Control of several gill diseases in cultured Penaeus vannamei

First, Gill disease caused by Vibrio.

The diseased shrimp floats slowly on the water surface, the Gill filaments are slightly swollen and dark gray, and the tip is denatured and necrotic. The active bacteria can be seen under a high power mirror. The pond where the disease occurred was seriously polluted and the water quality was poor. The peak season of the disease was from July to September.

Prevention and cure method: ① removes excessive silt, keeps it about 10 cm, thoroughly cleans the pond with quicklime and freezes the pond to dry the pond, so that the organic matter at the bottom of the pond is fully decomposed. ② applied zeolite powder, Haizhongbao and other bottom modifiers in the process of culture to change the bottom anaerobic state and stabilize the bottom pH value. ③ uses photosynthetic bacteria, EM bacteria, biological hydrolysins and other microbial agents to regulate water quality and inhibit the reproduction of Vibrio. ④ treatment: the whole pool was sprinkled with dibromohydantoin O.39. 0.1% allicin or 0.3% oxytetracycline was added to the feed for 5 to 7 days.

Gill disease caused by protozoa

Fixed ciliates and straw worms are a kind of adherent organisms, mainly including constrictor, monozoa, cumulus, bell worm and straw worms, which are often attached to the Gill and body surface of shrimp in the adult stage. When the quantity is large, a layer of gray-black fluffy substance can be seen on the shrimp surface, which is dirty and ugly, and the Gill area becomes black. It affects the respiration and normal growth and development of shrimp, and causes difficulty in shelling in severe cases, which can be diagnosed from the appearance symptoms, and more worms can be observed under low power microscope for diagnosis.

Prevention and control methods: due to the high content of organic matter in the water and the fertilizer of the pool water, ① can adjust the water quality by changing water, propagate an appropriate amount of phytoplankton, and regulate the ecological environment of the water. Many farmers in ② use sprinkling tea seed cake to stimulate shrimp shelling to solve this problem, but tea seed cake stimulation shelling is abnormal shelling. Therefore, after stimulating shelling, mineral elements, especially calcium and phosphorus, should be added to the feed, adding 2% of the feed, and improving nutrition. And this method can not be used frequently, otherwise it will affect the immunity of shrimp. Sprinkle zinc sulfate in the whole pool of ③ O.5~lg/m ³. Every other day, ④ sprinkles dibromohydantoin 0.2mm 0.39 0.5mL/m3 ³or xinjieruo ³in the whole pool, and 0.1% allicin is added to the diet.

Gill disease caused by filamentous bacteria

Shrimp Gill dark brown, loss of appetite, slow growth, difficult to shell. The pathogen is Mucor, which propagates by conidia. The hyphae are filamentous, unbranched, thicker at the base and finer at the end. During diagnosis, a large number of hyphae can be observed under high power microscope, the thicker end is fixed in the Gill, and the fine end is free. In the case of high culture density, water and fertilizer, it is easy to suffer from this disease.

Control method: ① controls the water fertility and reduces the content of organic matter in the pond. ② reduces residual bait and prevents pollution of sediment and water quality. ③ is sprinkled with copper chelate 0.59 Chloride ³whole pool or methylene blue 0.1 / 0.29 Chloride ³. Meanwhile, take florfenicol and feed with 1~29/kg feed for 5 days.

Fourth, Gill disease caused by poor water quality

The pond water load is heavy in the middle and later stage of culture, and harmful substances often accumulate. In addition, affected by typhoon, rainstorm, cold air and other bad weather, the pool water appears abnormal conditions such as stratification, convection, sediment flooding and so on. The deterioration of the water environment often causes pathological changes of Gill tissue, necrosis, yellowing and blackening, adhesion of foreign bodies, sometimes reddish shrimp and so on.

Prevention and control methods: ① often determines the water quality and grasps the changes of pond water quality. 5kg per mu of quicklime or caustic soda modified 0.5~lg/m ³was used to regulate pH, and compound microbial preparations such as EM preparation and biological water repellent were used every 10 to 15 days to control the dominant populations of algae and microorganisms in the pond. Absorb and transform various reducing substances, play a good role in stabilizing and repairing water quality. The pH value is stable at 7.8-8.5, ammonia nitrogen is less than 0.5mg/L, nitrite nitrogen is less than 0.1mg/L. Severe weather such as ② storm or continuous rain can cause strong stress reaction of shrimp, resulting in a decline in shrimp immunity. Water change should be controlled by adding oxygen, changing water, sprinkling water purifier and other measures, and according to the weather forecast, 0.2%Vc and 1% prawn root lotus detoxification powder should be added to the feed in advance.

5. Gill disease caused by malnutrition

If the amount of feed is small or the diet is lack of nutrition, the shrimp will become sick due to deficiency of body. Due to the lack of Vc, melanin deposits in the Gill area, and then fester, necrotic and blacken. In addition, necrosis of the stomach wall, hindgut wall, liver, especially the articular membrane of the body segment and appendages could be seen in the diagnosis.

Control method: ① grasps the appropriate feeding amount and improves the nutritional composition of the feed to make the formula meet the nutritional requirements of shrimp. ② added 0.3% vc and 0.2% shellfish per kilogram of feed.