How to prevent and treat hemorrhagic disease in black carp farming

I. Prevention

1. Blocking pathogens

① Seed source: cultivate healthy older fry to improve disease resistance of the fry. Establish a quarantine mechanism for broodstock and fry.

② Water source: require fresh, pollution-free water and set up pre-treatment facilities for incoming water. In addition, separate the inlet and drainage systems to reduce the chance of cross-infection.

③ Feed source: in addition to not feeding spoiled bait, bait disinfection measures should also be taken to prevent disease from entering through the mouth.

2. Improving the environment

① Thoroughly remove silt and disinfect: in order to eliminate infection sources, in addition to thoroughly removing silt, the pond should also be strictly disinfected. Methods such as sun exposure, plowing, and splashing quicklime and bleaching powder can be used.

② Appropriate mixed culture and rotational culture: this can fully utilize the pond's bait base, improve the water quality environment, and reduce the relative density of black carp. Rotational culture of different species can also reduce the environmental pressure caused by continuous farming of a single species.

③ Control farming density: high density causes stress responses in farmed organisms, leading to reduced immunity and increasing the chance of mutual infection. It is recommended that the mixed culture density be 50-150 fish/mu, which is more suitable.

④ Strengthen operational management: during farming, in addition to strengthening disinfection measures in each operating procedure, the misuse of antibiotics must also be explicitly prohibited, so as to maintain the ecological balance of the microbial population in the water and improve the disease resistance of black carp.

⑤ Strengthen water quality monitoring: regularly test whether the content of harmful physicochemical factors such as hydrogen sulfide, nitrite ions, toxic ammonia, and heavy metal ions in the water exceeds standards. In addition, strictly prevent wastewater from industrial and mining enterprises from being discharged into ponds.

3. Drug prevention

Use chemical drugs or Chinese herbal medicines, adopting the method of external disinfection and internal administration for prevention. Generally, disinfect the water body 1-2 times per month and administer medicated bait internally for 3-5 days. But pay attention to the dosage and course of treatment, otherwise drug-resistant pathogens may appear, making treatment more difficult. In addition, ecological prevention can also be adopted, such as applying biological preparations like photosynthetic bacteria (PSB) and EM preparations.

4. Immune prevention

Using vaccines to immunize against black carp hemorrhagic disease is a development direction. Before entering the pond, broodstock or fry are injected or soaked with immune vaccine so that the fry have better immune capacity. This is especially important under high-density specialized farming or black carp-dominated models.

II. Treatment

Use TCCA granules or powder and other bactericidal and disinfecting drugs, adopt heavy-handed methods (that is, appropriately exceed the dosage concentration), use continuously 3-4 times, and at the same time combine with drugs such as virazole mixed with bait for feeding, with a course of treatment of 6-8 days. Generally, it can be effectively controlled.