Freshwater fish fulminant hemorrhagic disease, also known as bacterial sepsis, is one of the most serious infectious diseases affecting farmed fish. The disease has an acute onset, many species of fish, a large age range, a wide epidemic area, a long epidemic season, and a high mortality rate, which is likely to cause serious losses to the freshwater aquaculture industry.

1. Etiology and epidemic characteristics

According to research and reports, the main pathogens of the disease are Aeromonas hydrophila, Aeromonas solutes, Yersinia ruckeri and so on. The main harmed fish are conventional freshwater fish such as crucian carp, silver carp, bighead carp, common carp, and grass carp. Both fingerlings and adult fish can be infected, and both ponds and reservoirs occur. Among them, July-August is the peak period of incidence. The incidence of water temperature is the highest at 25℃-30℃; the mortality rate can reach more than 80%, even 100%, and the harm is extremely serious.

The main clinical symptoms

Different degrees of hemorrhage or congestion in various organs and tissues of the fish. During acute infection, the mouth, head, orbit, gill cover, base of fin rays and both sides of the fish body are slightly congested. Congestion and redness of the mandible, redness and swelling of the anus, and enlargement of the abdomen. Anatomy showed that part or all of the intestinal tract was congested and red, vacuolated, with little food, mild inflammation or effusion in the intestinal tract, and yellow transparent or red cloudy ascites in the abdominal cavity. The liver, spleen, and kidneys are enlarged, and the liver tissue is fragile and mushy, or pink and edematous; the spleen is purple-black, and the gallbladder is enlarged, sometimes brown. Most of the sick fish do not eat food, stay still in the pool or swim madly in paroxysmal, and finally die of exhaustion.

Three, disease control methods

For the treatment of diseased fish, a comprehensive treatment method combining internal and external should be carried out.

1. Microscopic examination of the gills, if there are parasites, the parasites should be killed first.

2. Disinfect the water body and apply the blood twice for external use, once a day.

3. Use oral fungicides, enrofloxacin powder + Sanhuang powder + polyphosphate VC (or aquatic electrolysis multi-dimensional) for 5-7 consecutive days.

4. After 3-4 days after disinfection, the whole pool is sprinkled with EM original dew, Bacillus and other beneficial microorganism preparations or bio-organic fertilizers, which is conducive to maintaining the advantages of beneficial bacteria and inhibiting the growth of harmful bacteria.