Diagnosis and treatment methods for bacterial and viral diseases in fish
Grass carp viral hemorrhagic disease
Pathogen: Grass carp hemorrhagic disease virus, belonging to the family Reoviridae.
Symptoms: This is a viral fish disease. The fish body surface is generally dark with a slight reddish tint, with hemorrhage under the skin and in the muscles, congestion in the oral cavity, lower jaw, top of the head, or around the eyes, and even exophthalmos (bulging eyes), congestion at the base of the gill cover and fins.
Prevention and treatment methods: For bacterial hemorrhagic disease: you can use "Junker + VK3 powder + Sanhuang powder mixed into feed for oral administration," with external application of Jiniodine; for viral hemorrhagic disease: you can use "rifampicin (rifampicin) + virus killer," with external application of chlorine dioxide for water disinfection.
The above two formulas have very good efficacy in treating grass carp hemorrhagic disease. The treatment effect is more pronounced in ponds without automatic feeders than in those with automatic feeders. For ponds with automatic feeders, it is best to also feed a small amount of medicated bait at the downwind area, so that those fish that are slightly more severely affected and unable to compete for food can recover, reducing mortality at the fastest rate.
Bacterial gill rot disease
Pathogen: Cytophaga columnaris (formerly known as Flexibacter columnaris).
Symptoms: The diseased fish has a dark body color, especially pronounced on the head, which is why this disease is also called "black head plague." The diseased fish swims slowly, responds sluggishly to external stimuli, has difficulty breathing, and reduced appetite; the gill filaments have muddy gray, white, or waxy yellow spots, increased mucus on the gill surface and at the tips of gill filaments, often with attached mud, swollen gill filaments, and in severe cases, defects at the tips of gill filaments; the inner epidermis at the center of the operculum (gill cover) is often eroded into round or irregular transparent small windows, hence the name "open skylight."
Epidemiology: A widely prevalent fish disease. It mainly affects grass carp and black carp, but carp, crucian carp, silver carp, bream, and bighead carp can also be affected. It can occur at both the fingerling and adult fish stages. This disease generally begins to occur when water temperature is above 15°C, and within the range of 15-30°C, the higher the water temperature, the more likely it is to break out and spread. This disease often occurs concurrently with red-skin disease and bacterial enteritis.
Prevention: Fish ponds must use fermented manure or commercial fertilizers such as Sufei Bao, Feishui Gao, etc. for fertilizing and cultivating water. Use Junker at 200-250 g per mu·m, soaked in hot water for more than half an hour, and splash over the entire pond.
Treatment: Rifampicin (rifampicin) at 0.1-0.2 ppm splashed over the entire pond; Sanhuang powder mixed into feed for oral administration, twice daily for 3-5 consecutive days; Quansusha, Zhongren Jiniodine, chlorine dioxide, and the Chinese herbal disinfectant preparation "Shuanghuang Jinghua" and other series of disinfectants for water disinfection.
Enteritis disease
Pathogen: Aeromonas punctata.
Symptoms: Red and swollen anus; in severe cases, pressing the abdomen lightly causes blood or yellow mucus to flow from the anus; the intestine is partially or completely inflamed, appearing purplish-red. In the early stage, the foregut and hindgut are congested and reddened; in severe cases, the entire intestine is congested, inflamed, and hemorrhagic, forming septicemia. The diseased fish has a swollen abdomen, a red and protruding anus, sometimes yellow mucus can be squeezed out, a fecal mass trails behind the anus, and sometimes there is fluid accumulation in the abdominal cavity.
Treatment methods: Splash Zhongren Jiniodine or chlorine dioxide over the entire pond at 1 mu of water surface, for 2-3 consecutive days; use rifampicin (rifampicin) 2 g + VC 2 g + Kaiwei Yingjiling 2 g per kg of feed + Sanhuang powder, administered continuously for 3-5 days to cure. After fish deaths stop, administer medicated bait once daily for 1 week, otherwise the disease may relapse.
