What are the prevention and control methods for tremor disease in river crabs?
Prevention and control methods for tremor disease in river crabs
Prevention and control methods for tremor disease in river crabs
The plague disease of river crabs, also known as "tremor disease", "scratching disease" or "shaking disease". The diseased crab's pereopods become spasmodic and it cannot crawl; after being stimulated by light or sound, the pereopods tremble, the tip of the abdomen curls inward, and the bubbles it expels are first yellow-green, then turn brown-black. The incubation period of this disease can be as long as over one year, with sudden onset and a mortality rate above 70%; from juvenile crab culture to adult crab stage, it can occur from late April to the end of October every year. Once the disease breaks out, water disinfection and antibiotic treatment have no effect at all. According to research by scientists, the pathogenic agent of river crab tremor disease is a "spherical virus", which mainly damages the liver, spleen and stomach of river crabs.
The main routes of transmission of the river crab plague virus are contact infection or consumption of the carcasses of diseased shrimp and crabs carrying the virus. After virus-carrying juvenile crabs enter the pond, whether the disease breaks out is closely related to factors such as the ecological environment, scientific management and feed feeding. After more than three years of investigation, research and scientific experiments, the author proposes the following four prevention and control measures:
1. Strengthen disinfection, emphasizing the word "clean"
Doing a good job of pond clearing and disinfection can greatly reduce the incidence of common diseases and plague disease in river crabs. Bleaching powder can be used as the disinfectant, 15-20 kg per 667 sq m; when clearing the pond, not only should silt and weeds be removed, but overwintering button crabs in ponds where plague disease occurred the previous year should also be removed to prevent another outbreak of crab disease. The pond clearing time should not be too late; make the most of winter and spring drying and freezing of the pond, and carry out pond clearing and disinfection.
2. Plant aquatic plants to change the ecological environment
There should be submerged plants in the water, mainly Vallisneria and Hydrilla verticillata; there should be floating plants on the water surface, mainly water peanut and water spinach; tall-stemmed plants should also be planted at the pond edge, mainly wild rice stem. Aquatic plants can provide habitat for river crabs, give full play to the role of the water body, and appropriately increase stocking density; they can provide shelter for river crabs and improve the survival rate of river crabs and freshwater shrimp during molting; they can provide natural high-quality plant feed for river crabs; aquatic plants also provide shade for river crabs, and in the hot summer can regulate and lower water temperature; aquatic plants can also absorb inorganic salts, organic matter, ammonia and so on dissolved in the water to purify water quality; and submerged plants, during photosynthesis, can continuously release oxygen into the water, keeping dissolved oxygen in a saturated state. With aquatic plants in the pond, river crabs' constitution can be strengthened, their immunity improved, and the disease incidence reduced; river crabs grow fast, are large in size, taste fresh and fetch a high price.
3. Semi-closed culture, with moderate water fertilization for cultivation
During the epidemic of river crab plague disease, the incidence in river crabs raised by semi-closed culture with moderate water fertilization is far lower than that in river crabs raised in lean water. This is because the large amount of plankton cultivated in moderately fertilized water can engulf virus cells, and by using the ecological balance among microorganisms, the density of virus cells in the pond is reduced, lowering the chance of river crabs being infected by the virus. In semi-closed culture, water is not changed under normal circumstances, and fermented and disinfected organic fertilizer and monocalcium phosphate can be used to fertilize the water. If the water is too fertile, an appropriate amount of limewater can be splashed to adjust it.
4. Focusing on traditional Chinese medicine, comprehensive prevention and control of river crab plague and pox disease
Once river crab plague disease occurs, the efficacy of Western medicine is very unclear. Based on the treatment theories of traditional Chinese medicine and the principles of Chinese herbal compatibility, the author successively selected 10 formulas and conducted trials over two years, adopting the treatment methods of clearing toxins and purging toxins, and applying medication targeting the liver, spleen and stomach of river crabs, achieving relatively good results. Through observation and analysis, the author believes that the onset of river crab plague disease can be divided into three stages: Stage one, the symptoms of diseased crabs are climbing on water peanut or in shallow water, with the eight legs propped up, the abdomen lifted, and "cooling off" on the rack; at this time the river crab still feeds normally and is strong and active, which is the best period for treatment. Diseased crabs in stage two also show no special changes, except that when picked up by hand, the diseased crab spits out yellow or brown-black water; at this point it is already difficult to treat. Stage three is when the thoracic appendages are stiff and bent, unable to crawl, and tremble from time to time; this cannot be treated. If there are already diseased crabs in the pond that have reached stage three, then medication at this time can only save the stage-one and a few stage-two diseased crabs in the same pond.
Prevention and control of river crab plague disease should adhere to the principles of "prevention first" and "prevention is more important than treatment". Before river crabs become diseased, using medication to clear and purge the virus from their bodies can protect river crabs from the harm of plague disease. Because in ponds where river crab plague disease occurs, bacterial intestinal infection is generally also present concurrently, so while using traditional Chinese medicine, an appropriate amount of oxytetracycline, furazolidone, garlic paste, etc. should be added for comprehensive treatment, giving a better effect.
