation caused by handling and are sensitive to anesthetics;

Vaccination is only suitable for healthy fish that have not been subjected to any stimulation. It should not be performed when the fish is sick or has recently been severely handled or subjected to other environmental stimulation.

During immersion inoculation, the temperature difference between the vaccine diluent and the aquaculture water should not exceed 2;

Vaccination must be carried out in a disease-free environment, and the fish can be exposed to the disease or transferred to a disease-prone pool about 2 weeks after vaccination when the water temperature is 15 degrees Celsius. The higher the water temperature, the shorter the time required to produce immunity.