Red-skin disease (also known as hemorrhagic putrefactive disease)
Pathogen: Pseudomonas fluorescens.
Epidemiology: When the fish body surface is intact, the pathogen cannot invade the fish skin; only when the fish is damaged due to fishing, transportation, stocking, mechanical injury, frostbite, or parasite infestation on the body surface can the pathogen take advantage and cause disease. Grass carp, black carp, carp, crucian carp, blunt snout bream, and many other freshwater fish can contract this disease. In fish farming regions across China, it is prevalent year-round, especially most prone to outbreak and spread after fishing and transportation.
Symptoms: The body surface of the diseased fish is hemorrhagic and inflamed, with scales falling off, most noticeable on both sides and the abdomen; the base of the fins or the entire fins are congested, the fin tips rot, often losing a section, and the soft tissue between fin rays is often destroyed, making the fin rays appear broom-like, called "worm-eaten fins"; secondary saprolegniasis infection often occurs at the lesions on the body surface.
Treatment methods: External splashing of chlorine dioxide at 100 g per mu·m; oral administration of Junker + Shuanghuang Jinghua mixed into feed for 5-7 days; splash Quansusha or Shuanghuang Jinghua over the entire pond, or splash Zhongren Jiniodine at 125 ml per mu·m over the entire pond for 3 consecutive days. Using the above three methods in combination, the cure rate can reach over 90%; rifampicin (rifampicin) 2 g + VC 2 g + Kaiwei Yingjiling 2 g per kg of feed + Sanhuang powder, administered for 3-5 days to cure. After fish deaths stop, administer medicated bait once daily for 1 week, otherwise the disease may relapse.
Bacterial septicemia (explosive hemorrhagic disease)
Pathogen: Aeromonas, Vibrio.
Epidemic season: From late February to November, with the most severe outbreaks occurring at water temperatures around 28°C. The freshwater fish affected include crucian carp, bream, silver carp, bighead carp, carp, grass carp, etc. The infection rate is over 60%, and the mortality rate is 10%-80%.
Main symptoms: In the early stage of the disease, the affected fish mainly shows mild congestion in the oral cavity, abdomen, operculum, orbit, fins, and both sides of the body. As the disease progresses, the congestion on the body surface intensifies, hemorrhage appears in the flesh, congestion around the orbit, exophthalmos, and abdominal swelling and redness. The gill filaments appear grayish-white indicating anemia, and in severe cases the tips of the gill filaments rot. Upon opening the abdominal cavity, yellow or red ascites accumulates inside, the liver, spleen, and kidneys are swollen, and the intestinal wall is congested, gas-filled, and contains no food.
Treatment methods: Splash Shuanghuang Jinghua at 200 ml or chlorine dioxide at 150 g per mu of water surface over the entire pond; splash Quansusha or Zhongren Jiniodine over the entire pond at a dosage of 250 ml per mu·m for 3 consecutive days; oral administration of Junker + rifampicin (rifampicin) + VK3 powder + Sanhuang powder mixed into feed for 5-7 days to cure.
White head and white mouth disease
Pathogen: A type of Myxococcus.
Symptoms: The skin from the tip of the snout to the front of the eyes of the diseased fish appears milky white. The lips appear swollen, and the mouth opens and closes inflexibly, causing difficulty in breathing. The skin around the mouth ring rots, with slight flocculent material adhering to it, so when observing diseased fish swimming at the water surface from the edge of the tank, the "white head and white mouth" symptoms can be clearly seen. The diseased fish is thin and dark, reacts sluggishly, floats weakly, often stays at the pond edge, and soon dies.
Treatment methods: Splash chlorine dioxide at 150 g or Zhongren Jiniodine at 150 ml per mu of water surface over the entire pond for 2-3 consecutive days; use rifampicin (rifampicin) 2 g + VC 2 g + Kaiwei Yingjiling 2 g per kg of feed + Sanhuang powder, administered for 3-5 days to cure. After fish deaths stop, administer medicated bait once daily for 1 week, otherwise the disease may relapse.
