How to treat the mycosis of river crab

How to treat the mycosis of river crab

Pathogen: the pathogen of fungal disease of river crab is off-pot fungus. The mycelium of the strain is very long, irregular cross-branched, generally unseparated, curved, with a diameter of 8-40 microns. The hyphae absorb the nutrition of river crab larvae, grow and develop rapidly, and soon fill the host, no matter in the head, chest and abdomen, just like pine leaves and poplar roots. The color of the hyphae in the larvae of river crabs is constantly changing, showing black, green, green, gray, orange and other colors, and the hyphae near the surface of the larvae form cryptotheca.

Symptoms: fungi are generally more resistant to physical and chemical factors than bacteria, can tolerate a wide range of temperature, salinity and pH value, and can grow in the range of 0.7% sodium chloride and pH 5-11. The infected larvae had large head and small tail, black body, reduced food intake and reduced activity. The strain spreads so fast that 1% of the larvae may be parasitic on the first day, 100% of all the larvae are infected 2-3 days later, and all the serious ones die.

Epidemic situation: according to the investigation, at present, the disease has become the main disease in the artificial reproduction of river crabs in China, from Liaoning in the north to Hainan Island in the south, and from coastal to inland, most of the artificial breeding farms of river crabs have occurred. From the eggs of river crab embryos-larvae-crabs-adult crabs-parent crabs, fungi are parasitic, especially posing a great threat to larvae and young crabs. The general survival rate is only 5% and 6%. If the crab seedlings are soaked in drugs and then recultivate the young crabs, the survival rate can be increased by 1 to 3 times.

Prevention and control methods: at present, there is no effective way to kill the fungal pathogen, but the route of transmission and parasitic site have been mastered. Therefore, we should first try to cut off the route of transmission, it is appropriate to start from the parent crab, all river crab artificial breeding farm, should choose no off-pot bacteria parasitic adult crab as parent crab, in the parent crab to promote prenatal disinfection.