Diagnosis and treatment of grass carp disease

Grass carp (Ctenopharyngodon idellus) is one of the four major freshwater farmed fish in China. Because of its rapid growth and a wide range of feed sources, grass carp is the main freshwater fish culture object in China. If not managed properly, it may get sick. So, how to diagnose and treat grass carp disease?

Grass carp disease mainly includes bacterial complications, viral hemorrhagic disease and hepatobiliary syndrome. After the onset of these three diseases, a large number of grass carp will die. Therefore, it is of great significance to understand the symptoms and take timely prevention and treatment measures.

1. Bacterial complications

Diagnosis: the symptoms of fish suffering from this disease include red skin, rotten gills and enteritis. The diseased fish have black body color, black head, wandering alone, slow response, abdominal enlargement, erythema on both sides, obvious "fin decay", protruding redness and swelling of the anus, purplish red, light pressure on the abdomen, yellow mucus and blood pus. Open the abdomen, you can see peritoneal effusion, intestinal wall congestion and inflammation, especially the hindgut, intestinal mucosal cells often fester and fall off, and mixed with blood to form blood stains, filling in the intestines; the liver often has red spots and congestion. Gill filaments of diseased fish are punctate hyperemia, end decay, cartilage exposure, resulting in whitening of the edges, mucus and silt on the Gill filaments, hyperemia, inflammation and decay of the operculum epidermis in severe cases, and the middle part is often burned into a round transparent window, commonly known as "open skylight"; local inflammation on the body surface, scales loose and falling off, obvious on both sides of the abdomen, fin base hyperemia, end decay, scale exfoliation or fin decay often have water mold parasitism.

Treatment: thoroughly clear the pond and disinfect the pond, carry out "Sixiao" and "Siding", mix and feed 100 g allicin for 7 days for every 40 kg feed, and enrofloxacin 100 g for 3-5 days for every 40 kg feed, doubling the dosage on the first day.

2. Viral hemorrhagic disease

Diagnosis: in the early stage of the disease, the mouth, abdomen, operculum, orbit, fin and both sides of the fish showed mild hyperemia. When the abdominal cavity was opened, a small amount of food was still found in the intestines. With the development of the disease, the above body surface congestion intensified, flesh and bone showed bleeding symptoms, orbital congestion, exophthalmos, abdominal swelling, redness and swelling. Open abdominal cavity, due to damage to internal organs, resulting in the accumulation of yellow or red ascites, liver, spleen, kidney swelling, intestinal wall congestion, inflation and no food. Gill gray shows anemia, sometimes purple and swollen, and in severe cases, the ends of the Gill filaments rot.

Treatment: thoroughly clear the pond and disinfect the pond, carry out "Sixiao" and "Siding"; take 10% enrofloxacin 100g + Sanhuang powder 200g and feed 40kg for 5 days.

3. Hepatobiliary syndrome

Diagnosis: in the early stage of the disease, the diseased fish drifted by the pond, slow to respond, reduced food intake, no obvious symptoms on the visual body surface, only a small number of fish had red eyeballs and orbits, Gill filaments swollen, and there were no parasites in microscopic examination. Anatomy showed that there was no food in the intestine, the liver was swollen, white, green or yellow, and the severe liver adhered to the intestinal mucosa and fat and filled the chest, sometimes the gallbladder swelled and blackened, sometimes the gallbladder became absent, and the ascites was severe.

Treatment: 40kg was mixed with 100g Gandanning and 100g allicin to make bait for 5 days.

After grass carp get sick, in addition to treatment, we should also pay attention to prevention, such as soaking and disinfecting the fish with 3% salt water before stocking, regularly sprinkling the whole pool with disinfectants such as 0.2ppm chlorine dioxide or 0.3ppm bromochlorine hydantoin or 0.4ppm strong chlorine, pay attention to reasonable stocking density, do not feed rotten and deteriorated feed, do not directly apply unissued animal feces, often inject new water or use biological agents to improve water quality. Regular removal of feed residue, regular vaccination and so on.