White skin disease
Pathogen: Pseudomonas dermoalba.
Symptoms: At the onset of the disease, the end of the caudal fin appears somewhat white, and as the disease progresses, it rapidly spreads to the rear half of the fish trunk, with the affected area turning white, hence also called white tail disease. In severe cases, the caudal fin of the diseased fish rots off or becomes incomplete, and soon the fish turns head-down, tail-up, struggles swimming in the water, and soon dies.
Epidemiology: This disease is highly contagious, with peak prevalence in June-July. Due to careless handling during routine operations, the fish body is injured, and the pathogen takes the opportunity to invade, causing the disease to spread. The general mortality rate is about 30%, with the highest mortality rate reaching over 45%. The disease course is relatively short, taking only 2-3 days from onset to death, posing a significant threat to fish.
Treatment methods: Splash chlorine dioxide at 150 g or Zhongren Jiniodine at 150 ml per mu of water surface over the entire pond for 2-3 consecutive days.
Stamp disease
Pathogen: Aeromonas punctata.
Symptoms: The lesions mainly occur on the trunk portion behind the dorsal and anal fins, followed by both sides of the abdomen, and occasionally on the front part of the fish body. The affected area first shows circular red spots, resembling a red stamp pressed onto the fish skin, then the epidermis rots, scales in the middle area fall off, the rotting epidermis also breaks down and falls off, exposing the white dermis. The scales around the lesion area are embedded in the rotting epidermis, and the outer scales are loose and congested with inflammation, forming a distinct outline. In the middle and late stages of the disease course, a pot-bottom shape forms, and in severe cases even the muscles rot, exposing bones and internal organs, and the diseased fish soon dies.
Treatment methods: Use chlorine dioxide at 150 g per mu·m, splashing for 2-3 consecutive times to cure; use rifampicin (rifampicin) 2 g + VC 2 g + Kaiwei Yingjiling 2 g per kg of feed + Sanhuang powder, administered for 3-5 days to cure. After fish deaths stop, administer medicated bait once daily for 1 week, otherwise the disease may relapse.
Branchiomycosis (gill mold disease)
Pathogen: Branchiomyces, belonging to the mold category.
Symptoms and diagnosis: The diseased fish does not feed, swims slowly, and the gills appear congested and hemorrhagic. Spores produced by the mycelium enter the water and come into contact with the fish body, attaching to the gills and developing into hyphae. The hyphae grow continuously into the tissue, branch, and penetrate the tissue in an earthworm-like manner, branching along the gill filament blood vessels or penetrating into the cartilage, destroying tissue, blocking microvessels, and causing blood flow stagnation. The gill filaments undergo gangrenous disintegration, and defects are clearly visible at the necrotic and sloughed areas.
Epidemiology and harm: The prevalence of this disease is closely related to the deterioration of pond water, especially in ponds with high organic matter content and dirty water quality, where this disease is more likely to occur.
Treatment methods: Splash formalin at 50 ml per mu·m over the entire pond, or splash chlorine dioxide at 150 g per mu·m over the entire pond, or splash Quansusha at 250 ml per mu·m over the entire pond.
Grass carp "old three diseases" (red-skin disease, gill rot disease, enteritis disease)
1. Red-skin disease symptoms: The body surface of the diseased fish shows localized or extensive hemorrhage, congestion, inflammation, and scale loss, most noticeable on both sides and the abdomen. Some or all fin rays are congested at the base, fin tips rot into a broom-like shape, and at low temperatures secondary saprolegniasis often occurs at the lesions. Red patches often appear on the operculum and the upper and lower jaws of the fish. The diseased fish often swims alone at the water surface, moving slowly. Also known as hemorrhagic putrefactive disease, commonly called "red-skin plague."
Prevention and treatment methods: During fishing, transportation, stocking, and other operations, prevent fish injuries. Before stocking, soak in 5-10 ppm bleach solution for half an hour. Add sulfathiazole to the feed at a dosage of 5 g per 100 jin of fish weight, continuously feeding for 6 days. For external disinfection, splash bleach over the entire pond.