The plague disease of river crabs, also known as "tremor disease", "scratching disease" or "shaking disease". The diseased crab's pereopods become spasmodic and it cannot crawl; after being stimulated by light or sound, the pereopods tremble, the tip of the abdomen curls inward, and the bubbles it expels are first yellow-green, then turn brown-black. The incubation period of this disease can be as long as over one year, with sudden onset and a mortality rate above 70%; from juvenile crab culture to adult crab stage, it can occur from late April to the end of October every year. Once the disease breaks out, water disinfection and antibiotic treatment have no effect at all. According to research by scientists, the pathogenic agent of river crab tremor disease is a "spherical virus", which mainly damages the liver, spleen and stomach of river crabs.
The main routes of transmission of the river crab plague virus are contact infection or consumption of the carcasses of diseased shrimp and crabs carrying the virus. After virus-carrying juvenile crabs enter the pond, whether the disease breaks out is closely related to factors such as the ecological environment, scientific management and feed feeding. After more than three years of investigation, research and scientific experiments, the author proposes the following four prevention and control measures:
1. Strengthen disinfection, emphasizing the word "clean"
Doing a good job of pond clearing and disinfection can greatly reduce the incidence of common diseases and plague disease in river crabs. Bleaching powder can be used as the disinfectant, 15-20 kg per 667 sq m; when clearing the pond, not only should silt and weeds be removed, but overwintering button crabs in ponds where plague disease occurred the previous year should also be removed to prevent another outbreak of crab disease. The pond clearing time should not be too late; make the most of winter and spring drying and freezing of the pond, and carry out pond clearing and disinfection.
2. Plant aquatic plants to change the ecological environment
There should be submerged plants in the water, mainly Vallisneria and Hydrilla verticillata; there should be floating plants on the water surface, mainly water peanut and water spinach; tall-stemmed plants should also be planted at the pond edge, mainly wild rice stem. Aquatic plants can provide habitat for river crabs, give full play to the role of the water body, and appropriately increase stocking density; they can provide shelter for river crabs and improve the survival rate of river crabs and freshwater shrimp during molting; they can provide natural high-quality plant feed for river crabs; aquatic plants also provide shade for river crabs, and in the hot summer can regulate and lower water temperature; aquatic plants can also absorb inorganic salts, organic matter, ammonia and so on dissolved in the water to purify water quality; and submerged plants, during photosynthesis, can continuously release oxygen into the water, keeping dissolved oxygen in a saturated state. With aquatic plants in the pond, river crabs' constitution can be strengthened, their immunity improved, and the disease incidence reduced; river crabs grow fast, are large in size, taste fresh and fetch a high price.
3. Semi-closed culture, with moderate water fertilization for cultivation
During the epidemic of river crab plague disease, the incidence in river crabs raised by semi-closed culture with moderate water fertilization is far lower than that in river crabs raised in lean water. This is because the large amount of plankton cultivated in moderately fertilized water can engulf virus cells, and by using the ecological balance among microorganisms, the density of virus cells in the pond is reduced, lowering the chance of river crabs being infected by the virus. In semi-closed culture, water is not changed under normal circumstances, and fermented and disinfected organic fertilizer and monocalcium phosphate can be used to fertilize the water. If the water is too fertile, an appropriate amount of limewater can be splashed to adjust it.
4. Focusing on traditional Chinese medicine, comprehensive prevention and control of river crab plague and pox disease
Once river crab plague disease occurs, the efficacy of Western medicine is very unclear. Based on the treatment theories of traditional Chinese medicine and the principles of Chinese herbal compatibility, the author successively selected 10 formulas and conducted trials over two years, adopting the treatment methods of clearing toxins and purging toxins, and applying medication targeting the liver, spleen and stomach of river crabs, achieving relatively good results. Through observation and analysis, the author believes that the onset of river crab plague disease can be divided into three stages: Stage one, the symptoms of diseased crabs are climbing on water peanut or in shallow water, with the eight legs propped up, the abdomen lifted, and "cooling off" on the rack; at this time the river crab still feeds normally and is strong and active, which is the best period for treatment. Diseased crabs in stage two also show no special changes, except that when picked up by hand, the diseased crab spits out yellow or brown-black water; at this point it is already difficult to treat. Stage three is when the thoracic appendages are stiff and bent, unable to crawl, and tremble from time to time; this cannot be treated. If there are already diseased crabs in the pond that have reached stage three, then medication at this time can only save the stage-one and a few stage-two diseased crabs in the same pond.
Prevention and control of river crab plague disease should adhere to the principles of "prevention first" and "prevention is more important than treatment". Before river crabs become diseased, using medication to clear and purge the virus from their bodies can protect river crabs from the harm of plague disease. Because in ponds where river crab plague disease occurs, bacterial intestinal infection is generally also present concurrently, so while using traditional Chinese medicine, an appropriate amount of oxytetracycline, furazolidone, garlic paste, etc. should be added for comprehensive treatment, giving a better effect.