Penaeus vannamei has the characteristics of rapid growth, strong disease resistance and so on. In recent years, with the continuous expansion of the scale of breeding, the level of intensive cultivation has been increased, and the incidence of various diseases has been increasing year by year. Among them, red body disease is the most harmful shrimp disease. There are four types of red body disease caused by the production of Penaeus vannamei, ie viral red body, bacterial red body, stress red body, and white spot comprehensive red body. Because of the different pathogens, the onset time and the symptoms and harm of the diseased shrimp are different. Because the etiology of shrimp red body disease is diversified, it is difficult to diagnose correctly; in addition, due to the lack of scientific knowledge and driven by the interests of market economy, the phenomenon of misuse of fishery drugs often occurs, which not only results in poor treatment but also increases the cost of breeding. In 2009, the author conducted a demonstration of the red body disease prevention and control technology in Dajiahe Town, Ninghai County, Zhejiang Province, and established strict disinfection measures and virus monitoring procedures, which effectively reduced the incidence of red body disease in shrimp. The control techniques are summarized below.
Viral red body
The viral red body pathogenic virus is the taura virus. Once onset, it will cause massive deaths of white shrimp. Shrimp body surface is pale red, especially the tail fan and swim foot become red, it is also known as red tail disease; sick shrimp shell becomes soft, easy to separate from the muscle, severe disease shrimp have irregular black spots on the shell, hepatopancreas Dirty degeneration or erosion, redness and swelling of the intestines. The condition often has a period of latency, with no obvious early symptoms. The length of incubation depends on environmental conditions and physical health. With the deterioration of water quality, sick shrimp do not ingest or eat very much, and there are more individuals with empty stomachs, and soon die from water.
Prevention and control measures: There are no effective drugs and methods for the treatment of viral red body disease. Only comprehensive precautions can be taken. The first is to adjust the balance and stability of shrimp pond water quality. Reduce stress. Regular use of microbial agents regulates the quality of the water and the substrate improver improves the substrate. The second is regular water disinfection. 10 days to 15 days (especially after changing the water) Use strong chlorine or aquatic products such as dibromohydantoin or strong iodine to disinfect the whole pool. The third is drug control. In the onset season or onset, external use of iodine sterilization of strong red goods; at the same time, add the right amount of vitamin preparations in the feed, mix the feed after the spices, use for 4 days. The fourth is to enhance shrimp immune function. Long-term addition of immune polysaccharides, vitamins, etc. in feed to enhance shrimp disease resistance.
Bacterial red body
The bacterial red-body pathogens are mainly Vibrio parahaemolyticus and Aeromonas hydrophila. Shrimp appendages turn red, also known as red leg disease. Diseased shrimp decreased in vigour, was unresponsive, and slowly flowed on the water surface or did not move to the bottom; the diseased shrimp had pale yellow, hard shell, and hepatopancreas with no obvious mutation, no dark spots on the body, and the hemolymph fluid became thin. Blood cells become less, coagulate slowly or do not freeze. Occur in the high temperature and rainy season, ponds with high density and poor cultivation conditions.
Prevention measures: First, in the winter, the bottom of the pond should be thoroughly dredged and disinfected to prevent the presence of pathogenic bacteria. The second is to keep the water quality of the pond stable. The use of microbial preparations and the use of disinfectants on a regular basis can control the number of vibrio strains. If the number of vibrio strains is low, it will not cause red body disease. Third, when the shrimp became ill, the water body was promptly disinfected and gentle drugs were used to reduce irritation.
Stress red body
When the various physical and chemical factors in the environment, such as weather, salinity, pH value, water level difference, ammonia nitrogen, and nitrite, mutate, the shrimp will turn red to adapt to environmental changes, and the tip of the tail fan will turn red. Other symptoms. Sometimes artificial fishing, application of pesticides, etc. can also cause the shrimp body to be tentacles, tail fans and even the appendages. The stress red body mostly occurs in the high-temperature and rainy summer. The upper part of the antennae of the shrimp body turns red, and the tail fan only has red tail. The stress red body phenomenon can disappear in the short term with the stability of the water body factor. During the stress period, P. vannamei's autoimmune ability dropped sharply. At this time, it was easily infested by bacteria, viruses, etc., and secondary to bacterial diseases.
Prevention and control measures: First, keep various physical and chemical factors of water stable in the breeding process, so that the dissolved oxygen is above 4 metE, the pH value is between 7.6 and 8.8, the ammonia nitrogen and nitrite are controlled below 0.1 mr CL, and the transparency of the water is kept at 30 cm about. The second is that when you change water, you can not change too much at a time, but do not exceed 1/2 at most. In order to prevent temperature difference, poor salinity and poor pH value over the large bow caused by shrimp stress response. Third, if shrimps produce red bodies due to stress, detoxification and anti-stress drugs are put into the water. Increase water buffering, properly invest in probiotics and water improvers to improve the water environment, and at the same time, increase the number of anti-stress products that can boost immunity, and then recover the number. At this time, disinfectants should be used with caution to avoid irritation and increase Stress response
White spot synthetic red body
The disease is mainly due to the long-term lack of improvement in shrimp body disease and the weak physical constitution of the shrimp, thus showing the characteristics of red body disease. The symptoms are similar to those of stress red body disease. There is no isolation of the taura virus in the shrimp body. The external environment is not irritating and the water conditions are good, but the red body disease symptoms still exist. The early stage of leukoplakia occurred several days later with the symptoms of red-body disease. White spots appeared in the subcutaneous skin, shells and appendages of the shrimp body at the late stage of the disease. The shells and dermis were easily peeled, the shell and the dermis were separated, the shell showed dark red, and the hepatopancreas White swelling and other phenomena. During the various stages of shrimp culture, there may be outbreaks, long durations, and high mortality rates. The shrimp pool will be completely destroyed in 2 to 7 days.
Control measures: First, thoroughly dredge and disinfect the bottom of the pond; second, apply 5 mg/L povidone-iodine solution to soak for 10 minutes before the seedlings are released: Thirdly, if white spot disease is found, use 0.1% povidone iodine powder ( 10% content), 0.5% florfenicol and Ve were added to the feed, and the whole pool was splashed with povidone iodine solution, so that the concentration in the pool water reached 0.5 mg to 1.0 mg.
Comprehensive prevention measures
The prevention and treatment of red body disease of Penaeus vannamei must adhere to the principle of “prevention from prevention, prevention from prevention, and prevention from erodingâ€, and take the road of comprehensive prevention and control. Whether it is a bacterial red body disease or a viral red body disease, it will bring a devastating blow to the culture of white shrimp. In the production practice, the first is to do dredging and disinfection of ponds, remove pathogenic microorganisms and ammonia, sulfides and other harmful substances that pose a major threat to the growth of shrimp; the second is to strengthen the introduction of inspection and quarantine of shrimps, from the source to eliminate shrimp The seedlings carry the pathogenic factor Xitang; the third is to strengthen the management of the aquaculture process, first of all to ensure that the water quality is good and relatively stable, to conduct regular water quality monitoring, and to take corresponding measures based on the monitoring results.
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