2. Gill rot disease symptoms: The diseased fish often swims alone, moves slowly, and has a dark body color, most pronounced on the head. Opening the operculum reveals congestion, inflammation, and ulceration of the inner epidermis of the opercular bone; the tips of the gill filaments are rotten and defective, whitish in color, with cartilage exposed at the tips of the gill filaments. In severe cases, the edges of the gill lamellae rot into a mass, with white edges carrying mud. The center of the inner surface epidermis of the operculum is eroded, showing irregular transparent small holes, commonly called "open skylight" and "black head plague."
Prevention and treatment methods: When stocking fingerlings, soak in 1:100,000 bleach solution for 30 minutes. Splash bleach over the entire pond.
Treatment: Erythromycin (poultry grade, 1 million units per gram), splash over the entire pond at 0.07 ppm on the first day; on the second day, mix the powder into bait for oral administration at 0.5 g per 100 jin of fish, halved for days 2-6; for treating enteritis and gill rot complications with Chinese gallnut and furazolidone, the method is: boil Chinese gallnut into a medicinal liquid and splash over the entire pond including the residue, making the pond water concentration 1.4-3.0 ppm, while continuously feeding furazolidone for 6 days at 0.5 mg per 100 jin per day.
3. Enteritis disease symptoms: The diseased fish has a dark body color, red and swollen anus, sluggish reactions, and a swollen abdomen with light yellow ascites accumulated in the abdominal cavity. Upon opening the intestine, the intestinal wall shows localized or complete congestion and inflammation, poor elasticity, thinning of the intestinal wall, no food in the intestine, and light yellow mucus or purulent mucus. Light pressure on the abdomen causes blood or yellow mucus to flow from the anus. In the late stage, the intestine appears red or purplish-red. Commonly called "white dew plague."
Prevention and treatment methods: Add 10-15 g of furazolidone per 100 jin of feed, make into medicated bait and feed once daily for 5-6 consecutive days.
Grass carp "new three diseases" [bacterial complications (complications of red-skin, gill rot, and enteritis)], viral hemorrhagic disease, hepatobiliary syndrome, etc.
1. Bacterial complications (complications of red-skin, gill rot, and enteritis) symptoms: The diseased fish shows symptoms of all three diseases: red-skin, gill rot, and enteritis; the body surface shows localized or extensive hemorrhage, congestion, inflammation, and scale loss, most noticeable on both sides and the abdomen, some or all fin rays are congested at the base, fin tips rot into a broom-like shape, at low temperatures secondary saprolegniasis often occurs at the lesions, and red patches often appear on the operculum and upper and lower jaws. The diseased fish often swims alone at the water surface, moving slowly;
The diseased fish often swims alone, moves slowly, and has a dark body color, most pronounced on the head. Opening the operculum reveals congestion, inflammation, and ulceration of the inner epidermis of the opercular bone; the tips of the gill filaments are rotten and defective, whitish in color, with cartilage exposed at the tips of the gill filaments. In severe cases, the edges of the gill lamellae rot into a mass, with white edges carrying mud. The center of the inner surface epidermis of the operculum is eroded, showing irregular transparent small holes, commonly called "open skylight";
The diseased fish has a dark body color, red and swollen anus, sluggish reactions, and a swollen abdomen with light yellow ascites accumulated in the abdominal cavity. Upon opening the intestine, the intestinal wall shows localized or complete congestion and inflammation, poor elasticity, thinning of the intestinal wall, no food in the intestine, and light yellow mucus or purulent mucus. Light pressure on the abdomen causes blood or yellow mucus to flow from the anus. In the late stage, the intestine appears red or purplish-red.
Prevention and treatment methods: Thoroughly clear and disinfect the pond, implement the "four disinfection" and "four fixed" principles, do not directly apply unfermented animal manure, do not feed spoiled and deteriorated feed, and soak and disinfect fingerlings in 3% salt water before stocking.
