Prevention and treatment of trembling disease of river crab

Prevention and treatment of trembling disease of river crab

River crab plague, also known as "trembling disease", "scratching disease", "trembling disease". Sick crab chest foot spasm, can not crawl, after being stimulated by light or sound, chest foot tremble, abdominal tip inside the pick, spit out blisters first yellowish green, and then turn brown-black. Some of the disease has an incubation period of more than a year, with a sudden onset and a mortality rate of more than 70%. It may occur every year from young crabs to adult crabs from late April to the end of October. Once the disease occurs, water disinfection and antibiotic treatment have no effect. According to researchers, the pathogenic factor of river crab trembling disease is "globular virus", which mainly harms the liver, spleen and stomach of river crabs.

The main way of transmission of river crab plague virus is caused by contact with infected shrimp and crab carcass. The disease of young crabs with virus after entering the pond is closely related to ecological environment, scientific management, feed and other factors. After more than three years of investigation and scientific experiments, the author puts forward the following four prevention and control measures:

First, strengthen disinfection and highlight the word "Qing"

Doing a good job of clearing ponds and disinfection can greatly reduce the incidence of common diseases and plague of river crabs. The disinfectant can be bleached at 15 kg per 667 square meters. When clearing the pond, not only the silt weeds should be removed, but also the overwintering crabs in the pond where plague occurred last year should be removed to prevent crab disease from breaking out again. The time to clear the pond should not be too late. It is necessary to pay close attention to the freezing and drying of the dry pond in winter and spring and carry out pond cleaning and disinfection.

Second, plant aquatic plants and change the ecological environment

There should be submerged grass in the water, mainly bitter grass and verticillium verticillata; floating grass on the water surface, mainly water peanuts and hollow vegetables; and tall grass, mainly Zizania caduciflora, should be planted on the edge of the pool. Aquatic plants can provide habitat for river crabs, give full play to the role of water bodies and appropriately increase culture density; provide shelter for river crabs to improve the survival rate of molting of river crabs; provide natural high-quality plant bait for river crabs; aquatic plants also provide shade for river crabs, which can adjust and reduce water temperature in hot summer; aquatic plants can also absorb inorganic salts, organic matter and ammonia dissolved in water to purify water quality. During photosynthesis, submerged grass can continuously release oxygen into the water, making the dissolved oxygen in a state of saturation. With aquatic plants in the pond, it can enhance the physique of river crabs, improve their immunity and reduce the incidence of disease. river crabs grow fast, large, fresh meat and high price.

Third, semi-closed culture, moderate fertilizer and water cultivation

During the epidemic of river crab plague, the incidence of river crabs cultured in semi-closed culture and moderate fertilizer water was much lower than that of river crabs cultured in lean water. This is because a large number of plankton cultivated in moderate fertilizer and water can engulf virus cells, make use of the ecological balance among microorganisms, reduce the density of virus cells in the pond, and reduce the chance of river crabs being infected with the virus. Semi-closed culture, no special circumstances do not change water, fermented organic fertilizer and calcium dihydrogen phosphate can be used to fertilize water. If the water quality is too fat, you can sprinkle an appropriate amount of lime water to adjust.

Fourth, give priority to traditional Chinese medicine to comprehensively control river crab plague pox.

Once the plague of river crab occurs, the effect of western medicine is not obvious. According to the treatment theory of traditional Chinese medicine and the principle of compatibility of traditional Chinese medicine, the author successively selected 10 formulations for two years, and adopted the treatment techniques of detoxification and catharsis to treat the liver, spleen and stomach of river crab, and achieved good results. Through observation and analysis, the author thinks that the incidence of river crab plague can be divided into three stages: in the first stage, the symptoms of diseased crabs are crawling on water peanuts or in shallow water, eight feet are supported, abdomen is vacated, and the shed is "enjoying the cool". At this time, the feeding of river crabs is still normal and dynamic, which is the best time for treatment. There is no special change in the second stage of the diseased crab, but when caught by hand, the diseased crab spits out yellow or brown-black water, which is already difficult to treat. The third stage is that the chest limbs are stiff and curved, cannot crawl, and sometimes tremble, which is untreatable. If there are crabs suffering from the third stage of the disease in the pond, medication at this time can only save the first stage and a small number of second stage crabs in the same pond.

The prevention and control of river crab plague should adhere to the principle of "giving priority to prevention" and "prevention is more important than cure". Before the disease occurs, medicine should be used to purge the virus from the river crab, so that the river crab can avoid the harm of the plague. Because in the pond where the epidemic disease of river crab occurs, it is generally complicated with bacterial intestinal infection, so when using traditional Chinese medicine, appropriate amount of oxytetracycline, furazolidone and garlic paste should be used for comprehensive treatment, and the effect is better.