Control of carapace canker (Brown spot) of cultured Shrimp

The main results are as follows: (1) the bacteria that can be isolated from the focus are Vibrio, Pseudomonas and Flavohacterium. It is a gram-negative bacilli.

(2) there are dark brown or black spotted ulcers on the body surface carapace and appendages of shrimp with symptomatic ① disease, forming brown depressions. The middle part of the depression is deeper, and the periphery of the depression is shallow and slightly white. In patients with severe ②, the ulcer reaches the soft tissue under the carapace, and some diseased shrimps even frontal sword (the forehead xiphoid process of shrimp, also known as shrimp gun), appendages and tail fan are broken, and the cross section is black. Melanin is deposited around the ulcer of shrimp to inhibit the rapid expansion of the ulcer and form black spots. Pathogenic bacteria can invade shrimp from the wound, causing shrimp infection and death.

(3) the diagnosis can be diagnosed with the naked eye, but it should be distinguished from Fusarium disease. Fusarium disease is mainly manifested in the Gill area of cephalothoracic nail, while the location of carapace canker is scattered, such as dorsal nail, lateral nail, tail fan, antennal scales and forehead sword. Secondly, the mycelium and conidia of Fusarium oxysporum disease were observed under microscope, while brown spot disease was mostly motor bacilli.

(4) the epidemic situation is that the disease is caused by the reproduction of a large number of vibrio caused by poor water quality and sediment. In particular, shrimp injury is the most susceptible to infection, which is one of the common diseases of shrimp.

(5) Prevention and treatment of ① by feeding high quality feed. ② ensures that the water environment is good and the water quality is not polluted. ③ regularly sprinkles disinfectants and water quality improvers to maintain a stable environment.