Treatment methods: Regularly splash disinfectants such as 0.2 ppm chlorine dioxide, 0.3 ppm bromochlorohydantoin, or 0.4 ppm strong chlorine essence over the entire pond; use 100 g of allicin per 40 kg of feed, mixed into feed and fed continuously for 7 days; use 100 g of enrofloxacin per 40 kg of feed, mixed into feed and fed continuously for 3-5 days, with the first day's dosage doubled.
2. Viral hemorrhagic disease symptoms: The body surface of the diseased fish is dark with a slight reddish tint, it swims alone away from the group, stops feeding. There are three types of symptoms.
a. Red muscle type: The skin and muscles of the diseased fish show obvious congestion and hemorrhage;
b. Red fin and red operculum type: The diseased fish shows congestion on the operculum, fin bases, oral cavity, upper and lower jaws, top of the head, and around the orbit, and even exophthalmos;
c. Enteritis type: The body surface of the diseased fish shows basically no symptoms, but after dissection, the intestine is congested and reddened, internal organs show punctate hemorrhage, the intestinal wall is elastic with no rot or edematous lesions;
From March to April, the external inflammatory and congestive symptoms appearing in diseased fish are: most pronounced on the head, mouth, operculum, orbit, and both sides of the body surface, below the pelvic fins and the caudal peduncle, etc. Some diseased fish show exophthalmos, gill anemia, and internal organs with varying degrees of inflammation, and sometimes gas-filled distension of the intestine can also be seen.
After May, the symptoms of diseased fish are mainly congestion and inflammation on the lower edge of the operculum, fin bases, and internal organs on the body surface, and sometimes the oral cavity and flesh also show concurrent congestion and inflammation. This disease is widely prevalent in grass carp farming, and can occur at water temperatures between 9-36°C, with the most severe outbreaks at 28°C.
Prevention and treatment methods: Inject inactivated vaccine into fingerlings for prevention; use 8-10 jin of water peanut, 0.5 jin each of garlic and salt per 100 jin of fish, grind together into a paste, mix with 3 jin of rice bran to make medicated bait and feed once daily for 5 consecutive days; at the same time, use 0.6 jin of copper sulfate per mu of water at 1 m depth, add appropriate amount of water and splash over the entire pond for 5 consecutive days; use 0.5-1 jin of rhubarb or sweetgum leaves per 10,000 fingerlings, grind into powder, decoct or soak in hot water overnight, mix with feed and feed for 5 consecutive days, apply copper sulfate at 0.7 ppm depth, or copper acetate, or copper chloride solution, applying for 2 consecutive days.
3. Hepatobiliary syndrome symptoms: In the early stage of the disease, the diseased fish floats at the pond edge, reacts sluggishly, and has reduced food intake. Visually, there are no obvious symptoms on the body surface, with only a small number of fish showing reddened eyeballs and orbits, and swollen gill filaments; microscopic examination shows no parasites; dissection reveals no food in the intestine and a swollen liver. The color is pale, the gallbladder color is darker, and the liver becomes brittle and fragile. In the middle and late stages, the liver is obviously enlarged, turning yellow and white, forming a "flower liver" and even localized or mostly turning into "green liver." In severe cases, the liver is dispersed and adheres to the intestinal mucosa and fat, filling the thoracic cavity. The gallbladder is sometimes enlarged and blackened, sometimes absent, with severe ascites.
After a period of onset, the number of dead fish surges; the causes of this disease are relatively complex. Feeding deteriorated feed, feed with excessive fat content, or long-term feeding of feed containing olaquindox, and fish pond water polluted by copper, ammonia, and other substances can all trigger liver disease.
Prevention and treatment methods: Pay attention to reasonable stocking density, do not feed spoiled and deteriorated feed, do not directly apply unfermented animal manure, frequently add fresh water or use biological agents to improve water quality, frequently remove feed residue and establish a fish feed inspection system, keep feed fresh, and prevent protein and fat oxidation in feed.
The treatment principles are detoxification, liver supplementation, liver strengthening, regulation, and reducing swelling, promoting liver cell regeneration and restoration of normal gallbladder function; at the same time, eliminating pathogenic bacteria in the body.
(1) Cultivate good water quality, prepare nutritionally rich and comprehensive high-quality feed, and feed scientifically. Avoid overfeeding, prevent protein deterioration and fat oxidation, and prevent feed from becoming damp and moldy.
(2) Do not add low doses of drugs harmful to fish liver in feed for long periods, such as furazolidone, chloramphenicol, sulfonamides, olaquindox, tetracycline antibiotics, etc. Use drugs reasonably, and minimize the use of fish drugs with high side effects and high residues, such as deltamethrin, dichlorvos, trichlorfon, copper sulfate, decis, lindane, etc. Furthermore, pesticides must never be used as substitutes for fish drugs applied to water bodies.
(3) Supplement vitamins, mainly VC, VK, and VE.
(4) Adding appropriate amounts of betaine, choline chloride, carnitine, methionine, phosphorus, etc. to feed can promote fat metabolism in fish liver, reduce fat content in the liver, and has a significant effect on preventing fatty liver formation.
(5) Chinese herbal medicine: Select Chinese herbal medicines with detoxification and liver protection, liver soothing and qi regulating, and liver cell regeneration promoting properties to formulate prescriptions for preventing and treating liver disease. The following prescription can be used as reference: Angelica sinensis, white peony root, Salvia miltiorrhiza, Curcuma aromatica, Bupleurum, Astragalus, Codonopsis, Chinese yam, Rehmannia, Alisma, Isatis root, hawthorn, licorice, etc. This prescription has effects of resisting fatty liver, detoxifying, resisting liver damage, promoting liver cell regeneration and functional recovery, and inhibiting cirrhosis development.
(6) Liver powder and feed phospholipids: Liver powder from cattle, pigs, and other animals contains multiple vitamins and liver-protecting factors. It helps promote the regeneration of damaged liver cells, detoxification, and protein synthesis. It can improve fish body symptoms and increase appetite.
Treatment methods:
a. Regularly splash disinfectants such as 0.2 ppm chlorine dioxide, 0.3 ppm bromochlorohydantoin, or 0.4 ppm strong chlorine essence over the entire pond; use Gandanning 100 g + allicin 100 g mixed into 40 kg of feed to make medicated bait, feeding continuously for 5-7 days.
b. Stop feeding for 1-2 days, oral administration: Gandan Likang powder + Jundu Kang + Sanhuang powder + Andrographis paniculata powder + polypeptide, medicated bait once each in the morning and evening, with normal feed for the other two meals, for 4 consecutive days.
c. Feed medicated bait, generally for two courses. The first course is 7 days (any one of florfenicol, doxycycline, Sulikang) + Yingjiling + allicin + multivitamins + Vk3 + Gantai mixed into bait; the second course is 7 days, Gantai + Yingjiling + Sanhuang powder mixed into bait;
d. External application of any one of Youdian, Jingdian, Quandusha, Jundusha, chlorine dioxide, bromochlorohydantoin, strong chlorine essence. In severe cases, splash once each in the morning and afternoon, at 9:00-10:00 AM and 4:00-5:00 PM, and patrol the pond. If abnormalities are found, immediately add fresh water and start aeration equipment. Repeat once every 3-5 days.
Generally, a combination of oral administration and external splashing is adopted. External splashing mainly uses disinfectants such as bleach, chlorine dioxide, bromochlorohydantoin, dibromohydantoin, etc., for 3 consecutive days; for oral administration, "Sanhuang powder" medicated bait has better effects. Use 0.6 jin of Sanhuang powder (rhubarb 50%, Phellodendron 30%, Scutellaria 20%, ground into powder and mixed evenly) per 100 jin of fish body weight, mix with flour paste and then mix into feed for feeding, for 3-5 consecutive days.